UDC 693.814 669.14.018.29 d this publication may be ... · Shear buckling resistance of thin webs ... 3.4 Deductions for holes ... bending C Compression strength: ...

BS 5950 : Part 1 : 1990 UDC 693.814 . 669.14.018.29

@ B f i s h Standards I-. No pan d this publication may be photocopied or otherwise repmducsd w i t W the prior permision in writing d BSI

British Standard

Structural use of steelwork in building Part 1. Code of practice for design in simple and continuous construction: hot rolled sections

Aciers de construction Partie 1. Code de bonne pratique pour la conception des ouvrages de construction simple continue : profiles lamines a chaud

British Standards Institution

im Bauwesen Teil 1. Leitfaden fur die Vetwendung warmgewalzter Profilstahle in einfacher und Endlosbauweise

Stahlkonstruktion

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BS 5950 : Part 1 : 1990 BEST COPY AVAILABLE

Contents

Page

5 Back cover

Page

16 16 16 18 18 18 18

18 18

Foreword Committees responsible

Limiting proportions of cross sections General Classification of cross sections Classification of elements Webs of semi-compact sections Compound flanges Longitudinally stiffened flanges

Slender cross sections General Sections with thin webs required to carry shear Webs subject to moments and axial loads and circular hollow sections Other elements

Code of practice

Section one. General

1.0 Introduction 6 1.0.1 Aims of economical structural design 6 1.0.2 Overall stability 6 1.0.3 Accuracy of calculation 6

1.1 Scope

1.2 Definitions

1.3 Major symbols

1.4 Other materials 8

1.5 Design documents

1.6 Detailing

1.7 References to BS 5400

Section four. Design of structural elements

4.1 General 4.1.1 Scope 4.1.2 Class of cross section 4.1.3 Design strength Section two. Limit state design

General principles and design methods Limit state concept Methods of design

Loading General Dead, imposed and wind loading Dynamic loads and impact effects

Temperature effects

Ultimate limit states Limit state of strength Stability limit state Fatigue Brittle fracture Structural integrity

Serviceability limit states Deflection Durability

4.2 Members in bending 4.2.1 General 4.2.2 Full lateral restraint 4.2.3 Shear 4.2.4 Elastic shear stress 4.2.5 Moment capacity with low shear load 4.2.6 Moment capacity with high shear load

Lateral torsional buckling General Lateral restraints Torsional restraints Destabilizing load Effective lengths of beams Effective lengths of cantilevers Lateral torsional buckling resistance of members subject to bending

4.3.8 Buckling resistance moment for single angles

4.4 Plate girders 4.4.1 General Section three. Properties of materials and section

properties 4.4.2 .pimensions of webs and flanges 4.4.3 Besign strength of components 4.4.4 Moment capacity 4.4.5:. Shear buckling resistance of thin webs 4.4.6:. Design of intermediate transverse web

3.1 General 3.1 .I Strength of steel 3.1.2 Other properties of steel 3.1.3 Steel castings and forgings

stiffeners 3.2 Welds and fasteners 3.2.1 Welding consumables

Web bearing, buckling and stiffener design General Load carrying stiffeners Bearing stiffeners Design of load carrying stiffeners Design of bearing stiffeners Design of diagonal stiffeners Design of tension stiffeners Torsion stiffeners

3.2.2 Ordinary bolts, nuts and washers 3.2.3 Friction grip fasteners

3.3 Section properties 3.3.1 Gross section 3.3.2 Net area 3.3.3 Effective area at connections

3.4 Deductions for holes 3.4.1 Hole area 3.4.2 Holes not staggered 3.4.3 Staggered holes

4.5.9 Connection to web of load carrying and bearing stiffeners

4.5.10 Connection to flanges: stiffeners in tension

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4.5.1 1 Connection to flanges: stiffeners in compression 55

4.5.1 2 Hollow sections 55

4.6 Axially loaded tension members 55 4.6.1 Tension capacity 55 4.6.2 Eccentric connections 55 4.6.3 Effective areas of simple tension members 55 4.6.4 Laced or battened ties 5 6

4.7 Compression members 56 1 4.7.1 General 56 4.7.2 Effective lengths 56 4.7.3 Slenderness 56 4.7.4 Compression resistance 57 4.7.5 Compressive strength 57 4.7.6 Eccentric connections 67

1 4.7.7 Columns in simple construction 67 4.7.8 Laced struts 67 4.7.9 Battened struts 68

( 4.7.10 Angle, channel and T-section struts 68 4.7.1 1 Batten-starred angle struts 69 4.7.12 Battened parallel angle struts 69 4.7.13 Back-to-back struts 69

4.8 Axially loaded members with moments 7 2 4.8.1 General 7 2 4.8.2 Tension members with moments 72 4.8.3 Compression members with moments 72

4.9 Members with biaxial moments 7 3

4.10 Empirical design rules for members in lattice frames and trusses 73

4.1 1 Additional provisions for gantry girders 74 4.1 1 .I General 74 4.1 1.2 Crabbing of trolley 7 4 4.1 1.3 Lateral torsional buckling 74 4.1 1.4 Shear buckling 74 4.1 1.5 Local compression under wheels 74 4.1 1.6 Welded girders 74

4.12 Purlins and side rails 74 4.12.1 General 74 4.12.2 Deflections 7 4 4.12.3 Wind loading 7 4 4.12.4 Empirical design of purlins and side rails 74

4.13 Column bases 7 5 4.13.1 General 75 4.13.2 Empirical design of baseplates 76 4.13.3 Connection of baseplates 76

4.14 Cased sections 7 6 4.14.1 General 76 4.14.2 Cased members subject to bending 7 7 4.14.3 Cased struts 77 4.14.4 Cased members subject to axial load and

moment 7 7

4.15 Web openings 77 4.15.1 General 77 4.15.2 Sections other than castellated 78 4.15.3 Castellated beams 78

Section five. Continuous construction

5.1 General 5.1.1 Scope 5.1.2 Loading 5.1.3 Classification of multi-storey frames as sway

or non-sway

5.2 Elastic design

5.3 Plastic design 5.3.1 General 5.3.2 Type of loading 5.3.3 Grades of steel 5.3.4 Geometrical properties 5.3.5 Restraints 5.3.6 Stiffeners at hinge locations 5.3.7 Fabrication restrictions

Continuous beams Elastic design Plastic design

Portal frames General Elastic design Plastic design

Multi-storey rigid frames: elastic design General Non-sway frames Sway frames Subframes

Page

79 7 9 79

7 9

7 9

79 7 9 7 9 7 9 79 80 80 80

5.7 Multi-storey rigid frames: plastic design 83 5.7.1 General 83 5.7.2 Non-sway frames 83 5.7.3 Sway frames 83

Section six. Connections

General recommendations General l ntersections Joints in simple construction Joints in rigid construction Joints in semi-rigid construction Joints subjkt to vibration and/or load reversal Splices y. ~astener ipacing and edge distances Minimum spacing Maximum spacing in unstiffened plates Minimum edge and end distances Maximum edge distances

Ordinary bolting Effective areas of bolts Shear capacity Bearing capacity Long joints Large grip lengths Bolts subject to tension

Friction grip fasteners General

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Parallel shank friction grip fasteners Waisted shank fasteners: slip resistance Friction grip fasteners subject to external tension Combined shear and tension Holes for friction grip fasteners

Pin connections General Tension members and pin plates Design of pins

Weld detail and design General Details of fillet welds Partial penetration butt welds Welded details for structural hollow sections Design of fillet welds Design of butt welds

Holding-down bolts

Section seven. Loading tests

7.1 General

7.2 Test conditions

7.3 Test procedures 7.3.1 Test loads 7.3.2 Preliminary loading 7.3.3 Acceptance test 7.3.4 Strength test 7.3.5 Test to failure 7.3.6 Check tests

Appendices

A Formal statement of safety factor format adopted in BS 5950 : Part 1 to facilitate correlation with I S 0 2394 and BS 5400 : Part 3

B Lateral torsional buckling of members subject to bending

C Compression strength: Perry strut formula D Effective lengths of struts in simple construction E Effective lengths of struts in rigid frames F Frame instability G Design of restrained members with an

unrestrained compression flange H Web buckling

Tables

1 Limit states 9 2 Load factors and combinations 10 3 Factor K for location of material and tens~le

stress 11 4 Maximum thickness for adequate notch

thickness of parts subject to applied tensile stress 12 5 Deflection limits other than for pitched roof

portal frames 14 6 Design strengths. PI 15 7 Limiting width to thickness ratios 17 8 Strength reduction factors for slender elements 19 1 9 Effective length, L E , for beams 23

10 Effective length, L E , for cantilever of length L 11 Bending strength,^,, (in N/mm2) for rolled

sections 12 Bending strength,pb, (in N/mm2) for welded

sections 13 Use of m and n factors for members of uniform

section 14 Slenderness factor v for flanged beams of

uniform section 15 Slenderness correction factor, n. for members

with applied loading substantially concentrated within the middle fifth of the unrestrained length

16 Slenderness correction factor, n, for members with applied loading other than as for table 15

17 Moment diagram between adjacent points of lateral restraint

18 Equivalent uniform moment factor, m 19 Bending strength,^,, (in N/mm2) for rolled

sections with equal flanges (a) Py = 265 N/mmz (b) Py = 275 ~ / m m ~ (c) Py = 340 ~ / m m ~ (d) Py = 355 N/mm2

20 Slenderness correction factor, n, for standard load conditions

21 Critical shear strength, q,, (in N/mm2) (a) p, = 265 N/mm2 (b) p, = 275 N/mmz (c) p, = 340 N/mm2 (dl p, = 355 N/mm2

22 Basic shear strength, qb (in N/mm2 ) (a) p, = 265 N/mm2 (b) p, = 275 ~ I m m ' (c) . P, = 340 N/mmz (d) p, = 355 N/mm2

23 Flange dependent shear strength factor, qf (in Nlmm2 1 (a) p, = 260 N/mm2 (b) p, = 275 N/mm2 (c) p, = 340 N/mm2 (dl o, = 355 N/mm2

24 Nominakffective length, L E V for a strut 25 Strut table selection 26 Typeof section obtained for table 25 27 Compkessive strength, PC, (in Nlmm2) for struts 28 Angle, channel and T-section struts 29 Empirical values for purlins 30 Empirical values for side rails 31 Minimum edge and end distances to fasteners 32 Strength of bolts in clearance holes 33 Bearing strength on connected parts for

ordinary bolts in clearance holes, p,, 34 Bearing strength on parts connected by parallel

shank friction grip fasteners,~,, 35 Maximum dimensions of holes 36 Design strength, p, 37 Comparison of partial safety factors 38 Limiting h for box sections of uniform wall

thickness, including RHS 39 Equivalent uniform moment factor, m,

Page

24

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Figures

1 Staggered holes 2 Angles with holes in both legs 3 Dimensions of sections

1 4 Effective shear area of typical sections 5 End panel designed not using tension field

action 6 End panel designed using tension field action

(single stiffener) 7 End panel designed using tension field action

(double stiffener) 8 Stiff bearing length 9 Dimensions of castellated sections

10 Haunch restraints 11 Subframes

I 1 laMinimum edge and end distances 12 Joint length at splice 13 Pinended tension members 14 Welded end connections 15 Symmetrical fillet welds 16 Dimensions for symmetrical plate girders 17 Side stanchion 18 Side stanchion with restraints 19 Simple side stanchion with crane gantry

20 Compound side stanchion with crane gantry 21 Compound vallejt stanchion with crane gantry 22 Restraint coefficients for limited frame 23 Effective length ratio L E I L for a column in a

rigid-jointed frame braced against sidesway for k 3 = -

24 Effective length ratio L E I L for a column in a rigid-jointed frame with unrestricted sidesway fork, = 0

25 Effective length ratio L E / L for a column in a rigid-jointed frame with partial sway bracing of relative stiffness k, = 1

26 Effective length ratio L E I L for a column in a rigid-jointed frame with partial sway bracing of relative stiffness k j = 2

27 Critical buckling mode of frame braced against sidesway

28 Critical buckling mode of frame free to sway 29 Members restrained on tension flange 30 Typical haunch 31 Value of 0, 32 Intermediate moments

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BS 5950 : Part 1 : 1990

Foreword

This Part of BS 5950 has been prepared under the direction of the Civil Engineering and Building Structures Standards Policy Committee. This Part of BS 5950 replaces BS 5950 : I Part 1 : 1985 which is withdrawn. BS 5950 i s a document combining codes of practice to cover the design construction and fire protection of steel structures and specifications for materials, workmanship and erection.

This edition introduces technical changes but it does not reflect a full review or revision of the standard, which will be undertaken in due course.

The changes introduced are indicated by a single side line in the margin of the page.

I BS 5950 comprises the following Parts:

Part 1 Code of practice for design in simple and continuous construction: hot rolled sections

Part 2 Specification for materials, fabrication and erection: hot rolled sections

Part 3 Design in composite construction Section 3.1 Code of practice for design of simple and continuous composite beams 'Section 3.2 Code of practice for design of composite columns and frames

Part 4 Code of practice for design of floors with profiled steel sheeting

Part 5 Code of practice for design of cold formed sections

Part 6'Code of practice for design in light gauge sheeting, decking and cladding

Part 7'Specification for materials and workmanship: cold formed sections

Part 8 Code of practice for fire resistant design Part 9' Code of practice for stressed skin design

Part 1 gives recommendations for the design of structural steelwork in simple and continuous construction and its provisions apply to the majority of structures, although i t is recognized that cases will arise when other proven methods of design may be more appropriate.

This Part does not apply to other steel structures for which appropriate British Standards exist.

I t has been assumed in the drafting of this British Standard that the execution of its provisions i s entrusted to appropriately qualified and experienced people and that construction and supervision should be carried out by capable and experienced organizations.

The full list of organizations who have taken part in the work of the Technical Committee i s given on the back cover. The Chairman of the Committee i s Mr P R Brett and the following people have made a particular contribution in the drafting of the code.

Mr P A Rutter Vice-chairman Mr P H Allen Mr B Auger Mr R J Campion Mr E F Hole Mr B L Hurst Mr J C Kalra Mr E G Lovejoy Dr D B Moore Prof. D A Nethercot Dr M H Ogle Mr P R Salter Dr J E Spindel Mr R Taggart Mr J C Taylor Mr A D Weller Dr F J Whitbread

Compliance with a British Standard does not of itself confer immunity from legal obligations.

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BS 5950 : Part 1 : 1990 Section one

Section one. General

1.2 Definitions 1.0 Introduction

1.0.1 Aims of economical structural design

The aim of structural design i s to provide, with due regard to economy, a structure capable of fulfilling its intended function and sustaining the design loads for its intended life. The design should facilitate fabrication, erection and future maintenance.

The structure should behave as one three-dimensional entity. The layout of i t s constituent parts, such as foundations, steelwork, connections and other structural components should constitute a robust and stable structure under normal loading to ensure that in the event of misuse or accident, damage will not be disproportionate to the cause.

To achieve this i t is necessary to define clearly the basic structural anatomy by which the loads are transmitted to the foundations. Any features of the structure which have a critical influence on i t s overall stability can then be identified and taken account of in design.

Each part of the structure should be sufficiently robust and insensitive to the effects of minor incidental loads applied during service that the safety of other parts i s not prejudiced. Reference should be made to 2.4.5.

While the ultimate strength requirements within this standard are to be regarded as limiting values, the purpose in design should be to reach these limits in as many parts of the structure as possible, to adopt a layout such that maximum structural efficiency i s attained and to rationalize the steel member sizes and details in order to obtain the optimum combination of material and fabrication.

1.0.2 Overall stability

The designer responsible for the overall stability of the structure should ensure the compatibility of design and details of parts and components. There should be no doubt of this responsibility for overall stability when some or all of the design and details are not made by the same designer.

1.0.3 Accuracy of calculation

For the purpose of deciding whether a particular rule of the standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis should be rounded off. The number of significant places retained in the rounded off value should be the same as the value given in this standard.

1.1 Scope

This Part of BS 5950 gives recommendations for the design of structural steelwork with hot rolled steel sections, flats. plates and hollow sections in buildings and allied structures not specifically covered by other standards.

NOTE I . These recommendat~ons assume thar the standards of mater~als and constructfion are as specfified fin BS 5950 : Part 2 . NOTE 2 . The publicat~ons referred to in rhis standard are listed on the inside back cover

For the purposes of this Part of BS 5950, the following definitions apply. 1.2.1 beam. A member predominately subject to bending.

1.2.2 brittle fracture. Brittle failure of steel at low temperature.

1.2.3 buckling resistance. Limlt of force or moment which a member can withstand without buckling.

1.2.4 built-up. Constructed by interconnecting more than one plate to form a single member.

1.2.5 cantilever. A beam which i s fixed at one end and i s free to deflect at the other.

1.2.6 capacity. Limit of force or moment which may be applied without causing failure due to yielding or rupture.

1.2.7 column. A vertical member of a structure carrying axial load and possibly moments.

1.2.8 compact cross section. A cross section which can develop the plastic moment capacity of the section but in which local buckling prevents rotation at constant moment.

1.2.9 compound section. Constructed by interconnecting one or more sections or plates and sections to form a single member.

1.2.10 dead load. All loads of constant magnitude and position that act permanently, including self welght.

1.2.11 design strength. The yield strength of the material multiplied by the appropriate partial factor. See 3.1.1.

1.2.12 dynamic load. Part of an imposed load resulting from motion.

1.2.13 edge distance. Distance from the centre of a fastener hole to the nearest edge of an element.

1.2.14 effective length. Length between points of effective restraint of a member multiplied by a factor to take account of the end conditions and loading.

1.2.15 elastic design,Qeslgn which assumes no redlstribu tion of moments due 8 plastic rotation of a section throughout the structure.

5.

1.2.16 empirical method. Simplified method of design justified by experience or testing.

1.2.17 end distance. Distance from the centre of a fastener hole to the edge of an element parallel to the direction in which the fastener bears.

1.2.18 factored load. Specified load multiplied by the relevant partial factor.

1.2.19 fatigue. Damage to a structural member caused by repeated application of stresses that are insuffic~ent to cause failure by a single application.

1.2.20 foundation. Part of a structure whlch distributes load directly to the ground.

1.2.21 friction grip connection. A bolted connection which relies on frictlon to transmit shear between components.

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1.2.41 strength. Resistance to fallure by y ~ e l d ~ r ~ g or buckling

1.2.22 H-section. A section with one central web and two equal flanges which has an overall depth not greater than 1.2 times the width of the flange.

1.2.23 hybrid. Composed of elements of more than one strength grade of steel.

1.2.24 I-section. Section with central web and two equal flanges which has an overall depth greater than 1.2 times the width of the flange.

1.2.25 imposed load. Load on a structure or member, other than wind load,produced by the external environment and intended occupancy or use.

1.2.26 instability. Inability to carry further load due to vanishing stiffness.

1.2.27 lateral restraint

Fora beam. Restraint which prevents lateral movement of the compression flange.

For a compression member. Restraint which prevents lateral movement of the member in a particular plane.

1.2.28 longitudinal. Along the length of the member.

1.2.29 pattern loading. Loading arranged in such a manner as to give the most severe effect on a particular element.

1.2.30 pitch. Distance between centres of fasteners lying in the direction of stress.

1.2.31 plastic cross section. A cross section which can develop a plastic hinge with sufficient rotation capacity to allow redistribution of bending moments within the structure.

1.2.32 plastic design. Design method assuming redistribu. tion of moment in continuous construction.

1.2.33 plastic moment. Moment capacity allowing for redistribution of stress within a cross section.

1.2.34 pretensioned fastener. Fastener tensioned to a specified proportion of its proof stress before connected components are loaded.

1.2.35 semi-compact cross section. A cross section in which the stress in the extreme fibres should be limited to yield because local buckling would prevent development of the plastic moment capacity in the section.

1.2.36 serviceability limit states. Those limit states which when exceeded can lead to the structure being unfit for its intended use.

1.2.37 slender cross section. A cross section in which yield of the extreme fibres cannot be attained because of premature local buckling.

1.2.38 slenderness. The effective length divided by the radius of gyration.

1.2.39 slip resistance. L ~ m i t of shear that can be applied before slip occurs in a friction grip connection.

1.2.40 stability. Resistance of the structure or part of the structure to overturning or overall failure.

1.2.42 strut. A member of a structure carrylng predomt nant!y compressive axtal load.

1.2.43 subframe. Parr of a larger frame

1.2.44 transverse. D~rectlon perpendicular to the stronger of the rectangular axes of the member.

1.2.45 ultimate limit s t a t e . That state w h ~ h t f exceeded can cause col!apse of part or whole of the structure

1.2.46 design grade. Designation used t o define specific performance requirements of the material for design purposes, in particular strength and toughness.

1.2.47 product grade. Designation used to define mechanical and chemical properties and manufacturing requirements of the material as specified in BS 5950 : Part 2.'

1.3 Major symbols

A Area

A, Effective area

Ag Gross area

A, Shear area (bolts)

A, Tensile stress area (bolts)

A, Shear area (sections)

a Spacing of transverse stiffeners or Effective throat size of weld

B Breadth

b Outstand or Width of panel

b I Stiff bearing length Charpy impact value

Depth of section or Diameter of section or Diameter of hole

Depth of web or Nominal diameter of fastener

Modulus of elasticity of steel

End distance

Compressive force due to axial load

Shear force (bolts)

Tensile force

S b r force (sections)

~dm~ress i ve stress due to axial load

Shear stress

Shear modulus of steel

Warping constant of section

Storey height

Second moment of area about the major axis

Second moment of area about the minor axis Torsion constant of section Length of span

Effective length

Larger end moment

Ma, Maximum buckling moment about the major or minor axis in the presence of axial load

Buckling resistance moment (lateral torsional)

M,,,M,, Moment capacity of section about the major and minor axes in the absence of axial load

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Elastic critical moment

Mid-length moment on a simply supported span equal to the unrestrained length

Reduced moment capacity of the section about the major and minor axes in the presence of axial load Applied moment about the major and minor axes

Equivalent uniform moment about the major and minor axes

Equivalent uniform moment factor

Slenderness correction factor

Bearing capacity of a bolt

Bearing capacity of parts connected by friction grip fasteners

Bearing capacity of parts connected by ordinary bolts

Torsional index of sect~on

Specified minimum yield strength of steel

Elastic modulus about major and minor axes

Coefficient of linear thermal expansion

Modular ratio

Ratio of smaller to larger end moment

Overall load factor

Load variation factor, i.e. function of y ~ , and yr2

Material strength factor

Ratio M/Mo, i.e. the ratio of the larger end moment to the mid-length moment on a simply supported span equal to the unrestrained length

Deflection

I 275 ' I 2

constant (-d;) PC Compression resistance X Slenderness, i.e. the effective length divided by

the radius of gyration I P c x , P c y Compression resistance considering buckling A,, Elastic critical load factor about the major and minor axes only

hLo Limiting equivalent slenderness P, Shear capacity of a bolt

Equivalent slenderness P,, Slip resistance provided by a friction grip fastener

XO Limiting slenderness PC Tension capacity of a member or fastener

p . Slip factor p~ Shear capacity of a section

u Poisson's ratio P b Bending strength

P bb

p

p bs

PC

P E

Ps

Pt

Pw

pv Q b

Qcr

Qe

9f

r x . f y

s x , Sv

Bearing strength of a bolt

Bearing strength of parts connected by friction grip fasteners

Bearing strength of parts connected by ordinary bolts

Compressive strength

Euler strength

Shear strength of a bolt

Tension strength of bolt

Design strength of a fillet weld

Design strength of steel

Basic shear strength of a web panel

Critical shear strength of web panel

Elastic critical shear strength of web panel

Flange dependent shear strength factor

Radius of gyration of a member about i t s major and minor axes

Plastic modulus about the major and minor axes

s Leg length of a fillet weld

T Thickness of a flange or leg

t Thickness of a web or As otherwise defined in a clause

U, Specified minimum ultimate tensile strength of the steel

u Buckling parameter of the section

Vb Shear buckling resistance of stiffened web utilizing tension field action

Vc, Shear buckling resistance of stiffened or unst~ffened web without utilizing tension field action

v Slenderness factor for beam

1.4 Other materials Where other structural materials are used in association with steelwork they should comply with the appropriate British Standard. NOTE. Attent ion is drawn to the necessity of referring to local regulations.

1.5 Design documents The design documentsshould contain sufficient information to enable the design to be detailed and the structure fabricated and erected.

The design documen@ should show the assumed behaviour of the structure, the design assumptions and whether the forces and reactiorh included are factored or unfactored.

1.6 Detailing The connections between members should withstand the forces and moments to which they will be subjected, without undue deformation and without invalidating the design assumptions.

The detailing of the connections should take account of possible dimensional variations due to rolling margins and fabrication variations, leading to some degree of lack of fit.

1.7 References to BS 5400 In BS 5400 the breakdown of partial safety factors, the assessment of material strengths, etc. are different, and these differences should be recognized. I

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BS 5950 : Part 1 : 1990 Section two

Section two. Limit state design

2.1 General principles and design methods

2.1.1 Limit state concept

Structures should be designed by considering the limit states at which they would become unfit for their intended use, by applying appropriate factors for the ultimate limit state and the ser-viceability limit state.

Examples of limit states relevant to steel structures are given in table 1.

The overall factor in any design has to cover variability of:

Material strength: Y m

Loading: Yu

Structural performance: y ,

Table 1. Limit states

In this code the material factor, y,, is taken as 1.0 (see 3.1.1). Depending on the type of load, values of yk and y , are assigned. The product of yp and y, i s the factor yf, by which the specified loads are to be multiplied in checking the strength and stability of a structure (see table 2).

Ultimate

1 Strength (including general yielding, rupture, buckling and transformation into a mechan~sm)

2 Stability against overturning and sway

3 Fracture due to fatigue

4 Brittle fracture

A deta~led breakdown of y factors is given in appendix A.

Serviceability

5 Deflection

6 Vibration (e.9. wind induced oscillation)

7 Repairable damage due to fatigue

8 Corrosion and durability

2.1.2 Methods of design

2.1.2.1 General. The design of any structure or its parts may be carried out by one of the methods given in 2.1.2.2 to 2.1.2.5.

In all cases, the details of members and connections should be such as to realize the assumptions made in design without adversely affecting any other parts of the structure.

2.1.2.2 Simple design. The connections between members are assumed not to develop moments adversely affecting either the members or the structure as a whole.

The distribution of forces may be determined assuming that members cntersecting at a joint are pin connected. The necessary flexibility in connections may result in some nonelastic deformation of the materials, other than the fasteners.

2.1.2.3 Rigid design. The connections are assumed to be capable of developing the strength and/or stiffness required by an analysis assuming full continuity. Such analysis may be made using either elastic or plastic methods.

2.1.2.4 Semi-rigid design. Some degree of connection stiffness is assumed, but insufficient to develop full continuity as follows.

(a) The moment and rotation capacity of the joints should be based on experimental evidence, which may permit some limited plasticity providing the ultimate tensilecapacity of the fastener is not the failure criterion On this basis, the design should satisfy the strength, stability and stiffness requirements of all parts of the structure when partial continuity at the joints is to be taken into account in assessing moments and forces in the members.

(b) As an alternative, in simple beam and column structures an allowance may be made for the inter- restraint of the connections between a beam and a column by an end restraint moment not exceeding 10 % of the free moment applied to the beam, assuming this to be simply supported. provided that the following apply.

(1 ) The beams and columns are designed by the general rules applicable to simple design.

(2) The frame is provided with lateral support or braced against sidesway in both directions.

(3) The beams are designed for the maximum net moment which includes an allowance for the restraint moment at one or both ends.

(4) Each column i s designed to resist the algebraic sum of the restraint moments from the beams at the same level on each side of the column, in addition to moments due to eccentricity of connections.

(5) The assumed end restraint moment need not, however, be taken as 10 % of the free moment for all beams, provided that the same restraint moment is used in the design of the column and beam at each conyection.

(6) l%e beam-to-column connections are designed to transmit the appropriate restraint moment, in addition to'lhe end reactions assuming the beams are simply supported.

(7) The welds and fasteners should be designed for the actual moment capacity of the connection not the assumed moment.

2.1.2.5 Experimental verification. Where design of a structure or element by calculation in accordance with any of the preceding methods i s not practicable, or is inappropriate, the strength, stability and stiffness may be confirmed by loading tests in accordance with section seven.

I t i s necessary to maintain stability against sway and the provisions of 2.4.2.3 apply.

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2.2 Loading

2.2.1 General

All relevant loads should be considered separately and in such realistic combinations as to comprise the most critical effects on the elements and the structure as a whole. The magnitude and frequency of fluctuating loads should also be considered.

Loading conditions during erection should receive particular attention. Settlement of supports may need to be taken into account.

2.2.2 Dead, imposed and wind loading

Reference should be made to BS 6399 : Part 1, BS 6399 : I Part 3 and CP 3 : Chapter V : Part 2 for the determination of the dead, imposed and wind loads.

2.2.3 Dynamic loads and impact effects

These may be determined from BS 6399 : Part 1 in the case of cranes.

It is recommended that values for cranes of loading class Q3 and Q4 as defined in BS 2573 : Part 1 should be established in consultation with the crane manufacturer.

2.3 Temperature effects

Where, in the design and erection of a structure, i t i s necessary to take account of changes in temperature, it may be assumed that in the UK the average temperature of Where a structure or member is subiect to loads from two internal steelwork varies from -5 O C to +35 OC. The actual more cranes the crane loads should be taken as the range* depends On the locationr type and purpose maximum vertical and horizontal loads acting simuItaneously of the structure and special consideration may be necessary where this is reasonably possible. for structures in other conditions, and in locations abroad subjected to different temperature ranges. 2.4.2 Stability limit state

2.4 Ultimate limit states

Table 2. Load factors and combinations

2.4.2.1 General. In considering the overall stability of any structure or part, the loads should be increased by the

Loading

Dead load Dead load restraining uplift or overturning Dead load acting with wind and imposed

loads combined

Imposed load Imposed load acting with wind load

Wind load Wind load acting with imposed load or

crane load

Forces due to temperature effects

Crane loading effects

Vertical load Vertical load acting with horizontal loads

(crabbing or surge)

Horizontal load Horizontal load acting with vertical

Crane load acting with wind load"

relevant yf factors given in table 2. - 2.4.1 Limit state of strength The designer should consider overall frame stability which

2.4.1.1 General. In checking the strength and stability of embraces stability aMnst overturning and sway stability.

Factor, yf

1.4 1.0

1.2

1.6 1.2

1.4

1.2

1.2

1.6

1.4

1.6 1.4

1.2

the structure the loads should be multiplied by the relevant yf factors given in table 2. The factored loads should be applied in the most unfavourable realistic combination for the part or effect under consideration.

I The load capacity of each member and its connections, as determined by the relevant provisions of this standard, should be such that the factored loads would not cause failure.

2.4.1.2 Overhead travelling cranes. The -yf factors given in table 2 for vertical loads from overhead travelling cranes should be applied to the dynamic crane loads. i.e. the static

'When considering wind or imposed load and crane loading acting together the value of yf for dead load may be taken as 1.2.

... 2.4.2.2 Stability agahst overturning. The factored loads, considered separatqy and in combination, should not cause the structure or any; part of the structure (including the

I foundations) to overturn or l i f t off its seating. The combin. ation of dead, imposed and wind loads should be such as to I have the most severe effect on overall stability (see 2.2.1 ).

Account should be taken of probable variations in dead load during construction or other temporary conditions.

2.4.2.3 Sway stability. All structures, including portions between expansion joints, should have adequate stiffness I

vertical wheel loads increased by the appropriate allowance against sway.

for dynamic effects (see 2.2.3). To ensure this, in addition to designing for applied

For cranes on outdoor gantries the wind loads on the horizontal loads, a separate check should be carried out

gantry and supporting structure should be obtained from:

(a) BS 2573 : Part 1, for cranes in the working condition;

(b) CP 3 : Chapter V : Part 2, for cranes which are not working.

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These notional forces may arise from practical imperfections such as lack of verticality and should be taken as the greater of:

1 % of factored dead load from that level, applied horizontally;

0.50 % of factored load (dead plus vertical imposed) from that level, applied horizontally.

These notional forces should be assumed to act in any one I direction at a time and should be applied at each roof and floor level or their equivalent. They should be taken as acting simultaneously with the factored dead plus vertical

I imposed loads taken as:

1.4 X (unfactored dead load); and

1 1.6 X (unfactored vertical imposed load).

The notional force should not:

(a) be applied when considering overturning;

I (b) be combined with the applied horizontal loads;

(c) be combined with temperature effects;

I (d) be taken to contribute to the net reactions a t the foundations.

Sway stability may be provided for example by braced frames, joint rigidity or by utilizing staircase, l i f t cores and shear walls. Whatever system is used, reversal of loading should be accommodated. The cladding floors and roof should have adequate strength and be so secured to the structural framework as to transmit all horizontal forces to the points of sway resistance. Where such sway stability is provided by construction other than the steel framework. the steelwork designer should state clearly the need for such construction and the forces acting upon i t (see 1.5).

2.4.4 Brittle fracture

2.4.4.1 General. Brittle fracture need not be considered except in locations subject to tensile stresses in service due to applied axial load or moment.

Where such tension exists then the maximum thickness may be determined from 2.4.4.2 if the service temperature does not fall below that normal in the UK, taken as --5 O C for internal conditions and - 15 O C for external conditions. Where the steel is subjected to lower temperatures or where the steel grade or thickness used is not covered by table 4 then the energy absorption should comply with 2.4.4.3, which may also be used in place of table 4.

Where severe restraint conditions occur due to welding then reference should be made to BS 5400 or specialist advice.

The recommendations of this clause do not apply to grade 43A base plates (see 4.13).

2.4.4.2 Maximum thickness. The maximum thickness for adequate notch toughness should not exceed the value given in table 4 for the value of K determined from table 3.

2.4.4.3 Energy absorption. The Charpy impact value, C,, A

in joules, at the minimum service temperature should not I be less than:

Y,t 710K

where

Y, is the minimum yield strength of the material (in ~/mrn') ;

2.4.2.4 Foundation design. The design of foundations t i s the thickness of material from which the specimen I should be in accordance with BS 8004 and should accom- is taken (in mm):

modate all the forces imposed on them. Attention should K i s determined from table 3.

be given to the method of connecting the steel superstructure to the foundations and the anchorage of any holding down bolts as recommended in 6.7.

Where i t i s necessary t6 quote the foundation reactions i t should be clearly stated whether the forces and moments result from factored or unfactored loads. Where they result from factored loads the relevant yf factors for each load in each combination should be stated.

2.4.3 Fatigue

Fatigue need not be considered unless a structure or element is subjected to numerous significant fluctuations of stress.

Stress changes due to fluctuations in wind loading need not be considered but account should be taken of wind induced oscillations.

In the design of crane supporting structures only those 2.4.5 Structural integrity 1 members which support cranes of utilization classes U4 to

U9 as defined in BS 2573 need be checked for fatigue by 2.4.5.1 Requirements for a// StrUCtUreS. All Structures

I reference to 8s 5400 : Part 10. should follow the principles given in 1.0.1. The additional

When designing for fatigue a yf factor of 1.0 should be used. requirements in 2.4.5.2 to 2.4.5.5 apply to buildings.

Table 3. Factor K for location of material and tensile stress

Drilled or reamed holes

2

2

Tensile str& due to factored loads a\the locatiow.being considered

N/rnm2 < 100

> 100

Unreamad punched holes

2

1

Welded location

2

1

Non- w d d d location

2

2

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BS 5950 : Part 1 : 1990 S e c t i o n two

2.4.5.2 Requirements for all buildings. Every bu i ld ing This anchorage may be provided b y either beams or tie frame should be effectively t ied together a t each princcpal members. Where poss~ble these should be arranged i n f loor and roo f level. All columns should be effectively cont inuous lines as close as practicable t o the columns and restrained in t w o directions approximately a t r igh t angles a t t o each edge. A t re-entrant corners the peripheral t ~ e should each pr incipal f loor or roo f wh i ch they support. be anchored i n t o the steel f ramework.

Table 4. Max imum thickness fo r adequate notch toughness o f parts subject t o applied tensile stress

NOTE 1. For sections with flanges the thickness is the flange thickness defined in the relevant British Standard.

NOTE 2. The relevant structural steel standard may require Charpy values to be agreed for certain product grades and thicknesses.

NOTE 3. Where no value is shown, the maximum thickness for adequate notch toughness may be assumed to be in excess of 100 mm. NOTE 4. The inclusion of a thickness limit in the table does not necessarily imply that steel of that thickness can be supplied to that design grade in all product forms.

NOTE 5. For design grades 43BIT) and 50BITI. verification of the impact properties of quality B by testing should be specified under option 7 of BS EN 10025 when the steel i s ordered.

NOTE 6. The maximum thickness values are based on a minimum Charpy value of 27 J* at the following test temperatures.

Design grades 43-50 and 55

Quality Test temperature

" C A (no test) 8 +20 C 0 D -20 DD -30' E - 4 0 E E -50 F - 6 0

Lksign grado WR 50


" C

A o B 0 C -15

which is accepted as equivalent to 27 J at - 3 0 OC. -

(see notes

Design grade

43A 438 43B(T) 43C 43 D 43DD 43E 43EE

50A 508 50B(TI 50C 500 5000 50E 50EE 50F

55C 55EE 55F

WR5OA WR508 WR5OC

For Fe

External conditions

K = 1

m m

15 15 20 40 90 - - - 12 12 16 30 70

100 - - - 25 - -

30 30 55

40 J at

1 t o 6)

Internal

=

m m

30 30 40 80 - - - -

25 25 32 60 - - - - -

50 - -

60 60 -

-=O'C,

conditions

K = 1

m m

25 25 30 60 - - - - 20 20 25 45

100 - - - -

35 - -

45 45 85

510 DD, BS EN

K = 2

m m

50 50 60 - - - - -

40 40 50 90 - - - - -

70 - -

90 90 -

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Ties may be either steel members or steel reinforcement embedded in concrete or masonry provided that they are properly anchored to the steel framework.

