hs302_2012-07

RULES FOR CLASSIFICATION OF

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High Speed, Light Craft andNaval Surface Craft

PART 3 CHAPTER 2

STRUCTURES, EQUIPMENT

Hull Structural Design, SteelJULY 2012DET NORSKE VERITAS AS

FOREWORDDET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life,property and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification andconsultancy services relating to quality of ships, offshore units and installations, and onshore industries worldwide, andcarries out research in relation to these functions.The Rules lay down technical and procedural requirements related to obtaining and retaining a Class Certificate. It is usedas a contractual document and includes both requirements and acceptance criteria. Det Norske Veritas AS July 2012

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Rules for High Speed, Light Craft and Naval Surface Craft, July 2012Pt.3 Ch.2 Changes Page 3CHANGESGeneralThis document supersedes the January 2011 edition.

Text affected by the main changes in this edition is highlighted in red colour. However, if the changes involvea whole chapter, section or sub-section, normally only the title will be in red colour.

Main changes coming into force 1 January 2013

Sec.1 Structural Principles Item B401 is amended. Item I301 is amended.

Sec.3 Manufacturing, Inspection and Testing Item A104 is amended.

Sec.6 Steel Webframes and Girder Systems The whole item B500 is amended.

Sec.7 Steel Pillars and Pillar Bulkheads Item B104 is amended.

Corrections and ClarificationsIn addition to the above stated rule requirements, a number of corrections and clarifications have been made tothe existing rule text.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Contents Page 4CONTENTS

Sec. 1 Structural Principles .......................................................................................................................... 8

A. General ........................................................................................................................................................................... 8A 100 The scantling reduction......................................................................................................................................... 8

B. Bottom Structures ......................................................................................................................................................... 8B 100 Longitudinal stiffeners .......................................................................................................................................... 8B 200 Longitudinal girders.............................................................................................................................................. 8B 300 Engine room.......................................................................................................................................................... 8B 400 Double bottom ...................................................................................................................................................... 8B 500 Bilge keel .............................................................................................................................................................. 8B 600 Bottom transverses and girders............................................................................................................................. 9B 700 Docking................................................................................................................................................................. 9

C. Side Structure................................................................................................................................................................ 9C 100 Stiffeners ............................................................................................................................................................... 9C 200 Side transverses and stringers ............................................................................................................................... 9C 300 Cross ties............................................................................................................................................................... 9

D. Deck Structure............................................................................................................................................................... 9D 100 Plating ................................................................................................................................................................... 9D 200 Stiffeners ............................................................................................................................................................. 10D 300 Bulwarks ............................................................................................................................................................. 10

E. Flat Cross Structure.................................................................................................................................................... 10E 100 General................................................................................................................................................................ 10E 200 Stiffeners ............................................................................................................................................................. 10

F. Bulkhead Structures ................................................................................................................................................... 10F 100 Transverse bulkheads.......................................................................................................................................... 10F 200 Corrugated bulkheads ......................................................................................................................................... 10F 300 Supporting bulkheads ......................................................................................................................................... 11

G. Superstructures and Deckhouses............................................................................................................................... 11G 100 Definitions .......................................................................................................................................................... 11G 200 End bulkheads of superstructures and

deckhouses, and exposed sides in deckhouses.................................................................................................... 11

H. Structural Design in General ..................................................................................................................................... 12H 100 Craft arrangement ............................................................................................................................................... 12H 200 Continuity and transition of local members........................................................................................................ 12

I. Some Common Local Design Rules ........................................................................................................................... 12I 100 Definition of span ............................................................................................................................................... 12I 200 End connection of stiffeners ............................................................................................................................... 12I 300 End connections of girders.................................................................................................................................. 13I 400 Effective flange of girders .................................................................................................................................. 13I 500 Effective web of girders...................................................................................................................................... 14I 600 Stiffening of girders ............................................................................................................................................ 14I 700 Girder tripping brackets ...................................................................................................................................... 15I 800 Reinforcement at knuckles.................................................................................................................................. 16

J. Support of Equipment and Outfitting Details .......................................................................................................... 16J 100 Heavy equipment, appendages etc. ..................................................................................................................... 16J 200 Welding of outfitting details to hull.................................................................................................................... 17

K. Structural Aspects not Covered by the Rules........................................................................................................... 17K 100 Deflections .......................................................................................................................................................... 17K 200 Local vibrations .................................................................................................................................................. 17

Sec. 2 Materials and Material Protection ................................................................................................. 18

A. General ......................................................................................................................................................................... 18A 100 Introduction......................................................................................................................................................... 18A 200 Material certificates ............................................................................................................................................ 18

B. Hull Structural Steel ................................................................................................................................................... 18B 100 General................................................................................................................................................................ 18B 200 Material designations and material factors ......................................................................................................... 18B 300 Basic requirements.............................................................................................................................................. 19B 400 Material at cross-joints........................................................................................................................................ 19DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Contents Page 5C. Alternative Structural Materials ............................................................................................................................... 19C 100 Aluminium .......................................................................................................................................................... 19C 200 Connections between steel and aluminium......................................................................................................... 19C 300 Stainless steel ...................................................................................................................................................... 19

D. Corrosion Protection................................................................................................................................................... 20D 100 General................................................................................................................................................................ 20D 200 Specification and documentation of coating....................................................................................................... 20D 300 Application of coating ........................................................................................................................................ 20D 400 Provisions to avoid galvanic corrosion ............................................................................................................... 20D 500 Specification and documentation of cathodic protection.................................................................................... 21D 600 Interactions with other electrical systems ........................................................................................................... 21

E. Deck Composition ....................................................................................................................................................... 21E 100 General................................................................................................................................................................ 21

Sec. 3 Manufacturing, Inspection, Testing ............................................................................................... 22

A. General ......................................................................................................................................................................... 22A 100 Basic requirements.............................................................................................................................................. 22

B. Inspection..................................................................................................................................................................... 22B 100 Non-destructive testing ....................................................................................................................................... 22B 200 Magnetic particle testing..................................................................................................................................... 22B 300 Radiographic testing ........................................................................................................................................... 22B 400 Ultrasonic examination ....................................................................................................................................... 22

C. Extent of Examination ................................................................................................................................................ 22C 100 General................................................................................................................................................................ 22

D. Acceptance Criteria for NDT..................................................................................................................................... 22D 100 Acceptance criteria.............................................................................................................................................. 22

