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Page1prEN 1995-2 Second draft

prEN 1995-2

Eurocode 5 Design of timber structures

Part 2: Bridges

Second Draft

21 February 2003

Document CEN/TC 250/SC 5: N 197

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Contents

Foreword 4Section 1 General 7

1.1 Scope 71.1.1 Scope of Eurocode 5 71.1.2 Scope of EN 1995-2 71.1.3 Normative references 8

1.2 Assumptions 81.3 Distinction between principles and application rules 81.4 Definitions 8

1.4.1 Grooved connection 81.4.2 Laminated deck plates 91.4.3 Pre-stressing 10

1.5 Notations 11Section 2 Basis of design 12

2.1 Requirements 122.2 Principles of limit state design 122.3 Basis variables 122.4 Verification by the partial factor method 12Section 3 Material 14Section 4 Durability 154.1 Timber 154.2 Protection of metal parts 154.3 Sealing of deck and wearing pavements 16Section 5 Basis of structural analysis 175.1 General 175.2 Timber deck plates 17

5.2.1 General 175.2.2 Concentrated vertical loads 175.2.3 Simplified analysis 18

Section 6 Ultimate limit state 206.1 General 206.2 Deck plates 20

6.2.1 System strength 206.2.2 Stress-laminated deck plates 21(1)P The long-term pre-stressing forces after losses shall be such that no inter-laminar slip occurs. 21

6.3 Rolling shear 226.3.1 Timber-concrete composite members 22

6.4 Fatigue 23Section 7 Serviceability limit states 247.1 General 247.2 Limiting values for deformation 247.3 Vibrations caused by pedestrians 247.4 Vibrations caused by wind 24Section 8 Connections 258.1 General 258.2 Timber-concrete connections in composite beams 25

8.2.1 Laterally loaded dowel-type fasteners 258.2.2 Axially loaded rod-type fasteners 25

8.2.3 Grooved connections 26Section 9 Structural detailing and control 28

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Annex A (informative) 29Simplified fatigue verification 29A1 General 29A2 Fatigue loading 29A3 Fatigue verification 29Annex B (informative) 32Vibrations cause by pedestrians 32B1 General 32B2 Vertical Vibrations 32B.3 Horizontal Vibrations 33Annex C (informative) 35Bonded-in steel rods 35C.1 General 35C.2 Axially loaded rods 35

C.2.1 General 35C.2.2 Ultimate limit state 36

C.2.3 Serviceability limit states 38C.3 Laterally loaded rods 38C.3.1 Ultimate limit state 38C.3.2 Serviceability limit states 38

C.4 Combined laterally and axially loaded rods 39C.5 Execution 39

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Foreword

This European Standard EN 1995-1-1, Eurocode: Design of timber structures, Part 1.1:General Rules, General rules and rules for buildings, has been prepared on behalf ofTechnical Committee CEN/TC250 Structural Eurocodes , the Secretariat of which isheld by BSI. CEN/TC250 is responsible for all Structural Eurocodes.

The text of the draft standard was submitted to the formal vote and was approved byCEN as EN 1995-1-1 on YYYY-MM-DD.

No existing European Standard is superseded.

Background of the Eurocode programme

In 1975, the Commission of the European Community decided on an actionprogramme in the field of construction, based on article 95 of the Treaty. The objective

of the programme was the elimination of technical obstacles to trade and theharmonisation of technical specifications.

Within this action programme, the Commission took the initiative to establish a set ofharmonised technical rules for the design of construction works which, in a first stage,would serve as an alternative to the national rules in force in the Member States and,ultimately, would replace them.

For fifteen years, the Commission, with the help of a Steering Committee withRepresentatives of Member States, conducted the development of the Eurocodesprogramme, which led to the first generation of European codes in the 1980s.

In 1989, the Commission and the Member States of the EU and EFTA decided, on thebasis of an agreement1 between the Commission and CEN, to transfer the preparationand the publication of the Eurocodes to CEN through a series of Mandates, in order toprovide them with a future status of European Standard (EN). This links de facto theEurocodes with the provisions of all the Councils Directives and/or CommissionsDecisions dealing with European standards (e.g. the Council Directive 89/106/EEC onconstruction products CPD and Council Directives 93/37/EEC, 92/50/EEC and89/440/EEC on public works and services and equivalent EFTA Directives initiated inpursuit of setting up the internal market).

The Structural Eurocode programme comprises the following standards generallyconsisting of a number of Parts:

EN 1990 Eurocode : Basis of Structural DesignEN 1991 Eurocode 1: Actions on structuresEN 1992 Eurocode 2: Design of concrete structuresEN 1993 Eurocode 3: Design of steel structuresEN 1994 Eurocode 4: Design of composite steel and concrete structuresEN 1995 Eurocode 5: Design of timber structuresEN 1996 Eurocode 6: Design of masonry structuresEN 1997 Eurocode 7: Geotechnical design

1Agreement between the Commission of the European Communities and the European Committee for

Standardisation (CEN) concerning the work on EUROCODES for the design of building and civilengineering works (BC/CEN/03/89).

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EN 1998 Eurocode 8: Design of structures for earthquake resistanceEN 1999 Eurocode 9: Design of aluminium structures

Eurocode standards recognise the responsibility of regulatory authorities in eachMember State and have safeguarded their right to determine values related toregulatory safety matters at national level where these continue to vary from State toState.