Steel members provided for other purposes may be utilized as ties. When checked as ties other loading may be ignored. Beams designed to carry the floor or roof loading will generally be suitable provided that their end connections are capable of resisting tension.

All ties and their end connections should be of a standard of robustness commensurate with the structure of which they form a part and should be capable of carrying a factored tensile load of not less than 75 kN at floors or 40 kN at roof level.

Ties are not required at a roof level where steelwork supports cladding weighing not more than 0.7 kN/m2 and carries roof loads only.

Where a building i s provided with expansion joints, each section between expansion joints should be treated as a separate building for the purpose of this clause.

2.4.5.3 Additional requirements for certain multi-storey buildings. Local or national regulations may stipulate that tall multi-storey buildings be designed to localize accidental damage.

Steel-framed buildings which satisfy the recommendations of 1.0.1 and 2.4.5.2 may be assumed to meet this require- ment provided that the five additional conditions given below are met. - ~.

A tall multi-storey building which i s required to be designed to localize accidental damage but which does not satisfy these five additional conditions should be checked as recommended in 2.4.5.4.

(a) Sway resistance. The means of providing sway resistance as recommended in 2.4.2.3 (i.e. steel bracing, rigid joints, shear walls, staircase and l i f t cores, etc.) should be sufficiently distributed throughout the building so that no substantial portion of the structural frame i s solely reliant on a single plane of bracing in each orthogonal direction..

(b) Tying. The ties referred to in 2.4.5.2 should be arranged in continuous lines wherever practicable throughout each floor and roof level in two directions approximately at right angles. These and their connections should be checked for the following factored tensile loads, which need not be considered as additive to other loads.

(1) Generally. 0.5wfs,La for any internal ties and 0.25wtstL, for edge ties but not less than 75 kN for floors or 40 k N at roof level where

W , i s the total factored dead and imposed load per unit area of floor or roof;

s, is the mean transverse spacing of the tles;

La 1s the greatest distance, in the direction of the tie, between adjacent lines of columns or other vertical supports.

( 2 ) At theperiphery. Ties anchoring columns at the periphery of a floor or roof should be checked for the force given in ( 1 ) but not less than 1 % of the factored vertical load in the column at that level.

(c) Columns. All column splices should be capable of resisting a tensile force of not less than two-thirds of factored vertical load applied to the coluinn from the floor level next below the splice.

Except where the steel framework i s of continuous construct~on in at least one direction, the columr~s should be carried through at each beam-to-column connection.

(d) Integrity. Any beam which carries a column should be checked, together with the members which support it, for localization of damage as recommended in 2.4.5.4.

(e) Floor units. Where precast concrete or other heavy floor or roof units are used they should be effectively anchored in the directton of their span either to each other over a support or directly to their supports as recommended in BS 81 10.

2.4.5.4 Localization of damage. Where required by 2.4.5.3 a building should be checked to see whether at each storey in turn any single column, or beam carrying a column, could be removed without causing collapse of more than a limited portion of the building local to the member concerned. Where the removal of one of these members would cause failure in excess of appropriate l im~ts that member should be designed as a key element as recommended in 2.4.5.5.

For the purposes of this provision, i t may be assumed that substantial permanent deformation of members and their connections is acceptable.

In this check only one-third of the ordinary w ~ n d load and one-third of the ordinary imposed load need be considered together with the dead load. except that in the case of buildings used predominantly for storage. or where the imposed load i s of a permanent nature, the full imposed load should be used. The yt factor should be taken as 1.05 except that when considering overturning the dead load supplying the restoring moment should be mult~plled by a yt factor oSb.9.

2.4.5.5 Key elements. Where ~t i s required by 2.4.5.4 to design a member as a key element, the accidental loading should not be less than that stipulated.

Accidental loads should be applied to members from appropriate directions together with the reactions from other building components attached to the member which are subject to the same loading but limited to the ult~mate strength of these components or their connections.

In this check the effects of ordinary loads should also be considered, to the same extent and with the same 71 factors as recommended in 2.4.5.4 for localization of damage.

Any other steel member or other structuial component which prov~des lateral restraint vital to the stablllty of a key element should itself also be designed a s a key element for the same accidental loading.

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2 5 Serviceability limit states

2.5.1 Deflection

The deflection under serviceability loads of a building or part should not impair the strength or efficiency of the structure or its components or cause damage to the finish- ings.

When checking for deflections the most adverse realistic combination and arrangement of serviceability loads should be assumed, and the structure may be assumed to be elastic.

Table 5 gives recommended limitations for certain structural members. Circumstances may arise where greater or lesser values would be more appropriate. Other members may also need a deflection limitation to be established, e.g. sway bracing.

Generally the serviceability loads may be taken as the unfactored imposed loads. When considering dead load plus imposed load plus wind load only 80 % of the imposed load and wind load need be considered. In the case of crane surge and wind, only the greater effect of either need be considered in any load combination.

2.5.2 Durability

In order to ensure the durability of the structure under conditions relevant to both its intended use and intended life the following factors should be considered at the design stage:

(a) the environment;

(b) the degree of exposure;

(c) the shape of the members and the structural detailing;

(d) the protective measures if any;

(e) whether maintenance i s possible.

Reference should be made to BS 5493 in determining adequate methods of protection where applicable. Weather resistant steel may also be used.

Table 5. Deflection limits other than for pitched roof portal frames

(a) Deflection on beams due to unfactored imposed load

Cantilevers

Beams carrying plaster or other brittle finish

All other beams

Purlins and sheeting rails

Lengthf180

Span1360

Span1200

See 4.12.2

(b) Horizontal deflection of columns other than portal frames due to unfactored imposed and wind loads

Tops of columns in single-storey buildings

In each storey of a building with more than one storey

Height1300

Height of storey under consideration1300

(c) Crane gantry girders

Vertical deflection due to static wheel loads

Horizontal deflection (calculated on the top flange properties alone) due to

Span1600

crane surge Span1500

NOTE 1. On low-pitched and flat roofs the possibility of ponding needs consideration.

NOTE 2. For limiting deflections in runway beams refer to

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BS 5950 : Part 1 : 1990 Section three

Section three. Properties of materials and section properties

3.1 General

3.1.1 Strength of steel This standard covers the design of structures fabricated from weldable structural steels in designated design grades supplied to the appropriate product grade as given in BS 5950 : Part 2. Other steels, excluding rimming steels. may also be used provided that due allowance be made for variations in properties, including ductility and welda- bility (see BS 5950 : Part 2).

The design strength. p , , ( n a y htb taker) as 1 0 Y, but nor greater than 0 84U, where Y , and 0, a r e the rn~nlmum y~e ld strength and the rnlnlmum ult~lndte tans~le srrenqtli respectively as spec~fted In the appropriate product standard (see BS 5950 : Part 2). For the more common types of steel p , may be obta~nt!J from table 6.

For rolled sectlons the th~ckness should be taken as the specifled flange thickness from 8s 4.

r I Table 6. Design strengths, py

Design grade Thickness, Sections, plater and leor than or hollow sections equal to

mm

Additional properties of steel are required for use in plastlc design and reference should be made to 5.3.3.

3.1.2 Other properties of steel

The following values for the elastic properties should be used:

Modulus of elasticity E = 205 k ~ ! m m '

3.2 Welds and fasteners

3.2.1 Welding consurnables

All welding consumables (i.e. electrode wires, filler rods, flux, shielding gas, etc.) should comply with BS 5135.

3.2.2 Ordinary bolts, nuts and washers

Bolts and nuts should comply with BS 4190 or BS 3692. Bolts and nuts of material complying with BS 3692 made to the size and tolerances of BS 4190 are permitted.

Countersunk or cup headed bolts should comply with BS 4933. High strength friction grip bolts complying with BS 4395 may be used untorqued. Nuts should be of a strength grade equal to or higher than the grade of bolt.

Washers should comply with BS 4320.

3.2.3 Friction grip fasteners

High strength friction grip bolts and associated nuts and washers should comply with BS 4395.

Other types of friction grip fasteners may be used provided they have mechanical properties not inferior to bolts complying with BS 4395 and provided they can be reliably tightened to the minimum shank tensions specified in BS 4604.

3.3 Section properties

3.3.1 Gross section

Gross section properties should be determined using the specified size and profile of the member or elements. but allowance should be made for openings larger than required for fasteners. Battens or splices should not be included.

3.3.2 Net area

The net area of a section or element of a section should be taken as its gross area less deductions for fastener holes as given in 3.4.

3.3.3 ~ f f & v e area at connections

The effeqive area. A,, of each element of a member at a connection, where fastener holes occur may be taken as K, times its net area, but not more than its gross area, where:

K e = 1.2 for design grade 40 or 43

K e = 1 .I for design grade 50 or W R 50

K, = 1 .O for design grade 55

U Po~sson's ratlo u = 0 3 0 for other steels, K, = 0 75--I-

Coefflclent of llnear Y*

thermal expansion a = 12 K 1 0 . ~ p e r O ~ but G 1.2

where

3.1.3 Steel castlngs and forg~ngs U, IS the speclfled mtnlmum ult~mate tens~le strength, Steel casttngs and forqlngs may be used for components In Y, 1s the spec~f~ed mlnlmum yleld strength

1 Q72 bear~rlgs, lunctlons and other s~m~lar parts. Casttngs should comply w ~ t h BS 3100 and forg~ngs with BS 29 Design strengths corresponding to hot rolled steel of des~gn grade_ 43 may be adopted where no other information is available.

15 -

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3.4 Deductions for holes 3.4.1 Hole area

In deducting for holes for fasteners (including countersunk holes), the gross area of the hole in the plane of its axis and not that of the fastener should be deducted.

3.4.2 Holes not staggered

The area to be deducted should be the maximum sum of the sectional areas of the holes in any cross sections at right angles to the direction of stress in the member.

3.4.3 Staggered holes

When holes are staggered the area to be deducted should be the greater of :

(a) the deduction for non-staggered holes (see 3.4.2);

(b) the sum of the sectional areas of all holes in any zig-zag line extending progressively across the member or part of the member, less sp2 t /4g for each gauge space in the chain of holes

where

s, is the staggered pitch, i.e. the distance, measured parallel to the direction of stress in the member, centre-to-centre of holes in consecutive lines, see figure 1 ;

t is the thickness of the holed material;

g i s the gauge, i.e. the distance, measured at right angles to the direction of stress in the member, centre-to-centre of holes in consecutive lines, see figure 1.

For sections such as angles with holes in both legs the gauge should be taken as the sum of the back marks to each hole, less the leg thickness. See figure 2.

3.5 Limiting proportions of cross sections

3.5.1 General

Local buckling can be avoided by limiting the width to thickness ratios of each element of a cross section subject to compression due to moment or axial load. Elements and cross sections are classified as plastic, compact, senii- compact or slender. Cross sections may be composed of elements of different classes.

3.5.2 Classification of cross sections

Class 1. Plastic cross sections are those In which all elements subject to compressiori comply with the values given in table 7 for plastic elements. A plast~c hinge can be developed with sufficient rotation capacity to allow redistribution of moments within the structure.

Only class 1 sections may be used for plastic design.

Class 2. Compact cross sections are those in which all elements subject to compression comply with the values given in table 7 for compact elements. The full plastic moment capacity can be developed but local buckling may prevent development of a plastic hinge with sufficient rotation capacity to permit plastic design.

Class 2 sections can be used without restriction except for plastic design.

Class 3. Semi-compact sections are those in which all elements subject to compression comply with the values given in table 7 for semi-compact elements. The stress at the extreme fibres can reach the design strength but local buckling may prevent the development of the full plastic moment.

Class 3 sections are subject to limitations on their ca'pacity which are given in section four.

,

1 I , Q +- - --+-i

I I

- ----- 7 i r e c 6

* - + . + qt 7 I 1 -4- o f s t r e s s

h- x L l '

I x U m m I i

i B . C ~ mar* I

r- - 4

Figure 2. Angles with holes in both legs

/ ,, , -

7 ,/

i

-

I /

I - ' n j r /.a I I

I 4 I 1

i I I *.% cr'"--i

Figure 1. Staggered holes

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Table 7. Limiting width to thickness ratios (Elements which exceed these limits are to be taken as class 4, slender cross sections.)

I I

Type o f element

Outstand element of compression flange

Internal element of compression flange

Web, with neutral axis at mid-depth

Web, generally

Web, where whole section is subject to compression

Legs of single angle and double angle members with components separated

Outstand legs of double angle members with angles in contact back-to-back

Stems of T-sections

Circular tube subject to moment or axial compression

NOTE 1. D~mens~ons b, D, d, T, ta re as defined ~n

2 v c ,J .: - d

where yc Ir the d~stance from the plastic neutral axis to the edge of the web connected to the compression flange. But i f a > 2 the section should be taken as having compression throughout.

NOTE 2. Check webs for shear buckling in accordance wi th 4.4 when d:t > 63 E.

Type of section

Built-up by welding

Rolled sections

Buil tup by welding

Rolled sections

All sections

AII sections

Built-up by welding

Rolled sections

Rolled angle sections

Rolled angle sections

T-section

CHS or bui l tup by welding

f~gure 3.

Class of section

(1) Plastic

b - Q 7.56 T

b - Q 8.56 T

b - Q 236 T

b - Q 266 T

d - Q 796 t

d 796 - - t 0.4+0.6a

d - < 286 t

d - Q 396 t

b - < 8.56 T and d - Q 8.56 T

b - G 8.56 T 4

% 8.56 t

0 - < 406' t

(2 ) Compact

b - Q8.56 T

b -Q9.56 T

b -<25e T

b -< 326 T

d -Q986 t

-Q- 986 t cr

d - d 286 t

d - Q 396 t

b -Q9.56 T and d - =G 9.56 T

b -d9.5e T

d -<9.56 t

D - < 57e2 t

(3) Sami-compact

b - Q 136 T

b - < I 5 6 T

b - d286 T

b - Q 396 T

d -<I206 t

see 3.5.4

d - Q 286 t

d - Q 396 t

b d - a n d - Q 1 5 ~ T T

and b + d - Q 236

T

b -<I56 T

d - G I 9 6 t

--D Q 806' t

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Class 4. Slender sections are those which contain slender elements subject to compression due to moment or axial load. Local buckling may prevent the stress in a slender section from reaching the design strength.

Design of class 4 sections i s considered in 3.6.

3.5.3 Classification of elements

Flat elements in a cross section are either:

(a) internal elements attached on both longitudinal edges to other elements or to longitudinal stiffeners which are connected at suitable intervals to transverse stiffeners, or

I (b) outstand elements attached on only one horizontal edge to an adjacent element, the other edge being free.

Flat elements are generally of constant thickness. Tapered elements may be treated as flat elements havjng the average thickness defined in BS 4.

Elements may be classified as plastic, compact or semi- compact if they meet the limits given in table 7. Those which do not meet the limits for semi-compact elements are classified as slender.

3.5.4 Webs o f semi-compact sections

The limiting width to thickness ratio, dlt, for the web of a semi-compact section i s given by the following:

(a) when R is positive

(1) for sections built-up by welding

(2) for rolled sections

d 1206 - Q and < (G - 2) 6 t 1 + 1 . 5 R

( (b) when R i s negative

d 1206 1 7' ( l + R l 2 and Q 2506

in which R is the ratio of the mean longitudinal stress in the web top,, compression being taken as positive and tension as negative.

3.5.5 Compound flanges

The following width to thickness ratios should be considered:

(a) the outstand of the compound flange compared to the thickness of the original flange;

(b) the internal width of each added plate between the lines of welds or fasteners which connect i t to the original flange, compared to its own thickness;

3.5.6 Longitudinally stiffened flanges

The unsupported width, b, of a flange or part of a flange, which i s effectively supported along both edges either by a web or a longitudinal stiffener, should be taken as the width between adjacent lines of welds or fasteners connecting i t to the supporting elements. In rolled sections b should be measured as shown in figure 3.

Where the free edge of the flange is supported by a longitudinal stiffener, the flange thickness, T, should not be less than b/20 unless the edge st~ffener is itself supported at suitable intervals.

Where the flange is stiffened by transverse as well as longitudinal stiffeners or a web, the thickness, T, should not be less than 1/100 of the smaller panel dimension a or b, where a is a spacing of transverse stiffeners on the flange.

3.6 Slender cross sections

3.6.1 General

Local buckling may become the design criterion when the proportions of elements in a cross section exceed those given for semi-compact elements in table 7. Such cross sections are defined as slender and their capacity i s limited.

3.6.2 Sections with thin webs required to carry shear

Where thin webs which have a d l t ratio > 636 are required I to carry shear the capacity of the cross section should be calculated from 4.4.4.2.

3.6.3 Webs subject to moments and axial loads and circular hollow sections

In the absence of a more rigorous method of analysis a value of the design strength, p, , should be assumed such that the limiting proportions for semi-compact sections are met (see table 7). The same reduced value of p, should be used for that element throughout the design of the section whenever i t i s in compression, except that such reduction need not be made in the design of connections to that element.

3.6.4 Other elements.

Where a slender element is in compression the design strength, p y , shouldbe reduced by the factor given in table 8. The same reduced value of p, should be used for

I that element throughout the design of the section whenever i t is in compression except that such reduction need not be made in the design of connections to that element.

(c) any outstand of an added plate beyond the lines of welds or fasteners which connect i t to the original flange, compared to its own thickness.

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slender elements

Strength reduction factor

10 - b - - 3 TE

11 - b - - 4 TE

2 1

7 - - 7 TE

31

b - - T€

8

The lesser of 11

d - - 4 TE and

19

(b+d) -- 4

T€

11

- b - - 4 T €

14 - d - - 5 t E

in figure 3.

Table 8. Strength reduction

Type of element

Outstand element of compression flange

Internal element of compression flange

Legs o f single angle and double angle members w i th components separated

Outstand legs o f double angle members with angles i n contact back-to-back

Stems of T-sections

NOTE 1 . D~rnensions b, d,

NOTE 2. r = - ( :v5)1 NOTE 3. The strength of slender cross sections may be obtained from 3.6.2, 3.6.3 and 3.6.4 as appropriate. Alternatively the more rigorous approach given in BS 5950 : Part 5 may be used.

factors for

Type of section

Built up by welding

Rolled sections

Build up by welding

Rolled sections

Rolled angle section

angle

t, Tare as defined

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BS 5950 : Part 1 : 1 9 9 0 Section three

Rolled beams and columns

L - 4 Rolled channels

RHS b = 6 - 3t d = O - 3 t

I Tees CHS

Angles

Double angles

---

Fabricated sections A

Built-up sections (see 3.5.5)

Figure 3. Dimensions of sections

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BS 5950 : Part 1 : 1990 Section four

Section four. Design of structural elements

4.1 General

4.1.1 Scope

This section gives rules for the design of simple elements or elements comprising parts of frames.

4.1.2 Class of cross section

Reference should be made to 3.5 for the classification of cross sections.

4.1.3 Design strength

The design strength should be obtained from table 6. The reduction of 20 ~ l m m ' given in 4.7.5 for welded elements in compression does not apply to the element when it i s checked for other effects such as bending, shear and connections.

4.2 Members in bending

4.2.1 General

4.2.1.1 Span o f beams. The span of a beam should be taken between the effective points of support.

4.2.1.2 Length of cantilevers. The length of a cantilever should be taken as the distance from the effective point of the support to the t ip of the cantilever.

4.2.1.3 Generalconditions. All members in bending should meet the following conditions.

(a) At critical points the combination of maximum moment and co-existent shear, and the combination of maximum shear and co-existent moment should be checked.

(b) The deflection limits given in 2.5.1 should be considered.

(c) Unless the compression flange has full lateral restraint, as indicated in 4.2.2, the resistance of the member to lateral torsional buckling should be checked in accordance with 4.3.

(d l Local buckling should be considered as given in 3.6.

(e) When loads or reactions are applied through the flange to the web the conditions of 4.5 for bearing and buckling should be met.

4.2.2 Full lateral restraint

When full lateral restraint i s provided no reference need be made to 4.3 which deals with the lateral torsional buckling resistance of the member.

Full restraint exists i f the frictional or positive connection of a floor or other construction to the compression flange of the member is capable of resisting a lateral force of not

( less than 2.5 %of the maximum factored force in the compression flange of the member, under factored loading. This load should be considered as distributed uniformly

along the flange, provided that the dead load of the floor and the imposed load it supports together constitute the dominant loading on the beam. The floor construction should be capable of resisting this lateral force.

4.2.3 Shear

Shear force F, not greater than shear capacity P,, where Pv = 0.6p,Av and A, i s the shear area taken as follows:

(a) rolled I. H and channel sections, load parallel to web tD

(b) built-up sections and boxes, load parallel to webs

(c ) solid bars and plates 0.9A

(d) rectangular hollow sections, load parallel to webs

(e) circular hollow sections

( f ) any other case

where

t is the total web thickness;

B is the breadth;

D i s the overall depth;

d i s the depth of the web;

A i s the area of the section;

A, is the area of the rectilinear element of the section which has the largest dimension in the direction parallel to the load.

When the depth to thickness ratio, dlt , of a web exceeds 636 then it should be checked for shear buckling in accordance with 4.4.5.

4.2.4 Elastic shear stress

In sections where webs vary in thickness or have holes significantly larger than those required for fasteners, the shear stress should be calculated from first principles assuming elastic behaviour. In such cases the maximum shear stress, f,, should not exceed 0 . 7 ~ ~ .

4.2.5 M-nt capacity with low shear load

Where F, 2 0.6Pv the moment capacity, M,, should be taken ahfollows. -.

For pbstic or compact sections:

M, = p v S but < 1 . 2pvZ NOTE. The elastic limitation is to prevent plasticity at working load. If S > 1.22 then the 1.2 constant may be replaced bv the ratio of the factored load to the unfactored load.

For semi-compact sections:

M, = P,Z For slender sections:

M, = p V Z where

p, is the design strength (reduced for slender sections, see 3.6);

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S is the plastic modulus of the section about the relevant axis;

Z is the elastic modulus of the section about the relevant axis.

When the depth to thickness ratio, d l t , of a web exceeds 63e then it should be checked for shear buckling in accordance with 4.4.5.

4.2.6 Moment capacity with high shear load

Where Fv > 0.6Pv the moment capacity, Mc, should be taken a s follows.

(a) For plastic or compact sections:

Mc =py(S - Svpl ) but < 1.2pvZ

2.5Fv where p , = - - 1.5

pv and Sv is taken as follows:

For sectiohs with equal flanges: the plastic modulus of the shear area,A, (see figure 4(a));

For sections with unequal flanges: the plastic modulus of the gross section less the plastic modulus of that part of the section remaining after deduction of the shear area (see figure 4(b)).

(b) For semi-compact sections:

Mc = p v Z

(c) For slender sections:

Mc = pvZ

where py and Z are as defined in 4.2.5. When the depth to thickness ratio, dlt , of a web exceeds 636 then it should be checked for shear buckling in accordance with 4.4.5.

When a beam requires lateral restraint within its span, such restraint should have sufficient strength and stiffness to inhibit lateral movement of the compression flange relative to the supports. This may be provided by lateral restraints or torsional restraints (see 4.3.2 and 4.3.3).

All beams should also satisfy the requirements of 4.2.1 and 4.2.3 to 4.2.6 inclusive.

4.3.2 Lateral restraints

4.3.2.1 Where one or more lateral restraints are required at intervals within the span of a beam, these intermediate lateral restraints should be capable of resisting a total force of not less than 2.5 % of the maximum factored force in the compression flange, divided between the intermediate lateral restraints in proportion to their spacing.

The intermediate lateral restraints should either be connected to an appropriate system of bracing capable of transferring the restraint forces to the beam's effective points of support, or else connected to an independent robust part of the structure capable of fulfilling a similar function.

Where two or more parallel members require lateral restraint at intervals, i t is not adequate merely to connect the members together such that they become mutually dependent.

4.3.2.2 Where three or more intermediate lateral restraints are provided, each intermediate lateral restraint should be capable of resisting a force of not less than 1 % of the maximum factored force in the compression flange.

in this case, the bracing system should be capable of resisting the greater of the effects of:

(a) the 1 % restraint force considered as acting at only one point at a time;

4.3 Lateral torsional buckling (b) the restraint forces described in 4.3.2.1. 4.3.2.3 Where more than three parallel members share the

4.3.1 General same system of restraints, the combined lateral restraint

A beam not provided with full lateral restraint as defined in force should be taken as the sum of the three largest lateral

4.2.2 should be checked for resistance to lateral torsional restraint forces required for each individual restrained

buckling. member, as determined in accordance with 4.3.2.1 and 4.3.2.2.

Shear area = A, = to Shear area = A, = rd Shear area = A, = td

Rolled section Welded section Welded section

(al Equal flanges (bl Unequal flanges

Figure 4. Effective shear area of typical sections

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4.3.2.4 Purlins adequately restrained by sheeting need not normally be checked for the forces arising from the restraining of rafters of roof trusses or portal frames carrying predominantly roof loads, provided that either:

(a) there is bracing of adequate stiffness in the plane of the rafters; or

(b) the roof sheeting is capable of acting as a diaphragm.

4.3.3 Torsional restraints

A beam may be taken as torsionally restrained (about its longitudinal axis) at any point in its length where both the flanges are effectively held in position relative to each other by external means, (in the lateral direction).

Torsional restraint at support positions may be provided by bearing stiffeners acting in conjunction with the bearing of

, the beam (see 4.5.8).

Torsional restraint may be provided at any point by means of a suitable diaphragm between two similar members or else an equivalent panel of bracing. Alternatively such restraint may be provided by external means.

A torsional restraint should be capable of resisting a couple comprising forces of not less than 1 % of the maximum factored force in the compression flange, acting at a lever arm equal to thedepth between the centroidsof the flanges.

4.3.4 Destabilizing toad

Destabilizing load conditions exist when a load is applied to

( the top flange of a beam and both the load and the flange are free to deflect laterally (and possibly rotationally also) relative to the centroid of the beam.

4.3.5 Effective lengths of beams

When considering lateral torsional buckling, the effective length, L E , of a beam should be taken as follows.

(a) For beams with lateral restraints at the ends only, the value of LE should be obtained from table 9, taking L as the span of the beam. I f the conditions of restraint at each end differ, the mean value of LE should be taken.

(b) For beams with effective lateral restraints at intervals within their length, the value of LE should be taken as 1 .OL for normal loading conditions or 1.2L for destabilizing loading conditions (see 4.3.4). taking L as the distance between restraints.

(c) For a portion of a beam between one end and the first intermediate restraint, account should be taken of the conditions of restraint at the support. The effective length LE should be taken as the mean of the value given in item (b) and the value given by table 9 for the conditions of restraint at the support, taking L as the distance between the restraint and the support in both cases.

4.3.6 Effective lengths of cantilevers

4.3.6.1 With intermediate lateral restraint. I f a cantilever has intermediate restraints to the compression flange, or 1 when a moment is applied at the tip, the lengths between restraints should be treated as beams; the effective length, L E , should be taken from 4.3.5.

4.3.6.2 Without intermediate lateral restraint. When a cantilever has no intermediate restraint to the compression flange and no moment IS applied to the tip, the effective length, L E V should be taken from table 10.

4.3.7 Lateral torsional buckling resistance of members subject to bending

4.3.7.1 General. Equal flanged rolled sections may be checked using the conservative approach in 4.3.7.7. For other members, or a portion of a member, between

( Table 9. Effective length LE for beams I I Conditions of restraint at supports I Loading conditions I I I Normal ] Destabilizing I

Both flanges partially restrained against 0.85L rotation on plan I I I

Compression flange laterally restrained Beam fully restrained against torsion

0.7 L Both flanges fully restrahed against rotation on plan

Both flanges free to rotate on plan

I D is the depth of the beam. 1.

0.85L

Compression flange laterally unrestrained Both flanges free to rotate on plan

1 .OL 1.2L

Restraint against torsion provided only by positive connection of bottom flange to supports

Restraint against torsion provided only by dead bearing of bottom flange on supports

1.OL + 2 0

1.2L + 2 0

1.2L + 2 0

1.4L + 2 0

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adjacent lateral restraints, subject to bending about their major axis the following condition should be satisfied:

M < Mb

where

M i s the equivalent uniform moment;

Mb is the lateral torsional buckling resistance moment. NOTE. For box sectlons of uni form th4ckness ( includ~ng structural hollow sect~ons) t h ~ s check is unnecessary within the l~rnits given in 8.2.6.1 and M b may be taKen aspyS,. For circular hollow I sections a lateral torsional buckling check is not required.

4.3.7.2 Equivalent_uniform moment, i. The equivalent uniform moment, M, i s given by:

M = mM,

where

MA is the maximum moment on the member or the portion of the member under consideration;

m i s an equivalent uniform moment factor, determined from 4.3.7.6.

Table 10. Effective length, L E V for cantilever of length L

, /+-;, in at least one

Top flange restraint Torsional restraint Lateral and torsion restraint

NOTE. When values from thls table are used for L E the equivalent un~forrn moment factor, r n , and the slenderness correction factor. n , should be taken as 1 0.

Loading

Normal

3.0 L

2.7 L

2.4 L

2.1 L

1.OL

0.9 L

0.8L

0.7 L

0.8 L

0.7 L

0.6 L

0.5 L

Restraint conditions

A t support

Continuous with lateral restraint only

Continuous with lateral and torsional restraint

Built-in laterally and torsionally

, j

conditions

Destabilizing

7.5 L

7.5 L

4.5 L

3.6 L

2.5 L

2.5 L

1.5 L

1.2L

1.4 L

1.4L

0.6 L

0.5 L

Braced laterally

A t tip

Free

Laterally restrained on top flange only

Torsionally restrained only

Laterally and torsionally restrained

Free

Laterally restrained on top flange only

Torsionallyrestrainedonly

Laterally and torsionally restrained

Free

Lateral restraint on top flange only

Torsionally restrained anly

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4.3.7.3 Buckling resistance, Mb. For members with at least 4.3.7.4 Bending strength, pb. The bending strength,^,,, one axis of symmetry the buckling resistance moment, Mb, i s related to the equivalent slenderness, hLT, the design is given by: strength of the materiai,p,, and member type, i.e. rolled or

Mb =SXP, fabricated by welding. pb can be obtained from tables 11, 12 or from the formulae in B.2 on which these tables are

where based. Sx i s the plastic modulus of the section about the major

axis;

pb i s the bending strength determined from 4.3.7.4.

Table 12. Bending strength,^,, (in N/mm2) for welded sections

Table 11. Bending strength,^,. (in N/mmZ) for rolled sections

265

265 265 254 242 231

219 207 196 184 172

161 151 141 131 123

115 107 101 94 89

83 78 74 70 66

62 59 56 53 51

48 46 44 42 40

37 34

30 35 40 45 50

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220

28

245

245 245 238 227 217

206 195 185 174 164

154 144 135 126 118

111 104 97 91 86

81 76 72 68 64

61 58 55 52 50

47 45 43 41 39

36 33

275

275 273 262 250 238

226 213 201 188 176

165 154 144 134 125

117 109 102 96 90

84 79 75 71 67

63 60 57 54 51

49 46 44 42 40

37 34

28

325

325 316 302 287 272

257 241 225 210 195

181 168 156 144 134

125 116 108 101 95

89 83 78 74 70

66 62 59 56 53

51 48 46 44 42

38 35 32 30

28

340

340 328 313 298 282

266 249 232 216 200

186 172 159 147 137

127 118 110 103 96

90 84 79 75 70

66 63 60 56 54

51 49 46 44 42

39 35 33 30

29

355

355 341 325 309 292

274 257 239 222 205

190 175 162 150 139

129 120 111 104 97

91 85 80 75 71

67 63 60 57 54

51 49 47 44 42

39 36 33 30

29

415

408 390 371 350 329

307 285 263 242 223

204 188 173 159 147

136 126 117 108 101

94 88 83 78 73

69 65 62 59 56

53 50 48 46 43

40 36 33 31

29

430

421 402 382 361 338

315 292 269 247 226

208 190 175 161 148

137 127 118 109 102

95 89 84 79 74

70 66 62 59 56

53 50 48 46 44

40 37 34 31

450

438 418 397 374 350

325 300 276 253 231

212 194 178 163 150

139 128 119 111 103

96 90 84 79 75

70 66 63 59 56

53 51 48 46 44

40 37 34 31

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4.3.7.5 Determination of hLT. For flanged members symmetrical about at least one axis and uniform through its length:

XLT = nuvh

For members of other cross section, or of non-uniform section, refer to 8.2.6, 8.2.7 and 8.3.

In the above equation:

h is the minor axis slenderness: = L E / f y where

LE is the effective length from 4.3.5 to 4.3.6;

r, i s the radius of gyration about the minor axis of the member.

u i s a buckling parameter:

(a) for a ROLLED I, H, or channel section, u may be taken from appendix 6, published tables or conservatively as 0.9; (b) for any other section, u may be taken from appendix 8 or conservatively as 1 .O.

v i s a slenderness factor:

(1) for flanged members symmetric about one axis of uniform section v may be determined from table 1 4 using N and X/x in which:

l c f N = - I c f + l t f

where

I,,, I* are the second moments of area of the compression and tension flanges respectively about the minor axis of the section;

A is defined above;

x is the torsional index and may be determined from 8.2.5 or published tables. Alternatively, x may be taken as DlT, provided that u i s taken as 0.9 for rolled sections, or 1.0 for other sections.

NOTE. N = 0.5 for members w ~ t h equal flanges

(2) For other sections v may be determined from 8.2.5 using the formulae on which table 1 4 is based.

n i s a slenderness correction factor: determined from 4.3.7.6.

4.3.7.6 Factors m and n. Factors m and n should oe determined from the following.

(a) Members of uniform cross section, see table 1 3 .

(b) Members of nonuniform cross section, reference should be made to 8.3.

Table 13. Use of m and n factors for members of uniform section

Description

Members loaded between adjacent lateral restraints

Members not loaded between adjacent lateral restraints

Memben not subject to destabilizing loads (see 4.3.41

Sections with equal flanges

Sections with unequal flanges

Sections with equal flanges

Sections with unequal flanges

m

1 .O

1 .O

From table 18

1 .O

1 .O

Memben subject to destabilizing loads (see 4.3.41

Cantilevers without intermediate lateral restraints

n

From tables 15 and 16

1 .O

p 1 . 0

1 . 0

1 .O

m

1.0

1 .O

1 .O

1 .O

1 .O

n

1 .O

1 .O

1 .O

1 .O

1 .O

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- Table 14. Slenderness factor v for flanged beams of

T compression T

NOTE 2. v should be determ~ned from the general formulae given in 8.2.5, on qhich th~s table is based:

(a) for sections with LIPPED flanges (e.g. gantry g~rders composed of chan& + universal beam); and

(b) for intermediate values to the right of the stepped line in the table.

uniform section

I [ 0.5

1.00 0.99 0.97 0.96 0.93

0.91 0.89 0.86 0.84 0.82

0.79 0.77 0.75 0.73 0.72

0.70 0.68 0.67 0.65 0.64

0.61 0.59 0.57 0.55 0.53

0.52 0.50 0.49 0.48 0.47

with UNEQUAL

Tension

0.8

0.84 0.83 0.82 0.81 0.80

0.78 0.77 0.75 0.73 0.72

0.70 0.69 0.67 0.66 0.65

0.63 0.62 0.61 0.60 0.59

0.57 0.55 0.53 0.52 0.50

0.49 0.48 0.47 0.46 0.45

EQUAL flanges,

Compression

0.9

0.81 0.80 0.80 0.78 0.77

0.76 0.74 0.73 0.71 0.70

0.68 0.67 0.65 0.64 0.63

0.62 0.60 0.59 0.58 0.57

0.55 0.54 0.52 0.51 0.49

0.48 0.47 0.46 0.45 0.44

with

1 .O 0.4

1.11 1.10 1.08 1.06 1.03

1.00 0.97 0.94 0.91 0.88

085 0.82 0.80 0.78 0.76

0.74 0.72 0.70 0.68 0.67

0.64 0.61 0.59 0.57 0.55

0.53 0.52 0.50 0.49

0.48 r, v

flinger

0.5 1.0 1.5 2.0 2.5

3.0 3.5 4.0 4.5 5.0

5.5 6.0 6.5 7.0 7.5

8.0 8.5 9.0 9.5

10.0

11.0 12.0 13.0 14.0 15.0

16.0 17.0 18.0 19.0 20.0

NOTE. 1

0.7

0.88 0.87 0.86 0.85 0.83

0.82 0.80 0.78 0.76 0.75

0.73 0.71 0.70 0.68 0.67

0.65 0.64 0.63 0.61 0.60

0.58 0.56 0.54 0.53 0.51

0.50 0.49 0.47 0.46 0.45

N = 0.5.

0.79 0.78 0.77 0.76 0.75

0.74 0.72 0.71 0.69 0.68

0.66 0.65 0.64 0.63 0.61

0.60 0.59 0.58 0.57 0.56

0.54 0.53 0.51 0.50 0.49

0.47 0.46 0.45 0.44 0.43

For beams

0.6

0.93 0.92 0.91 0.89 0.88

0.86 0.84 0.82 0.80 0.78

0.76 0.74 0.72 0.70 0.69

0.67 0.66 0.64 0.63 0.62

0.60 0.58 0.56 0.54 0.52

0.51 0.49 0.48 0.47 0.46

For beams

0.3

128 1.27 1.24 120 1.16

1.12 1.07 1.03 0.99 0.95

0.92 0.89 0.86 0.83 0.80

0.78 0.76 0.74 0.72 0.70

0.67 0.64 0.61 0.59 0.57

0.55 0.53 0.52 0.50 0.49

refer to

Tension

0 2

1.57 1.53 1 .48 1.42 1.35

1 2 9 1 2 2 1.16 1.11 1.05

1.01 0.97 0.93 0.89 0.86

0.83 0.80 0.78 0.76 0.74

0.70 0.66 0.64 0.61 0.59

0.57 0.55 0 6 3 0.52 0.50

4.3.7.5.