E. Testing .......................................................................................................................................................................... 23E 100 Tanks................................................................................................................................................................... 23E 200 Closing appliances .............................................................................................................................................. 23

Sec. 4 Hull Girder Strength........................................................................................................................ 24

A. General ......................................................................................................................................................................... 24A 100 Introduction......................................................................................................................................................... 24

B. Vertical Bending Strength.......................................................................................................................................... 24B 100 Hull section modulus requirement ...................................................................................................................... 24B 200 Effective section modulus................................................................................................................................... 24B 300 Hydrofoil on foils................................................................................................................................................ 25B 400 Longitudinal structural continuity ...................................................................................................................... 25B 500 Openings ............................................................................................................................................................. 25

C. Shear Strength............................................................................................................................................................. 26C 100 Cases to be investigated ...................................................................................................................................... 26

D. Cases to be Investigated.............................................................................................................................................. 26D 100 Inertia induced loads ........................................................................................................................................... 26

E. Transverse Strength of Twin Hull Craft................................................................................................................... 26E 100 Transverse strength ............................................................................................................................................. 26E 200 Allowable stresses............................................................................................................................................... 27

Sec. 5 Steel Plating and Stiffeners.............................................................................................................. 28

A. General ......................................................................................................................................................................... 28A 100 Introduction......................................................................................................................................................... 28A 200 Definitions .......................................................................................................................................................... 28A 300 Allowable stresses............................................................................................................................................... 28

B. Plating .......................................................................................................................................................................... 29B 100 Minimum thickness............................................................................................................................................. 29B 200 Formulae ............................................................................................................................................................. 29B 300 Bottom and bilge plating..................................................................................................................................... 30B 400 Sea inlets and other openings.............................................................................................................................. 30

C. Stiffeners ...................................................................................................................................................................... 30C 100 Formulae and evaluations ................................................................................................................................... 30C 200 Bulkhead stiffeners other than longitudinals ...................................................................................................... 31DET NORSKE VERITAS AS

C 300 Machinery casings .............................................................................................................................................. 31

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Contents Page 6C 400 Weather deck hatch covers. Shell doors ............................................................................................................. 32

Sec. 6 Steel Webframes and Girder Systems............................................................................................ 33

A. General ......................................................................................................................................................................... 33A 100 Introduction......................................................................................................................................................... 33A 200 Definitions .......................................................................................................................................................... 33A 300 Allowable stress .................................................................................................................................................. 33

B. Web Frames and Girders ........................................................................................................................................... 34B 100 General................................................................................................................................................................ 34B 200 Strength requirements ......................................................................................................................................... 34B 300 Minimum thicknesses and geometrical ratios..................................................................................................... 35B 400 Weather deck hatch covers. Shell doors ............................................................................................................. 36B 500 Doors in watertight bulkheads ............................................................................................................................ 36

Sec. 7 Steel Pillars and Pillar Bulkheads................................................................................................... 38

A. General ......................................................................................................................................................................... 38A 100 Introduction......................................................................................................................................................... 38A 200 Definitions .......................................................................................................................................................... 38

B. Pillars............................................................................................................................................................................ 38B 100 Arrangement of pillars ........................................................................................................................................ 38B 200 Pillar scantlings................................................................................................................................................... 38B 300 Pillars in tanks..................................................................................................................................................... 40

C. Supporting Bulkheads ................................................................................................................................................ 40C 100 General................................................................................................................................................................ 40

Sec. 8 Welding and Weld Connections...................................................................................................... 41

A. General ......................................................................................................................................................................... 41A 100 Introduction......................................................................................................................................................... 41A 200 Welding particulars............................................................................................................................................. 41

B. Types of Welded Joints............................................................................................................................................... 41B 100 Butt joints............................................................................................................................................................ 41B 200 Lap joints and slot welds .................................................................................................................................... 41B 300 Tee or cross joints ............................................................................................................................................... 42

C. Load Based Weld Scantlings ...................................................................................................................................... 43C 100 Joints of abutting webs or plates......................................................................................................................... 43C 200 Steel and weld support of stiffeners to girders.................................................................................................... 45C 300 Steel and weld end connections of longitudinals................................................................................................ 46C 400 Weld end connections of stiffeners in general.................................................................................................... 46C 500 End connections of girders, pillars and cross ties ............................................................................................... 47

D. Minimum Weld Scantlings ......................................................................................................................................... 48D 100 Minimum fillet weld ........................................................................................................................................... 48

Sec. 9 Direct Strength Calculations ........................................................................................................... 49

A. General ......................................................................................................................................................................... 49A 100 Introduction......................................................................................................................................................... 49A 200 Application.......................................................................................................................................................... 49

B. Plating .......................................................................................................................................................................... 49B 100 General................................................................................................................................................................ 49

C. Stiffeners ...................................................................................................................................................................... 49C 100 General................................................................................................................................................................ 49C 200 Calculation procedure ......................................................................................................................................... 49C 300 Loads................................................................................................................................................................... 49C 400 Allowable stresses............................................................................................................................................... 50

D. Girders ......................................................................................................................................................................... 50D 100 General................................................................................................................................................................ 50D 200 Calculation methods ........................................................................................................................................... 50D 300 Design load conditions........................................................................................................................................ 50D 400 Allowable stresses............................................................................................................................................... 51D 500 Allowable deflections ......................................................................................................................................... 51DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Contents Page 7Sec. 10 Buckling Control .............................................................................................................................. 52

A. General ......................................................................................................................................................................... 52A 100 Definitions .......................................................................................................................................................... 52

B. Longitudinal Buckling Load ...................................................................................................................................... 53B 100 Longitudinal stresses........................................................................................................................................... 53

C. Transverse Buckling Load ......................................................................................................................................... 53C 100 Transverse stresses.............................................................................................................................................. 53

D. Plating .......................................................................................................................................................................... 53D 100 Plate panel in uni-axial compression .................................................................................................................. 53D 200 Plate panel in shear ............................................................................................................................................. 54D 300 Plate panel in bi-axial compression and shear .................................................................................................... 55

E. Stiffeners in Direction of Compression ..................................................................................................................... 56E 100 Lateral buckling mode ........................................................................................................................................ 56E 200 Torsional buckling mode .................................................................................................................................... 57E 300 Web and flange buckling .................................................................................................................................... 57

F. Stiffeners Perpendicular to Direction of Compression............................................................................................ 58F 100 Moment of inertia of stiffeners ........................................................................................................................... 58