Status and field of application of Eurocodes

The Member States of the EU and EFTA recognise that Eurocodes serve as referencedocuments for the following purposes: as a means to prove compliance of building and civil engineering works with the

essential requirements of Council Directive 89/106/EEC, particularly EssentialRequirement N1 Mechanical resistance and stability and EssentialRequirement N2 Safety in case of fire;

as a basis for specifying contracts for construction works and related engineeringservices ;

as a framework for drawing up harmonised technical specifications for constructionproducts (ENs and ETAs)

The Eurocodes, as far as they concern the construction works themselves, have adirect relationship with the Interpretative Documents2 referred to in Article 12 of theCPD, although they are of a different nature from harmonised product standards3.Therefore, technical aspects arising from the Eurocodes work need to be adequatelyconsidered by CEN Technical Committees and/or EOTA Working Groups working onproduct standards with a view to achieving full compatibility of these technical

specifications with the Eurocodes.

The Eurocode standards provide common structural design rules for everyday use forthe design of whole structures and component products of both a traditional and aninnovative nature. Unusual forms of construction or design conditions are notspecifically covered and additional expert consideration will be required by the designerin such cases.

National Standards implementing Eurocodes

The National Standards implementing Eurocodes will comprise the full text of theEurocode (including any annexes), as published by CEN, which may be preceded by a

National title page and National foreword, and may be followed by a National annex.

2According to Art. 3.3 of the CPD, the essential requirements (ERs) shall be given concrete form in

interpretative documents for the creation of the necessary links between the essential requirements andthe mandates for harmonised ENs and ETAGs/ETAs.3According to Art. 12 of the CPD the interpretative documents shall :a) give concrete form to the essential requirements by harmonising the terminology and the technical bases and

indicating classes or levels for each requirement where necessary ;b) indicate methods of correlating these classes or levels of requirement with the technical specifications, e.g.

methods of calculation and of proof, technical rules for project design, etc. ;c) serve as a reference for the establishment of harmonised standards and guidelines for European technical

approvals.The Eurocodes, de facto, play a similar role in the field of the ER 1 and a part of ER 2.

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The National annex may only contain information on those parameters which are leftopen in the Eurocode for national choice, known as Nationally Determined Parameters,to be used for the design of buildings and civil engineering works to be constructed inthe country concerned, i.e.: values and/or classes where alternatives are given in the Eurocode;

values to be used where a symbol only is given in the Eurocode;

country specific data (geographical, climatic, etc.), e.g. snow map;

the procedure to be used where alternative procedures are given in the Eurocode;

decisions on the application of informative annexes;

references to non-contradictory complementary information to assist the user toapply the Eurocode.

Links between Eurocodes and harmonised technical specifications (ENs andETAs) for products

There is a need for consistency between the harmonised technical specifications forconstruction products and the technical rules for works4. Furthermore, all theinformation accompanying the CE Marking of the construction products which refer toEurocodes shall clearly mention which Nationally Determined Parameters have beentaken into account.

Additional information specific to EN 1995-2

EN 1995 describes the Principles and requirements for safety, serviceability anddurability of timber bridges. It is based on the limit state concept used in conjunctionwith a partial factor method.

For the design of new structures, EN 1995-2 is intended to be used, for directapplication, together with EN 1995-1-1 and relevant Parts of EN 1991.

Numerical values for partial factors and other reliability parameters are recommendedas basic values that provide an acceptable level of reliability. They have been selectedassuming that an appropriate level of workmanship and of quality management applies.When EN 1995-2 is used as a base document by other CEN/TCs the same valuesneed to be taken.

National annex for EN 1995-2

This standard gives alternative procedures, values and recommendations with notesindicating where national choices may have to be made. Therefore the NationalStandard implementing EN 1995-2 should have a National annex containing allNationally Determined Parameters to be used for the design of buildings and civilengineering works to be constructed in the relevant country.

National choice is allowed in EN 1995-2 through clauses:2.3(1)P Load duration assignment2.4(1)P Partial factors4.1(6) Distances between timber parts and ground7.2(1)P Limiting values of deflection

4see Art.3.3 and Art.12 of the CPD, as well as clauses 4.2, 4.3.1, 4.3.2 and 5.2 of ID 1.

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Section 1 General

1.1 Scope

1.1.1 Scope of Eurocode 5

(1)P Eurocode 5 applies to the design of buildings and civil engineering works in timber(solid timber, sawn, planed or in pole form, glued laminated timber or wood basedstructural products for example LVL) or wood-based panels jointed together withadhesives or mechanical fasteners. It complies with the principles and requirements forthe safety and serviceability of structures, and the basis of their design and verificationthat are given in EN 1990 Basis of structural design.

(2)P Eurocode 5 is only concerned with requirements for mechanical resistance,serviceability, durability and fire resistance of timber structures. Other requirements,e.g concerning thermal or sound insulation, are not considered.

(3) Eurocode 5 is intended to be used in conjunction with:EN 1990 Eurocode Basis of structural designEN 1991 Actions on structuresENs for construction products relevant for timber structuresEN 1998 Design of structures for earthquake resistance, when timber structuresare built in seismic regions

(4) Eurocode 5 is subdivided in various parts:EN 1995-1 General rulesEN 1995-2 Bridges

(5) EN 1995-1 General rules comprises:EN 1995-1-1 General rules General rules and rules for buildingsEN 1995-1-2General rules Structural Fire Design

(6) Part EN 1995-2 refers to the General rules in Part 1-1. The clauses in part EN1995-2 supplement the clauses in EN 1995-1-1, however, clauses of EN 1995-1-1 thatare not valid for the structural parts of the bridge are identified in the relevant sectionsof EN 1995-2.

1.1.2 Scope of EN 1995-2

(1) Part 2 of Eurocode 5 gives general design rules for the structural parts of bridges,i.e. structural members of importance for the reliability of the whole bridge or majorparts of it, made of timber and other wood based materials, either singly or compositewith concrete, steel or other materials.