0.1

2.20 2.11 1.98 1.84 1.70

1.57 1.46 1.36 1.27 1.20

1.13 1.07 1.02 0.97 0.93

0.89 0.86 0.83 0.80 0.78

0.73 0.70 0.66 0.63 0.61

0.59 0.57 0.55 0.53 0.51

0 .O

12.67 6.36 4.27 3 2 4 2.62

2.21 1 .93 1 .71 1.55 1.41

1.31 1.22 1 .14 1 .08 1.02

0.98 0.93 0 9 0 0.86 0.83

0.78 0.73 0.69 0.66 0.63

0.61 0.58 0.56 0.55 0.53 SG

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Table 15. Slenderness correction factor, n, for members with applied loading substantially concentrated within the middle fifth of the unrestrained length

t N O T E 1. All hogg~ng moments are +ve. 4 k k maXlmUm NOTE 2. 0 i s defined ~n table 18.

- - - - . ---- ME&,, NOTE 3. Mo IS the m~d.length moment on a strnply flM supported span equal to the unrestra~ned length

(see table 17).

Unrestra~ned length L - ---- - - - -. - - -

0 positive

1 0 negative

"I=MIM, 1 .O 0.8 0.6 0.4 0 2 0 .O -0.2 4 . 4 4 . 6 -0.8 --1 .O

+50.00 1.00 0.96 0.92 0.87 0.82 0.77 0.72 0.67 0.66 0.66 0.65 +10.00 0.99 0.99 0.94 0.90 0.85 0.80 0.75 0.69 0.68 0.68 0.67 +5.00 0.98 0.98 0.97 0.93 0.89 0.84 0.79 0.73 0.71 0.70 0.70 +2.W 0.96 0.95 0.95 0.95 0.94 0.94 0.89 0.84 0.79 0.77 0.76 +1.50 0.95 0.95 0.94 0.94 0.93 0.93 0.92 0.90 0.85 0.80 0.80 +1.00 0.93 0.92 0.92 0.92 0.92 0.91 0.91 0.91 0.91 0.92 0.92 +0.50 0.90 0.90 0.90 . 0.89 0.89 0.89 0.89 0.89 0.88 0.88 0.88

0.00 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86

-0.10 0.85 0.85 0.85 0.85 0.85 0.86 0.86 0.86 0.86 0.86 0.86 -0.20 0.83 0.83 0.83 0.84 0.84 0.85 0.85 0.85 0.86 0.86 0.86 -0.30 0.81 0.82 0.82 0.83 0.83 0.84 0.85 0.85 0.86 0.86 0.87 -0.40 0.79 0.80 0.81 0.81 0.82 0.83 0.84 0.85 0.85 0.86 0.87 -0.50 0.77 0.78 0.79 0.80 0.82 0.83 0.85 0.86 0.86 0.87 0.88

-0.60 0.62 0.66 0.72 0.77 0.80 0.82 0.84 0.85 0.86 0.87 0.88 -0.70 0.56 0.56 0.61 0.67 0.73 0.79 0.83 0.85 0.87 0.88 089 -0.80 0.56 0.53 0.54 0.59 0.65 0.71 0.77 0.83 0.89 0.90 0.90 -0.90 0.59 0.57 0.54 0.53 0.57 0.64 0.71 0.77 0.84 0.88 0.91

-1.00 0.62 0.58 0.54 0.52 0.54 0.59 0.66 0.72 0.80 0.85 0.92

-1.10 0.66 0.62 0.57 0.54 0.54 0.57 0.63 0.68 0.76 0.83 0.89 -1.20 0.70 0.66 0.60 0.55 0.54 0.55 0.60 0.65 0.73 0.80 0.87 -1.30 0.73 0.69 0.63 0.57 0.55 0.54 0.57 0.61 0.69 0.77 0.83 -1.40 0.74 0.70 0.64 0.58 0.56 0.54 0.55 '4.60 0.66 0.74 0.81 -1.50 0.75 0.70 0.64 0.59 0.56 0.54 0.55 0.59 0.65 0.73 0.80

-1.60 0.76 0.72 0.65 0.60 0.57 0.55 0.55 ' 0.58 0.64 0.72 0.80 -1.70 0.77 0.74 0.66 0.61 0.58 0.56 0.55 , 0 58 0.63 0.70 0.78 -1.80 0.79 0.77 0.68 0.63 0.59 0 56 0.56 0.57 0.62 0.69 0.76 -1.90 0.80 0.79 0.69 0.64 0.60 0.57 0.56 0.57 0.61 0.67 0.75 -2.00 0.81 0.81 0.70 0.65 0.61 0.58 0.56 0.56 0.60 0.66 0.74

-5.00 0.93 0.89 0.83 0.77 0.72 0.67 0.64 0 61 0.60 0.62 0.65 -50.00 0.99 0.95 0.90 0.86 0.79 0.74 0.70 067 0.64 0.63 0.65

Infinity 1 .OO 0.96 0.91 0.86 0.82 0.77 0.72 0.68 0.65 0.65 0.65

N O T E 4. The values of n in this table apply only to members of U N I F O R M sectton.

N O T E 5. Values for intermediate values o f 0 and 7 may be interpolated.

N O T E 6. When n f rom this table is used, rn = 1.00.

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N O T E 1. A l l hoygtng moments are +ve.

N O T E 2. 0 is def ined i n table 18.

f fM NOTE 3. Mo IS the mtd-length moment o n a simply supported span equal t o the unrestrained length (see table 17)

l n f t n l t y I 100 1 0.96 1 091 10 86 1 0.82 0.77 0.72 0.68 0.65 0.65 0.65

NOTE 4 The values o f n In t h ~ s table apply on l y t o members o f UNIFORM sectton.

N O T E 5. Values f o r tntermedlare values of fi and y may be tnterpolated

N O T E 6. When n f r o m this table IS used, rnL 1.00.

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Table 17. Moment diagram between adjacent points of lateral restraint

M ~ h " ~ p + v e y + v e

.+DM p + v e y - v e

M+M p + v e y - ve

M

-'"S]/?M 0 - v e r + v e

n W 0 - v e y - v e n M

M%nM 0 - v e y - v e

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4.3.7.7 Equal flanged rolled sections. This clause gives a When using table 19 the effect of the loads and moments conservative approach. If a full analysis i s required or the between restraints may be considered by multiplying the

I sections are not equal flanged rolled sections, then the provisions effective length by the slenderness correction factor n. of 4.3.7.1 to 4.3.7.6 should be used. Reference may be made to 4.3.7.6 for the value of n . Wern. 4

Table 18. Equivalent uniform moment factor, m

I In each length between lateral restraints, the maximum atively, e k p t for destabilizing loads (see 4.3.41. n may be

moment should not exceed the buckling resistance moment, taken frOni table 20.

Beta positive

M ( l-i)flM

" Ib--1 " M

Beta negative

--

I Mb, of the section taken aspbSw

Where 4.3.8 ~uck l ing resistance moment for single angles

N O T E 1. The values o f m I n this table apply on l y t o end moments applled t o beams o f U N I F O R M section w l t h E Q U A L flanges. I n all other cases, m = 1.0.

NOTE 2. Values o f rn f o r intermediate valuer of 0 may be interpolated, or determined f r o m the equation:

m = 0.57 + 0.330 + O.lOP\ b u t no t less than 0.43.

N O T E 3. 0 IS the ra t io f o r the smaller end moment t o t he larger end moment o n a span equal t o the unrestrained length.

P 1 .O 0.9 0.8 0.7 0.6

0.5 0.4 0.3 0.2 0.1

0 .O -0.1 -4.2 4 . 3 -0.4

4 . 5 t o

-1 .o

~ ~

The buckling resistance moment for a single angle should be 1 pb is determined from table 19(a), (b), (c) or (dl, for h and x; taken as:

M, = 0.8pvZ for Llr, f 100 S, is the plastic modulus of the section about the x-x

axis; M, = 0.7p,Z for Llr, < 180

m

1 .OO 0.95 0.90 0.85 0.80

0.76 0.72 0.68 0.64 0.60

0.57 0.54 0.51 0.48 0.45

0.43

A is the slenderness of section = LEI'^ M, = 0.6pvZ for Llrvv < 300

L , IS the effective length from 4.3.5 or 4.3.6, where

'rv is the radius of gyration about the member minor Z is the smaller elastic modulus about the appropriate I axis; axis;

x is the torsional index (see 4.3.7.5) which may be rvv is the radius of gyration about the weakest ax&;

taken as DIT . L is the unrestrained length.

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Table 19. Bending strength,^,, (in ~I rn rn ' ) for rolled sections with equal flanges

(a) p, = 265 ~ / r n r n ~

10

265 265 265 265 26 1

255 250 245 240 235

230 226 222 217 213

209 206 202 198 195

191 188 185 182 179

176 173 170 167 165

1 62 160 157 155 153

1 48 144 140 136 132

30 3 5 40 45 50

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220 230 240 2 50

265 265 265 265 265

265 265 265 265 263

260 257 254 252 2 49

247 244 242 240 237

235 233 231 229 227

225 223 22 1 219 217

215 213 21 1 209 207

204 200 197 194 190

15

265 265 265 26 1 253

246 2 39 232 225 219

2 13 207 201 196 190

185 180 176 171 167

163 159 155 152 148

145 142 139 136 133

130 128 125 123 120

116 112 108 104 101

40

265 265 264 254 244

235 225 215 205 196

187 178 169 160 153

145 138 132 125 120

114 109 105 101 97

93 89 86 83 80

7 7 7 5 7 3 70 68

64 61 58 55 52

20

265 265 265 258 249

24 1 233 225 217 210

202 195 188 182 176

170 164 159 154 149

144 140 136 132 129

125 122 119 116 113

110 108 105 103 101

96 93 89 86 83

45

265 265 263 254 244

234 224 214 204 195

185 176 167 1 58 150

143 136 129 123 117

11 1 106 102 97 93

89 86 83 80 77

74 71 69 67 65

6 1 58 54 52 49

2 5

265 265 265 256 247

2 38 229 22 1 212 204

196 188 180 173 166

160 154 1 48 142 137

132 128 124 120 116

112 109 106 103 100

97 95 92 90 88

84 80 77 74 7 1

50

265 265 263 254 244

234 224 214 204 194

184 175 166 157 149

141 134 127 121 115

109 104 99 95 91

87 83 80 77 74

7 1 69 66 64 62

58 55 52 49 47

30

26' 265 264 255 246

236 227 218 209 200

191 183 175 167 160

153 147 1 40 135 129

124 119 115 111 107

103 100 97 94 9 1

88 86 83 8 1 79

75 7 1 68 65 63

35

265 265 264 254 - 245

235 226 216 207 198

189 180 171 163 156

1 48 142 135 129 124

119 114 109 105 101

97 94 9 1 88 85

82 79 77 75 73

69 65 62 59 57

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Table 19 (continued)

20

275 275 275 2 66 257

248 240 232 223 215

208 200 193 186 180

174 168 162 157 152

147 143 139 135 131

127 124 121 118 115

112 109 107 104 102

98 94 90 87 84

25

275 275 274 264 255

246 236 227 218 209

20 1 193 185 177 170

163 157 151 145 140

135 130 126 122 118

114 111 107 104 101

99 96 93 91 89

85 8 1 78 74 72

(b) p, = 275 ~/ rn rn*

45

275 275 272 2 62 252

241 231 22 1 210 200

190 180 171 162 153

146 138 131 125 119

113 108 103 99 95

9 1 87 84 81 78

75 72 70 68 65

62 58 55 52 50

10

275 275 275 275 269

263 258 252 247 242

237 233 228 224 219

21 5 21 1 207 204 200

196 193 190 186 183

180 177 174 171 169

166 163 161 158 156

151 147 143 139 135

30 35 40 45 50

55 60 65 70 7 5

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 100 165 170 175

180 185 190 195 200

210 220 230 240 250

50

275 275 272 262 251

241 230 220 209 199

189 179 169 160 152

144 136 129 123 116

11 1 106 101 96 92

88 84 8 1 78 7 5

72 70 67 65 63

59 55 52 50 47

30

275 275 273 263 253

244 234 224 215 206

196 188 179 171 164

156 150 143 137 132

126 121 117 113 109

105 101 98 95 92

89

87 6 84 82 80

76 72 69 66 63

15

275 275 275 2 69 261

254 2 46 2 39 232 225

219 213 207 201 195

190 185 180 175 171

167 1 62 159 155 151

1 48 144 141 1 38 135

133 130 127 125 122

118 114 110 106 103

275 275 275 275 275

275 275 275 274 271

2 68 265 262 260 257

254 252 250 247 245

2 42 240 2 38 236 233

231 229 227 225 223

22 1 219 217 215 213

209 206 202 199 195

35

275 275 272 263 253

243 233 223 213 203

193 184 175 1 67 1 59

151 1 44 1 38 132 126

120 115 111 106 102

99 95 92 89 86

83 80 78 76 74

70 66 63 60 57

40

275 275 272 262 2 52

242 232 22 1 21 1 20 1

191 182 173 1 64 156

1 48 141 134 128 122

116 111 106 102 98

94 90 87 84 81

78 76 7 3 7 1 69

65 62 58 56 53

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( c ) p, = 340 ~ / r n r n ~

30 35 40 45 50

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220 230 240 250

10

340 340 333 333 322

315 308 30 1 294 287

28 1 275 269 263 257

252 246 241 236 23 1

227 222 218 213 209

205 207 197 194 190

187 184 180 177 174

1 68 163 1 58 153 149

340 340 340 340 340

340 337 333 329 325

32 1 318 214 31 1 307

304 301 297 294 29 1

288 285 282 279 276

273 270 267 265 262

2 59 257 254 251 249

244 239 234 2 30 225

15

340 340 333 32 3 312

303 293 283 274 265

257 248 240 232 225

218 21 1 205 199 193

188 183 178 173 1 68

164 160 156 153 1 49

146 142 139 136 134

128 123 119 115 111

40

340 339 326 314 30 1

287 274 2 60 246 233

220 207 196 185 174

165 156 147 140 133

126 120 115 110 105

101 97 93 90 86

83 80 78

20

340 340 320 318 307

296 285 273 263 252

242 232 223 213 205

197 189 182 176 170

164 158 153 148 144

139 135 132 128 125

121 118 115

30

340 340 32 7 315 302

290 277 264 25 1 239

227 215 204 194 184

175 166 159 151 145

138 133 127 122 118

113 109 106 102 99

96 93 90

25

340 340 328 316 304

292 280 268 256 244

232 222 21 1 201 192

184 176 168 161 155

1 48 143 138 133 128

124 120 116 112 109

106 103 100

35

340 339 327 314 301

288 275 2 62 248 235

223 21 1 1 99 188 178 '

1 69 160 152 145 138

131 125 120 115 110

106 102 98 95 92

8 8 . 86 83

45

340 339 326 313 300

286 273 259 245 231

218 205 193 182 171

161 1 52 144 136 129

123 117 11 1 106 101

97 93 89 86 82

79 77 74

113 110

105 101 96 9 3 89

87 85

81 77 7 3 70 67

50

340 339 326 313 300

286 272 258 244 230

216 203 191 180 169

159 150 142 134 127

120 114 108 103 99

94 90 86 83 79

76 7 4 7 1

98 95

90 86 82 79 7 6

80,. 7 8 :

74 70 66 63 60

7 1 69

65 6 1 58 55 52

75 73

69 65 61 58 56

68 66

62 58 55 52 49

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Table 19 (concluded)

(d) p, = 355 ~ / r n r n ~

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4.4 Plate girders 4.4.2.2 Minimum web thickness for serviceability.

Table 20. Slenderness correction factor, n, for standard load

- 4.4.1 General

conditions

Load conditions

f ? -

f[-j

fmJ h P'"-1- h+i u+t

NOTE 1. For other load conditions, or 16.

For serviceability: rl U

The relevant conditions in 4.2 and 4.3 should be satisfied. (a) Without intermediate stiffeners: t > - 2 50

NOTE 2. For destabilizing loads (see 4.3.4). n should be taken as 1.0.

Bending moment diagram between lateral restraints

I

7

+ - - v n may be obtained from tables

4.4.2 Dimensions of webs and flanges (b) With transverse stiffeners only:

n

0.77 -

OaG5

0.94

0.94

0.94

15

4.4.2.1 General. Reference should be made to 3.5 for classification of sections.

The thickness of webs should comply with both 4.4.22 and 4.4.2.3.

d ( 1 ) where stiffener spacing a > d: t > -

250

( 2 ) where stiffener spacing a < d: t > -

(c) With longitudinal stiffeners: a s given in BS 5400.

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4.4.2.3 Minimum web thickness to avoid flange buckling. 4.4.5.2 Design of internal and endpanels. Internal panels

In order to avoid the flange buckling into the web: may be designed using tension field action and the end

d panels designed accordingly. Alternatively internal and end (a) Without intermediate stiffeners: t 2 - (m)

250 345 panels may be designed simply (but conservatively) without using tension field action.

(b) With intermediate transverse stiffeners: 4.4.5.3 Design without using tension field action.

(1 ) where stiffener spacing a > 1.5d: 2 This clause should be used for the design of unstiffened girders and may be used (conservatively) for the design of

1 .2 . d Internal and end panels of a st~ffened girder.

(2) where stiffener spacing a < 1.56: f 5 - (*) 250 455 The shear buckling resistance, Vc,, of a stiffened or

unstiffened panel is given by: where pYf i s the design strength of the compression flange.

Vcr = qcrdt 4.4.3 Design strength of components where The design strength should be obtained from 3.1.1. q,, is the critical shear strength as obtained from For hybrid girders due account should be taken of the tables 21 (a) to (dl as appropriate. For girders variation in design strength between the component parts. without intermediate stiffeners the spacing should be

taken as infinity. 4.4.4 Moment capacity

d i s the depth of the web; 4.4.4.1 General. The moment-capacity for a section with

t i s the thickness of the web. webs where dlt < 636 should be determined in accordance with 4.2.5 and 4.2.6. 4.4.5.4 Design using tension field action

1 4.4.4.2 Sections with thin or slender webs. Where the 4.4.5.4.1 General. This clause may be used for the design flanges of a section are plastic, Compact or semi-compact, of internal and end panels providing the end panels are

I but the web is thin (i.e. dlt a 636) or slender (see table 71, designed according to 4.4.5.4.2 or 4.4.5.4.3 as appropriate. . . . the moment capacity should be calculated using One the

The shear buckling resistance of a stiffened panel is given following methods. by :

(a) The moment and axial load may be assumed to be resisted by the flanges alone (each flange being assumed to be subject to uniform stressp,) and the web designed for shear only, see 4.4.5.

(b) The moment and axial load may be assumed to be resisted by the whole section, the web being designed for combined shear and longitudinal stresses, see H.3.

For a section with semi-compact flanges the moment in the web should be determined from simple elastic theory.

For a section with plastic or compact flanges, simple plastic theory may be used.

Vb = qbdt

If the flanges in the panel are not fully stressed the shear resistance may be increased to:

Vb = (qb + q f d K 1 ) dt but < 0 . 6 ~ ~ dt

where

qb i s the basic shear strength as obtained from tables 22(a) to (d) as appropriate;

qf is the flange dependent shear strength factor obtained from tables 23(a) to (d) as appropriate;

d i s the depth of the web;

(c) A proportion of the loading may be assumed to be t is the thickness of the web; resisted by method (b), the remainder of the loading u

1 M,f f being resisted by method (a) and the web designed Kf - - (1 - -&-); accordingly. 4Mpw

M,, is the plast~c moment capacity of the smaller flange 4.4.4.3 Sections with slender flanges. The moment capacity about its own equal area axis parallel to the flange; should be calculated from the reduced stress as given in 3.6.

f i s the mean longitudinal stress in the smaller flange

4.4.5 Shear bucklinq resistance of thin webs due to moment and/or axial load;

p,, is the design strength of the flange; 4.4.5.1 General. This clause applies to webs which are assumed to carry shear only, axial load and bending M,, i s the plastic moment capacity of the web about its

moment being carried entirely by the flanges. For webs own equal area axis perpendicular to the web.

carrying shear and direct stress, see H.3. 4.4.5.4.2 End panels designed not using tension field Webs without intermediate stiffeners should be designed action (see figure 5). This clause may be used for the design according to 4.4.5.3. of end panels in girders designed using tension field action.

Webswith intermediate stiffeners may be designed according In this case the end panel should be designed according

to 4.4.5.3 or 4.4.5.4. to 4.4.5.3. - Webs with longitudinal stiffeners should be designed to Additionally they should be checked as a beam spanning

BS 5400. between the flanges of the girder capable of resisting a shear force R,., and a moment M,, as given in 4.4.5.4.4 I

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The end stiffener should be capable of resisting the reaction plus a compressive force due to the moment M ~ .

4.4.5.4.3 End panels designed using tension field action (see figures 6 and 7). This clause may be used for the design of end panels in girders designed using tension field action. In this case the end panel should be designed according to 4.4.5.4.1.

Additionally i t should be provided with an end post consisting of a single or double stiffener, see figures 6 and 7, satisfying the following.

(a) Single stiffener, see figure 6. The top of the end post should be rigidly connected to the flange using full strength welds.

The end post should be capable of resisting the reaction plus a moment from the anchor forces equal to *j3 Mfl; where Mfl i s obtained from 4.4.5.4.4.

The width and thickness of the end post are not to exceed the width and thickness of the flange.

(b) Double stiffener, see figure 7. The end post should be checked as a beam spanning between the flanges of the girder capable of resisting a shear force R* and a moment Mfl due to the anchor forcesasgiven in 4.4.5.4.4.

I 4.4.5.4.4 Anchor force. The resultant longitudinal shear force Rtf and moment Mtf due to the anchor force H, should be obtained from the following:

where

d is the web depth;

t is the web thickness;

f, is the applied shear stress in the panel utilizing tension field action;

q, is the basic shear strength of the panel utilizing tension field action;

q,, i s the critical shear strength for the panel designed utilizing tension field action;

f v , 9 , and qcr are for the panel designed utilizing tension field action, i.e. panel A in figure 5 and panel B in figures 6 and 7. If fv <qb then the value of Hq may be multiplied by the ) ratio:

4.4.5.5 Panels with openings. Panels with an opening with any dimension greater than 10 % of the minimum panel dimension should be designed without using tension field action (see 4.4.5.3). The adjacent panels should be designed as an end panel as given in 4.4.5.4.2 or 4.4.5.4.3 as appropriate.

In addition reference should be made to 4.15.

Bearing stiffener L

I

Panel A: designed utilizing tension field action.

Pand B: designed without utilizing tension field action and for longitudinal shear Rtf and moment M,+ (see 4.4.5.4.4).

Boaring stiffonor: designed for the compressive force due to bearing plus the compression due to the moment Mtf.

Figure 5. End panel designed not using tension field action

1

C

/ d

Panel B Panel A SGK

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End post / \

Bear ing - - str f fener and end post


Panel 0 : designed utilizing tension field action.

Bearing stiffener: designed for compressive force due t o bearing.

End post: designed for hor~zontal shear RTf and moment Mtf.

Figure 7. End panel designed using tension field action (double stiffener)


Panel 8: designed utilizing tension field action.

Bearing stiffener and end post: designed for combinat~on of compressive loads due to bearing and a moment equal t o % MTfi

Figure 6. End panel designed using tension field action (single stiffener)

Panel B Panel A

/

/ I?

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Table 21. Critical shear strength, qCr (in ~ / r n r n ~ )

(a)

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p, = 265 ~/rnrn'

Stiffener

0.4

159 159 159 159 159

159 159 150 159 159

159 159 159 159 159

159 159 159 159 159

159 159 159 158 155

152 149 146 143 140

136 133 130 127 124

121 118 115 112 109

spacing

0.5

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 159 158 154 150

147 143 139 136 132

128 125 121 117 114

110 106 103 98 94

90 86 82 79 76

1.2

159 159 159 159 159

157 150 144 137 131

124 118 111 105 97

90 83 78 72 68

63 59 56 53 50

47 44 42 40 38

36 34 33 31 30

29 28 26 25 24

1 6

159 159 159 159 155

148 141 134 127 120

113 106 98 90 83

77 71 66 61 67

54 61 47 45 42

40 38 36 34 32

31 29

2%. 27.'; 26

24 23 22 22 21

1.4

159 159 159 159 158

152 145 138 131 124

118 111 104 96 88

82 76 71 66 61

58 54 51 48 45

43 40 38 36 35

33 31 30 29 27

26 25 24 23 22

ratio ald

0.6

159 159 159 159 159

159 159 159 159 159

159 159 159 158 154

150 145 141 137 133

128 124 120 116 111

107 103 98 93 88

84 80 76 73 70

67 64 61 59 56

1.8

159 159 159 159 152

145 138 131 123 116

109 102 93 86 79

73 68 63 59 55

51 48 45 43 40

38 36 34 32 31

! '29 28 27 25 24

23 22 21 21 20

0.7

159 159 159 159 159

159 159 159 159 159

159 155 150 146 141

136 131 126 122 117

112 107 102 97 91

86 82 77 73 70

66 63 60 58 55

53 51 48 46 45

2.0

159 159 159 158 150

143 136 128 121 114

106 98 90 82 76

70 65 61 56 53

49 46 44 41 39

37 35 33 31 30

28 27 26 25 23

22 22 21 20 19

1 .O

159 159 159 159 159

159 158 152 146 140

133 127 121 115 109

103 96 89 83 78

73 68 64 61 57

54 51 48 46 44

42 40 38 36 35

33 32 30 29 28

2.5

159 159 159 155 147

140 132 124 117 109

102 93 85 78 72

66 61 57 53 50

47 44 41 39 37

35 33 31 29 28

27 25 24 23 22

21 20 19 19 18

0.8

159 159 159 159 159

159 159 159 159 155

150 145 139 134 129

124 118 113 108 103

96 90 85 80 76

71 68 64 61 58

55 52 50 48 46

44 42 40 39 37

0.9

159 159 159 159 159

159 159 158 153 147

141 136 130 124 118

113 107 101 94 88

83 78 73 69 65

61 58 55 52 50

47 45 43 41 39

38 36 34 33 32

3.0

159 159 159 153 145

137 130 122 114 107

98 90 82 75 69

64 59 55 52 48

45 42 40 37 35

33 32 30 28 27

26 25 23 22 21

20 20 19 18 17

- 159 159 157 148 140

132 124 116 108 100

91 83 76 69 64

59 55 51 48 44

42 39 37 35 33

31 29 28 26 25

24 23 22 21 20

19 18 17 17 16

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(b)

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p, = 275 ~ / r n r n ~

165 165 160 152 143

135 126 118 110 100

91 83 76 69 64

59 55 51 48 44

42 39 37 35 33

31 29 28 26 25

24 23 22 21 20

19 18 17 17 16

3.0

165 165 165 157 148

140 132 124 116 108

98 90 82 75 69

64 59 55 52 48

45 42 40 37 35

33 32 30 28 27

26 25 23 22 21

20 20 18 18 17

1.4

165 165 165 165 162

155 148 141 134 126

119 112 105 96 88

82 76 71 66 61

58 54 51 48 45

43 40 38 36 3 5 E 33 $1

30 29 27

26 25 24 23 22

0.9

165 165 165 165 165

165 165 162 156 150,

144 138 132 126 120

114 108 101 94 88

83 78 73 69 65

61 58 55 52 50

47 45 43 41 39

38 36

34 33 32

Stiffener

0.4

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 165 162 158

155 152 149 146 142

139 136 133 130 126

123 120 117 114 110

0.7

165 165 165 165 165

165 165 165 165 165

164 159 154 149 144

139 134 129 123 118

113 108 103 97 91

86 82 77 73 70

66 63 60 58 55

53 51 48 46 45

1.6

165 165 165 165 159

151 144 136 129 121

114 107 98 90 83

77 71 66 61 57

54 51 47 45 42

40 38 36 34 32

31 29 28 27 26

24 23 22 22 21

1.0

165 165 165 165 165

165 162 155 149 142

136 130 123 117 110

104 96 89 83 78

73 68 64 61 57

54 51 48 46 44

42 40 38 36 35

33 32 30 29 28

0.8

165 165 165 165 165

165 165 165 165 159

154 148 142 137 131

126 120 114 109 103

96 90 85 80 76

71 68 64 61 58

55 52 50 48 46

44 42 40 39 37

spacing

0.5

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 162 158 154

150 146 142 138 134

131 127 123 119 115

111 107 103 98 94

90 86 82 79 76

2.0

165 165 16!5 162 154

146 138 131 123 115

107 98 90 82 76

70 65 61 56 53

49 46 44 41 39

37 35 33 31 30

28 27 26 25 23

22 22 21 20 19

1.8

165 165 165 164 156

148 141 133 125 118

110 102 93 86 79

73 68 63 59 55

51 48 45 43 40

38 36 34 32 31

29 28

- 2 7 25 24

23 22 21 21 20

1 2

165 165 165 165 165

161 154 147 140 133

126 119 112 106 97

90 83 78 72 68

63 59 56 53 50

47 44 42 40 38

36 34 33 31 30

29 28 26 25 24

ratio aid

0.6

165 165 165 165 165

165 165 165 165 165

165 165 165 162 158

153 149 144 140 135

131 126 122 117 113

108 103 98 93 88

84 80 76 73 70

67 64 61 59 56

2.5

165 165 165 158 150

142 134 126 118 110

102 93 85 78 72

66 61 57 53 50

47 44 41 39 37

35 33 31 29 28

27 25 24 23 22

21 20 19 19 18

SGK

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(C

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p , = 340 ~ / r n r n ~

Stiffener

0.4

204 204 204 204 204

204 204 204 204 204

204 204 204 204 204

204 204 204 204 202

198 194 189 185 180

176 172 167 163 158

154 150 145 141 136

132 127 122 117 112

1.6

204 204 201 191 181

171 160 150 140 129

117 107 98 90 83

77 71 66 61 57

54 51 47 45 42

40 38 36 34 32

31';

26'

24 23 22 22 21

spacing

0.5

204 204 204 204 204

204 204 204 204 204

204 204 204 204 201

196 190 185 179 174

169 163 158 153 147

142 137 131 125 119

113 108 103 98 94

90 86 82 79 76

ratio ald

0 6

204 204 204 204 204

204 204 204 204 204

204 198 192 186 179

173 167 161 155 148

142 136 130 122 115

109 103 98 93 88

84 80 76 73 70

67 64 61 59 56

1 8

204 204 198 188 177

167 156 146 135 123

112 102 93 86 79

73 68 63 59 55

51 48 45 43 40

38 36 34 32 31

29 2 9 ' 2 8

27 25 24

23 22 21 21 20

0.7

204 204 204 204 204

204 204 204 202 195

188 181 174 167 160

153 146 139 132 124

116 109 103 97 91

86 82 77 73 70

66 63 60 58 55

53 51 48 46 45

2 0

204 204 196 185 174

163 153 142 131 119

108 98 90 82 76

70 65 61 56 53

49 46 44 41 39

37 35 33 31 30

28 27 26 25 23

22 22 21 20 19

2.5

204 204 191 180 169

158 147 136 124 112

102 93 85 78 72

66 61 57 53 50

47 44 41 39 37

35 33 31 29 28

27 25 24 23 22

21 20 19 19 18

1.0

204 204 204 204 202

194 185 176 167 158

150 141 132 122 112

104 96 89 83 78

73 68 64 61 57

54 51 48 46 44

42 40 38 36 35

33 32 30 29 28

0 8

204 204 204 204 204

204 204 197 189 181

!74 166 158 151 143

135 127 118 110 103

96 90 85 80 76

71 68 64 61 58

55 52 50 48 46

44 42 40 39 37

3.0

204 202 189 178 167

155 144 133 120 108

98 90 82 75 69

64 59 55 52 48

45 42 40 37 35

33 32 30 28 27

26 25 23 22 21

20 20 19 18 17

1.2

204 204 204 202 193

183 174 164 155 146

136 126 115 106 97

90 83 78 72 68

63 59 56 53 50

47 44 42 40 38

36 34 33 31 30

29 28 26 25 24

0.9

204 204 204 204 204

202 194 186 177 169

161 153 144 136 127

117 109 101 94 88

83 78 73 69 65

61 58 55 52 50

47 45 43 41 39

38 36 34 33 32

- 204 195 183 171 160

148 136 123 111 100

91 83 76 69 64

59 55 51 48 44

42 39 37 35 33

31 29 28 26 25

24 23 22 21 20

19 18 17 17 16

1.4

204 204 204 196 186

176 166 156 146 136

125 114 105 96 88

82 76 71 66 61

58 54 51 48 45

43 40 38 36 35

33 31 30 29 27

26 25 24 23 22

SGK

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Table 21 (concluded)

(d )

dl t

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p , = 355 ~ I r n r n * .