G. Elastic Buckling of Stiffened Panels .......................................................................................................................... 58G 100 Elastic buckling as a design basis ....................................................................................................................... 58G 200 Allowable compression....................................................................................................................................... 58

H. Girders ......................................................................................................................................................................... 59H 100 Axial load buckling............................................................................................................................................. 59H 200 Girders perpendicular to direction of compression............................................................................................. 59H 300 Buckling of effective flange................................................................................................................................ 60H 400 Shear buckling of web ........................................................................................................................................ 60DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 8SECTION 1 STRUCTURAL PRINCIPLES

A. GeneralA 100 The scantling reduction101 The scantling reductions for high speed and light craft structures compared to the Rules for Classificationof Ships are based on:

thorough corrosion protection of steel, carried out under indoor conditions a certain stiffener spacing reduction ratio

s = chosen spacing in mmsr = basic spacing = 2 (240 + L) mm in general, including tank bulkheads = 760 mm for other bulkheads

longitudinal framing in bottom and strength deck extended global longitudinal and local buckling control a sea and weather service restriction.

B. Bottom StructuresB 100 Longitudinal stiffeners101 Single bottoms as well as double bottoms are normally to be longitudinally stiffened.102 The longitudinals should preferably be continuous through transverse members. If they are to be cut attransverse members, e.g. at watertight bulkheads, brackets connecting the ends of the longitudinals are to befitted or welds are to be dimensioned accordingly.103 Longitudinal stiffeners in slamming area should have a shear connection to transverse members.

B 200 Longitudinal girders201 Web plates of longitudinal girders are to be continuous in way of transverse bulkheads.202 Manholes or other openings should not be positioned at ends of girders without due consideration beingtaken of shear loading.

B 300 Engine room301 In way of thrust bearings additional strengthening is to be provided.302 Under the main engine, girders extending from the bottom to the top plate of the engine seating are to befitted.303 Engine holding down bolts are to be arranged as near as practical to floors and longitudinal girders.

B 400 Double bottom401 In case a double bottom is fitted, the following and 402 and 403 apply. Manholes are to be cut in the innerbottom, floors and longitudinal girders to provide access to all parts of the double bottom. The verticalextension of lightening holes is not to exceed one half of the girder height in general. Centre of lightening holesto be, as close as practicable, to the neutral axes of elements in question. Manholes in the inner bottom platingare to have reinforcement rings. Manholes are not to be cut in the floors or girders in way of pillars.402 In double bottoms with transverse stiffening, longitudinal girders are to be stiffened at every transverseframe.403 The longitudinal girders are to be satisfactory stiffened against buckling.

B 500 Bilge keel501 The bilge keel and the flat bar to which it is attached, is not to terminate abruptly. Ends are to be tapered,and internal stiffening is to be provided. Butts in the bilge keel and the flat bar are to be well clear of each other

ssr----DET NORSKE VERITAS AS

and of butts in the shell plating.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 9The bilge keel and flat bar are to be of the same material strength as the bilge strake to which they are attached.

B 600 Bottom transverses and girders601 For rise of floor > 45 the case with unsymmetrical side force from sea pressure may have to beinvestigated, and the efficiency of the support of floors is to be examined.

B 700 Docking701 A centre girder is normally to be fitted for docking purposes.702 For craft of special design and for large craft, the docking arrangement plan, giving calculated forcesfrom the docking blocks is to be submitted for information.Structure in way of docking blocks is to be evaluated for the given docking forces.

C. Side StructureC 100 Stiffeners101 The crafts sides may be longitudinally or vertically stiffened.

Guidance note:It is advised that longitudinal stiffeners are used near the bottom and strength deck.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

102 Where the crafts sides are longitudinally stiffened and depending upon the area under consideration, thecontinuity of the longitudinals is to be as required for the bottom and deck longitudinals, respectively.

C 200 Side transverses and stringers201 For weather deck stringer plate along wide hatch opening, the following may have to be investigatedabove ordinary side stringer requirements:

combined deflection of stringer and hatch coaming at weather tightening level, when subjected to side anddeck sea pressure

continuity of inner flange at hatch ends.

202 For web rings supporting deckhouses or deck equipment, reinforcements for the associated static anddynamic loads may be required.

C 300 Cross ties301 Cross ties may be regarded as effective for side vertical when:

the cross tie extends from side to side the cross tie is supported by other structure which may be considered rigid when subject to the maximum

expected axial loads in the cross tie the load condition may be considered symmetrical with respect to the cross tie.

302 Cross ties and panting beam scantlings are to be determined as for deck pillars, where the deck load is tobe substituted by the load on the supported side. Bending stress and suspended bending deflection of slendercross ties may have be taken into account.

D. Deck StructureD 100 Plating101 If the end bulkhead of a long superstructure is located within 0.5 L amidships, the stringer plate is to beincreased in thickness for a length of 3 m on each side of the superstructure end bulkhead. The increase inthickness is to be 20 %.102 If hatch opening corners of streamlined shape are not adopted, the thickness of deck plates in strengthdeck at hatch corners is to be increased by 25 %.The longitudinal extension of the thicker plating is not to be less than 1.5 R and not more than 3 R on both sidesof the hatch end. The transverse extension outside line of hatches is to be at least 2 R.R = corner radius.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 10103 The seam between the thicker plating at the hatch corner and the thinner plating in the deck area betweenthe hatches is to be located at least 100 mm inside the point at which the curvature of the hatch cornerterminates.

D 200 Stiffeners201 Decks taking part of the longitudinal strength are normally to be longitudinally stiffened. Where mainstresses are in the transverse direction, the deck may be transversely stiffened.202 Longitudinals should preferably be continuous through transverse members. If they are to be cut attransverse members, e.g. at watertight bulkheads, brackets connecting the ends of the longitudinals are to befitted.

D 300 Bulwarks301 The thickness of the bulwark plates is not to be less than required for the side plating in a superstructurein the same position.302 Where bulwarks on exposed decks form wells, ample provision is to be made for freeing the deck forwater.

E. Flat Cross StructureE 100 General101 Flat cross structure is horizontal structure above waterline like bridge connecting structure between twinhulls, etc.102 The cross structure should be arranged with the possibility for inspection of all parts of the structure.