(2) The following subjects are dealt with in Part 2:Section 1: GeneralSection 2: Basis of designSection 3: Material propertiesSection 4: DurabilitySection 5: Basis of structural analysisSection 6: Ultimate limit states

Section 7: Serviceability limit states

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Section 8: Connections with metal fastenersSection 9: Execution, control and maintenance

(3) Section 1 and Section 2 provide additional clauses to those given in EN 1990 Basisof structural design.

1.1.3 Normative references

(1) The following normative documents contain provisions which, through references inthis text, constitute provisions of this European standard. For dated references,subsequent amendments to or revisions of any of these publications do not apply.However, parties to agreements based on this European standard are encouraged toinvestigate the possibility of applying the most recent editions of the normativedocuments indicated below. For undated references the latest edition of the normativedocument referred to applies.

European Standards:

EN 1990:2002 Eurocode Basis of structural designEN 1991-2 Eurocode 1: Actions on structures Part 2: Traffic loads on bridgesEN 1991-1 Eurocode 1: Actions on structures Part 1-4: wind loadsEN 1992-1-1 Eurocode 2: Design of concrete structures Part 1-1: Common rules

for buildings and civil engineering structuresEN 1992-2 Eurocode 2: Design of concrete structures Part 2: BridgesEN 1995-1-1 Eurocode 5: Design of timber structures Part 1-1: Common rules

and rules for buildings

1.2 Assumptions

(1)P The general assumptions of EN 1990 apply. Additional requirements forexecution, maintenance and control are given in section 9.

1.3 Distinction between principles and application rules

(1)P The rules in EN 1990 clause 1.4 apply.

1.4 Definitions

(1)P The definitions of EN 1990 clause 1.5 and EN 1995-1-1 clause 1.3 apply.

(2)P The following terms are used in Part 2 of EN 1995 with the following meanings:

1.4.1 Grooved connection

(1)Shear connection consisting of the round or rectangular integral part of onemember embedded in the contact face of the other member. The connected partsare normally held together e.g. by screws or by connecting bolts.

NOTE: An example of a grooved connection is shown in figure 1.1.

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1.4.2 Laminated deck plates

(1)Deck plates made of edgewise or flatwise arranged laminations:

Deck plate made of individual vertical laminations are held together by nailing or

gluing and/or permanent lateral pressure; Deck plate made of laminations in layers of different grain direction (crosswise or at

different angles) whereby the layers are glued together or connected usingmechanical fasteners. See figure 1.3.

Note 1: Deck plates that are pre-stressed, but not glued are often called 'stress-laminated

decks' with the timber surfaces either sawn or planed. Examples of deck plates withedgewise laminations are shown in figure 1.2.

Note 2: Deck plates where the layers consist of simple boards are often called 'cross-laminatedtimber deck (CLT)', see figure 1.3.

2

1

3

Key:

1 Timber2 Concrete3 Fastener

Figure 1.1 Example of parts connected with grooved connection in shear andscrews

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a) b)

d)c)

1

Figure 1.2 Examples of deck plates made of edgewise arranged laminationsa) nail-laminated or screw-laminated

b) pre-stressed, but not gluedc) glued and pre-stressed

d) glued and pre-stressed (laminations made of glued laminated beams)

Figure 1.3 Deck plate made of flatwise arranged laminations

1.4.3 Pre-stressing

(1) A permanent effect due to controlled forces and/or deformations imposed on astructure.

NOTE: An example is the pre-stressing of timber deck plates by means of bars or tendons, seefigure 1.2 b to d.

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1.5 Notations

Drafting note: To be completed

For the purpose of this pre-standard, the following symbols apply.

Latin upper case lettersAef Effective areaAs Area of reinforcing barE Modulus of elasticityE0 Modulus of elasticity parallel to grainEmean Mean value of modulus of elasticityF ForceFv,d Design shear forceFt, Fc Tensile and compressive forceG0 Shear modulus parallel to grain

G90 Shear modulus perpendicular to grain (rolling shear)Kser Slip modulus

M Moment V Shear force..

Latin lower case lettersavert,,ahorAcceleration, vertical and horizontalbef Effective widthblam Width of the laminationd Diameter; distance

h Depth of beam; thickness of a platefvert,fhor fundamental natural frequency of vertical and horizontal vibrationsfv,d Design shear strengthfv,k Characteristic shear strengthfm,d Design bending strengthfc,90,d Design compressive strength perpendicular to grainfy,d Design yield strength of steelfu,k Characteristic ultimate strength of steelfh,k Characteristic embedding strengthkmod Modification factorksys System strength factorm Mass; mass per unit area; bending moment in plate

t Time; thicknessv Velocity.Greek upper case letters..Greek lower case letters

M Partial safety factor for materialsM,fat Partial safety factor for materials for fatigue verification

k Characteristic density

d Design value of coefficient of friction

c Compressive stress

Damping ratio

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Section 2 Basis of design

2.1 Requirements

(1)P EN 1990 clause 2.1 applies.

2.2 Principles of limit state design

(1)P EN 1990 clause 2.2 applies.

2.3 Basis variables

(1)P EN 1990 clause 2.3 applies

NOTE: Examples of load duration assignments are given in note to EN 1995-1-1 2.3.1. Therecommended load duration assignment for actions during erection is short-term. The National

choice may be given in the National annex.

(2) Variable actions due to the passage of traffic should be regarded as short-termactions.

(3) Pre-stressing forces perpendicular to the grain at the beginning, before thereduction caused by creep, should be regarded as short-term actions.

2.4 Verification by the partial factor method

(1)P EN 1995-1-1 2.4.1, 2.4.2 and 2.4.3 apply.