Stiffener

0.4

213 213 213 213 213

213 213 213 213 213

213 213 213 213 213

213 213 213 213 208

204 199 194 190 185

180 175 171 166 161

157 152 147 143 138

132 127 122 117 112

spacing

0.5

213 213 213 213 213

213 213 213 213 213

213 213 213 212 207

201 195 190 184 178

172 167 161 155 150

144 138 132 125 119

113 108 103 98 94

90 86 82 79 76

ratio

0.6

213 213 213 213 213

213 213 213 213 213

210 204 197 190 184

177 171 164 157 151

144 137 130 122 115

109 103 98 93 88

84 80 76 73 70

67 64 61 59 56

ald

0.7

213 213 213 213 213

213 213 213 208 200

193 186 178 171 163

156 148 141 133 124

116 109 103 97 91

86 82 77 73 70

66 63 60 58 55

53 51 48 46 45

0.8

213 213 213 213 213

213 210 202 194 186

178 169 161 153 145

137 127 118 110 103

96 90 85 80 76

71 68 64 61 58

55 52 50 48 46

44 42 40 39 37

0.9

213 213 213 213 213

208 199 190 182 173

164 155 146 137 127

117 109 101 94 88

83 78 73 69 65

61 58 55 52 50

47 45 43 41 39

38 36 34 33 32

1.0

213 213 213 213 208

199 190 180 171 161

152 143 132 122 112

104 96 89 83 78

73 68 64 61 57

54 51 48 46 44

42 40 38 36 35

33 32 30 29 28

1.2

213 213 213 208 198

188 178 168 158

, 1 4 8

138 126 115 106 97

90 83 78 72 68

63 59 56 53 50

47 44 42 40 38

36 34 33 31 30

29 28 26 25 24

1.4

213 213 212 201 191

180 170 159 148 138

125 114 105 96 88

82 76 71 66 61

58 54 51 48 45

43 40 38 36 35

3% 31'

n

26 25 24 23 22

1.6

213 213 207 196 185

174 163 152 142 129

117 107 98 90 83

77 71 66 61 57

54 51 47 45 42

40 38 36 34 32

31 29 28 27 26

24 23 22 22 21

1.8

213 213 204 192 181

170 159 148 136 123

112 102 93 86 79

73 68 63 59 55

51 4 8 45 43 40

38 36 34 32 31

29 28 27 25 24

23 22 21 21 20

2.0

213 212 201 190 178

167 155 144 132 119

108 98 90 82 76

70 65 61 56 53

49 46 44 41 39

37 35 33 31 30

28 27 26 26 23

22 22 21 20 19

2.5

213 208 197 185 173

161 150 138 124 112

102 93 85 78 72

66 61 57 53 50

47 44 41 39 37

35 33 31 29 28

27 25 24 23 22

21 20 19 19 18

3.0

213 206 194 182 170

158 146 134 120 108

98 90 82 75 69

64 59 55 52 48

45 42 40 37 35

33 32 30 28 27

26 25 23 22 21

20 20 19 18 17

- 213 200 188 175 163

150 138 123 111 100

91 83 76 69 64

59 55 51 48 44

42 39 37 35 33

31 29 28 26 25

24 23 22 21 20

19 18 17 17 16

SGK

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Table 22. Basic shear strength, q, (in ~ 1 r n t - n ~ )

(a )

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p, = 265 ~ l r n r n '

1.6

159 159 159 159 159

151 147 142 138 133

129 124 118 112 107

102 97 94 90 87

84 81 79 76 74

72 71 69 67 66

65 63

62\ , 61:. 6 0 '

59 58 58 57 56

Stiffener

0.4

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 159 151 150 149

148 147 146 145 144

143 142 141 140 139

0.7

159 159 159 159 159

159 159 159 159 159

159 159 159 159 148

146 144 142 140 138

135 133 130 127 125

122 119 117 115 113

111 109 107 106 104

103 101 100 99 98

1.8

159 159 159 159 159

149 145 140 135 130

125 120 113 107 102

97 93 89 85 82

79 76 74 72 70

68 66 65 63 62

1 6 0 59 58 57 56

55 54 53 53 52

spacing

0.5

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

151 150 149 147 146

145 143 142 140 139

137 136 134 132 130

129 127 125 124 122

ratio a ld

0.6

159 159 159 159 159

159 159 159 159 159

159 159 159 159 159

159 150 149 147 145

144 142 140 138 136

134 132 130 128 125

123 121 119 117 116

114 113 111 110 109

0.8

159 159 159 159 159

159 159 159 159 159

159 150 147 145 143

140 137 135 132 129

126 122 119 116 114

111 109 107 105 103

101 99 98 96 95

94 92 91 90 89

3.0

159 159 159 159 148

143 137 131 125 119

111 104 97 91 86

81 77 73 70 67

64 61 59 57 55

53 52 50 49 47

46 45 44 43 42

41 40 39 39 38

1.0

159 159 159 159 159

159 159 159 150 147

144 141 137 134 131

127 123 118 114 111

108 105 102 99 97

95 93 91 89 88

86 85 83 82 81

80 79 78 77 76

2.0

159 159 159 159 159

148 143 138 133 127

122 116 109 103 98

93 89 85 81 78

75 73 70 68 66

64 63 61 59 58

57 56 55 54 53

52 51 50 49 49

0.9

159 159 159 159 159

159 159 159 159 150

148 145 142 140 137

133 130 127 123 119

116 113 110 107 105

102 100 98 96 94

93 91 90 89 87

86 85 84 83 82

2.5

159 159 159 159 150

145 140 134 128 122

116 109 102 96 91

86 82 78 75 71

69 66 64 61 59

58 56 54 53 52

50 49 48 47 46

45 45 44 43 42

1.2

159 159 159 159 159

159 159 149 145 142

138 134 130 126 121

116 112 108 104 100

97 94 92 89 87

85 83 82 80 78

77 76 74 73 72

71 70 69 68 68

1.4

159 159 159 159 159

159 149 145 141 137

133 128 124 118 113

108 104 100 96 93

90 87 84 82 80

78 76 74 73 71

70 69 68 66 65

64 64 63 62 61

SGK

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BS5950 : Part 1 : 1990 Section four

BEST COPY AVAILABLE

t


(b)

dit

55 60 65 70 75

80 85 90 95

100

105 1 1 0

115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p, = 275 ~ I r n r n ~

Sti f fener

0.4

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 156 155 154

153 152 151 150 149

148 147 145 144 143

1.4

165 165 165 165 165

165 153 149 145 141

136 131 126 120 115

110 105 101 98 94

91 89 86 84 82

80 78 76 74 73

7 70'

69

67

66 65 64 64 63

1 2

165 165 165 165 165

165 156 153 149 146

142 137 133 129 123

118 114 110 106 102

99 96 94 91 89

87 85 83 82 80

79 77 76 75 74

73 72 71 70 69

1.6

165 165 165 165 165

155 151 146 142 137

131 126 120 114 108

103 99 95 92 88

85 83 80 78 76

74 72 70 69 67

66 65 64 63 62

61 60 59 58 57

0.9

165 165 165 165 165

165 165 165 165 155

152 150 147 143 140

137 134 130 125 122

118 115 112 109 107

105 102 100 99 97

95 94 92 91 90

88 87 86 85 84

spacing

0.5

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

156 155 153 152 150

149 148 146 144 143

141 140 138 136 134

132 130 129 127 125

3.0

165 165 165 165 152

147 140 134 127 120

112 105 98 92 87

82 78 74 71 68

65 62 60 58 56

54 52 51 49 48

47 46 45 44 43

42 41 40 40 39

1.8

165 165 165 165 165

153 149 144 138 133

127 121 114 109 103

98 94 90 87 83

80 78 75 73 71

69 67 66 64 63

62 60 59 58 57

56 56 55 54 53

1.0

165 165 165 165 165

165 165 165 154 151

148 145 141 137 134

130 125 121 117 113

110 107 104 102 99

97 95 93 91 90

88 87 85 84 83

82 81 80 79 78

ratio a l d

0.6

165 165 165 165 165

165 165 165 165 165

165 165 165 165 165

165 155 153 152 150

148 146 144 142 140

138 136 133 131 128

126 124 122 120 119

117 116 114 113 112

2.0

165 165 165 165 156

152 147 141 136 130

124 117 110 104 99

94 90 86 83 79

77 74 72 69 67

65 64 62 61 59

58 57 56 55 54

53 52 51 50 50

2.5

165 165 165 165 154

149 143 137 131 124

117 110 103 97 92

87 83 79 76 72

70 67 65 62 60

59 57 55 54 53

51 50 49 48 4 j

46 45 45 44 43

0.7

165 165 165 165 165

165 165 165 165 165

165 165 165 155 153

151 148 146 144 141

139 136 133 130 127

125 122 120 118 116

114 112 110 108 107

105 104 103 102 101

0.8

165 165 165 165 165

165 165 165 165 165

157 154 152 149 147

144 141 138 135 132

128 125 122 119 116

114 111 109 107 105

103 102 100 99 97

96 95 94 93 92

SGK

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+


(C

dlt

55 60 65 70 75

80 85 90 95 100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p , = 340 N/mm2

Stiffener

0.4

204 204 204 204 204

204 204 204 204 204

204 204 204 204 204

204 204 204 204 204

204 204 204 193 192

190 189 188 186 185

183 182 180 179 177

175 173 171 169 167

2.5

204 204 194 187 179

171 162 154 144 134

125 117 110 104 99

94 89 86 82 79

76 73 71 69 67

65 63 62 60 59

58 57 55 54 53

53 52 51 50 50

3.0

204 204 192 184 176

167 158 149 138 128

119 1 1 1 104 98 93

88 84 80 76 73

70 68 65 63 61

59 58 56 55 53

52 51 50 49 48

47 46 46 45 44

spacing

0.5

204 204 204 204 204

204 204 204 204 204

204 204 204 204 204

204 204 193 191 189

187 185 183 181 179

177 174 172 169 167

164 162 159 157 155

153 151 150 148 146

0.7

204 204 204 204 204

204 204 204 204 204

193 190 187 184 181

178 175 171 168 164

159 156 152 149 146

143 140 138 135 133

131 129 127 126 124

123 121 120 119 118

ratio ald

0.6

204 204 204 204 204

204 204 204 204 204

204 204 204 193 190

188 185 183 180 177

175 172 169 165 162

159 156 153 150 148

146 143 141 140 138

136 135 133 132 130

0.8

204 204 204 204 204

204 204 204 193 190

187 183 179 176 172

168 163 158 153 149

145 142 138 135 133

130 128 125 123 121

119 118 116 115 113

112 1 1 1 110 109 108

0.9

204 204 204 204 204

204 204 192 188 184

180 176 171 166 161

156 150 146 141 137

134 130 127 125 122

120 117 115 113 112

110 109 107 106 104

103 102 101 100 99

12

204 204 204 204 204

190 185 180 174 169

163 156 149 142 136

131 127 122 118 115

112 109 106 103 101

99 97 95 94 92

91 89 88 87 86

85 84 83 82 81

1.0

204 204 204 204 204

204 191 187 183 178

173 168 163 156 150

145 140 135 131 128

124 121 118 116 113

1 1 1 109 107 105 103

102 100 99 98 97

96 95 94 93 92

1.4

204 204 204 204 191

186 180 174 167 161

153 145 138 132 126

121 117 112 109 105

102 99 97 94 92

90 88 87 85 84

82 81 80 79 78

77 76 75 74 73

1.6

204 204 204 194 188

182 176 169 162 154

145 137 130 124 119

114 109 105 101 98

95 92 90 87 85

83 82 80 78 77

76 74

1.8

204 204 204 192 186

179 172 164 157 148

139 131 124 118 112

107 103 99 95 92

89 87 84 82 80

78 76 74 73 71

B 7 0 ' 6 9

2.0

204 204 204 190 183

176 169 161 153 143

134 126 119 113 107

103 98 94 91 87

85 82 79 77 75

73 72 70 68 67

66 65 63 62 61

61 60 59 58 57

73.,% 72: 71"

70 69 68 68 67

68 67 66

65 64

63 62 62

SGK

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BEST COPY AVAllABLE

Table 22 (conc/uded)

(d )

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

p, = 355 ~ / r n r n ~

Stiffener

0.4

213 213 213 213 213

213 213 213 213 213

213 213 213 213 213

213 213 213 213 213

213 213 202 201 199

198 196 195 193 191

190 188 186 185 183

181 179 177 175 173

1.2

213 213 213 213 202

197 191 186 180 173

167 159 152 145 139

134 129 125 121 118

114 111 109 106 104

102 100 98 96 95

93 92 91 90 89

88 87 86 85 84

1.4

213 213 213 213 198

192 186 179 172 165

156 148 141 135 129

124 119 115 111 108

105 102 99 97 95

93 92 89 87 86

a 83

$ 80

79 78 77 76 76

spacing

0.5

213 213 213 213 213

213 213 213 213 213

213 213 213 213 213

213 202 200 198 196

194 192 189 187 185

183 180 177 174 172

169 167 164 162 160

158 156 154 153 151

0.7

213 213 213 213 213

213 213 213 213 213

200 197 194 191 188

184 180 177 173 168

164 160 156 153 150

147 144 142 139 137

135 133 131 130 128

127 125 124 123 122

ratio ald

0.6

213 213 213 213 213

213 213 213 213 213

213 213 202 200 197

195 192 189 186 183

180 177 173 170 166

163 160 157 155 152

150 148 146 144 142

140 139 137 136 135

1.6

213 213 213 201 194

188 181 173 166 157

148 140 133 126 121

116 111 107 104 100

97 94 92 90 87

85 84 82 80 79

78 76 75 74 73

72 71 71

- 7 0 69

1.0

213 213 213 213 213

213 198 193 189 183

178 173

, 1 6 6 160 154

148 143 139 135 131

127 124 121 119 116

114 112 110 108 107

105 104 102 101 100

99 98 97 96 95

1.8

213 213 213 198 192

184 177 169 160 150

141 133 126 120 114

110 105 101 97 94

91 89 86 84 82

80 78 76 75 73

72 71 70 69 68

67 66 65 64 64

0.8

213 213 213 213 213

213 213 213 201 197

193 189 185 181 177

173 167 162 157 153

149 146 142 139 136

134 131 129 127 125

123 121 120 118 117

116 114 113 112 111

0.9

213 213 213 213 213

213 213 199 195 190

186 181 176 171 165

159 154 149 145 141

137 134 131 128 125

123 121 119 117 115

113 112 110 109 108

106 105 104 103 102

2.0

213 213 213 196 189

181 173 164 155 145

136 128 121 115 109

104 100 96 93 89

86 84 81 79 77

75 73 72 70 69

68 66 65 64 63

62 62 61 60 59

2.5

213 213 200 193 184

175 166 157 145 135

126 118 112 106 100

95 91 87 84 80

77 75 72 70 68

66 65 63 62 60

59 58 57 56 55

54 53 52 52 51

3.0

213 213 198 190 181

171 162 151 139 129

120 112 105 99 94

89 85 81 77 74

72 69 67 64 62

61 59 57 56 55

53 52 51 50 49

48 48 47 46 45

SGK

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A Table 23. Flange dependent shear strength factor, qf (in ~ / m m * )

- (a,

dlt

55 60 65 70 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 1 50

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250-

p, = 265 ~ / r n m ?

Stiffener

0.4

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

65 116 151 178 202

223 242 260 276 291

305 319 332 344 356

spacing

0.5

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0

86

133 166 194 218 239

258 275 292 307 321

335 348 360 374 387

399 409 419 427 435

1.0

0 0 0 0 0

0 0

51 116 155

184 208 228 247 263

278 293 307 318 328

336 343 349 355 359

364 367 371 374 377

379 382 384 386 388

389 391 392 394 395

ratio ald

0.6

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

91 138 172 200 224

245 264 282 298 313

327 341 356 370 382

392 402 411 418 425

432 438 443 448 452

0.7

0 0 0 0 0

0 0 0 0 0

0 0

79 132 168

197 221 243 262 279

296 311 325 340 354

366 377 386 394 402

408 414 420 425 429

433 437 441 444 447

1.2

0 0 0 0 0

0 67

120 154 180

201 219 235 250 264

277 288 297 304 310

316 321 325 329 332

335 337 340 342 344

346 347 349 350 351

352 354 355 355 356

1.6

0 0 0 0 0

79 119 145 165 182

196 209 221 232 241

248 254 259 263 267

270 272 275 277 279

280 282 283 285 286

287 288 289'. 2 8 9 ' 290

291 291 292 292 293

1.4

0 0 0 0 0

44 106 140 165 185

202 217 230 243 255

264 272 278 284 288

292 296 299 302 304

306 308 310 312 313

314 316 317 318 319

319 320 321 322 322

0.8

0 0 0 0 0

0 0 0 0 0

81 133 168 197 221

242 261 278 293 308

324 338 350 360 369

377 384 390 396 401

405 409 413 417 420

423 425 428 430 432

1.8

0 0 0 0

27

92 122 144 162 176

188 199 210 219 226

231 236 240 244 246

249 251 253 255 256

258 259 260 261 262

963 264 264 265 265

266 266 267 267- 268

0.9

0 0 0 0 0

0 0 0

29 110

151 182 207 229 248

266 281 296 312 325

336 346 354 361 368

373 378 383 387 391

394 397 400 402 405

407 409 411 412 414

2.0

0 0 0 0

52

96 122 141 156 168

179 189 198 205 211

216 220 223 226 228

231 232 234 235 237

238 239 240 241 241

242 243 243 244 244

245 245 245 246 246

2.5

0 0 0

. o 67

96 114 128 139 148

156 165 171 176 180

183 186 188 190 192

193 194 195 196 197

198 199 199 200 200

201 201 202 202 202

203 203 203 203 204

3.0

0 0 0 9 68

89 104 115 124 131

138 144 149 152 155

158 160 162 163 164

165 166 167 168 168

169 170 170 170 171

171 171 172 172 172

172 173 173 173 173

SGK

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--

BEST COPY AVAILABLE



(b) p, = 275 ~/rnrn*

I

dlt

( Stiffener spacing ratio ald SG

Kab

ir.co

m



(c)

dlt

55 60 65 7 0 75

80 85 90 95

100

105 110 115 120 125

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

205 210 215 220 225

230 235 240 245 250

L

p , = 340 ~ f r n r n '

Stiffener

0.4

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 103 167 212 249

280 309 334 357 379

399 419 437 454 470

486 504 521 536 550

1.8

0 0 0

110 157

188 212 232 249 265

279 289 297 304 310

314 318 321 324 327

329 331 333 334 336

337 338 339 340 341

? 3 4 2 342 343 343 344

345 345 345 346 346

2.0

0 0

33 118 156

183 204 221 236 251

262 270 277 283 288

291 295 297 300 302

304 305 307 308 309

310 311 312 313 313

314 315 315 316 316

317 317 317 318 318

spacing

0.5

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

53 148 202 244 279

309 337 362 385 406

426 445 463 483 501

518 532 545 557 567

577 586 594 601 608

ald

0.7

0 0 0 0 0

0 0 0 0

62

157 212 254 289 319

346 371 393 414 436

456 473 488 501 512

522 531 539 546 552

558 563 568 573 577

581 584 587 590 593

ratio

0.6

0 0 0 0 0

0 0 0 0 0

0 0

121 186 233

271 303 332 358 382

404 424 444 466 484

500 515 527 538 548

557 565 573 580 586

591 597 602 606 610

2.5

0 0

71 119 146

166 182 195 207 217

224 230 235 239 242

245 247 249 251 252

253 254 255 256 257

258 268 259 259 260

260 261 261 261 262

262 262 262 263 263

0.8

0 0 0 0 0

0 0 0

143 202

245 281 312 339 363

385 407 429 447 462

475 486 496 504 512

519 525 530 535 540

544 548 551 554 557

560 562 565 567 569

3 0

0 0

76 112 133

149 161 171 181 189

195 199 203 206 208

210 212 213 214 215

216 217 218 218 219

219 220 220 221 221

221 222 222 222 222

223 223 223 223 223

0.9

0 0 0 0 0

0 79

164 216 256

288 317 342 365 387

408 426 440 453 464

473 481 488 494 500

505 509 513 517 520

523 526 529 531 533

535 537 539 540 542

1.0

0 0 0 0 0

81 164 214 252 284

312 336 357 380 399

414 427 438 447 455

462 468 473 478 482

486 489 493 495 498

500 503 505 506 508

510 511 512 514 515

1.2

0 0 0 0

85

160 207 242 270 295

316 337 356 371 384

394 402 410 416 421

426 430 434 437 440

443 445 447 449 451

453 454 456 457 458

459 460 461 462 463

1.4

0 0 0

31 135

184 218 246 269 289

309 326 340 350 359

367 373 378 383 387

391 394 396 399 401

403 405 406 408 409

410 411 412 413 414

415 416 417 417 418

1.6

0 0 0

92 152

190 218 241 261 278

295 308 318 327 334

340 344 249 352 355

358 360 363 364 366

368 369 370 371 372

373 374 375. 3 7 9 ' 376

377 378 378 379 379

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BEST COPY AVAILABLE BS 5950 : Part 1 : 1990 Section four

Table 23 (concluded) - - -- -- - -

(d p , = 355 ~ / r n r n ~

Stiffener spacing ratio a /d SG

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ir.co

m


4.4.6 Design of intermediate transverse web stiffeners

4.4.6.1 General. lntermediate transverse stiffeners may be on one or both sides of the web.

4.4.6.2 Spacing. The spacing of intermediate stiffeners, where they are provided, should comply with 4.4.2, dependent on the thickness of the web.

4.4.6.3 Outstand of stiffeners. The outstand of the stiffeners should comply with 4.5.1.2.

4.4.6.4 Minimum stiffness. Transverse web stiffeners not subject to external loads or moments should have a second moment of area, I , , about the centreline of the web such that:

I , > 0.75dt3 for a 2 42 d

and

1 .5d3 t 3 I s > -

a' fora <\/2 d

where

d i s depth of the web;

t is minimum required web thickness for spacing a using tension field action as given in 4.4.5.4.1;

a i s the actual stiffener spacing.

4.4.6.5 Additional stiffness for external loading. When transverse web stiffeners are subject to lateral forces or to moments due to eccentricity of transverse loads relative to the web, the minimum value of I , given in 4.4.6.4 should be increased by:

(a) for lateral forces: 2 F D ' / E ~ ;

(b) for moments: M , D 2 1 ~ t

where

D is the overall depth of the section;

E is the modulus of elasticity;

F i s the factored lateral force to be taken by the stiffener and deemed to be applied at the compression flange;

M, is the moment on the stiffener due to eccentric applied load;

t i s the web thickness

No increase in the minimum value of I , is required for transverse loads in line with the web.

4.4.6.6 Buckling check on intermediate transverse web stiffeners. Stiffeners not subject to external loads or moments should be checked for a stiffener force:

where

V i s the maximum shear adjacent t o the stiffener

V, i s the shear buckling resistance of the web panel designed without using tension f~e ld action (see 4.4.5.3).

Stiffeners subject to external loads and moments should meet the conditions for load carrying web stiffeners in 4.5.2 In addition they should satisfy the following interaction expression:

If Fq < F, then (Fq - F,) should be taken as zero.

In the equation above:

f , is the stiffener force given above;

Pq is the buckling resistance of an intermediate web stiffener (see 4.5.1.5);

F, is the external load or reaction;

P, i s the buckling resistance of a load carrying stiffener (see 4.5.1.5);

M, is the moment on the stiffener due to eccentric applied load;

My, is the moment capacity of the stiffener based on its elastic modulus.

4.4.6.7 Connection to web of intermediate stiffeners. lntermediate transverse stiffeners not subject t o external loading should be connected to the web to withstand a shear between each component and the web (in kN per millimetre run) of not less than:

where

t is the web thickness (in mm);

b, is the outstand of the stiffener (in mm).

For stiffeners subject to external loading the shear between the web and the stiffener due to such loading has to be added to the above value.

Stiffeners not subject to external loads or moments may terminate clear of the tension flange and in such a situation the distance cut short on the line of the weld should be approximately 4t.

Stiffeners should exte?d to the compression flange but need not be connecta to it.

k\

4.5 Web bearing, buckling and stiffener design

4.5.1 General

4.5.1.1 Introduction. This clause covers the design of webs for beams and girders subject to loading through the flange parallel to the plane of the web. When the web of a member acting alone (i.e. without stiffeners) proves inadequate, stiffeners to cover the following should be provided.

(a) Load carrying stiffener: to prevent local buckling of the webdue to concentrated loading. See 4.5.2 and 4.5.4.

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(b) Bearing stiffener: to prevent local crushing of the web due to concentrated loading. See 4.5.3 and 4.5.5.

(c) Intermediate transverse web stiffener: to prevent buckling of a slender web due to shear. See 4.4.5 and 4.4.6.

(d) Torsion stiffener: to provide torsional restraint to beams and girders at supports. See 4.5.8.

(e) Diagonal stiffener: to provide local reinforcement of a web in shear and bearing. See 4.5.6.

( f ) Tension stiffener: to transmit tensile forces applied to a web through a flange. See 4.5.7.

The same stiffeners may perform more than one function and their design should comply with the requirements of those functions.

4.5.1.2 Outstand of web stiffeners. Unless the outer edge is continuously stiffened the outstand from the face of the web should not exceed 19t,~. When the outstand is between 13t,c and 19t,c then the stiffener design should be on the basis of a core section with an outstand of 1 3 t , ~ .

4.5.1.3 Stiff bearing length. The stiff bearing length, b I , is that length which cannot deform appreciably in bending. To determine b , the dispersion of load through a steel bearing should be taken as 45 O through solid material. See figure 8.

4.5.1.4 Eccentricity. Where a load or reaction i s applied eccentric to the centreline of the web or where the centroid of the stiffener does not lie on the centreline of the web, the resulting eccentricity of loading should be allowed for in design.

4.5.1.5 Buckling resistance of stiffeners. The buckling resistance should be based on the compressive strength p, (see 4.7.5) of a strut using table 27(c), the radius of gyration being taken about the axis parallel to the web. The effective section is the full area or core area of the stiffener (see 4.5.1.2) together with an effective length of web on each side of the centreline of the stiffeners limited to 20 times the web thickness.

The design strength used should be the minimum value obtained for the web or the st~ffener. The reduction of 20 N/mm2 referred to in 4.7.5 need not be taken unless the stiffener is attached to a welded section.

The effective length for intermediate transverse stiffeners used in calculating the buckling resistance, P,, should be taken as 0.7 times the length of the stiffener.

The effective length for load carrying web stiffeners used in calculating the buckling resistance, P,. assumes that the flange through which the load or reaction is applied is effectively restrained against lateral movement relative to the other flange. I t should be taken as:

(a) flange restrained against rotation in the plane of the stiffener (by other structural elements):

L E = 0 . 7 L

(b) flange not so restrained:

L E = L where L is the length of the stiffener.

I? the load or reaction i s applied to the flange by a cornpres- sion member, then unless effective lateral restraint is provided at that point, the stiffener should be designed as part of the compression member applying the load, and the connection should be checked for the effects of the strut action.

Figure 8. Stiff bearing length

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4.5.2 Load carrying stiffeners

4.5.2.1 Web check. Load carrying web stiffeners should be provided where compressive forces applied through a flange by loads or reactions exceed the buckling resistance, P,, of the unstiffened web, where:

Pw = (bl + n l ) tp,

where

b, i s the stiff bearing length (see 4.5.1.3);

n1 is the length obtained by dispersion at 45 " through half the depth of the section;

t is the web thickness;

p, is the compressive strength from 4.7.5 using table 27(c) and A as follows.

In determiningp, the slenderness, A, of an unstiffened web should be taken as 2.5dlt (where d is the depth of the web) provided that the flange through which the load or reaction i s applied is effectively restrained against:

(a) rotation relative to the web;

(b) lateral movement relative to the other flange.

If these conditions are not met the slenderness, A, of the web, acting as a strut, should be determined in accordance with 4.5.1.5 for the appropriate end restraint.

4.5.2.2 Web check between stiffeners. The compressive stress, f,, on the compression edge of a web, calculated as follows, due to loads or reactions applied direct, or through a flange, between web stiffeners, should not exceed the compressive strength for edge loading, p,.

The compressive stress, f,, on the edge of a panel between two web stiffeners should be calculated as follows.

(a) Divide point loads and distributed loads shorter than the smaller panel dimension by the smaller panel dimension a or d.

(b) Add the intensity (forcelunit length) of any other distributed loads.

(c) Divide by the web thickness t.

When the compression flange is restrained against rotation relative to the web:

OR when the compression flange i s not so restrained:

where a is the distance between transverse web stiffeners.

4.5.3 Bearing stiffeners

Bearing stiffeners should be provided for webs where forces applied through a flange by loads or reactions exceed the local capacity of the web at i t s connection to the flange given by:

(b l +%)tp,,

where

bl i s the stiff bearing length (see 4.5.1.3);

n, is the length obtained by dispersion through the flange to the flange to web connection at a slope of 1 :2.5 to the plane of the flange;

r i s the thickness of the web;

pvw is the design strength of the web

4.5.4 Design of load carrying stiffeners

4.5.4.1 Buckling check. The external load or reaction, F,, on a stiffener should not exceed the buckling resistance, P,, of the stiffener as given in 4.5.1.5. Where the stiffener also acts as an intermediate stiffener i t should be checked for the effect of combined loads in accordance with 4.4.6.6.

4.5.4.2 Bearing check. Load carrying web stiffeners should also be of sufficient size that:

0.8 F , A>-

pvs where

F, i s the external load or reaction;

A is the area of the stiffener in contact with the flange;

p,, is the design strength of the stiffener.

4.5.5 Design of bearing stiffeners

Bearing stiffeners should be designed for the applied load or reaction less the local capacity of the web as given in 4.5.3.

Where the web and the stiffener material are of different strengths the lesser value should be assumed to calculate the capacity of the web and the stiffener.

4.5.6 Design of diagonal stiffeners

Diagonal stiffeners should be designed to carry the portion of the applied shear and bearing that exceeds the capacity of the web.

Where the web and the stiffener are of different strengths the value taken for design should be taken as given in 4.5.5.

4.5.7 Design of tension stiffeners

Tension stiffeners sh&ld be designed to carry the portion of the applied load or reaction less the capacity of the web as given in 4.5.3 fa . bearing stiffeners.

Where the web andthe stiffener are of different strengths the value taken for design should be taken as given in 4.5.5.

4.5.8 Torsion stiffeners

Where bearing stiffeners are required to provide torsional restraint at the supports of the beam, they should meet the following criteria.

(a) The conditions of 4.5.3.

(b) The second moment of area of the stiffener section about the centreline of the web, I,, should be such that:

I, 2 0.34 a , ~ ' T,

where

a, = 0.006 for A Q 50;

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a, = 0.3Ih for 50 < A < 100;

a, = 30/A2 for A > 100;

D i s overall depth of beam at support;

T, is the maximum thickness of compression flange of the span under consideration;

A = L,/ry for the beam;

L, is the effective length of the beam.

4.5.9 Connection to web of load carrying and bearing stiffeners

Stiffeners which resist loads or reactions applied through a flange should be connected to the web by sufficient welds or fasteners to transmit a design force equal to the lesser of:

(a) the tension capacity of the stiffener;

(b) the sum of the forces applied when they act in the same direction or the larger of the forces when they act in opposite directions.

Stiffeners which do not extend right across the web should be of such length that the shear stress in the web due to the design force transmitted by the stiffener does not exceed the shear strength of the web. In addition, the capacity of the web beyond the end of the stiffener should be sufficient to resist the applied force.

4.5.10 Connection to flanges: stiffeners in tension

Stiffeners required to resist tension should be connected to the flange transmitting the load by continuous welds or non-slip fasteners.

4.5.1 1 Connection to flanges: stiffeners in compression

Stiffeners required to resist compression should either be fitted against the loaded flange or connected by continuous welds or non-slip fasteners.

The stiffener should be fitted against or connected to both flanges when:

(a) a load i s applied directly over a support;

or (b) i t forms the end stiffener of a stiffened web;

or (c) it acts as a torsion stiffener.

4.5.1 2 Hollow sections

Where concentrated loads are applied to hollow sections consideration should be given to local stresses and deforma- tions and the section reinforced as necessary.

4.6 Axially loaded tension members

4.6.1 Tension capacity

The tension capacity, PI, of a member should be taken from:

P, = Aepy

where A, is the effective area of the section as determined from 3.3.3 or 4.6.2 to 4.6.4.

4.6.2 Eccentric connections

When members are connected eccentric to the axis of the member the resulting moment has to be allowed for in accordance with 4.8.2, except for angles, channels and T-sections designed to 4.6.3 or 4.6.4 which may be treated as axially loaded members.

4.6.3 Effective areas of simple tension members

4.6.3.1 Single angles, channels and T-sections. For single angle ties connected through one leg only, single channel sections connected only through the web, and T-sections connected only through the flange, the effective area should be taken as the net area of the connected leg, plus the area of the outstanding leg multiplied by:

3a1 3al +a2

where

a, i s the net sectional area of the connected leg as given in 3.3.2;

a, i s the sectional area of the unconnected leg.

For double angle ties, connected to one side of a gusset or section, the angles may be designed individually as given above.

4.6.3.2 Double angles. For back-to-back double angles connected to one side of a gusset or section which are:

(a) in contact or separated by a distance not exceed~ng the aggregate thickness of the parts with solid packing pieces;

(b) connected by bolts or welding such that the slenderness of the individual components does not exceed 80;

then the effective area. A,, may be taken as the net area of the connected legs plus the area of the outstanding legs multiplied by:

5.3,

where

a, is thp net sectional area of the connected parts as g i v d in 3.3.2;

a, Ifthe sectional area of the unconnected parts. NOTE. Xhe area of the leg of an angle should be taken as the product of the th~ckness by the length from the outer corner mlnus half the thtckness, and the area of the leg of a T-section as the product o f the thickness b y the depth minus the thickness of the flange.

4.6.3.3 Other types. The following types of members should be designed using the net area from 3.3.2 and treated as axially loaded members.

(a) Single angle ties connected through both legs by lug angles or otherwise, single channel sections connected by both flanges and T-sections connected only through the leg or both the flange and the leg.

(b) Double angle ties connected to both sides of a gusset or section provided that the components are held

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longitudinally parallel and connected by bolts or welds in a t least two places and held apart by solid packing pieces. The outermost of such connections should be a t a distance from each end of approximately nine times the smallest leg length. The bolts should be of the same diameter as the end connections.

(c) The internal bays of continuous ties.

4.6.4 Laced or battened ties

Any lacing or battening systems should be designed to resist the greater of the following.

(a) Forces and/or moments induced by eccentric loads, applied moments or transverse forces, including self weight and wind resistance.

(b) Forces and/or moments induced by a transverse shear on the complete member at any point in its length equal to 1 % of the factored axial load in the member. These forces may be taken as shared equally between all transverse lacing or battening systems in parallel planes.

4.7 Compression members

4.7.1 General

4.7.1.1 Length. The length, L, of a compression member in any plane should be taken as the distance between the points at which i t has effective positional or directional restraint against buckling in that plane.

4.7.1.2 Restraints. A restraint should have sufficient strength and stiffness to inhibit movement of the restrained point in position or direction as appropriate.

Positional restraints should be connected to an appropriate shear diaphragm or system of triangulated bracing.

Positional restraints to compression members forming the flanges of lattice girders should satisfy the recommendations for lateral restraint of beams given in 4.3.2.

All other positional restraints to compression members should be capable of resisting a force of not less than 1 % of the axial force in the restrained member and transferring it to the adjacent points of positional restraint.

4.7.2 Effective lengths

For angles, channels and T-sections the effective length should be determined from its length centre-to-centre of intersections with restraining members in accordance with the conditions of restraint in the appropriate plane as given in table 24 or as limited by 4.7.10.

In other cases the effective length, LE , should be determined from the actual length and the conditions of restraint in the relevant plane, as follows.

(a) In determining the conditions of restraint, restraining members which under the same loading conditions are required to carry more than 90 % of their reduced moment capacity (i.e. reduced for axial load) should be taken as incapable of providing directional restraint to

(c) For stanchions in single storey buildings of simple construction see D.1.

Table 24. Nominal effective length, L E , for a strut

NOTE. For angle, channel and T-section struts, see 4.7.10.

(d) For members forming part of a frame with rigid joints see appendix E.

4.7.3 Slenderness

Effective length, L E

0.7 L

0.85 L

0.85 L

1 .OL

1.2L

1.5L

2.0 L

Conditions of restraint at ends (in plane under consideration)

4.7.3.1 General. The value of the slenderness, A, should be taken as the effective,kngth, LE, divided by the radius of gyration about the relkxant axis except as given in 4.7.9 for battened struts or 4.7.13 for back-to-back struts.

'-. 4.7.3.2 Maximum Senderness. The value of A should not exceed the following:

Effectively held in position a t both ends

One end

Effectively held in position and restrained in d~rection

(a) for members resisting loads other than wind loads 180

(b) for members resisting self weight and wind loads only 250

-- Restrained in direction at both ends

Partially restrained in direction at both ends

Restrained in direction at one end

NOT restrained in direction at either end

Other end

(c) for any member normally acting as a tie but subject to reversal of stress resulting from the action of wind 350

Not held in position

Members whose slenderness exceeds 180 should be checked for self weight deflection. If this exceeds length/1000 the effect of bending should be taken into account in design.

Effectively restrained in direction

Partially restrained in direction

NOT restrained in direction

the member under consideration.

(b] For standard conditions of restraint see table 24.

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4.7.4 Compression resistance

The compression resistance, PC, of a member should be obtained from:

(a) for plastic, compact or semi-compact sections:

PC =A,pc (b) slender sections:

I PC = Ag P C S where

A, is the gross sectional area (see 3.3.1);

pc i s the compressive strength (see 4.7.5);

I pcs is the compressive strength for slender sections (see 4.7.5 and 3.6).

Steel sections encased in structural concrete may be designed as cased struts in accordance with 4.14.

For single angle, channel and T-section struts reference should be made to 4.7.10.

4.7.5 Compressive strength

The compressive strength,^,, depends on the slenderness, h, of the gross section, the design strength,^,, or the reduced design strength for slender sections (see 3.6) and the relevant strut curve.

pc may be established first by reference to tables 25 and 26. These indicate, for any shape, thickness of steel and axis of buckling, which of the four strut tables 27(a) to (d), is relevant to the case. A1ternati~ely.p~ may be obtained from the formula given in appendix C.

For sections fabricated from plate by welding, the value of p, should be reduced by 20 N/mmz.

Table 25. Strut table selection

Type of section

Hot-rolled structural hollow section

Rolled I-section (or as shown in table 26(a))

Rolled H-section (or as shown in table 26(a))

Welded plate I or H-section (see note 2 and 4.7.5) (or as shown in table 26(c))

Rolled I or H-section with welded flange cover plates (as shown in table 26(b))

Welded box section (see note 3 and 4.7.5)

Round, square or flat bar

Rolled angle Rolled channel or T-section Two rolled sections laced or battened Two rolled sections back-to-back Compound rolled sections

NOTE 1. For thicknesses between 4 0 m m and 50 m m the value of p, thicknesses u p t o 4 0 mm and over 4 0 mm.

NOTE 2. For welded plate 1 or H-sections where i t can be guaranteed that the edges of the flanges w i l l only be flamecut, table 27(bl may be used for buckling about the y-y axis for flanges up to 40 mrn th ickrand table 27(cI for flanges over 4 0 m m thick.

NOTE 3. 'Welded box section' includes any box section fabr~cated from plates or rolled sections, provided that all longitudinal welds are near the corners of the section. Box sectlons w i th welded longitudinal stiffeners are not included in this category.

Thickness (see note 11

up to 40 mm over 40 mm




up to 40 mrn over 40 mm

may be taken as the

Axis of buckling

X-X

27(a)

27(a)

27(b) 27k)

27(b) 27(b)

27(b) 2 7 ( ~ )

27(b) 2 7 ( ~ )

27(b) 27(c)

Y -Y

27(a)

27(b)

2 7 ( ~ ) 27(d)

2 7 ( ~ ) 27(d)

27(a) 27b)

27(b) 2 7 ( ~ )

27(b) 27(c)

Buckling about any axis 2 7 ( ~ )

average of the values lo r

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Table 26. Type of section obtained for table 25

(a) Rolled I or H-section

B

?$ 0.25 <- B U < 0.8

fi NOTE. Large outstands may be subject to local buckling, see 3.6.

(b) Rolled I or H-section with welded flange cover plate

.!jqjj U

- > 0.8 B iFj

(c) Welded plate I or H-section

B

5 - B U d 0.25

NOTE. Large ourstands may be subject to local buckling, see 3.6.

-

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- - -- --- - - - - --

BEST COPY AVAILABLE BS 5950 : Part 1 : 1990 Section four

Table 27fa) .