E 200 Stiffeners201 Flat cross structure taking part of the longitudinal strength are normally to be longitudinally stiffened.Where main stresses are in the transverse direction, the flat cross structure may be transversely stiffened.202 Where the cross structure is transversely stiffened, transverse bulkheads and frames are to be continuousthrough longitudinal bulkheads.

F. Bulkhead StructuresF 100 Transverse bulkheads101 Number and location of transverse watertight bulkheads are to be in accordance with the requirementsgiven in Ch.1 Sec.1.102 The stiffening of the upper part of a plane transverse bulkhead is to be such that the necessary transversebuckling strength is achieved.

F 200 Corrugated bulkheads201 Longitudinal and transverse bulkheads may be corrugated.202 The lower and upper ends of corrugated bulkheads and those boundaries of vertically corrugatedbulkheads connected to ship sides and other bulkheads are to have plane parts of sufficient width to support theadjoining structures.203 For corrugated bulkheads the following definition of spacing applies (see Fig.1):

s = s1 for section modulus calculations. = 1.05 s2 or 1.05 s3 for plate thickness calculations in general.

= s2 or s3 for plate thickness calculation when 90 degrees corrugations.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 11Fig. 1Corrugated bulkhead

Section modulus and thickness formulae as for plane bulkheads may be used.204 Unless the buckling strength is proved satisfactory by direct stress calculation the following additionalrequirements apply to corrugated bulkheads (where t and s2 and s3 are taken in same units):

Intermediate values are obtained by linear interpolation. For a corrugated bulkhead with a section modulusgreater than required, the required thickness may be multiplied by:

Zrule required section modulus. May be taken at section in question based upon a direct stress calculation

F 300 Supporting bulkheads301 Bulkheads supporting decks are to be regarded as pillars. The compressive loads and buckling strengthare to be calculated as given in Sec.7 C.

G. Superstructures and DeckhousesG 100 Definitions101 Superstructure is defined as a decked structure on the freeboard deck, extending from side to side of thecraft or with the side plating not inboard of the shell plating more than 4 % of the breadth (B).102 Deckhouse is defined as a decked structure above the strength deck with the side plating being inboardof the shell plating more than 4 % of the breadth (B).Long deckhouse - deckhouse having more than 0.2 L of its length within 0.4 L amidships.Short deckhouse - deckhouse not defined as a long deckhouse.

G 200 End bulkheads of superstructures anddeckhouses, and exposed sides in deckhouses201 For deckhouse stiffeners the scantlings need not be greater than required for between deck frames withequivalent end connections.202 Front stiffeners are to be connected to deck at both ends with a connection area not less than:

a = 0.07 l s p (cm 2) Side and after end stiffeners in the lowest tier of erections are to have end connections.203 In long deckhouses, openings in the sides are to have well rounded corners. Horizontal stiffeners are tobe fitted at the upper and lower edge of large openings for windows.Openings for doors in the sides are to be substantially stiffened along the edges.204 For hull girder strength in way of rows of openings, see Sec.4.

S2

S 3

S1

ts250------ when

s2s3---- 0 5,==

ts270------ when

s2s3---- 1 0,=

ZruleZactual-----------------DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 12H. Structural Design in GeneralH 100 Craft arrangement101 The craft arrangement is to take into account:

continuity of longitudinal strength, including horizontal shear area to carry a strength deck along transverse bulkheads or strong webs web/pillar rings in the engine room twin hull connections superstructures and deckhouses:

direct support transitions

deck equipment support multi-deck pillars in line, as practicable external attachments, inboard connections.

H 200 Continuity and transition of local members201 Attention is drawn to the importance of structural continuity in general.202 Structural continuity is to be maintained at the junction of primary supporting members of unequalstiffness by fitting well rounded brackets. Brackets are not to be attached to unsupported plating. Brackets areto extend to the nearest stiffener, or local plating reinforcement is to be provided at the toe of the bracket.203 Gradual taper or soft transition is especially important in high speed steel craft, to avoid:

stress corrosion and fatigue in heavy stressed members impact fatigue in impact loaded members.

204 Sufficient transverse strength is to be provided by means of transverse bulkheads or girder structures.205 Web frames are to be continuous around the cross section i.e. floors, side webs and deck beams are to bealigned and connected. Intermediate floors may be used.206 In superstructures and deckhouses aft, the front bulkhead is to be in line with a transverse bulkhead inthe hull below or be supported by a combination of partial transverse bulkheads, girders and pillars. The afterend bulkhead is also to be effectively supported. As far as practicable, exposed sides and internal longitudinaland transverse bulkheads are to be located above bulkheads and/or deep girder frames in the hull structure andare to be in line in the various tiers of accommodation. Where such structural arrangements in line are notpossible, there is to be other effective support.207 Where practicable, deck pillars are to be located in line with pillars above or below. Pillars are to besupported by rigid hull structures.208 Below decks and platforms, strong transverses or longitudinal girders are to be fitted between verticalsand pillars, so that rigid continuous structures are formed.

I. Some Common Local Design RulesI 100 Definition of span101 The effective span of a stiffener (l) or girder (S) depends on the design of the end connections in relationto adjacent structures. Unless otherwise stated the span points at each end of the member, between which thespan is measured, is to be determined as shown in Fig.2. It is assumed that brackets are effectively supportedby the adjacent structure.

I 200 End connection of stiffeners201 Normally all types of stiffeners (longitudinals, beams, frames, bulkhead stiffeners) are to be connectedat their ends. In special cases, however, sniped ends may be allowed.202 Bracketless end connections may be applied for longitudinals and other stiffeners running continuouslythrough girders (web frames, transverses, stringers, bulkheads etc.), provided sufficient connection area isarranged for.203 Stiffeners with sniped ends may be allowed where dynamic loads are small and where vibrations areconsidered to be of small importance, provided the thickness of plating supported by the stiffener is not lessthan: DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 13l = stiffener span in m S = stiffener spacing in mp = pressure on stiffener in kN/m2.

I 300 End connections of girders301 Normally, ends of single girders, or connections between girders forming ring systems, are to beprovided with brackets. Brackets are generally to form a radius or be well rounded at their toes. The free edgeof the brackets are to be stiffened in case free edge length is in excess of 50t, where t is the bracket thickness.Bracketless connections may be applied provided adequate support of the adjoining faceplates is arranged for.The brackets shown in Fig.3 ALT. II and ALT. III are normally considered better than the basic design. Otherbrackets may be accepted after special consideration.