NOTE: For fundamental combinations, the recommended partial factors for material properties,m, are given in table 2.1. For accidental combinations, the recommended value of partial factor

is M = 1,0. Information on the National choice may be found in the National annex.

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Table 2.1 Recommended partial safe factors for material properties for ultimatelimit states, fundamental combinations

Timber and wood based materials

- normal verification solid timber

GLT

LVL, plywood, OSB

M

M

M

- fatigue verification M,fat

Steel used in joints

- normal verification M = 1,1

- fatigue verification M,fat

Steel used as composite members M, s = 1,15

Concrete used in composite members M,c = 1,5

Shear connectors between composite members

- normal verification M,v = 1,25

- fatigue verification M,v,fat

Pre-stressing steel elements M,s = 1,15

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Section 3 Material

(1)P Bridges or bridge parts that are not protected from water or direct weathering shallbe assigned to service class 3.

NOTE 1: Bridges or bridge parts protected from water or direct weathering are generallyassingned to service class 2. Water can be brought on the bridge by vehicles. Examples ofprotection from direct weathering are covered bridges by means of a roof and bridge deckplates acting as a roof.

NOTE 2: For bonded-in rods, see annex C (informative), the modification factor kmodis reducedfor service class 2.

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Section 4 Durability

4.1 Timber

(1)P The effect of precipitation, wind and solar radiation shall be taken into account.

(2) Direct weathering by precipitation or solar radiation of structural timber membersshould be avoided, or their effects be reduced by constructional preservation measures(see (3)) in relation to the life-time of the structure. Materials with sufficient naturaldurability or easy replaceability should be used.

(3) Where a partial or complete covering of the main structural elements is notpracticable, one or more of the following measures should be taken into account:

limitation of standing water on timber surfaces through appropriate inclination ofsurfaces;

limitation of openings, slots, etc., where water may accumulate or infiltrate;

limitation of direct absorption of water (e.g. capillary absorption from concretefoundation) through use of appropriate barriers;

prevention of fissures and delaminations, especially at locations where the endgrain would be exposed, by appropriate sealing and/or cover plates;

limitation of swelling and shrinking movements by ensuring an appropriate initialmoisture content and by reducing moisture changes through adequate surfaceprotection.

(4) Unless it can be ensured that the average equilibrium moisture content of loadbearing timber elements will only exceed 20% for a few weeks per year, then theseelements should be chemically protected by adequate means, or sufficiently naturallydurable timber should be used.

(5) The geometry of the structure should be such that the natural ventilation of alltimber parts is achieved.

(6) Where there is a risk of increased moisture near the ground, e.g. due to insufficientventilation due to vegetation between the timber and the ground, or sprinkling water,one or more of the following measures should be provided:

covering of the ground by course gravel or similar to limit vegetation; use a recommended distance between the timber parts and the ground level

NOTE: Values for distances between the timber parts and the ground are given below, where

the recommended values are underlined: at locations with dry conditions 100 to 200 mm

at locations of limited moisture in the ground 200 to 500 mm

at locations with high risk vegetation 500 to 800 mm.

The National choice may be specified in the National annex.

4.2 Protection of metal parts

(1)P Metal parts used in steel-to-timber joints or pre-stressing bars that becomeinaccessible

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for inspection once the bridge is completed, shall be adequately protected for the requireddesign working life.

(2) Under severe conditions, use should be made of stainless steel of appropriatecomposition, or of other corrosion-resistant materials whose durability canbe verified. Alternatively, consideration may be given to the use of plain carbon steelprotected by adequate galvanising, or by an appropriate paint system.

NOTE: An example of severe conditions is where corrosive de-icing cannot be excluded.

(3)P The possibility of stress corrosion shall be taken into account.

(4) Steel parts encased in concrete, such as reinforcing bars and pre-stressing cables,should be protected according EN 1992-1-1 clause 4.4.1 and EN 1992-2

4.3 Sealing of deck and wearing pavements

(1)P Seal layers shall be used to prevent water penetration in the deck systemsand to keep the timber plate dry during the life-time of the deck structure.

NOTE: A polymere modified bituminous layer is normally used.

(2) Attention should be paid on a sufficient elasticity of the seal layers.

(3) Before attaching the seal foil, the deck system should be dry and the surface shouldbe even.

(4) The pavement should be capable of transmitting shear forces, e.g due to braking

forces.

(5)P Where structural timber members are exposed to abrasion by traffic, the depthused in the design shall be the minimum permitted before the replacement.

(6) Sealings should be protected by the protection layer and wearing pavementswith sufficient durability in relation to the life-time of the deck system.

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Section 5 Basis of structural analysis

5.1 General

(1)P EN1995-1 section 5 applies.

5.2 Timber deck plates

5.2.1 General

(1) The analysis of timber deck plates should be performed according to:

the plate theory (advanced method);

the deck plate is replaced by a system of crossing beams.

(2) In an advanced analysis, for deck plates made of softwood laminations, the

relationships for the properties perpendicular to the laminations should be taken fromtable 5.1. The Poisson ratio may be taken as zero. The value of G90,meanincludes theeffect of the deformations of the connection.

Table 5.1 Material properties of laminated deck plates

Type of deck plate E90,mean/E0, mean G0,mean/E0,mean G90,mean/G0,mean

Nail-laminated

Stress-laminatedsawn

planed

Glued-laminated

0

0,015

0,020

0,030

0,06

0,06

0,06

0,06

0,05

0,08

0,10

0,15

NOTE: The values for E90,meanand G90,meanare system values for laminated deckplate.