225

struts

325

325 322 318 315 310

305 303 301 299 296

293 291 287 284 281

277 273 268 264 259

254 248 243 237 231

225 219 213 207 200

195 189 183 177 172

Compressive

245

245 244 241 239 236

233 231 230 228 227

225 223 222 220 218

216 214 211 209 206

204 201 198 194 191

188 184 181 177 173

169 166 162 158 154

15 20 25 30 35

40 42 44 46 48

50 52 54 56 58

60 62 64 66 68

70 72 74 76 78

80 82 84 86 88

90 92 94 96 98

410

409 405 400 395 389

382 378 375 371 367

363 358 353 347 341

335 328 320 312 304

295 287 278 269 260

251 243 234 226 218

211 203 196 190 183

225 225 222 220 217

214 213 212 210 209

208 206 205 203 201

200 198 196 194 192

189 187 184 182 179

176 173 170 167 164

161 158 154 151 147

255

255 254 251 248 245

242 240 239 237 236

234 232 230 228 226

224 221 219 216 213

210 207 204 200 197

193 189 185 181 177

173 169 165 161 157

335

335 332 328 324 320

315 312 310 307 305

302 299 295 292 288

284 280 275 270 265

259 253 247 241 235

229 222 216 209 203

197 191 185 179 173

415

414 410 405 399 393

386 383 379 375 371

367 362 366 350 344

337 330 322 314 306

297 288 279 270 261

252 243 235 226 218

211 203 196 189 183

355

355 351 347 343 338

333 330 327 325 322

318 315 311 307 303

298 293 288 282 276

270 264 256 249 242

235 228 221 214 208

201 194 188 182 176

340

340 337 333 329 324

319 317 314 312 309

306 303 299 296 292

288 283 278 273 268

262 256 250 243 237

230 224 217 211 204

198 192 186 do 114

1

395

394 390 386 381 375

368 365 362 359 355

351 346 342 336 331

325 318 311 304 296

288 280 272 264 255

247 239 231 223 215

208 201 194 187 181

430

429 424 419 414 407

399 396 392 388 383

379 373 367 361 354

347 339 331 322 313

303 294 284 275 265

256 247 238 229 221

213 206 198 191 185

strength,^,,

265

265 264 261 258 254

251 249 248 246 244

242 241 238 236 234

232 229 226 223 220

217 214 210 206 202

198 194 190 186 181

177 173 168 164 159

~ / m m ' )

305

305 303 299 296 292

287 285 283 281 279

277 274 271 268 265

262 259 255 251 247

242 237 233 227 222

217 211 206 200 195

189 184 179 173 168

450

448 444 438 432 425

417 413 409 404 399

394 388 381 374 366

358 349 340 330 320

310 299 289 279 269

259 250 240 231 223

215 207 200 192 186

( in

275

275 273 270 267 264

260 258 257 255 253

251 249 247 244 242

239 236 234 230 227

224 220 216 212 208

203 199 194 190 185

180 176 171 166 162

for

320

320 317 314 310 306

301 299 297 294 292

289 286 283 280 277

273 269 265 261 256

251 246 240 235 229

223 217 211 205 199

193 188 182 176 171 SGK

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Table 27 (a)

100 102 104 106 108

110 112 114 116 118

120 122 124 126 128

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220 230 240 250

260 270 280 290 300

310 320 330 340 350

(concluded}

245

150 146 142 139 135

132 128 125 121 118

115 112 109 106 104

101 95 89 84 79

74 70 66 63 59

56 54 51 49 46

42 39 35 33 30

28 26 24 23 21

20 19 18 17 16

225

144 141 137 134 131

127 124 121 118 115

112 109 107 104 101

99 93 87 82 78

73 69 65 62 59

56 53 51 48 46

42 38 35 33 30

28 26 24 23 21

20 19 18 17 16

340

169 163 158 153 149

144 140 135 131 127

124 120 117 113 110

107 100 94 88 82

77 7 3 " 69 65 61

58 55 53 50 48

43 40 36 33 31

29 27 25 23 22

20 19 18 17 16

395

175 169 163 158 153

148 143 139 135 130

127 123 119 116 112

109 102 95 89 83

78 74 70 66 62

59 56 53 50 48

44 40 37 34 31

29 27 25 23 22

20 19 18 17 16

355

1.71 165 160 155 150

145 141 136 132 128

125 121 117 114 111

108 101 94 88 83

78 73 69 65 62

58 55 53 50 48

43 40

3.G 3 31

\ ',29

27 25 23 22

20 19 18 17 16

255

153 149 145 141 137

133 130 126 123 120

116 113 110 107 105

102 96 90 84 79

75 70 67 63 60

57 54 51 49 47

42 39 36 33 30

28 26 24 23 21

20 19 18 17 16

275

157 153 149 145 141

137 133 129 125 122

119 115 112 109 106

103 97 91 85 80

75 71 67 64 60

57 54 52 49 47

43 39 36 33 30

28 26 24 23 21

20 19 18 17 16

265

155 151 147 143 139

135 131 128 124 121

118 114 111 108 105

103 96 90 85 80

75 71 67 63 60

57 54 51 49 47

42 39 36 33 30

28 26 24 23 21

20 19 18 17 16

305

163 158 154 149 145

140 136 132 129 125

121 118 115 111 108

105 98 92 86 81

76 72 68 64 61

58 55 52 49 47

43 39 36 33 31

28 26 25 23 21

20 19 18 17 16

410

176 170 165 159 154

149 144 140 135 131

127 123 120 116 113

110 102 95 89 84

79 74 70 66 62

59 56 53 51 48

44 40 37 34 31

29 27 25 23 22

20 19 18 17 16

430

178 172 166 160 155

150 145 141 136 132

128 124 120 117 113

110 103 96 90 84

79 74 70 66 62

59 56 53 51 48

44 40 37 34 31

29 27 25 23 22

20 19 18 17 16

415

177 171 165 159 154

149 144 140 135 131

127 123 120 116 113

110 102 96 89 84

79 74 70 66 62

59 56 53 51 48

44 40 37 34 31

29 27 25 23 22

20 19 18 17 16

450

179 173 167 161 156

151 146 141 137 133

129 125 121 117 114

111 103 96 90 89

79 74 70 66 63

59 56 53 51 48

44 40 37 34 31

29 27 25 23 22

21 19 18 17 16

320

166 161 156 151 146

142 138 134 130 126

122 119 116 112 109

106 99 93 87 82

77 72 68 65 61

58 55 52 50 47

43 39 36 33 31

29 27 25 23 22

20 19 18 17 16

325

167 161 156 152 147

143 138 134 130 126

123 119 116 113 109

106 99 93 87 82

77 72 68 65 61

58 55 52 50 47

43 39 36 33 31

29 27 25 23 22

20 19 18 17 16

335

168 163 158 153 148

144 139 135 131 127

123 120 116 113 110

107 100 93 87 82

77 73 69 65 61

58 55 52 50 48

43 40 36 33 31

29 27 25 23 22

20 19 18 17 16

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340

340 334 328 321 313

305 302 298 294 291

286 282 278 273 268

263 258 252 247 241

235 230 224 218 212

206 200 195 189 183

178 173

,168 3 158

I 1 5 3 149 144 140 136

struts

325

325 320 314 307 300

293 289 286 283 279

275 271 267 263 258

254 249 244 239 233

228 223 217 212 206

201 196 190 185 180

175 170 165 160 155

151 146 142 138 134

Table 27(b).

335

335 330 323 316 309

301 298 294 291 287

283 278 274 269 265

260 255 249 244 239

233 227 222 216 210

204 199 193 188 182

177 172 167 162 157

152 148 144 139 135

Compressive

245

245 243 239 234 229

224 222 220 218 215

213 210 208 205 202

200 197 194 191 188

185 181 178 175 171

168 164 161 157 154

150 147 143 140 137

133 130 127 124 121

15 20 25 30 35

40 42 44 46 48

50 52 54 56 58

60 62 64 66 68

70 72 74 76 78

80 82 84 86 88

90 92 94 96 98

100 102 104 106 108

355

355 349 342 335 327

318 314 310 306 302

298 293 288 283 278

272 266 261 255 249

242 236 230 223 217

211 205 199 193 187

181 176 171 165 160

155 151 146 142 138

225

225 224 220 216 211

207 205 203 201 199

197 195 192 190 188

185 183 180 178 175

172 169 167 164 161

158 155 152 149 146

143 139 136 133 130

127 124 122 119 116

255

255 253 248 243 238

233 231 228 226 223

221 218 215 213 210

207 204 200 197 194

190 187 183 180 176

172 169 165 161 158

154 150 147 143 139

136 132 129 126 123

395

394 387 379 371 361

351 347 342 337 332

327 321 315 309 302

295 288 281 274 267

259 252 244 237 230

222 215 209 202 195

189 183 177 171 166

161 156 151 146 142

410

409 401 393 384 374

364 359 354 349 343

337 331 325 318 311

304 296 289 281 273

265 257 249 241 234

226 219 212 205 198

192 185 179 173 168

162 157 152 148 143

strength,p,,

265

265 263 258 253 247

241 239 237 234 231

229 226 223 220 217

214 210 207 203 200

196 193 189 185 181

177 173 169 165 161

157 153 150 146 142

138 135 131 128 125

415

413 406 397 389 379

368 363 358 352 347

341 334 328 321 314

306 299 291 283 275

267 259 251 243 235

227 220 213 206 199

192 186 180 174 168

163 158 153 148 143

430

428 420 411 402 392

380 375 369 364 358

351 349 337 330 322

314 306 298 289 281

272 264 255 247 239

231 223 216 208 201

195 188 182 176 170

164 159 154 149 144

450

447 439 430 420 409

396 391 385 379 372

365 358 350 342 333

325 316 307 298 288

279 270 261 252 244

235 227 219 212 204

197 191 184 178 172

166 161 156 151 146

(in

275

275 272 267 262 256

250 248 245 242 239

237 234 230 227 224

221 217 213 210 206

202 198 194 190 186

181 177 173 169 165

161 156 152 148 145

141 137 133 130 126

~ / m r n ' )

305

305 301 295 289 283

276 273 270 267 263

260 256 253 249 245

241 236 232 227 223

218 213 208 204 199

194 189 184 179 174

169 165 160 156 151

147 143 139 135 131

for

320

320 315 309 303 296

288 285 282 279 275

271 267 263 259 255

250 246 241 236 231

226 220 215 210 205

199 194 189 183 178

173 168 164 159 154

150 146 141 137 133

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Table 27(b)

110 112 114 116 118

120 122 124 126 128

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220 230 240 250

260 270 280 290 300

310 320 330 340 350

(concluded)

245

118 115 112 109 106

104 101 99 96 94

92 86 81 77 72

69 65 61 58 56

53 50 48 46 44

40 37 34 31 29

27 25 23 22 21

19 18 17 16 15

225

113 111 108 105 103

100 98 96 94 91

89 84 79 75 71

67 64 60 57 55

52 49 47 45 43

39 36 33 31 29

27 25 23 22 20

19 18 17 16 15

255

120 117 114 111 108

105 103 100 97 95

93 87 82 78 73

69 66 62 59 56

53 51 48 46 44

40 37 34 31 29

27 25 23 22 21

19 18 17 16 15

335

131 128 124 121 117

114 111 108 105 102

99 93 87 82 77

73 69 65 61 58

55 53 50 48 46

42 38 35 32 30

28 26 24 22 21

20 18 18 17 16

355

134 130 126 122 119

116 112 109 106 103

101 94 88 83 78

73 69 66 62 59

56 53 51 48 46

42 38 35 32 30

28 26

- 2 4 e 3 ' 21

18 17 16

340

132 128 125 121 118

114 111 108 105 102

100 93 88 82 77

73 69 65 62 58

55 53 50 48 46

42 38 35 32 30

28 26 24 22 21

2 0 1 2 0 1 8 ' 1 9 18 17 16

265

121 118 115 112 109

107 104 101 99 96

94 88 83 78 74

70 66 63 59 56

54 51 48 46 44

40 37 34 31 29

27 25 24 22 21

19 18 17 16 15

395

137 133 129 125 122

118 115 112 109 106

103 96 90 84 79

75 70 66 63 59

56 54 50 48 46

42 39 35 33 30

28 26 24 23 21

20 19 18 17 16

275

123 120 117 114 111

108 105 102 100 97

95 89 84 79 74

70 66 63 60 57

54 51 49 47 44

41 37 34 32 29

27 25 24 22 21

19 18 17 16 15

410

139 134 130 126 123

119 116 112 109 106

103 96 90 85 80

75 71 67 63 60

57 54 51 49 46

42 39 35 33 30

28 26 24 23 21

20 19 18 17 16

305

128 124 121 117 114

111 108 105 103 100

97 91 86 81 76

72 68 64 61 58

55 52 49 47 45

41 38 35 32 29

27 26 24 22 21

20 18 17 16 15

415

139 135 131 127 123

119 116 113 110 106

104 97 91 85 80

75 71 67 63 60

57 54 51 49 46

42 39 35 33 30

28 26 24 23 21

20 19 18 17 16

320

130 126 123 119 116

113 110 107 104 101

98 92 87 81 77

72 68 65 61 58

55 52 50 47 45

41 38 35 32 30

28 26 24 22 21

20 18 17 16 15

430

140 136 132 128 124

120 117 113 110 107

104 97 91 85 80

75 71 67 63 60

57 54 51 49 47

42 39 36 33 30

28 26 24 23 21

20 19 18 17 16

325

130 127 123 120 116

113 110 107 104 101

99 93 87 82 77

72 68 65 61 58

55 52 50 48 45

41 38 35 32 30

28 26 24 22 21

20 18 17 16 15

450

141 137 133 129 125

121 118 114 111 108

105 98 92 86 81

76 71 67 64 60

57 54 52 49 47

43 39 36 33 30

28 26 24 23 21

20 19 18 17 16

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I Table 27(cl. Compressive rtrength,~., (in ~ l r n m ' ) for struts

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I Table 27(dl. Compressive strength,p,, (in ~ / r n m ' ) for struts

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340

108 105 103 100 97

95 93 90 88 86

84 79 74 70 66

63 60 57 54 51

49 46 44 42 41

37 34 32 29 27

25 24 22 21 19

18 17 16 15 14

Table 27(d)

110 112 114 116 118

120 122 124 126 128

130 135 140 145 150

155 160 165 170 175

180 185 190 195 200

210 220 230 240 250

260 270 280 290 300

310 320 330 340 350

355

110 107 104 102 99

96 94 92 89 87

85 80 75 71 67

64 60 57 54 52

49 47 45 43 41

37 34 32 29 27

25 24

, 22 'gl '20

:!I8 17 16 15 15

(concludedl

245

93 90 88 86 84

83 81 79 77 75

74 70 66 63 59

57 54 51 49 47

45 42 41 39 37

34 32 29 27 25

24 22 21 20 18

17 16 15 15 14

225

88 86 84 83 81

79 77 76 74 72

71 67 64 60 58

55 52 50 47 45

43 42 40 38 36

34 31 29 27 25

23 22 20 19 18

17 16 15 14 14

265

96 94 92 90 88

86 84 82 80 78

76 72 68 65 61

58 55 53 50 4%

46 43 42 40 38

35 32 30 28 26

24 23 21 20 19

18 17 16 15 14

255

95 92 90 88 86

84 82 81 79 77

75 71 67 64 61

58 55 52 50 47

45 43 41 40 38

35 32 30 28 26

24 23 21 20 19

18 17 16 15 14

275

98 96 94 91 89

87 85 83 81 79

77 73 69

66 62

59 56 53 51 48

46 44 42 40 39

35 33 30 28 26

24 23 21 20 19

18 17 16 15 14

395

115 112 109 106 103

100 97 95 93 90

88 83 78 73 69

65 62 59 56 53

50 48 46 44 42

38 35 32 30 28

26 24 23 21 20

19 18 17 16 15

430

118 115 112 109 106

103 100 97 95 93

90 85 80 75 71

67 63 60 57 54

51 49 47 44 42

39 36 33 30 28

26 24 23 21 20

19 18 17 16 15

450

120 117 113 110 107

104 102 99 96 94

91 86 81 76 71

67 64 60 57 54

52 49 47 45 43

39 36 33 30 28

26 24 23 21 20

19 18 17 16 15

410

116 113 110 107 104

102 99 96 94 92

89 84 79 74 70

66 63 59 56 54

51 48 46 44 42

39 35 33 30 28

26 24 23 21 20

19 18 17 16 15

415

117 114 110 107 105

102 99 96 94 92

89 84 79 74 70

66 63 59 56 54

51 48 46 44 42

39 35 33 30 28

26 24 23 21 20

19 18 17 16 15

305

103 101 98 96 93

91 89 87 84 83

81 76 72 68 64

61 58 55 52 50

47 45 43 41 40

36 33 31 29 27

25 23 22 20 19

18 17 16 15 14

325

106 103 101 98 96

94 91 89 87 85

83 78 74 70 66

62 59 56 53 51

48 46 44 42 40

37 34 31 29 27

25 24 22 21 19

18 17 16 15 14

320

105 103 100 98 95

93 91 88 86 84

82 77 73 69 65

62 59 56 53 50

48 46 44 42 40

37 34 31 29 27

25 23 22 21 19

18 17 16 15 14

335

108 105 102 99 97

94 92 90 88 85

83 79 74 70 66

63 59 56 54 51

48 46 44 42 40

37 34 31 29 27

25 24 22 21

-19

18 17 16 15 14

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4.7.6 Eccentric connections

Moments due to eccentricity of connections should be calculated and allowed for in design in accordance with 4.8 except as follows.

(a) Columns in simple construction. The eccentricity of . the beam end reactions or other loads should be as follows.

(1) For a beam supported on the cap plate, the load should be taken as acting at the face of the column, or edge of packing if used, towards the span of the beam.

(2) For a roof truss supported on the cap plate, eccentricity may be neglected provided simple connections are used which do not develop significant moments adversely affecting the structure.

(3) In all other cases the load should be taken as acting at a distance from the face of the steel column equal to 100 mm, or at the centre of the length of stiff bearing whichever gives the greater eccentricity.

(b) Laced, battenedstruts and batten-starred angle struts. These may be treated as single integral members and designed as axially loaded struts in accordance with 4.7.8,4.7.9 and 4.7.11 respectively.

1 (c) Angles, channels and T-sections. The effect of eccentric end connections may be neglected and the members designed in accordance with 4.7.10.

(d) Continuous construction. This should be in accordance with section five.

4.7.7 Columns in simple construction

In structures of simple construction i t is not necessary to consider the effect on columns of pattern loading. For the purpose of column design, all beams supported by a column at any one level may be assumed to be fully loaded. The nominal moments applied to the column by simple beams should be calculated from the eccentricities given in 4.7.6(a). Moments due to partial fixity in semi-rigid design should be added (see 2.1.2.4).

In multi-storey columns which are effectively continuous at their splices, the net moment applied at any one level should be divided between the column lengths above and below that level in proportion to the stiffness, I IL, of each length, except that when the ratio of the stiffnesses does not exceed 1.5 the moment may be divided equally.

The nominal moments applied to the column (including any

I restraint moments from 2.1.2.4(b)) may be assumed to have no effect at the levels above and below the level at which they are applied.

I Whenonly nominal moments are applied, the column should satisfy the following relationship:

where

F , is the compressive force due to axial load: P, is the compressive strength;

A, i s the gross cross-sectional area;

M, i s the nominal moment about the major axis;

My is the nominal moment about the minor axis;

Mbs is the buckling resistance moment for simple columns;

ZY i s the elastic modulus about the minor axis;

p, is the design strength.

The buckling resistance moment for simple columns M b s should be taken as the value of Mb determined as descr~bed in 4.3.7.3 and 4.3.7.4 but using the equivalent slenderness hLT of the column given by:

= 0.5 (Llr,)

where L is the distance between levels at which both axes

are restrained;

ry i s the radius of gyration about the minor axis.

NOTE. For circular hollow sections and for box sections of uniform wall thickness, including RHS,within the limits given in 8.2.6.1. Mb, equalspyS,.

4.7.8 Laced struts

A laced strut consisting of two or more main components may be designed as a single integral member, provided that the following conditions are met.

(a) The main components are effectively restrained against buckling by a lacing system of flats or sections.

(b) The lacing comprises an effectively triangulated system on each face and as far as practicable the lacing should not vary throughout the length of the member.

(c) Except for the panels referred to in (f), double intersection lacing systems and single intersection lacing systems mutually opposed in direction on opposite sides of two main components should not be combined with members or diaphragms perpendicular to the longitudinal axis of the strut unless all forces resulting from the deformation of the strut members are calculated and allowed for in the design.

(d) Single lacing systems mutually opposed in direction on opposite sides of two main components should not be ~sed~unless the resulting torsional effects are allowed for. !" (e) All lacings, whether in double or single intersection sysths, should be inclined at an angle between 40 O

and M " to the axis of the member.

(f) Tie panels should be provided at the ends of the lacing systems, at points where the lacing is interrupted, and at connections with other members.

Tie panels may take the form of battens complying with 4.7.9; alternatively cross braced panels of equivalent rigidity may be used.

In either case the tie panels should be designed to carry the loads for which the lacing system is designed.

(g) The maximum slenderness, A,, of a main component (based on its minimum radius of gyration) between consecutive points where the lacing is attached should not exceed 50. The maximum slenderness of the strut as a whole should not be taken as less than 1.4XC.

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(h) The effective length of a lacing should be taken as the distance between the inner end welds or fasteners for single intersection lacing and as 0.7 times this distance for double intersection lacing connected by welds or fasteners at the intersection. The slenderness of a lacing should not exceed 180.

( i) The lacings and their connections should be designed to carry the forces induced by a transverse shear a t any point in the length of the member equal to not less than

1 2.5 % of the maximum axial load in the member,divided equally amongst all transverse lacing systems in parallel planes. For members carrying bending stresses calculated from eccentricity of loading, applied end moments or lateral loading, the lacing should be proportioned to resist any shear due to bending in addition to the above

I mentioned value of not less than 2.5 %.

4.7.9 Battened struts

A battened strut consisting of two or more main components may be designed as a single integral member, provided that the following conditions are met.

(a) The main components are effectively restrained against buckling by a system of battens consisting of plates or sectiorls, so connected to the main components as to form with them an effectively rigid jointed frame.

(b) Battens are positioned opposite each other in each plane at the ends of the member and at points where it is laterally restrained. Intermediate battens should be

point in the length of a member equal to not less than 2.5 % of the maximum factored axial load in the member. I For members carrying bending stresses calculated from eccentricity of loading, applied end moments or lateral loads, the battens should be proportioned to resist any shear due to bending in addition to the above mentioned value of not less than 2.5 %.

NOTE For battened angle members see 4.7.11 or 4.7.12 as approprtate.

4.7.10 Angles, channels and T-section struts I 4.7.10.1 General. For struts composed of angles, channels and T-sections, the eccentricity of normal end connections may be ignored and the strut designed as an axially loaded member provided that the conditions of 4.7.10.2 to 4.7.10.5 are met.

Alternatively, in the internal bays of continuous struts, such as those forming the legs of towers or the compression flanges of lattice girders, the effective length may be determined from 4.7.2 and table 24.

The length L should be taken as the distance between the intersection of centroidal axes or the intersections of the setting out lines of the bolts, and r is the radius of gyration about the releuant axis. Axes are defined in table 28.

lntermediate restraints may be allowed for in determining the relevant length L for buckling about each axis, provided they lie at an angle of not more than 45 O to the plane of buckling considered.

- - - I - -*-uts. For a single angle connected lusser, or directly to another member, by:

(C) T~~ slenderness, of a main component (a ) two or more fasteners in line along the angle at each

(based on its radius of between end end or by an equivalent welded connection, the slender-

welds or end fasteners of adjacent battens should not ness X should be taken as the greatest of:

exceed 50. The slenderness of the battened strut, A,, 1 0.85Lvv/rvv but 2 0.7Lvvlrvv + 15;

about the axis perpendicular to the plane of the battens 2 1 0 L a a / r a but 2 0.7Laalraa + 30; should be calculated from: (31 0.85Lbb/rbb but 2 0.7Lbb/rbb + 30;

X, = (A,' + hC2)'/2 (b) a single fastener at each end. the compression where

A, is the ratio LE/f of a whole member about that axis;

A, isasdefined above.

The maximum slenderness of the battened strut about

1 the axis perpendicular to the plane of the battens should not be taken as less than 1 .4Ac.

(d) The thickness of plate battens should be not less than 1/50 of the minimum distances between welds or fasteners. The slenderness of sections used as battens should not exceed 180. The width of an end batten along the axis of the main components should be not less than the distance between centroids of thd main members and not less than half this distance for intermediate battens. Further, the width of any batten should be not less than twice the width of the narrower main component.

(el The battens and the connections between them and the main components should be designed to carry the forces and moments induced by a transverse shear at any

resistance should be taken as 80 % of the compression resistance of an axially loaded member and the slenderness X should be $ken as the greatest of:

(1 1 l.OLvv/r but 2 0.7 LVv/r,, + 15; Y

(2) l.OLaa/r+ but 2 0.7 Laa/raa + 30;

(3) l.OLbb/fbb but > 0.7Lbb/rbb + 30;

4.7.10.3 Double angle struts. For double angle struts interconnected back-to-back as recommended in 4.7.13 or battened as recommended in 4.7.12 and connected a t each end by one leg of each angle to a gusset, or directly to another member, as follows:

(a) to one side of a gusset or member at each end by two or more fasteners in line along each angle or by an equivalent weld, the slenderness X should be taken as the greater of:

(11 l .OLxx/rxx but 2 0.7Lxx/rXx + 30;

(2) [ ( 0 . 8 5 ~ , ~ / r ~ ~ ) ~ + Xc2]%but > 1.4Ac;

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BEST COPY AVAILABLE

(b) to one side of a gusset or member at each end by one fastener in each angle, the slenderness A should be taken as the greater of:

(11 l .OLxx/rxx but 2 0.7Lxx/rxx + 30;

(2) [ ( l . O ~ , , ~ / r ~ ~ ) ~ + Ac2 1% but 2 1.4Ac;

(c ) to both sides of a gusset or member a t each end by two or more fasteners in line along the angles, the slenderness A should be taken as the greater of :

(1) 0.85Lxx/rxx but 2 0.7Lxx/rxx + 30;

(2) [ ( ~ ~ , , / r ~ ~ ~ * f AC2]% but 2 1.4Ac;

(d) to both sides of a gusset or member at each end by a single fastener through each angle, the compression resistance should be taken as 80 % of the compression resistance of an axially loaded member and the slenderness A should be taken as the greater of:

(1) l .OLxx/rxx but 2 0.7Lxx/rxx + 30;

(2) [(~,~/r,,)~ + kc2 1% but 2 1 .4~,;

In (a) to (d) A, = Lvv/rvv with L,, measured between interconnecting fasteners for back-to-back struts or between end welds or end fasteners of adjacent battens for battened angle struts.

4.7.10.4 Single channel struts. For a single channel connected only by its web to a gusset, or directly to another member, by:

(a) two or more rows of fasteners arranged symmetrically across the web at each end, or an equivalent welded connection, the slenderness X should be taken as the greater of:

(1 1 0.85Lxx/rxx;

(2) l.OL,v/rv, but 2 0.7Lyy/ryy + 30;

(b) two or more fasteners arranged symmetrically in a single row across the web at each end, or an equ~valent welded connection, the slenderness A should be taken as the greater of :

(1 1 1 .OLxx/rxx;

(2) 1 .OL,,/r,, but 2 0.7L,,/r,, + 30;

4.7.10.5 Single T-section struts. For a single T-section connected only by its flange to a gusset, or directly to another member, by:

(a) two or more rows of fasteners arranged symmetrically across the flange at each end, or an equivalent welded connection. the slenderness A should be taken as the greater of:

(1) l .OLxx l rxx but 2 0.7Lxx l rxx + 30;

(2) 0.85L,,lr,,;

(b) two or more fasteners arranged symmetrically in a single row across the flange a t each end, or an equivalent welded connection, the slenderness A should be taken as the greater of:

(1) l .OLxx/ fxx but > 0.7Lx,/rxx t 30;

(2) 1 .OLv,/rvv;

4.7.1 1 Batten-starred angle struts

A battened strut of cruciform section may be designed as a single integral member provided that i t meets the cond~tions given in 4.7.9 except as follows.

(a) Battens should be connected to the backs of angles parallel to both the rectangular axes of the member. They should alternate in each plane and the effective length of a main component should be taken as the spacing centre-to.centre of the battens in the same plane

(b) The transverse shear of not less than 2.5 % of the I factored axial load should be taken as acting perpendicular to the minor axis of the member. The battens in each plane should be designed for the components of this shear resolved perpendicular to the rectangular axes plus any transverse shear due to the weight or wind resistance of the member.

4.7.12 Battened parallel angle struts

A battened parallel angle strut composed of two similar angles arranged symmetrically with their corresponding rectangular axes aligned may be designed as a single integral member providing that in all other respects i t meets the conditions given in 4.7.9.

The eccentricity of end connections should be allowed for as recommended in 4.7.10.3. 1 4.7.1 3 Back-to-back struts

4.7.13.1 Components separated. A strut composed of two angles, channels or T-sections, separated back-to-back by a distance not exceeding that required for the end gusset connection, may be designed as a single integral member provided the following conditions are met.

(a) The main components should be of similar cross section with their corresponding rectangular axes aligned.

(b) The main components should be interconnected by fasteners. Where the components are connected together by welding the member should be designed as a battened strut as given in 4.7.9.

(c) The member should not be subjected to transverse loads perpendicular to the connected surfaces other than the w e w t or the wind resistance of the member.

(d) The slenderness, A, of the compound strut about the $cis parallel to the connected surfaces should be calculated from 4.7.9(c) for battened struts.

(e) The main components should be connected at intervals so that the member is divided into at least three bays of approximately equal length. At the ends of the member the main components should be interconnected by not less than two fasteners along each line along the length of the member.

(f) The interconnecting fasteners should be designed to transmit the longitudinal shear between the main components induced by a transverse shear Q a t any point in the member; O should be taken as not less than 2.5 % of the factored axial compression in the member plus any load due to self weight or wind resistance of the member. In no case should the fasteners be less than 16 mm in diameter.

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I Connection Sections and axes Slenderness ratios (see not= 1 and 2 )

x x axis: 0.85Lxx/rxx

yy axis: 1.OLyy l rYy but20.7L, , l ryy + 30

~~

x x axis: 1 . O L x x l r x x

yy axis: l . O L y Y / r Y y but > 0 . 7 L y y / r Y y + 30

xx axis: l . O L x x l r x x but 2 0 . 7 L x x l r x x + 30

yy axis:0.85L Yy/ryy

x x axis: l . O L x x l r x x but > 0 . 7 L x x l r x , + 30

yy axis: l .OLyy/ry,

- -

NOTE 1. The length L is taken between the intersectlons of the centroidal axes or the intersectlons of the setting out lines of the bolts, irrespective o f whether the strut is connected to a gusset or directly t o another member.

I NOTE 2. Intermediate lateral restraints reduce the value of L for buckling about the relevant axes. For single angle members, L, is taken between lateral restraints perpendicular t o either aa or bb.

NOTE 3. For s~ngle or double angles connected b y one bolt, the compression resistance is also reduced t o 80 % o f that for an axially loaded member, see 4.7.10.2(b) and 4.7.10.3(dj.

NOTE 4. Oouble angles are either bartened (see 4.7.121 or interconnected back-to-back (See 4.7.13). Battens or interconnecting fasteners are also needed at the ends of members.

NOTE 5. & = Lvvlrvv wl th L v v measured between ~nrerconnecting fasteners for back-to.back struts or between end welds or end fasteners of adlacent battens for battened angle struts.

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The longitudinal shear per interconnection should be taken as 0.25QXc, where A, i s the slenderness of the main component centre-to-centre of interconnections.

(g) At all interconnections the fasteners should pass through solid steel packings, washers or gussets. In struts at least two fasteners should be provided in line across the width of all members that are sufficiently wide to accommodate them.

4.7.13.2 Components in contact. A strut composed of two angles, channels or T-sections in contact back-to-back or separated by continuous steel packing may be designed as a single integral member providing that the following conditions are met.

(a) The main components should be similar sections arranged symmetrically with their corresponding rectangular axes aligned.

(b) Interconnection should be as follows.

(1) When interconnection i s by means of fasteners at least two fasteners should be provided in line across the width of the member providing it is sufficiently wide. The spacing of the fasteners should not exceed 300 mm or 32t where r is the thickness of the thinner part joined.

(2) When interconnection is by means of welds both pairs of edges of the main components should be welded. The spacing centre-to-centre of interconnections should be taken as the spacing centre-to-centre of consecutive effective lengths of weld on the same edge. The space between consecutive welds on the same edge should not exceed 300 mm or 16r where t is the minimum thickness of the parts joined.

(c) The member should not be subject to transverse load perpendicular to the connected surfaces other than the weight or wind resistance of the member.

(d) The slenderness, A, of the compound strut about the axis parallel to the connected surfaces should be

I calculated from 4.7.9(c).

(e) The main components should be connected at intervals so that the member i s divided into at least three bays of approximately equal length. At the ends of the member the main components should be interconnected by not less than two fasteners in each line along the length of the member, or by equivalent welds.

(f) The interconnecting welds or fasteners should be designed to transmit the longitudinal shear between the components as given in 4.7.13.1 (f).

(g) In members exposed to the weather or other corrosive influences the components should be connected by continuous welds, or fasteners as laid down in 6.2.4.

4.8 Axially loaded members with moments 4.8.1 General

Members should comply with 4.2 to 4.7 inclusive, covering the treatment of members subject to moments and axial loads applied separately. in addition to the recommendations given in 4.8.2 and 4.8.3.

Moments in angle, channel and T-section members due to eccentricity of connections may be treated as recommended in 4.6.3 for tension members or 4.7.10 for struts.

4.8.2 Tension members with moments

Tension members with moments should be checked for resistance to lateral-torsional buckling in accordance with 4.3 under moment alone. They should also be checked for capacity under the combined effects of axial load and moment a t the points of greatest bending moments and axial loads, usually at the ends.

The following relationship should be satisfied:

where

F is the applied axial load in member;

A, i s the effective area (see 3.3.3);

p, is the design strength;

M, is the applied moment about the major axis at critical region;

M,, i s the moment capacity about the major axis In the absence of axial load (see 4.2.5 and 4.2.6);

M, is the applied moment about the minor axls at critical region;

M,, i s the moment capacity about the minor axis in the absence of axial load (see 4.2.5 and 4.2.6).

Alternatively for greater economy in plastic or compact cross sections only the following relationship should be satisfied.

where

M,, i s the reduced moment capacity about the major axis in the presence of axial load obtained from published tables;

Mrv is the reduced moment capacity about the minor axis in the pr ence of axial load obtained from published t a 8' es;

I, is a constaqt taken as:

2.0 for I arid H sections; 2.0 for solid and hollow circular sections; 513 for solid and hollow rectangular sections; 1.0 for all other cases.

z 2 is a constant taken as:

1.0 for I and H sections; 2.0 for solid and hollow circular sections; 513 for solid and hollow rectangular sections; 1.0 for all other cases.

4.8.3 Compression members with moments

4.8.3.1 General. Compression members should be checked for local capacity at the points of greatest bending moment and axial load (usually at the ends). This capacity may be limited either by yielding or local buckling depending on the section properties. The member should also be checked

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for overall buckling by either the simplified or more exact approach.

4.8.3.2 Localcapacity check. The appropriate relationship given below should be satisfied.

(a) For semi-compact and slender cross sections (and as

I an alternative simplified approach for plastic or compact cross sections):

F M M -+.+Y<1 A,Pv Mcx Mcy

NOTE. For slender cross sectlons a reduced effective value of p y should be used in accordance w ~ t h 3.6.

(b) For plastic and compact cross sections:

where for (a) and (b) Ag is the gross cross-sectional area and other notations are as given in 4.8.2.

4.8.3.3 Overall buckling check

4.8.3.3.1 Simplified approach. The following relationship should be satisfied:

where . .

F is the applied axial load in the member;

pC i s the compressive strength;

A, i s the gross cross-sectional area;

where

Mcx i s the moment capacity about the major axis obtained from 4.2.5 or 4.2.6;

MCv is the moment capacity about the minor axis obtained from 4.2.5 or 4.2.6 but not subject to the restriction Mc < 1.2p,Z;

PC, is the compression resistance about the major axis;

PC, i s the compression resistance about the minor axis.

NOTE. In cases where M, or My approaches zero the more exact approach may be more conservative than the simplified approach. In such situations the values satisfying the simplified approach may be used.

4.9 Members with biaxial moments Members subject to biaxial moments in the absence of both tensile and compressive axial forces may be designed in accordance with the rules given in 4.8.3, with the value of F taken as zero.

4.10 Empirical design rules for members in lattice frames and trusses This clause i s applicable to the design of lattice frames and trusses except where fatigue is a design consideration.

Generally it may be assumed that secondary stresses will be insignificant i f the slenderness of the chord members

m is the equivalent uniform moment factor obtained in the plane of the truss i s greater than 50 and that of most

from table 18; of the web members i s greater than 100.

M, is the buckling resistance moment capacity (about The following assumptions may be made. major axis) (see 4.3.7); (a) For the purpose of calculating the forces in the

Z, is the elastic section modulus about the minor axis; member the connections are pinned.

pY i s the design strength. (b) For the purpose of calculating the effective length of members the fixity of the connections and the rigidity

4.8.3.3.2 More exact approach. The following relationship of ad,acent members may be taken into account. should be satisfied.

(c) Where the exact position of point loads relative to mM, mM - + 2 9 1 the connection of the rafter to the web members i s not M a May known%e local bending moment may be taken as equal

where to:

Ma, i s the maximum buckling moment about the major - bIf% axis in the presence of axial load, taken to be the 6 ' lesser of:

F ( 1 - -\

(d) Ties to chords should be properly connected to an adequate restraint system.

(el The length of chord members may be taken as the distance between connection to the web members in plane and the distance between longitudinal ties or purlins out of plane.

M, ( 1 - k) governing lateral/torsional buckling; ( f ) Purlins in light frames and trusses need not be ' C , ' checked for compressive stresses originating from their

Ma, i s the maximum buckling moment about the minor function as restraints. axis in the presence of axial load taken as:

F (g) Where the sheeting spans from truss to truss in the

( 1 - 7) absence of purlins the stability of the rafter should be considered and the sheeting should be adequately fixed. This method of providing restraint to the rafter should only be used where the loading is mainly roof loading. -

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4.1 1 Additional provisions for gantry girders 4.1 1.1 General

lnaddition to thegeneral rules for beams given in 4.2 to 4.5 gantry girders should fulfil the conditions given in 4.1 1.2 to 4.1 1.6.

Gantry girders should be designed to resist factored loading as given in 2.2.3 and 2.4.1.

4.1 1.2 Crabbing of trolley

I , is the second moment of area of the crane rail about its horizontal centroidal axis:

K R is a constant taken as:

(a) when the crane rail is mounted directly on the beam flange K R = 3.25;

(b) where a suitable resilient pad not less than 5 mm thick is interposed between the crane rail and the beam flange K R = 4.0.

The stress obtained by dispersing the load over th~s length should not be greater than p,,

Gantry girders intended to carry cranes of loading class Q l 4.1 Welded girders and Q2 as defined in BS 2573 : Part 1 need not be designed for the effects of crabbing action. Welds should be continuous throughout. Top flange welds

should preferably be full penetration butt welds and should Gantry girders intended carry cranes of class Q3 and O4 be checked for the effects of local compression, see 4.11.5, as defined in BS 2573 : Part 1 should be designed for the in addition to ail other effects. ~t be that following couple due to crabbing action. This couple need this force is wholly transmitted by the welds to the web. not be combined with the horizontal loads obtained from 2.2.3. The couple is due to the crabbing action of two wheels or bogies comprising two equal and opposite forces, 4.12 Purlins and side rails F R , acting transverse to the rail, one a t each end of the wheel base.