Fig. 2Span points

I 400 Effective flange of girders401 The section modulus of the girder is to be taken in accordance with particulars as given in the following.Structural modelling in connection with direct stress analysis is to be based on the same particulars whenapplicable. Note that such structural modelling will not reflect the stress distribution at local flange cut-outs orat supports with variable stiffness over the flange width. The local effective flange, which may be applied instress analysis, is indicated for construction details in various Classification Notes on "Strength Analysis ofHull Structures".402 The effective plate flange area is defined as the cross-sectional area of plating within the effective flangewidth. Continuous stiffeners within the effective flange may be included. The effective flange width be isdetermined by the following formula:

be = C b (m)

C = as given in Table I1 for various numbers of evenly spaced point loads (r) on the spanb = the sum of the plate flange width on each side of girder, normally taken to be half the distance from the

nearest girder or bulkheada = the distance between points of zero bending moments

= S for simply supported girders= 0.6 S for girders fixed at both ends

r = number of point loads.

t 1 25, l 0 5, s( ) s pf1

-------------------------------- (mm)=DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 14403 For plate flanges having corrugations parallel to the girder, the effective width is as given in 402. If thecorrugations are perpendicular to the direction of the girder, the effective width is not to be taken greater than10 % of the value derived from 402.

I 500 Effective web of girders501 The web area of a girder is to be taken in accordance with particulars as given in 502 and 503. Structuralmodelling in connection with direct stress analysis is to be based on the same particulars when applicable.502 Holes in girders will generally be accepted provided the shear stress level is acceptable and the bucklingstrength is sufficient. Holes are to be kept well clear of end of brackets and locations where shear stresses arehigh.503 For ordinary girder cross sections the effective web area is to be taken as:

Aw = 0.0 1 hn tw (cm2)

hn = net girder height in mm after deduction of cut-outs in the cross section considered= hnl + hn2.

If an opening is located at a distance less than hw/3 from the cross section considered, hn is to be taken as thesmaller of the net height and the net distance through the opening. See Fig.4.

I 600 Stiffening of girders601 The web plate of transverse vertical girders are to be stiffened where:

hw > 90 tw (mm)

tw = web thickness in mmhw = web height in mm

with stiffeners of maximum spacing:s = 90 t w (mm)

within 20% of the span from each end of the girder and where high shear stresses appear.Elsewhere stiffeners are required where:

hw > 140 tw (mm) with stiffeners of maximum spacing:

s = 140 t w (mm)for girders supporting other girders, the end requirements may have to be applied all over the span.

Table I1 Values of Ca/b 0 1 2 3 4 5 6 7

C (r > 6) 0.00 0.38 0.67 0.84 0.93 0.97 0.99 1.00C (r = 5) 0.00 0.33 0.58 0.73 0.84 0.89 0.92 0.93C (r = 4) 0.00 0.27 0.49 0.63 0.74 0.81 0.85 0.87C (r < 3) 0.00 0.22 0.40 0.52 0.65 0.73 0.78 0.80DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 15Fig. 3Bracket design

602 The web plate is to be especially stiffened at openings when the mean shear stress exceeds 60 f1 N/mm2.

I 700 Girder tripping brackets701 The spacing value, ST, of tripping brackets is normally not to exceed the values given in Table I2 whichis valid for girders with symmetrical face plates. For others, the spacing will be especially considered.

Tripping brackets are furthermore to be fitted near the toe bracket, near rounded corner of girder frames and inway of cross ties.702 The tripping brackets are to be fitted in line with longitudinals or stiffeners, and are to extend the wholeheight of the web plate. The arm length of the brackets along the longitudinals or stiffeners, is not to be lessthan 40 % of the depth of the web plate, the depth of the longitudinal or stiffener deducted. The requirementmay be modified for deep transverses.

Table I2 Spacing between tripping bracketsGirder type ST (m)Bottom and deck transversesStringers and vertical webs in generalLongitudinal girders in general

0.02 bfmaximum 6

Longitudinal girders in bottom and strength deck for L > 50 m within 0.5 L amidshipsStringers and vertical webs in tanks and machinery spacesVertical webs supporting single bottom girders and transverses

0.014 bfmaximum 4

If the web of a strength member forms an angle with the perpendicular to the crafts side of more than 10 , ST is not to exceed 0.007 bf.bf = flange breadth in mmDET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 16Fig. 4Effective web area in way of opening

703 Tripping brackets on girders are to be stiffened by a flange or stiffener along the free edge if the lengthof the edge exceeds:

0.06 tt (m)thickness in mm of tripping brackets.The area of the stiffening is not to be less than:

10 lt (cm2)

lt = length in m of free edge.

The tripping brackets are to have a smooth transition to adjoining longitudinals or stiffeners exposed to largelongitudinal stresses.704 Girders with unsymmetrical face plates are to have tripping brackets spaced not more than 10 times thewidth of face plate, maximum 1.5 metres.

I 800 Reinforcement at knuckles801 Whenever a knuckle in a main member (shell, longitudinal bulkhead, etc.) is arranged, it is important tohave some form of stiffening fitted at the knuckle to transmit the transverse force.

J. Support of Equipment and Outfitting DetailsJ 100 Heavy equipment, appendages etc.101 Whether the unit to be supported is covered by classification or not, the forces and moments at points ofattachment have to be estimated and followed through hull reinforcements in line, through craft girder andpillar systems until the forces are safely carried to the crafts side or bulkheads taking into account the hullstresses that already exist.102 Doublers should be avoided normal to a tensile force.

tw

hn2

lshn

a

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.1 Page 17Fig. 5Span points

J 200 Welding of outfitting details to hull201 Generally connections of outfitting details to the hull are to be such that stress-concentrations areminimized and welding to high stressed parts are avoided as far as possible.Connections are to be designed with smooth transitions and proper alignment with the hull structure elements.Terminations are to be supported.202 Equipment details such as clips for piping, support of ladders, valves, anodes etc. are to be kept clear ofthe toe of brackets, edges of openings and other areas with high stresses.Connections to the top flange of girders and stiffeners are to be avoided, if not well smoothened. Preferably,supports for out-fittings are to be welded to the stiffener web.203 All materials welded to the hull shell structure are to be of ship quality steel, or equivalent, preferablywith the same strength group as the hull structure the item is welded to.

K. Structural Aspects not Covered by the RulesK 100 Deflections101 Rule requirements to minimum moment of inertia or maximum deflection under load are limited tostructures in way of hatches and doors and some other special cases.102 Deflection problems in general are left for the designers consideration.