(3) For deck plates made of flatwise arranged laminations (see Figure 1.3) sheardeformations should be taken into account. The modulus of elasticity perpendicular tograin E90may be taken as zero.

(4)P For composite action of deck plate systems, the influence of the joint slip shall betaken into account.

NOTE: See clause 8.2

5.2.2 Concentrated vertical loads

(1) Loads should be referred to the middle plane of the deck plate.

(2) For concentrated loads an effective contact area with respect to the middle plane ofthe deck plate should be assumed, see figure 5.2,

where:

bw is the width of the load area on the contact surface of the deck plate;

bw,middle is the width of the load area referred to the middle plane of the deck plate;

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1, 2 are angles of distribution according to table 5.3.

Key:

1 Pavement2 Timber deck plate

3 Middle of timber deck plate

Figure 5.2 Distribution of concentrated loads of contact area width bw

Table 5.3 Distribution angle of concentrated loads in different directions andmaterials

1or 2

Pavement, boards and planks 45

Laminated timber deck plates:

in the direction of the laminations

45

perpendicular to the lamination

15

Plywood and cross-laminated deck plates 45

5.2.3 Simplified analysis

(1) In a simplified analysis, the deck plates may be replaced by one or several beamsin direction of the laminations with the effective width befcalculated as

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= +ef w,middleb b a (5.1)

where:

bw,middle should be calculated according to 5.2.2(2);

a should be taken from table 5.4.

Table 5.4 Width a in m for determination of effective width of beam

Deck plate system a

m

Nail-laminated deck plate

Stress-laminated or glued laminated

Composite action timber/concrete

0,1

0,3

0,6

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Section 6 Ultimate limit state

6.1 General

(1) P EN 1995-1 section 6 applies.

6.2 Deck plates

6.2.1 System strength

(1) The relevant rules given in EN 1995-1-1 clause 6.7 apply

(2) The bending and shear strength of the deck plate should be calculated as:

m,d,deck sys m,d,lam=f k f (6.1)

v,d,deck sys v,d,lam=f k f (6.2)

where:

fm,d,lam is the design bending strength of the laminations;

fv,d,lam is the design shear strength of the laminations;

ksys is the system strength factor, see EN 1995-1-1. For decks in accordance toFig. 1.2d line 1 should be used.

The number of loaded laminations should be taken as

= ef

lam

bn

b(6.3)

withbef is the effective width, see figure 6.4, or according to clause 5.2.3(1);

blam is the width of the lamination.

(3) The effective width befshould be taken as (see figure 6.3):

= max,beamef,max,platey

Mb

m(6.4)

where:

Mmax,beam is the maximum bending moment in a beam representing the plate;

my,maxplate is the maximum bending moment in the plate calculated by a plateanalysis.

NOTE: In 5.2.3 a simplified method is given for the determination of the effective width.

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l

F

Mbeam

Mbeam,max

my,plate,maxx

y

my,plate

F

Figure 6.3 Example of determination of effective width

6.2.2 Stress-laminated deck plates

(1)P The long-term pre-stressing forces after losses shall be such that no inter-laminarslip occurs.

The following requirement should be satisfied:

hF min,pdEd,v (6.5)

where:

Fv,Ed is the design shear force per unit length, caused by vertical and horizontalactions

d is the design value of coefficient of friction

p,min is the minimum long-term residual compressive stress due to pre-stressing(see figure 6.5)

h is the thickness of the plate

(2) The resulting pre-stressing forces should act centrally on the timber cross section.

(3) The following design values of the coefficient of friction d should be assumed:

sawn wood to sawn wood: d= 0,45

planed wood to planed wood: d= 0,35 planed to sawn d= 0,45 wood to concrete: d= 0,4

NOTE: The coefficient of friction is a function of wood species, roughness of contact surface,treatment of the timber and residual stress level between laminations.

(4) In areas subjected to wheel loads, the minimum long-term residual compressive

stress p,mindue to pre-stressing between laminations should be not less than 0,35N/mm2.

NOTE: The long term residual prestressing stress may normally be assumed not to be less than0,35 N/mm2provided the original prestressing was at least 1,0 N/mm2, the moisture content of

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the lamellas at the time of stressing is not more than 16% and that the variation of moisturecontent in the deck plate is limited by adequate protection.

(5) For compression perpendicular to grain at anchorage plates EN 1995-1-1 clause6.1.4 should be taken into account.

(6) Not more than one butt joint should occurin any four adjacent laminations within adistance with min{2d; 30t; 1.2meters}.where d ist the distance between the prestressingelements and t is the width of the laminations.

(7) In calculating the longitudinal strength of stress-laminated deck plates, the sectionshould be reduced in proportion to the number of butt joints within a distance of 5 timesthe thickness of laminations.

6.3 Rolling shear

(1)P EN 1995-1-1 clause 6.1.6 applies.

(2) For locations with rolling shear stresses in combination with tension stressesperpendicular to the grain the following expression shall be satisfied

1dR,

dR,

dt,90,

dt,90, +ff

(6.6)

where:

t,90,d acting tension stress perpendicular to grain;

ft,90,d design tensile strength perpendicular to grain;

R,d acting rolling shear;

fR,d design rolling shear strength.

NOTE: The rolling shear strength is approximately equal to the tensile strength perpendicular tograin.

6.3.1 Timber-concrete composite members

(1) This clause contains provisions for timber-concrete composite components, wherecomposite action is achieved by the use of steel fasteners or steel fasteners incombination with grooved connections.

(2)P The concrete part shall be designed according to EN 1992.

(3) The connection between the composite components should be ductile to ensure allconnectors to attain their presupposed force.