4.12.1 General

Purlins and side rails may be designed on the assumption L C Ww F R = - ww

but 2- that the cladding provides lateral restraint to an angle 40aw 20 section, or to the face against which it is connected in the

where case of other sections. In both cases, the type of cladding

LC is the span of the crane; and i t s fixings should be such that it is capable of acting in this manner.

W, is the factored maximum load on a wheel or bogie pivot; 4.1 2.2 Deflections is the distance the centres of the end The deflections of purlins and side rails should be limited to wheels Or between the pivots Of the bogies (where suit the characteristics of the particular cladding system. horizontal guide rails are used a, i s the wheelbase of the guide rails).

4.1 1.3 Lateral torsional buckling

No account should be taken of the effect of moment gradient, i.e. n and m should be taken as 1.0 (see 4.3)

4.1 1.4 Shear buckling

The shear buckling resistance should be calculated without using tension field action (see 4.4.5.3).

4.1 1.5 Local compression under wheels

Local compression on the web may be obtained by distributing the crane wheel load over a length x , where:

X , = 2 ( H R + T)

4.12.3 Wind loading

Wind loading should be determined in accordance with CP 3 : Chapter V : Part 2. The effects of local pressures need not be considered in the design of the purlins and s~de rails.

4.12.4 Empirical design of purlins and side rails C

4.12.4.1 General. As an alternative to other methods of design, purlins and side rails fabricated from hot rolled angles or hollow hctions may be designed in accordance with empirical rules given in 4.12.4.3 or 4.12.4.4. Purl~ns and side rails fabricated from cold formed sections should be designed in accordance with BS 5950 : Part 5. I

where 4.1 2.4.2 General rules for empirical design

HR i s the rail height; (a) The members should be of steel to a minimum of

T i s the flange thickness. design grade 43

Alternatively where the properties of the rail are known: (b) Unfactored loads should be considered for empirical cf : ' R Y design, i.e. effectively -yf = 1 .O.

x R = KR - (c) The span of the members should not exceed 6.5 m centre.to-centre of main supports.

where (d) Where the members generally span only one bay each t is the web thickness; member should be connected by at least two fasteners at

1, is the second moment of area of the flange about ~ t s each end. horizontal centroidal axis; (e) Where the members are generally continuous over

two or more bays, with staggered joints in adjacent lines

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of members, at least one end of any single bay members should be connected by not less than two fasteners.

4.1 2.4.3 Specific rules for the empirical design of purlins

(a) Slope. The slope of the roof should not exceed 30 O .

(b) Loading

(1) The loading on the purlin should be substantially uniformly distributed. Not greater than 10 % of the total roof load on the member should be due to other types of load.

(2) Imposed load should be determined as recommended in 2.2, but should not be taken as less than 0 . 7 5 k ~ l m ' .

(c) Elastic modulus. The elastic modulus, Z, of a purlin about i t s axis parallel to the plane of the cladding should be not less than the values given in table 29.

(d) Dimensions. The dimension D of the member perpendicular to the plane of the cladding, and, where applicable, the dimension B parallel to the plane of the cladding should be not less than the values given in table 29.

4.1 2.4.4 Specific rules for empirical design of side rails

(a) Slope. The slope of the cladding should not exceed 15 O from the vertical.

(b) Loading. Side rails should not generally be subjected to loads other than wind load and the self weight of the cladding. Not more than 10 % of the total load on the member about the axis under consideration should be due to loading from other sources or due to loads which are not uniformly distributed. Notwithstanding the above, side rails may be used to provide restraint to their supporting members.

(c) Section moduli. The elastic section moduli,Z, and Z? , of the side rail about its axes parallel to and perpendicular to the plane of the cladding respectively should be not less than the values given In table 30.

Tabla 29. Empirical values for purlins

(d) Dimensions. The dimension D of the member perpendicular to the plane of the cladding and the dimension B parallel to the plane of the cladding should be not less than the values given in table 30, except that when Z, is greater than the minimum value from table 30, the minimum value of D may be reduced in the same proportion. However, in no case should D be less than B.

of the cladding respectively (in kN).

L is the span of the rail (in mm), taken as:

(a) for 2, and 0 : the span centre-to-centre of maln

Ib) for 2, and 8: the span centre-to-centre of main supports OR where properly supported sag rods are provided, the spacing of the sag rods.

B

mm

L I60

-

Ll150 4.1 3 Column bases

Wp is the total unfactored load on one span of the purlin (in kN) due to either (dead + imposed) or (wind - dead) whichever is the greeter.

L is the length-centre-to-centre of main (vert~cal) supports. but where properly supported sag rods are provided, may be taken as the sag rod spacing for the dererminarron o f B onlv (in mm).

L

D

mm

L I45

L I65

Ll70

Purlin section

Angle

CHS

RHS

4.13.1 General

Z lmin.) ----.

cm3

W,L 1800

WPL 2000

W P L - 1800

Column bases should be of sufficient size, stiffness and strength to transmit the axial load, bending moments and shear for- in columns to their foundations or other support without exceeding the load carrying capacity of such supports.

The nominal bearing pressure between the baseplate and the support may be determined on the basis of a linear distribution of pressure. For concrete foundations the bearing strength may be taken as 0.4fcu where f,, is the characteristic concrete cube strength a t 28 days.

Baseplates may be designed either by the empirical method given in 4.13.2 or by other rational means.

The connection of the column to the baseplate should comply with 4.13.3.

Baseplates of design grade 43Asteel subject to compression only should not be limited in thickness by the brittle fracture requirements. Baseplates of design grade 43A steelnoments 4 transmitting moments ib the foundation should not exceed 50 mm unless special i s given to brittle fracture.

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4.73.2 Empirical design of baseplates

4.13.2.1 Oversized baseplates. When the size of a baseplate is more than the minimum required, any portion of its area may be taken as ineffective, provided that the bearing pressure calculated on the remaining effective area does not exceed the bearing strength.

4.13.22 Concentric forces. I f a rectangular plate i s loaded concentrically by !, H, channel. box or RHS, its minimum thickness should be:.

but not less than the flange thickness of the column supported, where:

a i s the greater projection of the plate beyond the column:

4.13.3 Connection of baseplates

Provided that the contact areas on the baseplate and the end of thecolumn (including, in stiffened bases, the contact surfaces on the stiffeners) are in tight bearing contact, compression may be transmitted to the baseplate in direct bearing. Welds or fasteners should be provided to transmit any shear or tension developed at the connection due to all realistic combinations of factored loads (see 2.2.1 ).

Where the contact surfaces are not suitable to transmit compression in direct bearing, welds or fasteners should be provided to transmit all forces and moments.

4.14 Cased sections 4.14.1 General

As an alternative to the method given in BS 5950 : Section 1 3.2", a section encased in concrete may be designed by the I b is the lesser projection of the plate beyond the empirical method presented in 4.14.2,4.14.3 or 4.14.4 as

column; appropriate,provided that it meets the following conditions.

w i s the pressure on the underside of the plate (a) The steel section i s either a single rolled or fabricated

assuming a uniform distribution; I or H.section with equal flanges or two similar rolled

pvp i s the design strength of the plate (from 3.1.1 or channel sections in contact back-to-back or separated table 6) but not greater than 270 ~ / m m ' . hack.to-back by not less than 20 mm nor more than half

I f gussets are used for transmitting forces to the baseplate, the projecting distances, a and b, are measured from the extremities of the gussets, provided that the gussets are designed for the resulting forces (see 4.13.2.4).

For solid round or hollow columns, where loading on the cap or under the base i s uniformly distributed over the whole area including the column shaft, the minimum thickness (in mm) of a square or circular cap or baseplate should be:

where

0, i s the length of the side or diameter of cap or baseplate, not less than 1.540 + 75) mm;

D i s the diameter of the column.

4.13.2.3 Eccentric forcesand non-rectangularplates. I f the bearing pressure beneath a baseplate is not uniform, or if the baseplate i s not rectangular, calculations should be carried out to determine the bending moments in the baseplate. The maximum moment should not exceed 1.2p,,Z ( p , , < 270 ~ / m m ~ ) whereZis the elastic modulus of the baseplate.

4.13.2.4 Gussets. In a stiffened base, the moment in a gusset due to the bear~ng pressure on the effective area used in the design of the baseplate should not exceed pvgZ

where

Z is the elastic modulus of the gusset;

P,, is the design strength of the gusset < 270 ~ / m m ~

When the effective area of the baseplate i s less than its gross area, the connections of the gussets should be checked for the effects of a nominal distribution of bearing pressure on the gross area as well as for the effects of the distr~bution used in the design of the baseplate.

their depth; double channel sections should meet the conditions of 4.7.13.2 if in contact, otherwise they should be laced or battened to meet the conditions of 4.7.8 or 4.7.9 respectively.

(b) The overall dimensions of the steel section does not exceed 1000 mm x 500 mm, the dimension of 1000 mm being measured parallel to the web or webs.

(c) Primary structural connections to the member should preferably be made directly to the steel section. In such cases the eccentricity given in 4.7.6(a) should be taken I from the face of the steel section.

(d l The steel section i s unpainted and free from oil, grease. dirt, or loose rust and millscale.

(e) The steel section i s solidly encased in ordinary dense structural concrete of at least grade 20 to BS 81 10. ( 1 ) There is a mi um rectangle of solid casing, which may be chamfere T at the corners and provides a cover to the outer face and edges of the steel of not less than 50 mm. '.

(g) The concrete casing extends the full length of the member and connections. Concrete i s thoroughly compacted especially in areas under cleats, cap plates and beam soffits. Sufficient clearance is provided at all points so that the concrete can be efficiently worked around the steel elements.

(h) The casing i s reinforced using steel fabric complying with BS 4483, reference 098. Alternatively. steel reinforcement or wire of not less than 5 mm diameter or their equivalent, complying with BS 4449 or BS 4482 1 may be used at a maximum spacing of 200 mm to form a cage of closed links and longitudinal bars.

' In preparation.

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The reinforcement is so arranged as to pass through the centre of the concrete cover of the flanges; the minimum PC, = (A, + 0.25 - A, ) P,

lap of the reinforcement, and the details of the links, P ,

should comply with BS 81 10. where

(i) The effective length, L E , of the cased section is A, is the gross sectional area of the concrete,

limited to 40bc, 100b~ /d , or 250r whichever is least, but neglecting any casing in excess of 75 mm from the overall dimensions of the steel section

where and neglecting any applied finish:

b, IS the minimum width of solid casing within the deoth of the steel section; A, i s the gross sectional area of the steel strut;

~, ~

d, i s the minimum depth of solid casing within the width of the steel section:

f,, i s the characteristic concrete cube strength at 28 days of the encasement but < 40 ~ / m m ' ;

r is the minimum radius of gyration of the steel p, is the compressive strength of the steel section determined as given in 4.7.5 using r, and r, as section alone. defined in (a) and takingp, < 355 ~ I m m ' ;

4.14.2 Cased members subject to bending p, is the design strength of the steel < 355 N/mmz

Cased beams which meet the conditions given in 4.14.1 4.14.4 Cased members subject to axial load and moment

should be designed as for an uncased section (see 4.2 A cased section meeting the conditions given In 4.14.1 and and 4.3) except that the radius of gyration, r,, may be subject tocombined axial compression and bend~ng moment taken as 0 . 2 B + 100) mm or r,. of the uncased section should satisfy the following relationships. whichever i s greater. All other properties should be taken as

(a) For capacity: for the uncased section. The buckling resistance moment. M,, should not exceed 1% times that permitted for the F, M M

- - + X + Y < l uncased section, where B is the width of the flange. pa MCK M c y

In the calculation of deflections, the effective moment of (b) For buckling resistance: inertia of the cased section may be taken to be that of the

F c mM mM, < , steel section plus the transformed net area of the concrete, -+x+- i.e.: Pc Mb Mcv

1, - Is I,, = Is + - -

u e

where

I,, i s the second moment of area of cased section:

Is i s the second moment of area of steel section.

1, i s the second moment of area of gross concrete section;

a, is the modular ratio.

where

F, i s the compressive force due to axial load;

PC is the compression resistance (see 4.14.3) ;

PC, is the short strut capacity (i.e. the compression resistance of a cased strut of zero slenderness):

M, is the a ~ ~ l i e d moment about the major axis; . .

M, i s the applled moment about the mlnor axis;

m i s the equjvalent uniform moment factor obtained from table 18:

4.14.3 Cased struts M,, is the major axis moment capacity of the steel Cased struts which meet the conditions given in 4.14.1 , section (see 4.2.5 or 4.2.6); may be designed on the following basis. . .

M,,qs the minor axis moment capaclty of the steel (a) The radius of gyration, r v , of the member about its section (see 4.2.5 or 4.2.6); axis in the plane of its web or webs should be taken & i s the buckling resistance moment obtained as O.Zb,, but not more than 0.2(B + 150) mm where b, from 4.3.7.3 using section properties as given is the minimum width of solid casing within the depth of in 4.14.2. the steel section and B is the overall width of the steel flange or flanges. Where the radius of gyration of the steel section alone is greater than that o f the composite section, the radius of gyration of the steel section alone may be used.

The radius of gyration, r , , of the member about its axis parallel to the planes of the flanges should be taken as that of the steel section alone.

(b) The compression resistance. PC, of the cased section should be determined from:

p, but not greater than

4.1 5 Web openings 4.15.1 General

Except as prov~ded for in 3.3 for holes for fasteners. the effects of openings should be considered in the design. At all points where the applied shear or moment at the net section exceeds the capacity of the member adequate reinforcement should be provided.

Members should comply with 4.2 to 4.4 as appropriate and 4.5. In addit~on they should comply with 4.15.2 or 4.1 5.3 as appropriate.

the short strut capacity given by:

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4.1 5.2 Sections other than castellated

4.15.2.1 General. Where holes occur which will affect the strength of the member, consideration should be given to the clauses which apply to castellated beams.

4.15.2.2 Unreinforced circular openings Unreinforced circular openings may be located in the webs of compact beams and girders withoutconsidering net section properties provided that:

(a) the load on the member is substantially uniformly distributed and point loads should not be situated within a distance equal to the depth of the member from the centre line of the hole nor should they generate a shear in the web greater than 10 % of the shear resistance of the section;

(b) the section has an axis of symmetry in the plane of bending;

(c) the openings are located within the middle third of thedepth and the middle half of the span of the member;

(d) the spacing between the centres of any two adjacent openings measured parallel to the axis of the member is a minimum of 2.5 times the diameter of the larger opening;

(e) the factored maximum shear a t the support does not exceed 50 % of the shear resistance of the section.

When the dimensions and position of openings are not in accordance with (a) to (el, consideration should be given to the net section properties and design should be in accordance with 4.15.3.

4.15.2.3 Reinforced openings. Web reinforcement should be provided adjacent to the openings to equal the cross- sectional area of the web removed. The reinforcement should be carried past the opening for such a distance that the local shear stress, due to load being transferred from the reinforcement to the web, does not exceed 0 . 6 ~ ~ .

4.15.3 Castellated beams

4.1 5.3.1 Types The following rules apply to a castellated beam of dimensions as shown in figure 9 and care should be exercised when applying them to sections of different dimensions.

4.15.3.2 Moment capacity. The moment capacity of the section should be calculated from the net section properties (see 3.3) with due allowance for the secondary vierendeel effects of shear at the openings and the local effects of point loads if any, at any point in the length of the beam.

4.15.3.3 Shear stress. The shear stress across the net section of the web, and between openings should be calculated using elastic distribution and the maximum shear stress should not exceed 0 . 7 ~ ~ .

4.1 5.3.4 Incomplete lateral restraint. Beams with incomplete lateral restraint should be designed in accordance with 4.3 except that the equivalent slenderness, hLT, should be calculated using the section properties applicable to a cross section through the centreline of the opening.

4.15.3.5 Local buckling. The constituent parts of the section should be checked for local buckling in accordance with 3.5.

4.15.3.6 Deflection. The secondary deflections occurring a t openings should be added to the principal deflections of the section.

4.15.3.7 Supports and concentrated loads At points of support and concentrated load the effects of bearing and buckling should be considered in accordance with 4.5.

Openings except for fasteners should be filled and stiffeners provided as necessary.

1

D IS the serlal deqth of the original beam.

Figure 9. Dimensions o f castellated sections

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BS 5950 : Part 1 : 1990 Section five

Section five. Continuous construction

5.1 General 5.1.1 Scope

Section five applies to structures or elements of structures which are connected by rigid joints (see 6.1.4) or are continuous over supports. Rules are given for both elastic and plastic methods of design.

In addition to the limitations for sway stability given in this section i t i s recommended that the deflection limits given in 2.5.1 are not exceeded.

5.1.2 Loading

5.1.2.1 Verrical load. Vertical loads should be arranged in the most unfavourable but realistic pattern for each element. Dead load factors need not be varied when considering such pattern loading, but should be varied when considering stability against overturning.

5.1.2.2 Horizontal loads. For load cases involving horizontal loads, pattern loading of vertical loads need not be considered.

5.1.2.3 Notional horizontal loads. To check the sway stability of the structure notional horizontal forces should be applied. These notional forces may arise from practical imperfections such as lack of verticality and should be taken as:

0.5 % of the factored dead plus vertical imposed load applied horizontally.

These notional forces should be assumed to act in any one direction at a time and should be applied at each roof and floor level or their equivalent.

The notional forces should not:

( (a) be applied when considering overturning;

(b) be combined wcth the applied horizontal loads;

(c) be combined with temperature effects;

Sway stiffness may be provided by:

(a) an effective bracing system;

(b) the bending stiffness of the frame members;

(c) the provision of l i f t shafts, shear walls, etc.

A rigid jointed multi-storey frame may be considered as a non-sway frame if in every individual storey the deflection. 6 , in storey height, h, due to the notional horizontal loading given in 5.1.2.3 satisfies the following crlter~a.

(1) For clad fram'es where the stiffening effect of the cladding i s not taken into account in the deflection calculations:

h 6 < -

2000

(2) For unclad frames or clad frames where the stiffening effect of the cladding i s taken into account in the deflection calculations:

A rigid jointed multi-storey frame which does not comply with the above criteria should be classed as a sway frame, even if i t is also braced.

5.2 Elastic design

Elastic analysis should be carried out under factored loads.

5.3 Plastic design

5.3.1 General

Plastic design may be utilized in the design of structures or elements of structures provided that the conditions in 5.3.2 to 5.3.7 are met.

I (d l be taken to contribute to the net reactions at the foundations. 5.3.2 Type of loading

1 5.1.2.4 Base stiffness. In the analysis of all frames the same base stiffness about the axis under consideration should be used for all calculations. In the absence of detailed knowledge of the foundation stiffness the following should be assumed.

(a) Where the column is rigidly connected to a suitable foundation the stiffness of the base should be taken as equal to the stiffness of the column, except as in 5.7.3.1.

(b) Where the column is nominally connected to the foundation a base stiffness of 10 % of the column stiffness may be assumed.

(c) Where an actual pin or rocker i s provided the base stiffness should be taken as zero.

Plastic design may be used where loading i s predominantly static and, therefore, fatigue i s not a design criterion.

ii 5.3.3 Grades of steel

Steel forplastic design should comply with all three of the following:'

(a) the stress strain diagram has a plateau at the yield stress extending for at least six times the yield strain;

(b) the ratio of the specified minimum ultimate tensile strength to the specified minimum yield strength is not less than 1.2;

(c) the elongation (on a gauge length of 5.6h/s,) I is not less than 15 %, where So i s as glven in BS EN 10002:l

A\ 5.1.3 Classification of multi-storey frames as sway or 5.3.4 Geometrical properties /1. non-sway Where plastic hinges occur in a member the proportions of

A multi.storey frame may be classed as non.sway (whether its cross section should not exceed the lcm~ting values for

or not i t is braced) i f its sway is such that secondary plastic design given in table 7. The cross section should be

moments due to non.vert,cality of columns can be symmetrical about its axis perpendicular to the axis of the hinge rotation.

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The cross section of members not containing plastic hinges should be compact unless under an elastic analysis of the frame they satisfy the recommendations of section four.

5.3.5 Restraints Torsional restraint should be provided at a plastic hinge location if practicable (except as in 5.5.3.1). Where impracticable the restraint should be provided within a

I distance of D/2 of the plastic hinge location along the member.

Within a member containing a plastic hinge the maximum distance L, from the hinge restraint to an adjacent restraint should be calculated by one of the following methods.

(a) Conservatively L, (in mm) may be taken as:

where

f , is the average compressive stress due to axial load (in ~ / m m * ) ;

p , is the design strength (in ~ I m m ' ) ;

r , is the radius of gyration about the minor axis (in mm);

x is the torsional index.

Where the member has unequal flanges r, should be taken as the lesser of the values for the compression flange only or the whole section.

Where the cross section of the member varies within the length L, the minimum value of r , and the maximum value of x should be used.

(b) The method given in appendix G taking account of restraint to the tension flange, or the conservative method in 5.5.3.5 may be used with the ratio of the depth of haunch to the depth of rafter = 1.

The spacing of restraints to member lengths not containing a plastic hinge should be such as to satisfy the recommendations of section four. Where the restraints are placed at the

I limiting distance L, no further checks on restraint spacings are required.

5.3.6 Stiffeners at hinge locations

Web stiffeners should be provided where a load is applied within Dl2 of a plastic hinge location which exceeds 10 % of the shear capacity of the member (see 4.2.3). The stiffener should be provided within a distance of half the depth of the member either side of the hinge location and be designed to carry the applied load in accordance with 4.5.4 and 4.5.5. If the stiffeners are flat plates the outstand to thickness ratio, b,/t,, should not exceed 9. Where sections are used the ratib:

(!$ should not exceed 9

where

I, is the second moment of area of the stiffener about the face of the element;

.I ic tho tnrsion constant of the stiffener.

5.3.7 Fabrication restrictions

Within a length equal to the member depth either side of a plastic hinge location the following restrictions should be applied to the tension flange and noted in the design documents.

(a) Holes should be drilled or else punched 2 mm undersize and reamed.

(b) All sheared or hand flame cut edges-should be finished smooth by grinding, chipping or planing.

These restrictions should also be applied where local yield lines are assumed in the design of rigid connections, (see 6.1.4) and where repetition of loading makes fatigue a design criterion (see 6.1.6).

5.4 Continuous beams 5.4.1 Elastic design

When an elastic analysis is used the capacity and buckling resistance of the section should be calculated from section four.

For a compact section the elastic moment diagram for each span may be modified by up to 10 % of the peak elastic moment provided that the moments and shear remain in equilibrium with the factored loads.

5.4.2 Plastic design

Plastic analysis may be used provided the conditions of 5.3 are met.

5.5 Portal frames 5.5.1 General

In the elastic or plastic design of portal frames attention should be paid to thedeflection of the frame at serviceability loading.

5.5.2 Elastic design

When an elastic analysis is used the recommendations of 5.4.1 should be applied. The stability of the frame should be checked i6ccordance with 2.4.2, and the stability of individual components checked in accordance with section four q appendix G. -.

5.5.3 Plastic desigil

5.5.3.1 General. Plastic analysis may be used provided the conditions of 5.3 are met. The conditions of 5.3.5 need not be met at the last hinge to form provided it can be clearly identified.

5.5.3.2 Sway stability. In the absence of a rigorous analys~s of frame stability the following condition should be satisfied.

The horizontal deflection, 6, calculated by linear elastic analysis at the top of any column due to the notional horizontal loading given in 5.1.2.3 applied in the same direction at the top of each column should not exceed h11000, where h is the height of the column. In calculat~ng 6 allowance may be made for the restraining effect of cladding.

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Irrespective of the effects of cladding this condition may be satisfied provided that in each bay:

Lb 4 4 L P

in which L,, is the effective span of the bay. When the depth of the haunches (as shown in figure 10) is not less than 2 0 then:

L, = L - L,

I otherwise, L,, should be taken as equal to L

where

p = (7) ($1 for a single bay frame;

P = (2) ($) for a multi-bay frame;

I L,, is the haunch length. If the haunches at each side of the bay are different, the mean value should be taken.

L is the span of the bay;

h is the column height;

I, is the minimum second moment of area of the column for bending in the plane of the frame (taken as zero if the column is not rigidly connected to the rafter);

I , is the minimum second moment of area of the rafters for bending in the plane of the frame;

p,, is the design strength of the rafters;

L , is the total developed length of the rafter;

R is the arching ratio W r / W o ;

Wr is the factored vertical load on the rafters;

Wo is the maximum value of Wr which could cause plastic failure of the rafter treated as a fixed ended beam of span L.

5.5.3.3 Snap-through stability of rafter. In each internal bay of a multi-bay frame (i.e. greater than two bays) snap-through instability may occur due to spread of columns and inversion of the rafter.

0 is the minimum depth of the rafters;

I

Depth of haunch

Depth o f haunch

Oepth o f haunch

+$ Restra~nt

X Restra~nt

or v~rtual restraint (see second paragraw L of 5.5.3.5.21

Figure 10. Haunch restraints

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To prevent this the rafter slenderness should be such that:

where

8, for the symmetrical ridged frame is the rafter slope;

for any other roof shape:

where

h , is the height of the apex above the top of the columns.

No limit need be placed on LID when 52 d 1

5.5.3.4 Column stability. At or adjacent to plastic hinge locations the conditions of 5.3.5 should be met. In addition the stability of the column between restraints to the compression flange where plastic hinges do not occur should satisfy the recommendations of section four. Alternatively restraint to the tension flange may be taken into account by satisfying the recommendations of appendix G.

5.5.3.5 Rafter stability.

5.5.3.5.1 The spacing of restraints to the compression flange asshown in figure 10should be limited to L,obtained from 5.5.3.5.2 or 5.5.3.5.3 as appropriate.

NOTE. In figure 10 the restraints to the bottom flange extend a t least UP to the point of contraflexure. The number of such restraints i s governed by the limiting spacing L,.

5.5.3.5.2 Where the tension flange is restrained at intervals such that the recommendations given in 4.8.3.3.1 (or 5.3.5 adjacent to a plastic hinge location) are satisfied when checked using an effective length L E equal to the spacing of the tension flange restraints, then the limiting spacing Ls for compression flange restraints may be obtained from (a) or (b) as follows.

(a) Provided that:

(1) the rafter is a UB section;

(2) the depth of the haunch is not greater than three times the depth of the rafter;

(3) the haunch flange is not smaller than the rafter flange;

then L , may conservatively be taken as:

K l r,x for design'grade 43 steel

Depth of haunchldepth of rafter = 1: K I = 620, K2 = 645

= 2: K I = 495, K2 = 515 = 3: K, = 445, K2 = 465

(b) Where conditions (1) to (3) of alternative (a) are not met or if the spacing of the compression flange restraints exceeds the conservative value of L, given by alternative (a), then reference should be made to appendix G.

Provided that the purlins and their connections to the rafter are capable of providing torsional restraint to the top flange of the rafter, a virtual lateral restraint to the bottom flange may be assumed a t the point of contraflexure. Such torsional restraint may be assumed when conditions ( 1 ) and (2) in (a) above are satisfied and in addition:

(i) every length of purlin has at least two bolts in each purlin-to-rafter connection;

(ii) the depth of the purlin section i s not less than 0.25 times the depth of the rafter.

5.5.3.5.3 If the tension flange is not restrained as described in 5.5.3.5.2, then the limiting spacing L, for compression flange restraints should be such as to satisfy the recommends. tions given in 5.3.5 adjacent to a plastic hinge location, or those given in 4.8.3.3.1 elsewhere.

For this restraint condition, an effective lateral restraint to the bottom flange should not be assumed a t the point of contraflexure, unless one is specifically provided at that ~ o i n t .

5.6 Multi-storey rigid frames: elastic design 5.6.1 General

When an elastic analysis is used the conditions of 5.1 and 5.2 should be met.

In elastic design the forces and moments in the members under vertical loading may be determined from a linear elastic analysis of the entire frame or of suitable subframes (see 5.6.4).

Moments due to hoaontal loads should be determined by a linear elastic analysis of the whole frame.

The elastic momeb diagram for any member may be modified by up to.10 % of the peak elastic moment in that member for the same combination of loads prov~ded that:

(a) the forces and moments in the frame remain in equilibrium;

Kz'VX for design.grade 50 steel (b) a l l the members in which the moments are reduced ( 9 4 ~ 2 - 1 0 ~ ) ~ ~ ~

where

have compact cross sections;

(c) moments are not reduced about the minor axis of

r, is the minimum radius of gyration of the rafter any column.

section; The capacity and buckling resistance should be determined

x i s the torsional index of the rafter section; in accordance with section four.

K , and K2 have the following values: 5.6.2 Non-sway frames

A frame which satisfies theconditionsof 5.1.3 for non-sway frames should be analysed using ordinary linear elastic methods (including the use of suitable subframes).

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BS 5 9 5 0 : Part 1 : 1990 Section f ive

The effective length of the columns may be obtained from appendix E taking the columns as braced against sidesway.

Vertical load and horizontal loads should be applied in accordance with 5.1.2.1 and 5.1.2.2.

5.6.3 Sway frames

A frame which does not satisfy the conditions of 5.1.3 for non-sway frames should be designed as a sway frame.

Initially the frame should be checked under pattern vertical loading as for a non-sway frame. For this purpose the effective length of the columns should be obtained from appendix E taking the columns as braced against sidesway.

The effects of sway should then be accounted for under all combinations of loading. When considering vertical loading in the absence of wind loads the notional horizontal loads given in 5.1.2.3 should also be applied. Either of the following methods may be used.

(a) Extended simple design. The effective length of the columns in the plane of the frame should be obtained from appendix E allowing for sidesway.

(b) Amplified sway method. The moments due to horizontal loading should be amplified by the factor:

Acr

(h- - 1 ) where )L, is the elastic critical load factor obtained from appendix F.

The effective length of the columns in the plane of the

I frame should be taken as 1.0 L.

5.6.4 Subframes

5.6.4.1 Vertical loads. In the elastic analysis of any rigid frame the subframes shown in figure 1 1 may be used to determine the forces and moments due to vertical loads.

Alternative1 y the beam moments may be obtained by analysing the beams as continuous over simple supports at the columns, the column moments being obtained from the column design subframe in figure 11 *.

5.6.4.2 Horizontal loads The moments due to horizontal loads should be determined separately by means of a linear elastic analysis of the whole frame.

5.7 Multi-storey rigid frames: plastic design

5.7.1 General

Plastic design may be used provided the frame is effectively braced against sidesway out of its own plane. The conditions of 5.1 and 5.3 should be satisfied.

5.7.2 Non-sway framer

For the purpose of this clause a non-sway frame should have an effective system of bracing, satisfying the criteria of 5.1.3, independent of the bending stiffness of the frame

members. Plastic design may then be carried out providing that the buckling resistance of the members is checked by reference to 4.8.3.3.

5.7.3 Sway frames

5.7.3.1 General. Plastic design may be used where proper allowance is made for frame instability effects. This may be done by carrying out a full elastic-plastic sway analysis or by using the simplified method given in 5.7.3.3. The load factors employed should be those given in table 2. I The frame should be checked under all combinations of loading taking the effective length of the columns in the plane of the frame as 1.OL. When considering vertical loading in the absence of wind load the notional horizontal loading of 5.1.2.3 should be applied.

Where the strength of the frame is increased for any reason the stability of the columns may be checked using the original factored loads rather than the enhanced collapse loads of the frame.

5.7.3.2 Pattern loading. The columns should also be checked against pattern vertical loading using an effective length from appendix E taking the column as braced against sidesway.

5.7.3.3 Simple check for frame stability. The following conditions should be satisfied.

(a) The plastic hinge mechanism should be a sway mode with hinges assumed in all the beams and at the base of each column but no other plastic hinges in the columns.

(b) The lower lengths of the columns should be designed to remain elastic under the theoretical hinge moments assumed in (a).

(c) Under all combinations of unfactored loading (including the notional horizontal force when wind loads are not included in the combination) it should be possible by means of moment redistribution to produce sets of moments and forces throughout the frame which are in equilibrium with the applied loads and under which all members remain elastic.

(d) In 'ed frames where no account is taken of the stiffening effect of wall panels the following relationship should be satisfied:

x. (t) A,, > 4.6;

O.9Xc, (2) when 4.6 <Acr < 1 0 : A, > -.

(Aer - 1)'

(3) when X, > 1 0 : A, > 1;

where

A, is the elastic critical load factor from appendix F;

A, is the rigid-plastic load factor of the overall frames but should not be less than 1 locally.

A, i s the ratio by which each of the fact0re.d loads would have to be increased to cause plastic collapse of the actual frame determined in accordance with (a) and (b).

'Further deta~ls of subframes may be obtained from: Institution of Structural Engineers. Joint Committee Report on Fully Rigid Multi- - Storey Welded Steel Frames, Dec. 1964.

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BS 5950 : Part 1 : 1990 Section f ive

Where the steel frame is suitably encased in concrete the ( 1 A,, 2 5.75; increased second moment of area o f the section may be 0.95Acr used t o determine A,, (expressed in equivalent steel units). (2) when 5.75 < A,, < 2 0 : A, Z - .

(Acr - 1 ) ' (e) In unclad frames or in clad frames where the stiffness of the cladding is taken into account the following

(3) when A,, > 20 : A, > 1;

relationship should be satisfied: where A,, and A, are as in (dl.

Span considered

General Sub-span

NOTE. Full length of beams and columns IS to be used, except for roof beams where there are no upper columns

(a) Beam design sub-frames

Column length cons~dered - C ii

L

General External

NOTE. Full length of beams and columns is to be used except for the top storey where there are no upper columns

(b) Column design sub-frames

Figure 11. Sub-f rarnes

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BS 5950 : Part 1 : 1990 Section six

Section six. Connections

6.1 General recommendations 6.1.5 Joints in semi-rigid construction

6.1.1 General

Connections should be designed on the basis of a realistic assumption of the distribution of internal forces, having regard to relative stiffnesses. Such assumption should correspond with direct load paths through the elements of connections. It i s essential that equilibrium with the external applied factored loads is maintained.

Where members are connected to the surface of a web or flange or a section, the local ability of the web or flange to transfer the applied forces should be checked and stiffening provided where necessary.

Ease of fabrication and erection should be considered in the design of joints and splices. Attention should be paid to clearances necessary for tightening of fasteners, welding procedures, subsequent inspection, surface treatment and maintenance.

The ductility of steel assists the distribution of forces generated within a joint. Therefore residual stresses and stresses due to tightening of fasteners and normal accuracy of f it-up need not usually be calculated.

Joints between members in semi-rigid construction should provide a predictable degree of interaction between members, as described in 2.1.2.4. They should be capable of transmitting the restraint moments in addition to the other forces and moments at the joints. I t is important that the connection i s neither too rigid nor too flexible to fulfil accurately the assumptions made in design.

6.7.6 Joints subject to vibration and/or load reversal

Where a connection is subject to impact or vibration, pretensioned friction grip fasteners, locking devices or welding should be used.

Where a connection is subject to reversal of stress (unless such stress is due solely to wind) or where for some special reason slipp~ng of bolts is unacceptable, then pretensioned friction grip fasteners or welding should be used.

Where repetition of loading makes fatigue a design criterion (see 2.4.3). the fabrication restrictions given in 5.3.7 should be applied.

6.1.7 Splices

When different forms of fasteners are used to carry a shear 6.1.7.1 General. Splices should be designed to hold the load or when welding and fasteners are combined. then connected members in place and wherever practicable the

one form of connection should normally be designed to members should be arranged so that the centroidal axis of

carry the total load except that torqued friction grip the splice coincides with the centroidal axis of the members fasteners may be designed to share the load with welding joined. If eccentricity i s present then the resulting forces provided the bolts are fully tightened after welding. should be catered for.

6.1.2 Intersections 6.1.7.2 Splices in compression members Where the members are not prepared for full contact in bearing the

Usually, members meeting a t a joint should be arranged with their centroidal axes meeting at a point. Where there is

splice should be designed to transmit all the moments and forces to which the member at that point i s subjected.

eccentricitv at intersections the members and connections should be designed to accommodate the moments which Where the members are prepared for full Contact in bearing

result. In the case of bolted framing of angles and tees the the Splice should provide continuity of stiffness about both

setting out lines of the bolts may be adopted instead of the axes and resist any tension where bending is present centroidal axis. The splice should be as near as possible to the ends of the

6.1.3 Joints in simple construction

Joints between members in simple construction should be capable of transmitting the forces calculated in design and should be capable of accepting the resulting rotation (see 2.1.2.2). They should not develop significant moments adversely affecting members of the structure.

6.1.4 Joints in rigid construction

Joints between members in rigid construction should be capable of transmitting the forces and moments calculated from the design method. For elastic design the r~g~di ty of the joint should be not less than that of the members. For plastic design the moment capacity of a joint a t a

member or points of inflexion. Where this is not achieved account should be taken of the moment induced by strut action. See C.3.

6.1.7.3 Splices in tension members. The splice covers should beyesigned to transmit all the moments and forces to which the member a t that point is subjected.

k.

6.1.7.4 .Splices in beams Beam splices should be designed to transmit all the forces and moments in the member at that point and have adequate stiffness.

6.2 Fastener spacing and edge distances

plastic hinge location should be not less than that of the 6.2.1 ~i~i~,,,,, member and in addition the joint should possess sufficient

The distance between centres of fasteners should be not less plastic rotation capacity. than 2.5 times the nominal diameter of the fastener.

I The fabrication restrictions given in 5.3.7 should also be applied where local yield lines are assumed in the design of 6.2.2 ~~~i~~~ spacing in unstiffened plater elements of rigid connections. Th~s applies irrespective of whether or design is used for the structure,

The distance between centres of two adjacent fasteners in a line lying in the direction of stress should not exceed 14 t where t is the thickness of the thinner element. Where the members are exposed to corrosive influences the maximum

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spacing of fasteners in any direction should not exceed 16t or 200 mm, where t i s the thickness of the thinner outside ply.