K 200 Local vibrations201 The evaluation of structural response to vibrations caused by impulses from engine and propeller bladesare not covered by classification, but the builder is to provide relevant documentation.

Guidance note:IMO HSC Code:3.4 Cyclic loads, including those from vibrations which can occur on the craft should not:

.1 impair the integrity of structure during the anticipated service life of the craft or the service life agreedwith the Administration;

.2 hinder normal functioning of machinery and equipment; and

.3 impair the ability of the crew to carry out its duties.---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

DET NORSKE VERITAS AS

Upon request such evaluation may be undertaken by the Society.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.2 Page 18SECTION 2 MATERIALS AND MATERIAL PROTECTION

A. GeneralA 100 Introduction101 In this section requirements regarding the application of various structural materials as well as protectionare given.

A 200 Material certificates201 Rolled steel for hull structures is normally to be supplied with Det norske Veritas material certificatesin compliance with the requirements given in Pt.2.202 Requirements for material certificates for forgings, castings and other materials for special parts andequipment are stated in connection with the rule requirements for each individual part.

B. Hull Structural SteelB 100 General101 Where the rules for material grade in this section are dependent on plate thickness, the requirements arebased on the thickness as built.

B 200 Material designations and material factors201 Hull materials of various strength groups will be referred to as follows:

NV-27 denotes high strength structural steel with yield point not less than 265 N/mm2. NV-32 denotes high strength structural steel with yield point not less than 315 N/mm2. NV-36 denotes high strength structural steel with yield point not less than 355 N/mm2. NV-40 denotes high strength structural steel with yield point not less than 390 N/mm2 NV420 denotes extra high strength structural steel with yield point not less than 420 N/mm2. NV460 denotes extra high strength structural steel with yield point not less than 460 N/mm2. NV500 denotes extra high strength structural steel with yield point not less than 500 N/mm2. NV550 denotes extra high strength structural steel with yield point not less than 550 N/mm2. NV620 denotes extra high strength structural steel with yield point not less than 620 N/mm2. NV690 denotes extra high strength structural steel with yield point not less than 690 N/mm2.

Normal, high strength and extra high steel may also be referred to as NS-steel, HS-steel and EHS-steelrespectively.202 Hull materials of various grades will be referred to as follows:A, B, D and E denotes NS-steel grades. AH, DH and EH denotes HS-steel grades. HS-steel may also be referred to by a combination of grade andstrength group. In that case the letter H is substituted by one of the numbers indicated in 201, e.g. A 36-steel.AEH, DE, EEH and FEH denote EHS-steel grades. EHS-steel may also be referred to by a combination ofgrade and strength group. In this case the letters EH is substituted by one of the numbers indicated in 201, e.g.D 550-steel.203 The material factor f1, which may be included in the various formulae for scantlings and in expressionsgiving allowable stresses, is dependent on strength group as follows:

For NV-NS: f1 = 1.00 For NV-27: f1 = 1.08 For NV-32: f1 = 1.28 For NV-36: f1 = 1.39 For NV-40: f1 = 1.43 For NV 420: f1 = 1.75 For NV 460: f1 = 1.92 For NV 500: f1 = 2.08 For NV 550: f1 = 2.29 For NV 620: f1 = 2.58 For NV 690: f1 = 2.88DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.2 Page 19For a 34-steel (with yield point not less than 335 N/mm2) the material factor may be taken as f1 = 1.35.

B 300 Basic requirements301 For a thickness more than 15 mm special consideration will be made with respect to material grade,according to the Rules for Classification of Ship Pt.3 Ch.1 Sec.2 Table B1.

B 400 Material at cross-joints401 In important structural cross-joints where high tensile stresses are acting perpendicular to the plane ofthe plate, special consideration will be given to the ability of the plate material to resist lamellar tearing. For aspecial test, see Pt.2 Ch.2 Sec.1.

C. Alternative Structural MaterialsC 100 Aluminium101 Aluminium structures are to be designed and built according to Pt.3 Ch.3.102 In designing a combined steel and aluminium structure, the difference in modulus of elasticity andcoefficient of expansion must be taken into account.

C 200 Connections between steel and aluminium201 If there is risk of galvanic corrosion, a non-hygroscopic insulation material is to be applied between steeland aluminium.202 Aluminium plating connected to a steel boundary bar is as far as possible to be arranged on the sideexposed to moisture.203 Direct contact between exposed wooden materials, e.g. deck planking, and aluminium is to be avoided.204 Bolts with nuts and washers are either to be of stainless steel or cadmium plated or hot galvanized steel.The bolts are in general to be fitted with sleeves of insulating material.For superstructures and deckhouses, the spacing is normally not to exceed 4 times the bolt diameter.205 In case of rolled bi-metallic connections, high tensile forces normal to the bi-metallic contact surfaceshould be avoided.206 For earthing of aluminium superstructures and deckhouses to steel craft, see Pt.4 Ch.8.

C 300 Stainless steel301 For clad steel and solid stainless steel due attention is to be given to the reduction of strength of stainlesssteel with increasing temperature. For austenitic stainless steel and steel with clad layer of austenitic stainlesssteel the material factor f1 included in the various formulae for scantlings and in expressions giving allowablestresses is given in 302 and 303.302 For austenitic stainless steel the material factor f1 can be taken as:

f = yield stress in N/mm2 at 0.2 % offset and temperature + 20 C ( 0,2).t = cargo temperature in C.

For end connections of corrugations, girders and stiffeners the factor is due to fatigue not to be taken greaterthan:

f1 = 1.21 3.2 (t 20) 10 -3

303 For clad steel the material factor f1 can be taken as:

f = yield stress in N/mm2 at 0.2 % C (0,2).fb = yield strength in N/mm2 of base materialt = cargo temperature in C

f1 is in no case to be taken greater than that given for the base material in B203. The calculated factor may be

f1 3 9,t 20650

-------------+ f 4 15, t 20( ) 220+ 103

=

f11 67, f 1 37, t

1000---------------------------------------- 41 5, fb

0 7, 1 6,+=DET NORSKE VERITAS AS

used for the total plate thickness.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.2 Page 20304 For ferritic-austenitic stainless steel the material factor will be especially considered in each case.Guidance note:For ferritic-austenitic stainless steels with yield stress 460 N/mm2, the following material factor will normally beaccepted:

f1 = 1.6 at + 20 C= 1.36 at + 85 C

For end connection of corrugations, girders and stiffeners the factor should due to fatigue not be taken greater than:f1 = 1.39 at + 20 C

= 1.18 at + 85 CFor intermediate temperatures linear interpolation may be applied for the f1 factor.