(4) The steel fasteners and the grooved connections shall be designed to transmit allforces due to composite action. Friction and adhesion between wood and concreteshall not be taken into account, unless a special investigation is carried out.

(5) The effective width of the concrete plate of composite timber-web/concrete deckstructures should be determined as for a concrete T-section, see EN 1992-1-1, sub

clause 5.3.2.1.

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(6)P For the determination of cross section properties cracks in the concrete plate shallbe taken into account.

NOTE: The effect of concrete tension stiffening may be included. As a simple approach thestiffness of the concrete cross section in cracked condition may be taken as 40% of the stiffnessin un-cracked condition. As the structural analysis consequently will yield reduced sectionalforces in such areas the need for an adequate crack distributing reinforcement should beobserved.

(7) The load-bearing behaviour of composite systems based on bonded-in-rods,smooth or deformed, should be determined using suitable tests or generally acceptedcalculation models.

6.4 Fatigue

(1)P For structures or structural parts and connections that are subjected to frequent

stress variations from traffic or wind loading it shall be verified that no failure or majordamage will occur due to fatigue.

NOTE: A simplified verification method is given in annex A (informative)

(2) A fatigue verification is normally not required for footbridges and other bridges thatare predominantly statically loaded, unless such bridges or parts of them are likely tobe excited by wind loads or by pedestrians.

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Section 7 Serviceability limit states

7.1 General

(1) When calculating deflections or the fundamental natural frequencies mean valuesshould be used of moduli of elasticity and of the slip moduli Kseraccording to EN 1995-1-1 4.2(1).

7.2 Limiting values for deformation

(1) Where relevant, deflections caused by changes of moisture content shouldbe regarded

NOTE1: The recommended limiting values of deflections due to traffic load alone for beams withspan l is given in Table 7.1. The National choice may be given in the National annex.

Table 7.1 Limiting values for deflections

TrussesConstruction

partAction Beams and

platesDeformation ofconnections nottaken intoaccount

Deformation ofconnectionstaken intoaccount

Main system characteristictraffic load

Pedestrian loadandLow traffic load

l/400

l/200

l/800

l/400

l/400

l/200

NOTE 2: Deformations in the direction of the grain in timber deck plates need normally not betaken into account.

7.3 Vibrations caused by pedestrians

(1) For comfort criteria EN1990 Annex A2 applies.

(2) In the calculations, mean values of density and moduli of elasticity should be used.

(3) The damping ratio should be taken as:

= 0,010 for structures without mechanical joints; = 0,015 for structures with mechanical joints.

NOTE: A simplified method for simply supported beam is given in Annex B.

7.4 Vibrations caused by wind

(1)P EN 1991-1-4 applies

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Section 8 Connections

8.1 General

(1) EN1995-1-1 should be applied with the following exceptions:

axially loaded nails; stapled connections; connections made with punched metal plate fasteners.

(3)The effect of fatigue should be taken into account, see section 9.

8.2 Timber-concrete connections in composite beams

8.2.1 Laterally loaded dowel-type fasteners

(1) The characteristic strength of joints with screws, dowels and annular ringed shankand threaded nails, inserted perpendicular to the shear plane, should be taken 20 %higher than for corresponding timber-to-timber joints according to ENV 1995-1-1.

(2) The stiffness of joints with screws, dowels and annular ringed shank and threadednails, inserted perpendicular to the shear plane, should be taken 100 % higher than forcorresponding timber-to-timber joints according to ENV 1995-1-1

(3) Where there is an intermediate non-structural layer between the timber and theconcrete (e.g. for formwork), see figure 8.1, the strength and stiffness parametersshould be determined by a special analysis or by tests.

1

2

3

Key:1 Concrete2 Non-structural intermediate layer3 Timber

Figure 8.1 Intermediate layer 2 between concrete 1 and timber

8.2.2 Axially loaded rod-type fasteners

(1)Two examples of analytical models are presented in figures 8.2 and 8.3.

(2) Uni-directional inclined fasteners should not be used if the direction of shear forcescan vary for different load cases.

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Key:1 Concrete2 Timber

Figure 8.2 Analytical model for uni-directional inclined fasteners

Key:1 Concrete2 Timber

Figure 8.3 Analytical model for bi-directional inclined fasteners

8.2.3 Grooved connections

(1) For grooved connections, see figure 1.1, the shear force should be taken by directcontact pressure between the wood and the concrete cast in the groove.

(2) It should be verified that the resistance of the concrete part and the timber part ofthe connection is sufficient.

(3)P The concrete and the timber part shall be connected together so that they can notseparate.

(4) The connection should be designed for a tensile force between the timber and theconcrete given as:

=Ed v,Ed0,1F F (8.1)

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where:

FEd is the design tensile force between the timber and the concrete;

Fu,Ed is the design shear force between the timber and the concrete.

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Section 9 Structural detailing and control

(1)P The relevant rules given in Part 1 of EN 1995 Section 10 also apply to thestructural parts of bridges, with the exception of clauses 10.8 and 10.9.

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Annex A (informative)Simplified fatigue verification

A1 General

(1) This simplified method is based on an equivalent constant amplitude fatigueloading, representing the fatigue effects of the full spectrum of loading events.

NOTE: More advanced fatigue verification for varying stress amplitude can be based on acumulative linear damage theory (Palmgren-Miner hypothesis).

(2) The stress should be determined by an elastic analysis under the specified action.The stresses should include stresses in stiff or semi-rigid connections and secondaryeffects from deformations and distortions.