6.2.3 Minimum edge and end distances

The distance from the centre of a fastener hole to the edge or end of any part should be not less than the value given in table 31. The edge distance is the distance from the centre of a hole to the adjacent edge at right angles to the direction of stress. The end distance i s the distance from the centre of a hole to the adjacent edge in the direction in which the fastener bears. The end distance should also be sufficient to provide adequate bearing capacity (see 6.3.3.3 and 6.4.2.2).

For slotted holes, edge and end distances should be measured from the centre of the end radius of the slot, a t the end nearest the edge or end of the material, see figure 1 l a .

I Table 31. Minimum edge and end distances to fasteners I

area, A,, as specified in the appropriate British Standard. For bolts where the tensile stress area is not defined A, should be taken as the area at the bottom of the threads.

Where it can be shown that the threads do not occur in the shear plane A, may be taken as the shank area A.

In the calculation of thread length allowance should be made for tolerance and thread run off.

Quality of cut

For a rolled, machine flame cut. sawn or planned edge

For a sheared or hand flame cut edgeand any end

6.3.2 Shear capacity

Provided that no reductions are required for long joints (see 6.3.4) or large grips (see 6.3.5) the shear capacity, P,, of a bolt should be taken as:

P, = P A where

p, is the shear strength obtained from table 32;

A , is the shear area as defined in 6.3.1, i.e. A or A,.

Edge and end distanca

1.250

1.400

6.3.3 Bearing capacity

6.3.3.1 General. The effective capacity of a bolt in bearing on any ply should be taken as the lesser of the bearing capacity of the bolt (see 6.3.3.2) and the bearing capacity of the connected ply (see 6.3.3.3).

6.3.3.2 Capacity of bolt. The bearing capacity of the bolt itself should be taken as:

1 1 where

I

D is the diameter of the hole.

I I e = end or edge distance

Pbb = d r ~ b b

d is the nominal diameter;

t i s the thickness of the connected ply, or, if the bolts are countersunk, the thickness of the ply minus half the depth of countersinking;

pbb i s the bearing strength of the bolt obtained from table 32.

6.3.3.3 Capacity of connected ply. The bearing capacity, Pbs, of the connected ply should be taken as:

Pbr = d t ~ br G '/z etp, where

pbr is the bearing &ength of the connected parts obtained from table 33;

I I Figure l l a . Minimum edge and end distances I d i s the nomir?44 diameter of the bolt;

e is the end distance, as defined in 6.2.3;

6.2.4 Maximum edge distances t is the thickness of the ply, as defined in 6.3.3.2. I The maximum distance to the nearest line of fasteners from an edge of any unstiffened part should not exceed 1 1 te. This rule does not apply to fasteners interconnecting the components of back-to-back tension members (see 4.6.3). Where the members are exposed to corrosive influences the maximum edge distance should.not exceed 40 mm + 4r.

6.3 Ordinary bolting

6.3.1 Effective areas of bole

6.3.4 Long joints

When the joint length, Li, of a splice or end connection in a compression or tension element containing more than two bolts (i.e. the distance between the first and last rows of bolts, measured in the direction of which the load is transferred) exceeds 500 mm, the shear capacity, P,. should be taken as:

but not more than given in 6.3.5 for large grips, if applicable Since threads can occur in the shear plane, the area A, for resisting shear should normally be taken as the tensile stress

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where

p, is the shear strength of the bolt, table 32;

A, is the shear area;

L, is the joint length (in mm), see figure 12.

6.3.5 Large grip lengths

When the grip length. T,, (i.e. the total thickness of the connected plies) exceeds five times the nominal diameter,d, of the bolts, the shear capacity, P,, should be taken as:

but not more than given in 6.3.4 for long joints, if applicable.

6.3.6 Bolts subject to tension

6.3.6.1 Tension capacity. The tension capacity, P,, of a bolt (including countersunk bolts) should be obtained from:

P, = P,A, where

p, is the tension strength obtained from table 32;

A, is the tensile stress area as specified in the appropriate British Standard. For bolts where the tensile stress area is not defined A, should be taken as the area at the bottom of the threads.

6.3.6.2 Prying. In connections subject to tension prying action need not be taken into account provided the strengths given in table 32 are used.

6.3.6.3 Combined shear and tension. When bolts are subject to both shear and tension then in addition to the conditions in 6.3.1 to 6.3.6.2 the following relationship should be satisfied:

Table 32. Strength of bolts in clearance holes

6.4 Friction grip fasteners

Table 33. Bearing strength of connected parts for ordinary bolts in clearance holes, pb,

where 6.4.1 General

F, is the applied shear; For a parallel shank friction grip fastener the transverse

F, i s the applied tension; capacity should be obtained from the minimum value given by the slip resistance (see 6.4.2.11, the bearing capacity

P, i s the shear capacity (see 6.3.2); (see 6.4.?&) and, where appropriate, the resistance of long P, is the tension capacity (see 6.3.6.1). joints (see 6.4.2.3).

,.

I

Other grader of fasteners

Nlrnm'

0.48Uf but < 0.69 Yf

0.72 (Uf + Y f )

0.58Uf but < 0.83 Yf

Shear strength, p,

Bearing strength, p,, (but see table 33)

Tension strength, p,

I Figure 12. Joint length at splice

Yf is the specified minimum yield strength of the fastener.

Ut is the specified minimum ultimate tensile strength of the fastener.

Other grades d steel

Nlrnm'

O.65(Us + Y,)

Design grade of steel

Bolt grade

Y, is the specified minimum yield strength.

Us is the specified minimum ultimate tensile strength.

gr 4.6

Nlmm'

160

460

195

gr 55

Nlmm'

650

gr 43

Nlmm'

460

gr 8.8

Nlmm'

375

1035

450

gr 50

Nlmm'

5 50

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For a waisted shank fastener the capacity should be obtained from the slip resistance (see 6.4.3) only and the bearing and long joint capacities need not be checked. NOTE. The slip resistance of a parallel shank friction grip fastener is based on a serviceability criterion but for ease of calculation has been presented in a form which may be checked against factored load. The result of this is that the connection will slip into bearing between the working and the failure load, and for this reason the bearing capacity should be checked against factored load. The shear capacity at the failure load is automatically satisfied by limiting the slip factor, p , to 0.55 provided that the connection is not a long joint. The capacity of long joints is a shear capacity check.

The slip resistance of a waisted shank friction grip fastener is a failure criterion. The connection will not slip into bearing until the factored load has been reached and it is, therefore, not necessary to check the bearing and long joint capacities.

6.4.2 Parallel shank friction grip fasteners

6.4.2.1 Slip resistance. The slip resistance, P,,, provided by a parallel shank friction grip fastener should be taken as:

P,, = 1.1 K y P ,

where

Po is the minimum shank tension as specified in BS 4604;

K, = 1.0 for fasteners in clearance holes;

= 0.85 for fasteners in oversized and short slotted holes, and for fasteners in long slotted holes loaded perpendicular to the slot;

= 0.6 for fasteners in long slotted holes loaded parallel to the slot;

1.1 i s the slip factor as defined below Q 0.55. The slip factor, p, should be determined from the results of tests as specified in BS 4604, except that for general grade fasteners (i.e. friction grip fasteners complying with BS 4395 : Part 1 or having similar mechanical properties) in connections where the surfaces in contact meet the requirements for untreated surfaces specified in BS 4604 : Part 1 the slip factor may be taken as 0.45.

6.4.2.2 Bearing resistance. The bearing capacity, Pbg, for parallel shank friction grip fasteners should be taken as:

Pbg = dtpbg < l/3 etPbO

where

d is the nominal diameter of the fastener;

e is the end distance (i.e. the edge distance in the direction in which the fastener bears);

t i s the thickness of the connected ply;

p,, is the bearing strength of the parts connected obtained from table 34.

6.4.2.3 Long joints. Where the joint length. L i , of a splice or end connection containing more than two fasteners (i.e. the distance between the first and last rows of fasteners measured in the direction which the load is transferred) exceeds 500 mm, the slip resistance, P,,, of parallel shank fasteners should be taken as:

where L, IS the ioint length (in mm), see f~gure 12. F --'-r than that glven by 6.4.2.1 and 6.4.2.2.

1 :45 --- -

6.4.3 Waisted shank fasteners: slip resistance

Table 34. Bearing strength of parts connected by parallel shank friction grip fasteners, pb,

The slip resistance, P,,, provided by a waisted shank friction grip fastener should be taken as:

P,, = 0.9KspP,

where Ks, p and Po are as defined in 6.4.2.1.

Other grades of steel

Nlmm' 2.2US but < 3.0 Ys

Design grade of steel'

6.4.4 Friction grip fasteners subject to external tension

Y, is the specified minimum yield strength of the steel.

Us is its specified minimum ultimate tensile strength.

gr 43

Nlmm' 825

6.4.4.1 Permitted types. Friction grip fasteners required to carry externally applied tension should comply with BS 4395 : Parts 1 or 3. Fasteners complying with BS 4395 : Part 2 should not be subjected to externally applied tension.

6.4.4.2 Tension capacity. The tension capacity, P,, of a friction grip fastener complying with 6.4.4.1 should be taken as 0.9P0, where Po is the minimum shank tension as specified in BS 4604.

gr 50

Nlmm' 1065

6.4.5 Combined shear and tension

gr 55

Nlrnm' 1210

When friction grip fasteners are subject to both shear and tension then in addition to the conditions given in 6.4.1 and 6.4.4 the following relationship should be satisfied:

where

F, is the applied shear;

F, i s the external-applied tension. td

6.4.6 Holes for friction grip fasteners

6.4.6.1 General. slearance holes should be specified for all friction grip conkt ions unless oversize or slotted holes are required, when consideration should be given to minimum spacing, edge and end distance, bearing strength and tension capacity in order to provide the necessary strength in the connected parts.

6.4.6.2 Size of holes

6.4.6.2.1 General. The size of holes for friction grip fqsteners should not exceed the dimensionsgiven in table 35.

6.4.6.2.2 Oversize and short slotted holes Oversize and short slotted holes may be used in all plies of a friction grip connection provided that a standard hardened washer is positioned over the holes in the outer plies.

6.4.6.2.3 Long slotted holes. Long slotted holes should not be used in more than one of the connected plies at any individual faying surface. -

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Where long slotted holes are used in an outer ply an external plate having sufficient size to completely cover the slot should be provided. Such a washer or plate should be a t least 8 mm thick and of structural material but need not be hardened. Hardened washers should also be placed under the turned element.

Table 35. Maximum dimensions of holes

6.5 Pin connections

6.5.1 General

Pin connected tension members and their connecting parts should comply with 6.5.2. Pin connected compression members need not.

Bolt shank diameter

mm

< 22 24

B 27

Where the connected elements are clamped together by external nuts the limits on thickness do not apply to internal plies.

d is nominal bolt diameter (in mm).

Long slotted hole dimensions

6.5.2 Tension members and pin plates

The thickness of an unstiffened element containing a pinhole should be greater than or equal to 0.25 times the distance from the edge of the hole to the edge of the element, measured at right angles to the axis of the member. See figure 13.

Clearance hole diameter

mm

d + 2 d + 2 d + 3

mm

d + 2 d + 2

d + 3

The net area beyond a pinhole parallel to, or within 45 " of the axis of th_e member should be greater than or equal to the net area A required for the member. The sum of the areas a t the pinhole perpendicular to the axis of the member should be at least 1.33A. See figure 13.

mm

2.5d 2.5 d 2.5d

Pin plates provided to increase the net area of a member or to increase the bearing capacity of a pin should be arranged to avoid eccentricity and should be of sufficient size to distribute the load from the pin into the member.

Oversize hole diameter

mm d + 5 d + 6

d + 8

6.5.3 Design of pins

6.5.3.1 General. The capacity of a pin connection should be determined from the shear capacity of the pin at the shear planes, see 6.5.3.2, and the bearing capacity on each connected ply, see 6.5.3.3, with due regard to the distribution of load between the plies. The bending moment on the pin should also be checked (see 6.5.3.4).

Short sloned hole dimensions

1 6.5.3.2 Shear capacity. The shear capacity of a pin should be taken as:

mm

d + 2 d + 2 d + 3

where

p,, is the design strength of the pin;

A is the cross-sectional area of the pin.

6.5.3.3 Bearing capacity. The bearing capacity of a pin should be taken as:

1.2p,dt

where

d is the diameter of the pin;

t is the thickness of the connected part;

p, i s the lower of the design strengths of the pin and the connected part.

6.5.3.4 Bending. The bending moments on a pin should be calculated on the assumption that the forces transmitted between the pin and the connected parts are uniformly distributed along the length in contact in each case. The moment capacity of the pin should be taken as:

1.2p,,z where

Z is the elastic modulus of the pin;

p,, is the design strength of the pin.

mm

d + 6 d + 8 d + 1 0

6.6 Weld detail and design

The details of all welded connections should comply with 6s 5136

6.6.2 Details of fillet welds

6.6.2.1 End returns. Fillet welds terminating at the ends or sides of parts should be returned continuously around the corners for a distance of not less than twice the leg length. s, of the weld unless access or the configuration renders this impracticable. This detail i s particularly important for fillet welds on the tension side of parts carrying a bending

I load.

6.6.2.2 Lap joints In lap joints the minimum lap should be not less than 4 t where t i s the thickness of the thinner part joined. Single fillet welds should only be used where the parts are restrained to prevent opening of the joint.

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A = D ~ x ~ - - (11 t >0.25D4

(2) D, x t >A (3) 2 X D4 X t > 1.332

Figure 13. Pin-ended tension members

6.6.3 Partial penetration butt welds

Partial penetration butt welds should not be used inter- mittently or in fatigue situations.

6.6.4 Welded details for structural hollow sections

A weld connecting two structural hollow sections end-to-end should be a full penetration butt weld.

A weld connecting the end of a structural hollow section to the surface of another member should be continuous and may be either a butt weld throughout, a fillet weld throughout or a fillet weld in one part with a butt weld in another with a continuous change from one to the other.

6.6.5 Design of fillet welds

6.6.5.1 Design strength. The design strength, p,, of a fillet 6.6.2.3 End connections. Where the end of an element i s weld made using covered electrodes complying with connected only by longitudinal fillet welds the length of BS 639 should be each weld. L , should be not less than the transverse spacing, obtained from table 36 for the lowest grade of material T, (see figure 14). joined.

---I

+=I-+

1 Weld stopped short

L>T,

Figure 14. Welded end connections

6.6.2.4 Single fillet welds A single fillet weld should not be subject to a bending moment about the longitudinal axis of the weld.

6.6.2.5 Intermittent fillet welds lntermittent fillet welds should not be used in fatigue situations or where capillary action could lead to the formation of rust pockets.

The longitudinal spacing along any one edge of the element between effective lengths of weld, as given in 6.6.5.2,

I should not exceed the lesser of 300 mm or 16t for compression elements or 24r for tension elements, where t i s the thickness of the thinner part joined.

Back-to-back struts and ties should have spacing of welds in accordance with 4.7.13 and 4.6.3 respectively.

End runs of fillet welds should extend to the end of the part connected.

Where the fillet welds are symmetrically disposed as shown in figure 15 the sbngth of the weld may be taken as equal to the design strerigth of the parent metal provided that:

(a) the weld'h made with a suitable electrode (or other welding cons2mable) which will produce all weld tensile specimens as specified in BS 709 having both a minimum yield strength and a minimum tensile strength not less than those specified for the parent metal;

-

Table 36. Design strength, p,

Tension in connected plate T

Figure 15. Symmetrical fillet welds

Other types

Nlmm'

0.5 U, but Q 0.54 Us

Design grade of steel

40 or 43 WR50and 50

5 5

*Only applies to electrodes having a minimum tensile strength of 550 Nlmm' and a minimum yield strength of 450 Nlmm'. U, is the minimum tensile strength of the electrode based on

all weld tensile tests as specified in BS 709. Us is the specified minimum ultimate tensile strength of the

steel.

Electrode strength to BS 639

E43

Nlmm2 215 215

-

€51

Nlmm' 215 255

255

€51.

Nlmm' - -

275'

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(b) the sum of the throat sizes is not less than the 6.6.6.2 Throat thickness of partial penetration butt welds connected plate thickness; The throat thickness of a partial penetration butt weld

the weld is principally subject to direct compression welded from one side or the thickness of each throat

or tension. welded from both sides should be taken as the minimum death of oenetration.

6.6.5.2 Effective length. The effective length of a run of In the case of a V or bevel weld the depth of penetration fillet weld should be taken as the overall length less one leg length, s, for each end which does not continue round a

should be taken as the depth of preparation minus 3 mrn.

corner. Except where it can be shown that greater penetration can consistently be achieved the depth of penetration on one

The effective length should be not less than 4s. side for a J or U weld should be taken as the depth of weld

6.6.5.3 Throat size. The effective throat size, a, of a fillet weld should be taken as the perpendicular distance from the root of the weld to a straight line joining the fusion faces which lies within the cross section of the weld. It should not, however, be taken as greater than 0.7 times the effective leg length, s.

6.6.5.4 Angle of intersection of members connected by fillet welds. Where the fusion faces form an angle of

I greater than 120 O or less than 60 O the adequacy of the joint should be demonstrated by test.

6.6.5.5 Design rules for fillet welds The vector sum of the design stresses due to all forces and moments transmitted

preparation.

The specified penetration should be not less than 2 d t where t is the thickness of the thinner part joined (in mm).

6.6.6.3 Design rules for partial penetration butt welds. When the weld i s unsymmetrical relative to the parts joined .the resulting eccentricity should be allowed for when calculating the maximum stress and the joint restrained against rotation.

The capacity of a weld comprising of a partial penetration butt weld and a superimposed fillet weld should be calculated as for a fillet weld, as given in 6.6.5.

by the weld should not exceed the design strength, p,. The design stress in a fillet weld should be calculated on a 6.7 Holding-down bolts thickness equal to the effective throat size, a.

Holding-down bolts should be designed to resist the effect For a fillet weld with unequal size legs, a deep penetration of factored loads determined in accordance with 2.4. fillet weld or a partial penetration butt weld with a They should provide resistance to tension due to uplift superimposed fillet weld, the shear and tension stress on the forces and bending moments and shear where appropriate. fusion line should not exceed 0 . 7 ~ ~ and l.Op, respectively.

Holding-down bolts required to transmit tension should be

6.6.6 Design of butt welds anchored into the foundation by a washer plate or other load distributing member embedded in the concrete;

6.6.6.1 Design strength of butt welds The design strength this plate or member should be designed to span any grout of a full or partial penetration butt weld should be taken as tubes or adjustment tubes provided for the holding-down equal to that of the parent metal, provided that the weld i s bolts. made with a suitable electrode (or other welding consumable) The embedment length of the holding down bolts and the which will produce all weld tensile specimens as specified arrangement of the load distributing assembly should be in BS 709 having both a minimum yield strength and a such that in transmitting the loads from the anchorage to minimum tensile strength not less than those specified for the foundation the load capacity of the foundation is not the parent metal. exceede*

td The tension capacity of the bolt should be determined in accordance with 6.3.6.

Rag bo~f; and indented foundation bolts should not be used to resist uplift forces.

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BS 5950 : Part 1 : 1990 Section seven

Section seven. Loading tests

7.1 General

Testing may be undertaken when:

(a) the design or construction i s not entirely in accordance with sections one to six of this standard and use is made of experimental verification as recommended in 2.1.2.5 (see tests ( 1 ) and (2) below);

(b) design load limits are to be established from a knowledge of the ultimate capacity of a component or structure (see test (3) below);

(c) confirmation is required of the consistency of production of components or structures originally justified by t e s t (see test (4) below);

(d) the actual performance of an existing structure is to be established if its capacity i s in question (see test (1) below).

To meet these situations a basis i s presented for four types of tests:

(1) an acceptance test for confirmation of general structural behaviour;

(2) a strength test against the required factored loads;

(3) a tes t to determine the ultimate capacity and mode of failure;

(4) a check test to establish consistency of production.

Because circumstances and test facilities vary greatly, the test procedure should be agreed in advance by all concerned.

These test procedures are intended for steel structures only. For structures of composite construction in steel and concrete reference should be made to BS 5950 : Section 3.1 I and Part 4.

Structures qualifying for acceptance from loading tests should be of robust and practical construction and reasonably insensitive to incidental loads.

Testing of scale models or of items subject to fluctuating loads which could cause fatigue to become the design criterion is not covered by this section.

7.2 Test conditions

The design of the test rig should be such that the loading system adequately simulates the magnitude and distribution of the loading and allows the specimen to perform in a manner representative of service conditions. The specimen should be free to deflect under load and lateral and torsional restraints should be representative of those in service. Care should be taken to avoid inadvertent eccentricities at the points of application of the test loads and at the supports.

Due attention should be paid to the safety of the test arrangements particularly in ultimate tests. Failure of a test specimen should not lead to general instability of the test rig.

Careful consideration should be given to the positions at which deflections are to be measured. The anticipated

magnitude of such deflections should be estimated in advance with generous allowances made for movement beyond the elastic range. I t i s important to ensure that the loading system can follow the movements of the specimen without interruption or abnormal restraint. Load and deflection measurements should be controlled as closely as practicable.

In some situations i t may be desirable to determine the magnitude of stresses in a specimen. This may be demonstrated qualitatively by means of brittle coatings or quantitatively by measurements of strain. Such information should be considered supplementary to the overall behaviour as determined by deflections.

Where tes t results are used to establish or confirm the behaviour of similar structures or components the properties of the steel used in the relevant items should be established by coupon tests to validate comparisons between tests carried out on different specimens or a t different times. Coupons should either be cut from the same sections or plates or else recovered from unyielded areas of the specimen after test.

Loading should be applied in a number of regular increments at regular intervals in each phase. At each increment the specimen should be carefully examined for signs of rupture, yield or buckling. A running plot should be maintained of loading against principal deflection. When this indicates significant non-linearity, load incrementsshould be reduced.

On the attainment of maximum load for either acceptance or strength tests, the load should be maintained for at least 1 hour with recordings of load and deflection being taken at the beginning and end of this period to establish whether the specimen is subject to creep.

Unloading should be completed in regular decrements with deflection readings taken at each stage.

7.3 Test procedures

7.3.1 Test loads

The test load for acceptance tes t should be actual dead load present durinaest x 1.0 + remainder of the dead load x 1.15 + imposed load x 1.25 but need not be taken as more than the a.Pprage of the factored and unfactored load.

The test load for a strength test should be based on the factored load calculated in accordance with section two of this standard with appropriate factors applied to dead, imposed and wind loads separately or in combination as appropriate.

It is important to recognize that the self weight of the specimen may not be representative of the actual dead load in service. Allowance for any difference should be made in the calculation of the test loads to be applied.

7.3.2 Preliminary loading

Prior to any test i t may be advantageous to apply (and then remove) preliminary bedding down loading not exceeding the unfactored loads.

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BS 5950 : Part 1 : 1990 Section seven

7.3.3 Acceptance test

This test i s intended as a non-destructive tes t for confirming structural performance.

The assembly should prove capable of sustaining the test loading as given in 7.3.1. It should be recognized that such loading applied to certain structures may cause permanent local distortions. Such effects may not indicate structural failure in an acceptance test but the possibility of their occurrence should be agreed before testing.

The assembly should demonstrate substantially linear behaviour under test loading and on removal of the test load the residual deflection should not exceed 20 %of the maximum recorded. If these conditions are not met the test should be repeated and the assembly should demonstrate substantially linear behaviour under test loading and the residual deflection should not exceed 10 % of the maximum recorded.

Where this test is being used to relate to performance established in earlier tests, the deflections should be measured at the same positions. The original maximum deflections should not be exceeded by more than 20 %.

7.3.4 Strength test

The strength test is used to confirm the calculated capacity of a structure or component. Where a number of items are to be constructed to a common design, and one or more prototypes are tested to confirm their strength, the others may be accepted without further tests provided they are similar in all relevant respects to the prototype (see 7.3.6).

Before carrying out the strength test the specimen should first be submitted to and satisfy the acceptance test described in 7.3.3.

The capacity of the assembly under test will be dependent on the material properties. The actual yield strength of the steel or steels in the assembly should be determined from coupon tests. An averaged value should be taken from such tests having regard to the importance of each element in the assembly. The test load (including self weight) is given by:

averaged yield strength Test load = ) x factored load

design strength

At this load there should be no failure by buckling or rupture of any part of the specimen.

On removal of the test load the deflection should be reduced by at least 20 %.

7.3.5 Test to failure

I t is only from a test to failure that the real mode of failure and true capacity of a specimen can be determined. Where the item is not required for use i t may be advantageous to secure this additional information after a strength test.

Alternatively the objective may be to determine the true design capacity from the ultimate test capacity. In this situation i t is s t i l l desirable to carry out the load cycling of the acceptance and strength tests. An estimate should be made of the anticipated design capacity as a basis for such tests.

Before a test to failure the specimen should first satisfy the strength test described in 7.3.4. Where the design capacity

has been estimated it may be desirable to adjust its value in the light of the specimen's behaviour.

During a test to failure the loading should first be applied in increments up to the strength test load. Consideration of the principal deflection plot should then determine subsequent load increments.

The ultimate test load is defined as that point at which the specimen is unable to sustain any further increases in load. At this point gross permanent distortion is likely to have occurred and in some cases gross deformation may define the test limit.

Provided that there is a ductile failure the design capacity of a similar assembly may be determined from:

design strength Design capacity = K,

averaged yield strength

x ultimate test load

In the case of a sudden ('brittle') failure the averaged yield strength should be replaced by the averaged ultimate tensile strength of the steel, or by 1.2 times the averaged yield strength in the case of a sudden buckling-type failure.

In cases where the failure has occurred due to strut or lateral torsional buckling the ratio may be calculated using the two values for the design strength on the appropriate curve for the 'design strength' and 'averaged yield strength'. These values are to be taken at the slenderness ratio appropriate to the situation.

For a single test K, should be taken as 0.9 unless the resulting capacity falls below the design capacity confirmed by the strength test, when the latter should be taken. For two or more related tests K, may be taken as 1.0 provided that the lowest of the individual ultimate test loads is used.

7.3.6 Check tests

Where the assembly i s designed on the basis of tests as defined in 7.l(a) or (b) and a production run i s carried out of that assembly the following precautions should be observed.

(a) An propriate number of samples (not less than two) P should e selected from each production batch at random.

(b) h e samples should be carefully examined to ensure they are similar in all respects to the prototype tested, particular attention being given to the following items:

(1) dimensions of components and connections;

(2) tolerance and workmanship;

(3) quality of steel used. checked with reference to mill certificates.

(c) Where it i s not possible to determine either the variations or the effect of variations from the prototype an acceptance test should be carried out. The maximum recorded deflection should not exceed 120 % of the deflection recorded during the acceptance test on the Rrototype and the residual deflection should not be more than 105 % of that recorded for the prototype.

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BS 5950 : Part 1 : 1990 Appendix A

Appendices

Appendix A. Formal statement of safety coefficient yc which can be considered to be a function of

factor format adopted in BS 5950: two partial coefficients, ycl and y c 2 , defined as follows.

Part 1 to facilitate correlation with I S 0 2394 and BS 5400 : Part 3

y,, is to take account of the nature of the structure and its behaviour, for example structures or parts of structures in which collapse or partial collapse can occur without warning, where redistribution of

A.l Design loads internal forces i s not possible, or where failure of a element can lead to overall collapse.

The design loads, O f , are determined from the nominal y,, is to take account of the seriousness of attaining a loads, Qk, by the relationship: limit state from other points of view, for example

Q* = YQ, Y P ~ Q k economic circumstances, danger to community.

where In general, for the purposes of the design of structures in

y p , takes account of the possible deviation of loads from accordance with the recommendations of this standard,

their specified value; the effects of y,, and yc2 can be considered to be already incorporated in the values of y, or ym adopted. yp, takes account of the reduced probability that

various loadings acting together will simultaneously reach their characteristic value. A.5 Verification of structural adequacy

A.2 Design load effects A.5.1 For a satisfactory design:

R* > S* 1

The design load effects, S*, are determined from the design i.e. - function loads, Q * , by the relationship: ypm

S* = Effects of y,, Q* A.5.2 In BS 5950 : Part 1, the relationship in A.5.1 is where expressed as:

y,, takes account of the possible deviation of the behaviour of the structure from that of the design function ($) Z Effects of h Q k (dead loadsl + model. + yf Qk (imposed loads)

A.3 Design resistance

The design resistance. R * , i s determined from the relationship:

1 R* = -

' Y P ~ where

fk is the characteristic strength of the material;

y,, takes account of the possible deviation of the behaviour of the material in the structure from that assumed in design;

y,, takes account of the possible reduction in strength of the material from the characteristic value;

where

y m = yml ym2 and is taken account of in table 6 for design strength;

Yf = YPm'YprrQl ' Y Q ~ and is as given in table 2.

A.9.3 In BS 5400 : Part 3 the relationship in A.5.1 i s expressed as:

1 function ( f , ) > The effects of r f L Q k

YfoYml7mz

where P Yf3 = YpmTpr *

y,, and T,, ace taken as a single factor ym

YfL ='Yfl'Yf2 :,

y,, takes account of manufacturing tolerances. A.6 Comparison of partial safety factors

A4 Modification coefficient y, A comparison of methods of application of partial safety

Where necessary, e.g. for the design of key elements, factors in IS0 2394, BS 5400 : Part 3 and BS 5950 i s given in table 37.

the value of the partial cooefficients may be modified by a

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BS 5950 : Part 1 : 1990 Appendix A

Appendix B. Lateral torsional buckling of members subject to bending

Table 37. Comparison of partial safety factors

8.1 Introduction When an unrestrained beam deflects due to bending in plane, it also deforms out of plane and twists about its longitudinal axis due to imperfections and initial out-of- straightness. This effect is then amplified by the application of further moment and eventually the beam may buckle at an applied moment less than the full moment capacity of the section. This effect is known as 'lateral torsional buckling'.

The theoretical case for lateral torsional buckling is taken as the elastic critical moment of a simply supported member of uniform section with a uniform moment applied about i t s major axis. the member being restrained at its supports against torsion (i.e. rotation about its longitudinal axis) and lateral deflection but otherwise unrestrained.

Yc 1 Ycz

Ycl Y a

Yc

Y C 1 Y C 2

Yc

Y c ~ Y C z

Y C

Partial safety factors

IS0 2394

BS 5400 : Part 3

BS 5950 : Part 1

For real members with other conditions of support, loading or restraint, the actual elastic critical moment varies and modification to the theoretical case may be made in two ways.

NOTE. 7, is implicitly covered in modification of other factors where necsssary.

(a) When the member carries no transverse loading in the length between restraints (i.e. bending i s induced by moments applied at its end or the restraints) the

71 Yz

YSI Yry

Yr l Y f 2

Y ~ L = Y f l Yf2

7111 Y Q 2

Y P = Ynl Y P Z L

equivalent uniform moment factor, m, (< 1) should be used. This factor i s used to modify the factored applied moment to produce an equivalent uniform moment which is then considered as the design moment.

(b) For other cases, the value of the equivalent slenderness should be adjusted by use of the slenderness correction factor, n, resulting in a modified value of the buckling resistance moment.

Whichever method i s used the factor for the other method should be taken as 1 .O.

8.2 s%kling resistance moment

Y P m YPS

Y a

Y f3

Ypm YPS

Y p = Ypm Y p s

8.2.1 General

The buckling resistance moment, M , , may be obtained from:

Y m I Ym2

Y m I Ymz

Y ~ I Ym2

Yrn

Y ~ I Ym2

Y m Y

2

Yf = YuYp

M, + (VLT + ME 46 = 2

where

included in design strength

ME i s the elastic critical moment (see 8.2.2);

M, is the plastic moment capacity = p,S,

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BS 5950 : Part 1 : 1990 Appendix B

S, i s the plastic modulus about the major axis;

p , is the design strength;

qLT is the Perry coefficient (see B.2.3).

The above formula for Mb is the smaller root of:

(ME - Mb)(Mp - Mb) = V L T M E M ~

8.2.2 Elastic criticarmoment

The elastic critical moment should be taken as:

where XLT is the equivalent slenderness (see 8.2.5).

B.2.3 Perry coefficient

The Perry coefficient, qLT, for lateral-torsional buckling should be taken as follows:

(a) for rolled smtions:

VLT = ~ ~ ( A L T - ALO), but

VLT 2 0 (b) for wIded sections:

VLT = ~ Q ~ X L O but

VLT 24b(ALT - ALo)

VLT Z Q ~ ( ~ L T - ALO)

VLT 2 0 where

ALT is the equivalent slenderness (see 6.2.5);

A,, is the limiting equivalent slenderness (see 8.2.4);

ab is a constant, taken as 0.007.

6.2.4 Limiting equivalent slenderness

The limiting equivalent slenderness should be taken as:

8.2.5 Determination of equivalent slenderness

The equivalent slenderness should be taken as:

ALT = nuvh

where

A = LEIr ,

n, u, v are defined as follows.

(a) n is determined from consideration of the loading and restraint conditions of the member. For members of uniform cross section throughout their length, n may be obtained from table 13. For lnembers of varying cross section throughout their length, n should be obtained from 6.3.

(b) u, the buckling parameter, and x, the torsional index. are given by:

for flanged sections symmetrical about the minor axis:

'/4

u = (-) x = 0.566h,(~/J)'/~

for flanged sections symmetrical about the major axis:

In the above:

S, i s the plastic modulus about the major axis;

7 is a factor = 1 - 2 . ( i x ) , I, is the second moment of area about the major

axis;

I , is the second moment of area about the minor axis;

A is the cross-sectional area of the member;

H is the warping constant which may be obtained from published tables or the approximate formula for flanged sections given in 6.2.5(c);

J is the torsion constant which may be obtained from published tables or the approximate formula for flanged sections given in 6.2.5(c);

h , i s the distance between the shear centres of the flanges.

(c) J, the torsion constant, and H, the warping constant, for flanged sections (see figure 16) may be obtained from the followinq approximate formulae:

'1. where - .

b l and b2 are the flange widths;

r l and t 2 are the flange thicknesses;

t, is the web thickness;

h, i s the distance between the shear centres of the flanges;

h , is the web depth.

For plates of normal proportions J = 0.32br3 and thus for flanged sections symmetrical about the minor axis:

Cbt + hwtw '/2 x = h , ( Zbr3 + hw tw3 )

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BS 5950 : Part 1 : 1990 Appendix B

Figure 16. Dimensions for s;rnmetrical plat* girders

B.2.6 Box sections (including R H S )

8.2.6.1 For a box section subject to a moment:

hLT = " 2.25 (Gb A) I"

where

&, is the buckling index = - C:') A is the area;

J is the torsion constant which may be obtained from the approximate value given in 8.2.6.2;

y ' i s the factor (I- 2 ) ( I - &Ix)

NOTE. Box sections of uniform wall thickness need not be checked for lateral torsional buckling effects provided that A = is not greater than the limiting values of A given in table 38.

where

b is the breadth of each plate element;

t is the thickness of each plate element.

(dl v, the slenderness factor, i s qiven by: , .

where

I, . N is the ratio - (Id + I * ) '

I, is the second moment of area of the compression flange about the minor axis of the section;

I,, is the second moment of area of the tension flange 8.2.6.2 For a box section the value of the torsion constant,

about the minor axis of the section; J, may be obtained from the following approximate formula:

$ is the monosymmetry index, determined as follows: J = 4 ~ , $ / ~ ( s l t ) For I or T-section with lipped flanges. J, can be where

I calculated from: s i s the breadth of each enclosing element;

9 = 0 . 8 ( 2 N - 1) ( 1 + - :;) for N > 0.5

9 = 1.0(2N- 1 ) ( 1 + - :;) for N < 0.5

t i s the thickness of each element.

For an RHS a more accurate value i s given by:

Table 38. Limiting for box sections of uniform wall thickness, including RHS

where where

DL is the depth of the lip; h i s the mean perimeter; D is the overall depth of the section. A, i s the area enclosed by the mean perimeter;

NOTE. When the flange of the section is not lipped. DL = 0. is the thickness of the section. and hence

- Dl13

1

2

3

4

+ .= 0.8(2 N-1 I for N > 0.5

JI = l.O(ZN-1) for N < 0.5

A

00

350 x 275

p v

225 x 275

p v

170 x 275

p v

0, 8 are overall depth, breadth of box respectively.

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BS 5950 : Part 1 : 1990 Appendix C and D

8.2.7 Plates and flats

For an individual plate, flat, or other solid rectangular section subject to a moment about i t s major axis:

L d '12 A,, = n 2.8 (*)

where

L E is the effective length;

d i s the depth;

t i s the thickness;

n is as given in 4.3.7.6.

8.3 Beams of varying section throughout their length When the section of a beam varies along i t s length between restraint points, the bending strength, p,, is determined using the properties of the section at the point of maximum moment. This value of p , applies throughout the length between adjacent restraints.

Provided that Rf is not less than 0.2, the value of n to be used in the expression for hLT should be determined from:

n=(1 .5 - 0.5Rf) but>l.O;

where

Rf is the ratio of the flange area at the point of minimum moment to that at the point of maximum moment between adjacent restraint points;

Rf refers either to the ratio of total area of both flanges or to the area of the compression flange only, whichever gives the smaller value of R,.

For non-uniform sections, m = 1.0 (see 4.3).

C.2 Perry factor The Perry factor, 17, for flexural buckling under load should be obtained from:

17 = 0.001a(h- A,) but not less than zero

where

a is the Robertson constant, which has the following values:

2.0 for table 27(a) 3.5 for table 27(b) 5.5 for table 27(c) 8.0 for table 27(d)

h is the slenderness (see 4.7.3):

X, is the limiting slenderness, which should be taken as:

C.3 Strut action The moment due to strut action has a maximum value Mmax midway between points of inflexion of the buckled shape (the points between which the effective length is measured) given by:

where

f , is the compressive stress due to axial load;

S is the plastic modulus.