D. Corrosion ProtectionD 100 General101 All steel surfaces except in tanks for oil for the crafts use are to be protected against corrosion by paint ofsuitable composition or other effective coating. Inner bottom and decks for dry cargoes will be especially considered.102 In way of other materials (e.g. propellers), provisions are to be made to avoid galvanic corrosion.

D 200 Specification and documentation of coating201 A coating specification including steel surface preparation and coating application procedure is to bepresented for approval. The builder is to present documentation of steel surface treatment and coatingapplication in accordance with the approved specification.202 Specifications for coating including antifouling shall state details of:

metal surface cleaning and treatment before application of primer coat, including welds and edges build-up of the coating system with individual coats including the thickness of individual and final coating curing times and overcoating intervals acceptable temperatures of air and metal surface and dryness/humidity conditions during above mentioned

operations thicknesses of individual and final coating.

D 300 Application of coating301 The minimum cleanliness standard of steel for coating application is normally blast cleaning to Sa 2,5according to SIS 055900, near-white according to SSPC-SP10, or an equivalent standard.302 Shop primers applied over areas which will subsequently be welded, are to be of a quality accepted bythe Society as having no detrimental effect on the finished weld.See "Registers of Approved Manufacturers and Type Approved Products".303 Coating systems are to be compatible with any previously applied shop primer. Proper cleaning of anyprimer or intermediate coating which has been exposed to the yard atmosphere for some time is necessarybefore application of the next coat.304 The requirement for dry conditions during all essential steps of blast cleaning and coating applicationsis normally that:

the steel surfaces are to be minimum 3 C above the dew point. the air humidity is at a maximum of 85 %.

D 400 Provisions to avoid galvanic corrosion401 Acceptable provisions are either one of or a combination of:

coating of water/moisture exposed surfaces (mandatory according to 101) electrical insulation of different metals from each other cathodic protection.

Guidance note:Full electrical insulation of e.g. the propeller from the hull might be difficult. Electrical contact between the propellerand the hull may be established when the propeller is idle.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.2 Page 21402 External cathodic protection of steel hulls in addition to the coating can be obtained with aluminium orzink sacrificial anodes or impressed current.403 If impressed current systems are applied, precautions are to be taken to avoid overprotection by meansof anode screen and overprotection alarm.

D 500 Specification and documentation of cathodic protection501 Specifications of cathodic protection systems shall state details of:

areas to be protected current density demand anode material and manufacturer anode mass, distribution and total number calculation of service life and estimated protective potential to be obtained.

Guidance note:The current density demand will vary dependent on the speed of the hull, the speed of the propeller, etc.


502 For documentation of instrumentation and automation, including computer based control andmonitoring, see Pt.4 Ch.9 Sec.1.503 The designed service life of cathodic protection systems is normally to be at least 5 years.504 An acceptable criterion of efficient cathodic protection is that it is found successful at annual survey, i.e.that no corrosion has occurred.Potential measurements may be required when considered necessary. The protective potential for steel hullsurfaces in clean sea water is 800 mV versus the Ag/AgCl reference electrode. The limit for overprotectionis 1050 mV at the same conditions.

D 600 Interactions with other electrical systems601 Stray DC currents may impose rapid electrolytic corrosion damages to hulls and are to be avoided.Due consideration should be made to the above when utilizing onshore electrical current connection.

Guidance note:Other stray DC current sources may be railways, cranes, cables, unproperly grounded welding machines, etc.


E. Deck CompositionE 100 General101 Deck compositions are subject to type approval. They are to be of an elastic, non-hygroscopic material.Deck compositions for application in cargo areas are to be suitably reinforced.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.3 Page 22SECTION 3 MANUFACTURING, INSPECTION, TESTING

A. GeneralA 100 Basic requirements101 Welding of important structures, machinery installations and equipment are to be carried out by qualifiedwelders using approved welding procedures and welding consumables, see Pt.2 Ch.3.102 For welding ambient temperature and welding details, see Sec.8.103 Shot blasting, priming and coating is to be carried out under indoor conditions. For coating specificationand documentation, see Sec.2.104 For all craft a non-destructive testing (NDT) plan is to be submitted for approval to the surveyor.

B. InspectionB 100 Non-destructive testing101 Welds are to be subjected to visual survey and inspection, as fabrication proceeds. NDT is to beperformed according to established procedures and if required, qualified for the work.102 All testing is to be carried out by qualified personnel. The NDT operators are to be qualified accordingto a recognised certification scheme accepted by the Society. The certificate is to state clearly the qualificationsas to which examination method and within which category the operator is qualified.

B 200 Magnetic particle testing201 Magnetic particle testing shall be carried out as specified in the approved procedures.

B 300 Radiographic testing301 Radiographic testing shall be carried out as specified in the approved procedures.302 Processing and storage are to be such that the films maintain their quality throughout the agreed storagetime. The radiographs shall be free from imperfections due to develop processing.

B 400 Ultrasonic examination401 Ultrasonic testing shall be carried out as specified in the approved procedures. Ultrasonic examinationprocedures shall contain sketches for each type of joint and dimensional range of joints which clearly showscanning pattern and probes to be used.402 The examination records shall include the imperfection position, the echo height, the dimensions(length), and the depth below the surface and, if possible, the defect type.

C. Extent of ExaminationC 100 General101 All welds are to be subjected to 100 % visual examination. In addition to the visual examination at least2 to 5 % of the total welded length is to be tested by magnetic particle examination and/or radiographicexamination. For highly stressed areas the extent of examination may be increased.102 If defects are detected, then the extent of the examination shall be increased to the satisfaction of thesurveyor.

D. Acceptance Criteria for NDTD 100 Acceptance criteria101 All welds shall show evidence of good workmanship. The quality shall normally comply with ISO 5817quality level C, intermediate. For highly stressed areas more stringent requirements, such as ISO level B, maybe applied.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.3 Page 23E. TestingE 100 Tanks101 Protective coating systems may be applied before water testing.All pipe connections to tanks are to be fitted before testing. If engine bed plates are bolted directly on the innerbottom plating, the testing of the double bottom tank is to be carried out with the engine installed.102 All tanks are, unless otherwise agreed, to be tested with a water head equal to the maximum pressure towhich the compartment may be exposed. The water head is no case to be less than to top of air pipe or to a levelh0 above the top of tank, except where partial filling alone is prescribed.

h0 = 0.03 L 0.5 (m) minimum 1 generally.= pressure valve opening pressure when exceeding the general value.