(3) A fatigue verification is not required if the ratio between the stress range for

fatigue loading = |max- min| and the corresponding design strength fk/M,fat is notgreater than: Members in compression perpendicular or parallel to grain: 0,6 Members in bending and tension: 0,2 Members in shear: 0,15 Joints with dowels: 0,4 Joints with nails: 0,1

A2 Fatigue loading

(1) A simplified fatigue load model is built up of reduced loads (effects of actions)compared to the static loading models. It is meant to represent loading situations,which are frequently repeated during the lifetime of the structure. The load modelshould give the maximum and minimum stresses in the actual structural members.

(2) The fatigue loading from traffic should be obtained from the project specification inconjunction with EN 1991-2. For the simplified fatigue check of road bridges, fatigueload model 1, 2 or 3 given in clause 4.6 of EN 1991-2 may be applied in conjunctionwith the traffic data specified by the competent authority.

(3) The number of constant amplitude stress cycles should either be taken from table4.5 of EN 1991-2 or, if more detailed information about the actual traffic is available, betaken as:

=obs ADT L365N n t (A.1)

where:

Nobs is the number of constant amplitude stress cycles, per year;

nADT is the expected annual average daily traffic over the lifetime of the structure;the value of nADTshould not be taken less than 1000;

is the expected fraction of heavy lorries passing over the bridge (e.g. = 0,1);

tL is the design service life of the structure expressed in years.

A3 Fatigue verification

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(1) For a constant amplitude loading the fatigue verification criterion is:

maxffat,d (A.2)

where:max is the numerically largest stress from the fatigue loading;

ffat,d is the design fatigue strength.

(2) The design fatigue strength should be taken as:

= mod kfat,d fat

M,fat

k ff k (A.3)

where:

fk is the characteristic strength for static loading;

kfat is a factor representing the reduction of strength with number of load cycles;

kmod is a modification taking into account the effect of the moisture content.

NOTE: The value of kmodshould be taken as 1,0 as the effect of moisture may be considerednegligible. The effect of load duration is included in the factor kfat.

(3) The value of kfatshould be taken as:

( ) ( )

=

fat 10 obs1

1 log 0R

k Na b R

(A.4)

where:

R is the stress ratio, given as = min maxR with 1 R1;

min is the numerically least stress from the fatigue loading;

max is the numerically largest stress from the fatigue loading;

Nobs is the number of constant amplitude stress cycles as defined above;

is a design fatigue factor based on the damage consequence for the actualstructural; component;;

a, b are coefficients representing the type of fatigue action according to table B.1.

The value of should be taken as:

Substantial consequences: = 3

Without substantial consequences: = 1

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Table A.1 Values of coefficients aand b

a b

Wooden members in- compression perpendicular and parallel to grain 2,0 9,0

- bending and tension 9,5 1,1- shear 6,7 1,3

connections with- dowels

a6,0 2,0

- nails 6,9 1,2

aThe design curve for dowels is mainly based on tests with 12 mm tight fitting

dowels. For the use of significantly larger diameter dowels or non-fitting boltsmay have less favourable fatigue properties.

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Annex B (informative)Vibrations cause by pedestrians

B1 General

(1) For a simply supported beam systems, the following rules for the determination ofthe acceleration caused by pedestrians should be applied.

B2 Vertical Vibrations

(1) For a single pedestrian crossing the bridge the vertical acceleration of the bridgeshould be calculated as:

= <

vert

vert,1

vert

200for 2,5 Hz

100for 2,5 Hz 5,0 Hz

fM

af

M

(B.1)

with

=M m l

where:

M is the total mass of the beam;

fvert is the fundamental natural frequency with vertical deformation of the bridge;

fhor is the fundamental natural frequency with horizontal deformation of the bridge;

l is the span of the beam;

m is the mass per unit length (self-weight) of the bridge in kg/m;

is the damping ratio.

(2) For a single person running over the bridge, the vertical acceleration avert,1of thebridge should be calculated as:

=

vert,1 vert

600for 2,5 Hz 5,0 Hza f

M(B.3)

(3) For several persons crossing the bridge, the vertical acceleration avert,nshould be

calculated as:

=vert,n vert,1 vert0,23a a n k (B.4)

with:

= 13n for a distinct group of pedestrians;

= 0,6n A for a continuous stream of pedestrians;

where:

A is the area of the bridge deck;kvert is a coefficient according to figure B.1.

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B.3 Horizontal Vibrations

(1) For one pedestrian crossing the bridge the horizontal acceleration should becalculated as:

=

hor,1 hor 50 for 0,5 Hz 5,0 Hza f

M(B.5)

(2) For a group of npersons crossing the bridge, the horizontal acceleration ahor,nshould be calculated as:

=hor,n hor,1 hor 0,18a a n k (B.6)

with

= 13n for a distinct group of pedestrians;

= 0,6n A for a continuous stream of pedestrians.

where:

khor should be taken from figure B.2;

A is the area of the bridge deck.

0

0.5

1

0 1 2 3 4 5

fvert

Figure B.1 Relationship between the vertical fundamental natural frequency fvertand the coefficient kvert

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0

0.5

1

0 0.5 1 1.5 2 2.5

fhor

Figure B.2 Relationship between the horizontal fundamental natural frequencyfhorand the coefficient khor

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Annex C (informative)Bonded-in steel rods

C.1 General

(1) The use of bonded-in rods should be limited to structural parts assigned to serviceclasses 1 and 2.

(2) It should be verified that the properties of the adhesive and its bond to steel andwood are reliable during the lifetime of the structure within the temperature andmoisture ranges envisaged.

(3) Rods should be threaded or deformed bars.

Note: The durability of adhesion of smooth steel surfaces is not well-known. The adhesion canbe influenced negatively e.g. by corrosion.