The moment at any other point can be obtained by assuming a sinusoidal variation, i.e. the moment due to strut action at a point, distance Lx from a point of inflexion, is given by:

Appendix C. Compression strength: Perry strut formula

C.l Basis The compressive strength, p,, may be obtained from:

where 4 = py + ( q + I ) P E

2

where

p, is the Euler strength (n2 €/A2 );

p, is the design strength;

q is the Perry factor.

The above formula for p, i s the smaller root of:

I @ E -pC)@y - p c ) = W E P ,

Appendix D. Effective lengths of struts in simple construction

D.l Stanchions for single storey buildings (see 4.7.2(c)) D. 1.1 Typical cases

Figures 17 to 21 illustrate how the effective lengths of typical stanchions in single storey buildings may be determined provided the following conditions apply.

(a) In the plane of the diagram the stanchions act as cantilevers tied together by the roof trusses, but in this plane the tops of the stanchions are not otherwise held in position or restrained in direction.

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BS 5950 : Part 1 : 1990 Appendix D

(b) Perpendicular to the plane of the diagram, the tops of the stanchions are effectively held in position by members connecting them to a braced bay, or by other suitable means. In the case of figures 19 to 21 the braced bay also holds the columns in position at crane girder level.

(c) The bases of the stanchions are effectively held in position and restrained in direction in both planes.

(d) The foundations are capable of providing restraint commensurate with that provided by the base.

0.1.2 Variations

Where the conditions differ from those given in D.l. l the following variations to the effective lengths shown in figures 17 to 21 may arise.

(a) If, in the plane of the diagram, the tops of the stanchions are effectively held in position by horizontal bracing or other suitable means, the effective lengths in this plane may be obtained from table 24.

(b) If, in the plane of the diagram, the roof truss or other roof member is connected to the stanchions by a connection capable of transmitting appreciable moment. the effective length of the stanchion in this plane may be determined in accordance with appendix E.

(c) If, perpendicular to the plane of the diagram, one flange only of the stanchion is restrained at intervals by sheeting rails, then for buckling out of the plane of the diagram the method given in appendix G may be used.

(d) If, perpendicular to the plane of the diagram, the base of the column i s not effectively restrained in direction the effective lengths 0.85 L or 0.85 L , in figures 17 to 21 should be increased to 1.0 L or 1.0 L 1 respectively.

1.

Effectiue length of stanchion Axis X-X - 1.5L Axis Y-Y = 0.85L

Figure 17. Side stanchion

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Alternative methods of restraint

Effective length of stanchion Axis X-X = 1.5L Axis Y-Y = 0.85Ll, 1 .OL, or l.OL,

whichever is the greatest

Figure 18. Side stanchion with restraints

Effective length of stanchion Axis X-X = 1.5L Axis Y-Y = 0.85L1

Figure 19. Simple side stanchion with crane gantry

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1 I I

'2 - - --.A. -- -Y2 I

I . i

X Effective length of stanchions

Upper roof stanchion Axis X-X = 1.5L, Axis Y-Y = Y,-Y, = L ,

L2 Lower roof stanchion Axis B-B = 0.85L AxlsY-Y = L , . L , , L , o r L ,


Crane stanchion '3 Axis B-B = 0.85L

Axts Y , -Y , = L,, L , , L, or L , whichever is the greatest

Combined roof and crane stanchions Axis A-A = 1.5L

L4 Axis B-B = 0.85L

Lower roof stanchion ,.

Figure 20. Compound side stanchion with crane gantry

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Roof stanchion

A

B,-- +- --B1

Effective length of stanchions

Roof stanchion Axis B, -8 , = L ,

A Axis A-A = 1 .5L1

Axis B-B = 0.85 L Ax isY-Y=L, .L , ,L , o r L ,


Combined crane stanchion Axis A-A = 1.6L Axis B-B = 0.85L

A

Figure 21. Compound valley stanchion with crane gantry

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BS 5950 : P a n 1 : 1990 Appendix E

Appendix E. Effective lengths of struts in rigid frames

E.l General The effective length, L E , of a column in a multi-storey beam and column-type frame with rigid joints may be assessed using the limited frame method given in E.2. For buildings which do not satisfy the conditions for a non-sway frame given in 5.1.3 the stiffening effect of infill wall panels may be taken into account using the method given in E.3. Other cases including the effects of axial loads in the restraining members may be dealt with by reference to E.4.

E.2 Limited frame method

E.2.1 Effective length

The effective length, L E , of a column may be obtained by using the limited frame shown in figure 22. The effective length ratio, L E / L , may be obtained from figures 23 or 24 as appropriate using the joint restraint coefficients, k , and k 2 , obtained from:

Total column stiffness at joint k =

Total stiffness of all members a t joint

Where any member shown in figure 22 is not present in the actual structure or is not rigidly connected to the column being designed i t s stiffness should be taken as zero.

Where under the same loading condition any restraining member is required to carry more than 90 % of its reduced moment capacity (i.e. moment capacity reduced for axial load) its stiffness should be taken as zero. If one end of the column is loaded to more than 90 %of its reduced moment capacity then the joint restraint coefficient, k, for that end should be taken as unity.

E.2.2 Beam stiffness

The stiffness, K,, of a beam directly supporting a concrete floor slab should be taken as I IL.

In any other case K, should be determined as given in E.4.1.

k , = Kc + Ku

Kc + Ku + KTL + KTR

k l = Kc + K L

K ~ + K L + K B L + K B R

where K, and K L are the values for I I L for the adjacent upper and lower column lengths

and KT,, KT,, KsL and KBR are the values of I / L for the adjacent beams

Figure 22. Restraint coefficients for limited frame

KT L '(1

E.2.3 Base stiffness

K"

KT R

The base stiffness should be determined by reference to 5.1.2.4.

Column being designed

KBL

K( = I / L

KBR

k2

KL

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BS 5950 : Part 1 : 1990 Appendix E

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E.3 Partial sway bracing

E.3.1 Introduction

Where buildings do not satisfy the conditions for non-sway frames given in 5.1.3 the stiffening effect of wall panels may be taken into account. Providing that the panels comply with E.3.2, figures 25 and 26 may be used in association with the method given in E.2.

The relative stiffness, k 3 , is given in E.3.3. For intermediate values of k 3 between 0 and 1 or 1 and 2 interpolation may be carried out using figure 24 for k 3 = 0.

E.3.2 Wall panels

To be effective a wall panel should be located in the plane of the frame and extend the full clear height of the storey. I t may be composed of any material capable of resisting a diagonal compressive force.

E.3.3 Relative stiffness

The relative stiffness, k 3 , of the effective bracing in any storey may be taken as:

where

h is the storey height;

CS, is the sum of the spring stiffnesses (horizontal force per horizontal unit deflection) of the panels in that storey of the frame (see E.3.4);

E is the modulus of elasticity of steel;

Z Kc i s the sum of the stiffnesses I IL of the columns in that storey of the frame.

where


b i s the width of the panel;

t is the thickness of the panel;

E, is the modulus of elasticity for the panel material.

E.4 Critical buckling mode of frames

E.4.1 Rectilinear frames

In a beam and column type rigid jointed frame (other than a frame where the beams support a concrete floor slab) the limited frame method given in E.2 may be used provided that the frame is reasonably regular in layout. In determining the stiffness, K,, of a beam due account should be taken of the degree of fixity afforded to its far end in the relevant buckling mode of the frame.

The critical mode for a rectilinear frame in which sway is prevented i s shown in figure 27. The beams are bent in single curvature and the relevant beam stiffness Kb = 0.5//L.

The critical sway mode for a rectilinear frame is shown in figure 28. The beams are bent in double curvature and the relevant beam stiffness, Kb, should be taken as 1.51/L. Where the in-plane effective lengths have a significant influence on the design it may be preferable to obtain the effective lengths from the elastic critical load factor, A,,, of the frame (see appendix F).

E.4.2 Axial loads

The limited frame method given in E.2 may be extended to rigid jointed frames in which the restraining members are subject to axial loads. This is providing that:

(a) the frame satisfies the conditions of 5.1.3 for non-

E.3.4 Stiffness of panels sway frames;

The spring stiffness, S,, of a wall panel may be determined (b) Proper account is taken of the effects of axial load from: on the stiffness of the restraining members.

Figure 27. Critical buckling mode of frame braced against sidesway

Figure 28. Critical buckling mode of frame free to sway

I

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BS 5950 : Part 1 : 1990 Appendix F and G

Appendix F. Frame instability

F.l General Frame instability, as covered by this appendix, is related to the design of multi-storey rigid-jointed frames subject to sidesway. The elastic critical load factor, X,,, which may be determined using the deflection method as given in F.2 or any other recognized method, i s used in the amplified sway moments method (see 5.6.3(b)) for elastic design and in the simple check for frame-stability (see 5.7.3.3) for plastic design. The elastic critical load factor, A,,, of a frame is the ratio by which each of the factored loads would have to be increased to cause elastic instability.

F.2 Deflection method

F.2.1 Introduction

where


b is the width of the braced bay;

CK, is the sum of the stiffness. I IL, of the columns in that storey.

Appendix G. Design of restrained members with an unrestrained compression flange

G.l General

G. 1.1 lntroduction

This appendix deals with the design of members or portions of members between effective torsional restraints to both flanges which are restrained by intermediate restraints in such a way as to leave a compression flange unrestrained. See fioure 29.

An accurate method (ordinary linear elastic) should be used -

to determine the horizontal deflections of the frame due to 6.1.2 Failure mode horizontal forces applied at each floor level and equal to 0.5 %of the factored vertical loads applied at that level. 6.1.2.1 The capacity of the member should be checked

in accordance with 4.8.3.2. Allowance should be made in this deflection calculation for

I the degree of rigidity of the base as given in F.2.2.

F.2.2 Base stiffness

The base stiffness should be determined by reference to 5.1 2.4.

F.2.3 Value of A,, 1

Acr = 2006~rnax

where $,,,, is the largest value for any storey of the sway index, 4, (see F.2.4).

6.1.2.2 The buckling resistance should be checked between intermediate restraints as given in 4.8.3.3 using an I effective length LE equal to the spacing of the intermediate restraints.

6.1.2.3 The overall buckling of the member in the torsional mode between effective torsional restraints to both flanges should be checked according to the provisions of this appendix.

6.1.3 Elastic stability

Members or portions of members restrained as in G.l.l which do not contain plastic hinge locations should be

F.2.4 Sway index, @, checked according to G.2(a) to ensure stability between

The sway index, $,, of each storey is given by: effective torsional restraints to both flanges.

6" - 6, $,= 7 G.1.4 Plastic stability

~ e m b e n B r portions of members restrained as in G.l.l where which contain plastic hinge locations should be checked

h i s the storey height; accordkg to G.Z(b) to ensure stability between effective torsionil restraints to both flanges.

6 , is the horizontal deflection of the top of the storey; Full lateral restraint should be provided to the compression

6, is the horizontal deflection of the bottom of the flange at all plastic hinge locations, or where this i s storey. impracticable within Dl2 of the hinge location where D is

the depth of the member. F.2.5 Partial sway bracing

In any storey the stiffening effect of infill wall panels as given in E.3.3 (up to a maximum relative stiffness, k , , of 2) G.2 Stability may be allowed for by introducing a diagonal strut in that storey of area A given by: Members or portions of members restrained as in (3.1.1

A = [I + (hlb) '1 "' should satisfy one of the following conditions to ensure

h (hlb) stability between effective torsional restraints.

(a) Elastic stability (see 6.1.3)

(1 ) Uniform members

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BS 5950 : P a n 1 : 1990 Appendix G

I

JC -B

X Compression flange Y

Uniform member

& - -

I

% Compression flange

- /B -4e -x-x-x-x-x-x-x-xX-8

Compression flange

Lt . - - - - -- - - - - - --

Tapered members Effective torsional restraints to both flanges. A-A Reference axis.

x Lateral restraints to one flange. B-B Restraint axis. F Axial load where present. 1, Length under consideration. M Applied moment in either direction.

Figure 29. Members restrained on tension flange

(2) Tapered members

F M - + - Qpb at any section. A Sx

(b) Plastic stability (see G.1.4). For uniform members use (1) or (2); for tapered members use (2).

( 1 ) Lengths without lateral loads

(2) Lengths with lateral loads

where

F i s the applied axial load where present;

P, is the compression resistance determined in accordance with 4.7.4 except that for buckling about the minor axis the slenderness should be taken as A,,;

XTC is as defined in 6.3.2;

M =rn,MA;

m, is as defined in G.3.4; MA is the maximum moment on the member or portion

of the member under consideration; Mb = pbSx Q P ~ Z ; p, i s the lateral torsional buckling resistance

determined in accordance with 4.3.7 except that the equivalent slenderness should be taken as A,,;

XTB i s as defined in G.3.3; M i s the applie+poment at the section considered; A is the cross-s8ctional area at the section considered;

S, i s the plastic modulus a t the section considered; M, =pvSx; ? '

Mpr =pVSrx; S,, i s the reduced plastic modulus due to axial load; a i s as defined in G.3.1; Lk i s as defined in G3.5; n, is as defined in G.3.6; c is as defined in 6.3.3.

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BS 5950 : Part 1 : 1990 Appendix G

G.3 Determination of factors

G.3.1 General

See figure 30.

6.3.2 Minor axis slenderness ratio, ATc The minor axis slenderness ratio used to determine the compression resistance in G.2 should be taken as:

ATC ' Y A where

A is the slenderness L/rY of the member between effective torsional restraints to both flanges;

B d - + - + - + - + - + - * . -

a is as defined in G.3.1;

A-*

h, is the distance between the shear centres of the flanges;

x is as defined in 4.3.7.5.

L Lt - x Lateral restraints to one flange

Effective torsional restraints to both flanges A-A Reference axis 0-0 Restraint axis a Distance between reference axis and restraint axis

L , Length over which buckling is to be checked

Figure 30. Typical haunch

*-rA

G.3.3 Minor axis slenderness ratio, ATE The minor axis slenderness ratio, XTB, used to determine the bending resistance in G.2 should be taken as:

ATE = n,uv,cA

r 4a 1 ' A -

r

For tapered members v, is calculated by reference to the smallest section:

d

where

a is as defined in G.3.1;

A is as defined in G.3.2;

h, is as defined in G.3.2;

x is as defined in 4.3.7.5;

u is as defined in 4.3.7.5 except for tapered members where u should be taken as 1.0;

n, i s taken as 1.0 where there are no intermediate loads betyeen restraints; otherwise n, i s as defined in G.3.6;

i c i s taten as 1.0 for uniform members and as follows

ffr tapered members:

where

R is the ratio of the greater depth to the lesser depth of thesection between effective torsional restraints;

q i s the ratio of the tapered length to the total length of the section between effective torsional restraints.

G.3.4 Equivalent uniform moment factor, m,

The value of m, should be taken as 1.0 when intermediate loads are applied between effective torsional restraints.

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BS 5950 : Part 1 : 1990 Appendix G

Otherwise m, should be obtained from table 39 where: Only positive values of N should be included.

y is obtained from G.3.2; N i s positive when it produces compression in the unrestrained flange.

0, is the ratio of the algebraically smaller end moment to the larser. Moments which produce compression on Where axial load is present see G.3.6.2. - the unrestrained flange should be taken as positive. MI to M, are the moment capacities of the sections When 0, < - 1 the value of 0, should be taken as - 1. corresponding to N , to N, , but see G.3.6.3. See f idire 31. Ns . Nz N3 Na

NOTE. This definition of 0, is different to that given for p - i s the greater of - - - Ms M2' M ~ ' M4

in 4.3.7. NE . NI Nj - IS the greater of - -

G.3.5 Limiting length, L, ME MI ' M5

The limiting length, L k , should be taken as: Only positive values of (2 - 3 ) should be

(5.4 + 600 3) rvx ME E included.

Lk =

(5.4 EX x 2 - l ) l h G.3.6.2 Axial loading. Where elastic stability i s considered E no allowance should be made in the value of n, for the

wherex is as defined in 4.3.7.5. For tapered members L, effects of axial load. should be calculated for the smallest section. Where plastic stability is being considered the values of N,

to NS should be taken as: G.3.6 Slenderness correction factor, n, N + a F

G.3.6.1 General. The general expression of the slenderness where correction factor, n,, is given by: a i s the distance between the reference axis and the axis

of restraint; + - F is the applied axial load.

l/2 G.3.6.3 Moment capacities. For elastically designed members of uniform section M I to M S should be taken as:

M = P,Z, where

where Z, is the elastic modulus for the compression flange NI to N S are the values of the applied moments at the of the section,

ends of the quarter points and mid length of the length between effective torsional restraints In Other cases is given by:

as shown in figure 32. M = P,S, where S, i s the plastic modulus of the section. I

taken as - 1.0.

I Figure 31. Value of P, I

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BS 5950 : Part 1 : 1990 Appendix G and H

Figure 32. Intermediate momentri

Q

Table 39. Equivalent uniform moment factor, m,

Appendix H. Web buckling where

X, is the equivalent slenderness of the web given by: H.l Shear buckling without utilizing

(0.6~,,,/q.)"~ tension field action qe is the elastic critical shear strength of the panel (in

The critical shear strength, q,, of a web panel is given by ~/rnrn' ) given by:

the following. 1 1000 (1 1 when a/d < 1 : qe = [o-75 + [=] (a) When A, Q 0.8

0

Qcr = 0 . 6 ~ ~ ~ (b) When 0.8 < X, < 1.25

0.1

0.76 0.78 0.80 0.81 0.83

0.85 0.86 0.88 0.89 0.90

0.92

0.93 0.94 0.95 0.96 0.97

0.98 0.98 0.99 1.00 1.00

0.5

0.39 0.40 0.41 0.42 0.44

0.46 0.48 0.50 0.53 0.55

0.58

0.62 0.65 0.69 0.72 0.76

0.81 0.85 0.90 0.95 1.00

-1.0 -0.9 -0.8 -0.7 -0.6

-0.5 -0.4 -0.3 -0.2 -0.1

0.0

0.1 0.2 0.3 0.4 0.5

0.6 0.7 0.8 0.9 1.0

qcr = 0.6pvw [ I - 0.8(XW - 0.8)]

(c) When A, 2 1.25

0.7

0.31 0.32 0.34 0.36 0.38

0.40 0.43 0.45 0.48 0.51

0.55

0.58 0.62 0.66 0.70 0.75

0.79 0.84 0.89 0.95 1.00

0.6

0.35 0.36 0.37 0.39 0.40

0.42 0.45 0.47 0.50 0.53

0.56

0.59 0.63 0.67 0.71 0.75

0.80 0.85 0.90 0.95 1.00

1.00 1.00 1.00 1.00 1.00

1.00 1.00 1.00 1.00 1.00

1.00

1.00 1.00 1.00 1.00 1.00

1.00 1.00 1.00 1.00 1.00

a is the spacing of transverse stiffeners;

d is the depth of the web;

0.2

0.61 0.63 0.64 0.66 0.67

0.69 0.70 0.72 0.74 0.76

0.78

0.80 0.82 0.84 0.86 0.88

0.91 0.93 0.95 0.98 1.00

Qcr = 4e t is the thickness of the web;

0.8

0.28 0.30 0.32 0.34 0.36

0.38 0.41 0.44 0.47 0.50

054

0.57 0.61 0.65 0.70 0.74

0.7s 0.84 0.89 0.95 1.00

p,, is the design strength of the web.

0.3

0.51 0.52 0.53 0.55 0.56

0.58 0.59 0.61 0.63 0.65

0.68

0.70 0.73 0.76 0.79 0.82

0.85 0.89 0.92 0.96 1.00

0.9

0.26 0.28 0.30 032 0.34

0.37 0.40 0.43 0.46 0.49

0.53

0.57 0.61 0.65 0.69 0.74

0.79 0.84 0.89 0.94 1.00

0.4

0.44 0.45 0.46 0.47 0.49

0.50 0.52 0.54 0.57 0.59

0.62

0.65 0.68 0.71 0.75 0.78

0.82 0.87 0.91 0.95 1.00

1.0

0.24 0.26 0.28 0.30 0.33

0.36 0.39 0.42 0.45 0.49

0.52

0.56 0.60 0.65 0.69 0.74

0.79 0.84 0.89 0.94 1.00

1.1

0.22 0.24 0.27 0.29 0.32

0.35 0.38 0.41 0.45 0.48

0.52

0.56 0.60 0.64 0.69 0.74

0.79 0.84 0.89 0.94 1.00

1.2

0.21 0.23 0.26 0.28 0.31

0.34 0.37 0.41 0.44 0.48

0.52

0.56 0.60 0.64 0.69 0.74

0.79 0.84 0.89 0.94 1.00

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BS 5950 : Part 1 : 1990 Appendix H

H.2 Shear buckling utilizing tension field action The basic shear strength of the web panel, q,, i s given by:

where

y , is the basic tension field strength given by:

Y b = d O y w 2 - 34,r2 + @ t 2 ) " 2 - 4% -

in which 4, = (1 + (aldI2 ) %

The flange-dependent shear strength factor, q f , is given by:

qf = [ 4 ~ 3 sin (5) ( * ) l h ] P V W x 0 . 6 p y w

where 0 = tan-' (3 a i s the spacing of transverse stiffeners;

d is the depth of the web;

t is the thickness of the web;

pyw is the design strength of the web. NOTE. If q b i s greater than 0 . 5 7 p y w it may be taken as equal to but not greater than 0 . 6 ~ ~ ~ .

H.3 Thin or slender webs designed for combined stresses H.3.1 General

I This clause is for checking thin or slender webs which have been designed as subject to longitudinal stresses due to bending or directly applied loads. The longitudinal stresses should be considered as consisting of either:

(a) pure bending stress (equal compressive and tensile stresses symmetrical about the middepth of the panel);

(b) pure bending stress combined with uniform axial stress. This arises whenever the middepth of the panel does not coincide with the neutral axis of the girder, whether or not an axial load is applied.

H.3.2 Combination of stresses

I The following interaction expression should be satisfied:

When compressive edge loading is also applied (see 4.5.2.2) the term f C / p c . , , should be replaced as follows:

(a) when fc is compressive

[( - fc )' + ( " d ) - ' 1 Pc.cr p e d

(b) when fc is tensile

[ ( f e d ) 2 ( f c ) 2 ] - - when ( f e d ) 2 , ( f c ) 2 - - P e d P c . c r P e d pc.cr

( f e d ) 2 ] % ( f ~ ) i f e d ) or - - - - when - 2 > -

P c . c r P e d p c . c r \ P e d

where

M, is the maximum moment in the web panel;

Mcr i s the buckling resistance moment of the web panel given by:

Mcr = P b . c r S w ; pb,cr i s the critical bending strength of the web panel

given by:

1 6 3 0

S, i s the plastic modulus of the web

fc is the mean longitudinal compressive stress in the web (if this stress is tensile fc i s negative);

p,, , , is the critical axial strength of the web panel given by the following:

(1) when one flange is in tension:

(2) when both flanges are subject to compression:

(i) for sections built-up by welding

81 5 2

43PY

16 + dltc

(ii) for rolled sections

fv i s tho maxhum shear stress in the panel;

pq i s tho shear buckling strength of the web panel. Generally pq = qcr but i f the web is designed using tension field action as given in 4.4.5.4 then Pq q b ;

qb i s the basic shear strength of the web panel as given in 4.4.5.4.1;

qcr is the critical shear strength of the web panel as given in 4.4.5.3;

fed is the compression stress due to edge loading as given in 4.5.2.2 (if edge loading i s tensile fed i s zero);

ped i s the compressive strength for edge loading as given in 4.5.2.2.

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Publications referred to BS 4 Structural steel sections

Part 1 Specification for hot rolled sections

BS 29 Specification for carbon steel forgings above 150 m m ruling section BS 639 Specification for covered carbon and carbon manganese steel electrodes for manual metal . arc weld~ng BS 709 Methods of destructive testing fusion welded joints and weld metal in steel BS 2573 Rules for the design of cranes

Part 1 Specification for classification, stress calculations and design criteria for structures BS 2655 Specification for lifts, escalators, passenger conveyors and paternosters BS 2853 Specificat~on for the design and testing of steel overhead runway beams BS 3100 Specification for steel castings for general engineering purposes BS 3692 Specification for I S 0 metric precision hexagon bolts, screws and nuts. Metric units BS 4190 Specification for I S 0 metric black hexagon bolts, screws and nuts BS 4320 Specification for metal washers for general engineering purposes. Metric units

BS 4395 Specification for high strength friction grip bolts and associated nuts and washers for structural engtneering Part 1 General grade Part 2 Higher grade bolts and nuts and general grade washers Part 3 Higher grade bolts (waisted shank), nuts and general grade washers

BS 4449 Specification for carbon steel bars for the reinforcement of concrete BS 4482 Specification for cold reduced steel wire for the reinforcement o f concrete BS 4483 Specification for steel fabric for the reinforcement o f concrete BS 4604 Specification for the use of high strength fr ict ion grip bolts in structural steelwork. Metric series

Part 1 General grade Part 2 Higher grade (parallel shank) Part 3 Higher grade (waisted shank)

BS 4848 specification for hot rolled structural steel sections Part 2 Hollow sections Part 4 Equal and unequal angles Part 5 Bulb flats

BS 4933 Specification for I S 0 metric black cup and countersunk head bolts and screws wi th hexagon nuts BS 5135 Specification for the process of arc welding o f carbon and carbon manganese steels BS 5400 Steel. concrete and composite bridges

Part 3 Code o f practice for the design of steel bridges Part 10 Code of practice for fatigue

BS 5493 Code of practice for protective coating of iron and steel structures against corrosion BS 5950 Structural use of steelwork i n building

Part 2 Specification for materials, fabrication and erection : hot rolled sections Part 3 Design i n composite construction Section 3.1 Code o f practice for design of single and continuous composite beams

'Section 3.2 Code of practice for design of composite columns and frames Part 4 Code o f practice for design of floors wi th profiled steel sheeting Part 5 Code o f practice for design of cold formed sections

BS 6399 Loading for buildings Part 1 Code o f practice for dead and imposed loads Part 3 Code of practice for imposed roof loads

BS 8004 Code of practice for foundations BS 81 10 Structural use of concrete

Part 1 Code o r practice for design and construction CP 3 Code of basic data for the design of buildings

Chapter V Loading Part 2 Wind loads

I S 0 2394 General principles on reliability for structures

BS E N 10002-1 Metallic materials - Tensile tasting - Part 1 Method of test BS EN 10025 Hot rolled products of non-alloy structural steels: Technical d e l i v e ~ n d i t i o n r '

I n preparation.

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BS 5950 : Part 1 : 1990

This British Standard, having been prepared under the direction of implementing the standard, of necessary deta~ls such as symbols and the Civil Engineering and Building Structures Standards Policy size, type or grade des~gnatrons. Enqu~r~es should be addressed to Committee. was published under the authority of the Board of BSI the Publications Manager, BSI. L ~ n f o r d Wood, M ~ l t o n Keynes

and comes into effect on31 July 1990 MK14 6LE. The number for telephone enqulrles IS 0906 220022

@British Standards Institution. 1990 and for telex 825777.

First published August 1985

Second edition July 1990

ISBN 0 580 18566 4

The following BSI references relate t o the work on this standard: Committee reference CSBl27 Draft for comment 87115229 DC

British Standards Institution. Incorporated by Royal Charter, BSI IS the independent natlonal body for the preparation of Br~tish Standards. I t is the UK member of the lnternat~onal Organization for Standardization and U K sponsor of the Br~tish Natronal Committee o f the lnternat~onal Electrotechnrcal Commrss~on.

In addition to the preparation and promulgation of standards, BSI

Contract requirements. A B r ~ t ~ s h Standard does not purport to rnclude all the necessary provtstons of a contract Users o f Brltlsh Standards are resoons~ble for thew correct anolicatlon

Revision of British Standards. Brit~sh Standards are rev~sed, when necessary, by the Issue elther of amendments or of revised e d ~ t ~ o n s It is important that users of British Standards should ascertain that they are In possession of the latest amendments or ed~ t~ons .

Automatic updating service. BSI provides an economlc, ~ ~ d r v ~ d u a l and automatic standards updat~ng servlce called PLUS Deta~ls are ava~lable from BSI Enqu~ry Sect~on at M ~ l t o n Keynes, telephone 0908 221 166, telex 825777.

offers specialist services including the proviston of informat~on through the BSI Library and Standardline Database; Technrcal Help to Exporters. and other servlces Adv~ce can be obta~ned from the lnformatlon on all BSI ,,ubllcatlons Is In the BS, catalogue Enqu~ry Sect~on, BSI, M ~ l t o n Keynes MK14 6LE, telephone ~ ~ p p l e m e n t e d each month by BSI News w h ~ c h IS ava~lable to 0908 221 166. telex 825777 subscrrb~ng members of BSI and glves deta~ls o f new publ~cat~ons. Copyraght. Users of B r ~ t ~ s h Standards are rem~nded that copyright revtslons, amendments and w~thdrawn standards Anv person who subs~sts In all BSI publ~cat~ons N o part of thls publlcatlon may be when mak~ng use of a B r ~ t ~ s h Standard, encounters an Inaccuracy or reproduced In any form w ~ t h o u t the prlor permlsston ~n wrrtlng of amb~qurty, IS requested t o n o t ~ f y BSI w ~ t h o u t delay In order that BSI T h ~ s does not preclude the free use, ~n the course o f the matter may be invest~yated and approprtate actton taken

Committees responsible for this British Standard The preparation o f this British Standard was entrusted by the Civil Engineering and Building Structures Standards Policy Committee (CSBI-) t o Technical Committee CSB127, upon which the fol lowing bodies were represented:

British Constructional Steelwork Association L t d British Railways Board British Steel Industry Department o f the Environment (Property Services Agency) Department o f the Environment (Building Research Establishment) Department o f the Environment (Construction Industries

Directorate) Health and Safety Executive lnst i tut ion of Civil Engineers Insti tut ion of Structural Engineers Royal Institute o f British Architects Steel Construction Institute Welding Institute

Amendments issued since publication w

British Standards Institution 2 Park Street London W1A 2BS . Telephone 071-629 9000 . Telex 266933

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Amendment No. 1 published and effective from 28 February 1992 to BS 5950 : Part 1 : 1990

Structural use of steelwork in building Part 1. Code of practice for design in simple and continuous construction: hot rolled sections

AMD 6972

Revised text

AMD 6972 Contents February 1992 In the l i s t of tables:

(a) delete the title of table 4 and substitute 'Maximum thickness for adequate notch thickness of parts subject to applied tensile stress';

(b) delete the title of table 6 and substitute 'Design strengths,~,,';

(c) in items (a) to (dl of tables 21 to 23, delete all references to 'Grade 43 steel' and 'Grade 50 steel' and delete the brackets around the text quantifyingp,,.

AMD 6972 Clause 1.2 Definitions February 1992 Ar the end of the definitions clause, insert the following new definitions.

'1.2.46 design grade. Designation used to define specific performance requirements of the material for design purposes, in particular strength and toughness.

1.2.47 product grade. Designation used to define mechanical and chemical properties and manufacturing requirements of the material as specified in BS 5950 : Part 2.'

AMD 6972 February 1992

Clause 2.4.4.2 Maximum thickness Delete the second sentence.

AMD 6972 Table 4. Maximum thickness of parts subject to applied tensile stress February 1992 Delete the entire table and substitute the following new table. SG

Kab

ir.co

m

AMD 6972 Clause 2.5.2 Durability February 1992 In the last line, delete 'to BS 4360'.

AMD 6972 Clause 3.1.1 Strength of steel February 1992 Delete paragraph 1 and substitute the following.

I

Table 4. Maximum thickness for adequate notch toughness of parts subject to applied tensile stress

'This standard covers the design of structures fabricated from weldable structural steels in designated design grades supplied to the appropriate product grade as given in BS 5950 : Part 2. Other steels, excluding rimming steels, may also be used provided that due allowance be made for variations in properties, including ductility and welda- bility (see BS 5950 : Part 21.'

NOTE 1. For sections with flanges the thickness is the flange thickness defined in the relevant British Standard.

NOTE 2. The relevant structural steel standard may require Charpy values to be agreed for certain product grades and thicknesses.

NOTE 3. Where no value is shown, the maximum thickness for adequate notch toughness may be assumed to be in excess of 100 mm.

NOTE 4. The inclusion of a thickness limit in the table does not necessarily imply that steel of that thickness can be supplied to that design grade in all product forms.

NOTE 5. For design grades 43B(T) and 50B(T), verification of the impact properties of quality B by testing should be specified under option 7 of BS EN 10025 when the steel is ordered.

NOTE 6. The maximum thickness values are based on a minimum Charpy value of 27 J" at the following test temperatures.

Design grad- 43.50 and 55


c A (no test) B +20 C 0 D -20 DD -30' E -40 E E -50 F -60

Design grade WR 50


O C

A o B 0 C -15

In paragraph 2, line 4, delete 'BS 4360 (or agreed with steelmaker).'and substitute 'the appropriate product standard (see BS 5950 : Part 2).'

which is accepted as equivalent to 27 J at -30 OC.

(see notes

Design grade

43A 438 43B(T) 43C 430 43DD 43 E 43EE

50A 500 50B(T) 50C 500 50DD 50E 50EE 50F

55C 55EE 55 F

WR5OA WR50B WR50C

For Fe

External conditions

K = 1

mm

15 15 20 40 90 - - -

12 12 16 30 70

100 - - -

25 - -

30 30 55

40 J at -20

1 to 6)

Internal

=

mm

30 30 40 80 - - - -

25 25 32 60 - - - - - 50 - -

60 60 -

*c ,

conditions

K * 1

mm

25 25 30 60 - - - -

20 20 25 45

100 - - - -

35 - -

45 45 85

510 OD, BS EN

K = 2

mm

50 50 60 - - - - -

40 40 50 90 - - - - -

70 - -

90 90 -

10025 specifies

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Table 6. Design strengths, p, , for steel t o BS 4360 Delete the entire table and substitute the following new table.


r

Table 6. Design strengths,py

Clause 3.1.3 Steel castings and forgings Delete the las t sentence and substitute the following.

'Design strengths corresponding to hot rolled steel of design grade 43 may be adopted where no other information is available.'


Sections, plates and hollow sections

P~

N/mm2

275 265 255 24 5 235

355 34 5 335 325 31 5

450 430

400

h i g n grade

43

50

55

1

Clause 3.3.3 Effective area at connections In lines 3 and 4, delete 'where for steels complying with BS 4360:' and substitute 'where:'.

Insert 'design' before 'grade' in each of lines 5,6 and 7.

Thickness. less than or equal to

mm

16 40 63 80

100

16 40 63 80

1 00

16 25 40 63


Table 7. Limit ing w id th t o thickness ratios Against the entry for 'Legs of single angl)and double angle members with components separated', in column 5, insert 'and' between the two rows of formulae.


Table 8. Strength reduction factors fo r slender elements In the heading for column 3, delete 'Stress'and substitute 'Strength'.

In the entry for 'Internal element of compression flange', in column 2, delete 'Build' and substitute 'Built'.

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Clause 4.3.7.7 Equal flanged rolled sections In paragraph 1, line 3, insert 'not' between 'are' and 'equal'

In the definition of 'A', delete ' L E / r l and substitute ' L E / r y l

In the definition of 'r', delete 'r' and substitute 'r,'.

In paragraph 4, line 4, insert 'the' between 'for' and 'value'.


Table 21. Critical shear strength, qCr In the headings of items (a) to (d) of the table, delete al l references to 'Grade 43 steel' and 'Grade 50 steel' and delete the brackets around the text quantifying p,,.


Table 22. Basic shear strength, qb In the headings of items (a) to (d) of the table, delete all references to 'Grade 43 steel' and 'Grade 50 steel' and delete the brackets around the text quantifying p,.


Table 23. Flange dependent shear strength factor, q,

In the headings of items (a) to (d) of the table, delete all references to 'Grade 43 steel' and 'Grade 50 steel' and delete the brackets around the text quantifying p,.


Clause 4.1 2.4.2 General rules fo r empirical design In item (a). line 2, delete 'grade 43 of BS 4360' and substitute 'design grade 43'.

AMD 6.972 Clause 4.1 3.1 General February 1992 In paragraph 5, line 1, delete 'of grade 43A' and substitute 'of design grade 43A'.

In line 3, delete 'Grade 43A baseplates' and substitute 'Baseplates of design grade 43A steel'.

AMD 6972 Clause 5.3.3 Grades o f steel February 1992 Delete paragraph 1 and substitute the following.

'Steel for plastic design should comply wi*pll three of the following:'

In item (c), line 2, delete 'BS 18' and substitute 'BS EN 10002-1'.

AMD 6972 Clause 5.5.3.5.2 February 1992 In item (31 of (a):

(a) immediately after the first formula, insert 'design' between 'for' and 'grade';

(b) immediately after the second formula, insert 'design' between 'for' and 'grade'

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Table 33. Bearing strength of connected parts for ordinary bolts in clearance holes, p,, In the overall heading of columns 1 to 3, delete 'Steel to BS 4360' and substitute 'Design grade of steel'.

*

AMD 6972 Table 34. Bearing strength of parts connected by parallel shank friction February 1992 grip fasteners, p,,

In the overall heading of columns 1 to 3, delete 'Steel to BS 4360' and substitute 'Design grade of steel'.

AMD 6972 Clause 6.6.5.1 Design strength February 1992

In paragraph 1, line 3, delete 'on steel complying with BS 4360'


Table 36. Design strength, p, In the heading of column 1, delete 'Grade of steel in BS 4360' and substitute 'Design grade of steel'.

AMD 6972 Publications referred to February 1992

Delete the entries for BS 18 and BS 4360.

To the bottom of the list, insert the following new entries.

'BS EN 10002-1 Metallic materials - Tensile testing - Part 1 Method of test BS EN 10025 Hot rolled products of nonalloy structural steels: Technical delivery conditions'

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UDC 693.814 669.14.018.29 d this publication may be ... · Shear buckling resistance of thin webs ... 3.4 Deductions for holes ... bending C Compression strength: ...

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