C.2 Axially loaded rods

C.2.1 General

(1) The load-carrying capacity of connections made with bonded-in axially loaded rodsshould be verified for the following failure modes:

- failure of the steel rod

- failure of the adhesive and its bond to steel and wood

- failure of the timber adjacent to the glue-line

- failure of the timber member (e.g. pull-out failure of a whole timber block withseveral bonded-in rods.

(2) The load-carrying capacity should generally be limited by the strength of the rod,not by the load transfer capacity of the adhesive and its bond to the rod and wood or bythe strength of the timber.

NOTE: This requirement is aimed at preventing brittle failure.

(3) The expressions given are based either on the outer diameter dof the rod; or whenstrength of the adhesive is not critical, on an equivalent diameter dequequal to thesmaller of the hole diameter and 1,15d.

Note: For threaded rods, the outer diameter is equal to the nominal diameter; for most deformedreinforcing bars used as rods, the outer diameter is about 10 % greater than the nominaldiameter.

(4) It should be verified, that the thickness of the bond layer is without remarkableinfluence on the deformation of the joint.

(5) Minimum spacings and distances should be taken according to figure C.1

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la

2,5d 2,5d5d

2,5d 2,5d5d

2,

5d

5d

la

Figure C.1 Minimum spacings and distances for axially loaded rods loadeda) perpendicular to the grain

b) parallel to the grain(6) The minimum anchorage length la,minshould be taken as

=

2

a,min

0,5max

10

dl

d(C.1)

where:la,min is the minimum anchorage length in mm, see figure C.1;

d is the outer diameter of the rod in mm.

Note: The minimum anchorage length la,minaccording to expression (C.1) is aimed at preventingfailure of the adhesive and its bond to steel and wood.

C.2.2 Ultimate limit state

C.2.2.1 Failure of individual rod

(1) The axial resistance in tension of the steel rod should be determined with respect tothe yield strength of the steel; in compression, the possibility of buckling should be

taken into account for design compression stresses greater than 300 N/mm

2

.

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(2) The characteristic axial resistance corresponding to shear in the wood should betaken as:

=, ,ax Rk equ a v k F d l f

(3) The characteristic shear strength of the wood around the hole should for softwoodbe taken as:

fv,k= 4,0 N/mm2 for la250 mm

fv,k= 5,25 0,005 la for 250 mm < la500 mm

fv,k= 3,5 0,0015 la for 500 mm < la1000 mm

(4) The shear strength of the adhesive and its bond to steel and wood should beverified by tests.

(5) For service class 2 the values of kmodaccording to EN 1995-1-1 clause 3.1.3 should

be reduced by 20 %.

C.2.2.2 Failure in the timber member

(1) The effective timber failure area,Aef, of a rod inserted in direction parallel to thegrain, see figure C.2, should be taken as the smaller of

an effective width, bef, of 3don each side of the centre of the rod; the area derived from the actual geometry where the distance is smaller than 6dor

the edge distance is smaller than 3d.

(2) In a group of rods inserted in direction parallel to the grain, the characteristic

resistance parallel to the grain of one rod, Fax,Rk, should be taken as:=ax,Rk t,0,k ef F f A (C.2)

where:

Fax,Rk is the characteristic load-carrying capacity of one rod;

ft,o,k is the characteristic tensile strength of the wood;

Aef is the effective timber failure area.

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la 6d 6d

6d

6d

6d

2,5d

3d

Fax,Ek

Fax,Ek

Fax,Ek

Figure C.2: Effective areas for anchorage forces parallel to the grain with bef= 6d

(3) For rods inserted at an angle to the grain, EN 1995-1-1 clause 8.1.4 applies, whereheis the loaded edge distance to the end of the rod and bis replaced by be.

C.2.3 Serviceability limit states

(1) The instantaneous slip modulus Kserin N/mm per rod should be taken as

1,51,8

ser k0,005= dK (C.3)

where:

d is the diameter of the rod in mm

k is the characteristic density of the wood in kg/m3.

C.3 Laterally loaded rods

C.3.1 Ultimate limit state

(1) The provisions of EN 1995-1-1 section 8 for laterally loaded dowels apply.

(2) For laterally loaded bonded-in rods inserted parallel to the grain, the embeddingstrength should be taken as 10 % of the embedding strength perpendicular to the grain.

(3) For bonded-in rods inserted at an angle to the grain, linear interpolation should beapplied.

C.3.2 Serviceability limit states

(1) For rods inserted perpendicular to the grain, the slip modulus Kserin N/mm per rodshould be taken as

=

1,5ser k0,05K d (C.4)

whered is the effective rod diameter, in mm;

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k is the characteristic density of the wood in kg/m3.

Note: For threaded rods the effective diameter of the rod corresponds to about 90 % of theouter diameter; for deformed reinforcing bars to the nominal diameter.

(2) For rods inserted parallel to the grain, Ksershould correspondingly be taken as

=

1,5ser k0,01K d (C.5)

(3) For bonded-in rods inserted at an angle to the grain, linear interpolation should beapplied.

C.4 Combined laterally and axially loaded rods

(1) For combined laterally and axially loaded bonded-in rods, the following conditionshould be satisfied:

2 2

ax,Ed la,Ed

ax,Rd la,Rd

1F F

+F F

(C.6) (C.

where Fax,Rdand Fla,Rdare the design load-carrying capacities of the bonded-in rod withaxial load Fax,Edor lateral load Fal,Edalone.

C.5 Execution

(1) The surfaces of the holes should be clean cut.

(2) With several rods in a group to be tightened, the tightening should be uniform.

(3) It should be insured that the hole is completely filled with adhesive.

(4) At the time of gluing the rods, the moisture content of the timber should not be morethan 15 %.