E 200 Closing appliances201 Inner and outer doors below the waterline are to be hydraulically tested.202 Weathertight and watertight closing appliances not subjected to pressure testing, are to be hose tested.The nozzle inside diameter is to be 12.5 mm and the pressure at least 250 kN/mm2 at the nozzle. The nozzleshould be held at a distance of maximum 1.5 m from the item under test.Alternative methods of tightness testing may be considered.203 All weathertight/watertight doors and hatches are to be function tested.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.4 Page 24SECTION 4 HULL GIRDER STRENGTH

A. GeneralA 100 Introduction101 In this section requirements for longitudinal and transverse hull girder strength is given. In addition,buckling control according to Sec.10 may be required.102 Longitudinal strength has generally to be checked for the craft types and sizes mentioned in theintroduction to Ch.1 Sec.3.103 For new designs (prototypes) of large and structurally complicated craft (e.g. multi-hull types) acomplete 3-dimensional global analysis of the transverse strength, in combination with longitudinal stresses, isto be carried out.104 Buckling strength in bottom and deck may, however, have to be checked also for the other craft. For thispurpose formulae for estimate of section modulus to deck and bottom based on bottom and deck cross sectionalareas have been given in Ch.1 Sec.3 A700.

B. Vertical Bending StrengthB 100 Hull section modulus requirement101 The section modulus is calculated as follows:

M = the longitudinal midship bending moment in kNm from Ch.1 Sec.3. = 175 f1 N/mm2 in general.

When is taken greater than 175 N/mm2, the bottom structure is to be assessed with respect to fatigue.Guidance note:Simultaneous end impacts over a hollow are considered less frequent, and giving lower moments than the crestlanding. Simultaneous end impacts need not be investigated if deck buckling resistance force is comparable to that ofthe bottom.


B 200 Effective section modulus201 When calculating the moment of inertia and section modulus of the midship section, the effectivesectional area of continuous longitudinal strength members is in general to be taken as the net area afterdeduction of any openings.Superstructures which do not form a strength deck are not to be included in the net section. This applies alsoto deckhouses and bulwarks.202 The effect of openings are assumed to have longitudinal extensions as shown by the shaded areas inFig.1, i.e. inside tangents at an angle of 30 to each other. Example for transverse section III:

bIII = b + b + b

Z M----- 103 cm3( )=DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.4 Page 25Fig. 1Effect of openings

203 For twin hull vessels the effective breadth of wide decks without longitudinal bulkhead support will beespecially considered.

B 300 Hydrofoil on foils301 For hydrofoils the sections in way of the foils are to be considered, in addition to the calculations for themidship section.

B 400 Longitudinal structural continuity401 The scantling distribution of structures participating in the hull girder strength in the various zones of thehull is to be carefully worked out so as to avoid structural discontinuities resulting in abrupt variations ofstresses.402 At ends of effective continuous longitudinal strength members in deck and bottom region large transitionbrackets are to be fitted.

Guidance note:Height to length ratio of the transition brackets is to be 1: 4 or better.


B 500 Openings501 A keel plate for docking is normally not to have openings. In the bilge plate, within 0.5 L amidships,openings are to be avoided as far as practicable. Any necessary openings in the bilge plate are to be kept clearof a bilge keel.502 Openings in strength deck are as far as practicable to be located well clear of crafts side and hatchcorners.503 Openings in strength members should generally have an elliptical form. Larger openings in deck may beaccepted with well rounded corners and are to be situated as near to the crafts centreline as practicable.504 For corners with rounded shape the radius is not to be less than:

r = 0.025 Bdk (m)Bdk = breadth of strength deck.r needs not be taken greater than 0.1 b (m) where b = breadth of opening in m. For local reinforcement of deckplating at circular corners, see Rules for Classification of Ships Pt.3 Ch.1 Sec.5 E400.

b'

30ob''

b'''

I II

b3

III

b2

b1DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.4 Page 26505 Edges of openings are to be smooth. Machine flame cut openings with smooth edges may be accepted.Small holes are to be drilled.506 Studs for securing small hatch covers are to be fastened to the top of a coaming or a ring of suitablethickness welded to the deck. The studs are not to penetrate the deck plating.

C. Shear StrengthC 100 Cases to be investigated101 If doors are arranged in the crafts side, the required sectional area of the remaining side plating will beespecially considered.102 If rows of windows are arranged below the strength deck, sufficient horizontal shear area must bearranged to carry down the midship tension and compression.103 For the cases in 101 and 102 and for other locations with doubtful shear area, the allowable shear stressmay be taken as:

D. Cases to be InvestigatedD 100 Inertia induced loads101 Transversely framed parts of the forebody are to be checked for the axial inertia forces given in Pt.3 Ch.1Sec.3 A700 as follows:

FL = al (kN)

al = maximum surge acceleration, not to be taken as less than:

.

The height distribution of stresses will depend on instantaneous forward immersion and on height location ofcargo.102 Bottom structure in way of thrust bearings may need to be checked for the increased thrust when the craftis retarted by a crest in front.103 Allowable axial stress and associated shear stresses will be related to the stresses already existing in theregion.104 For passenger craft, a separate analysis is to be performed to investigate the structural consequence whensubjected to the collision load as given in the International Code of Safety for High-Speed Craft, 4.3.3 (see Ch.7Sec.1 B300).

Guidance note:Inertia forces from collision deceleration should be considered for shear and buckling in the foreship area, and for theforces acting on the supporting structure for cargo.


E. Transverse Strength of Twin Hull CraftE 100 Transverse strength101 The twin hull connecting structure is to have adequate transverse strength related to the design loads andmoments given in Ch.1.

allowable shear stress allowable bending stress3

-----------------------------------------------------------=

0,4 g for VL

------- 5

0,2 g for VL

------- 3

linear interpolation of al for 3VL

------- 5<

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.4 Page 27102 When calculating the moment of inertia, and section modulus of the longitudinal section of theconnecting structure, the effective sectional area of transverse strength members is in general the net area witheffective flange after deduction of openings.The effective shear area of transverse strength members is in general the net web area after deduction ofopenings.

E 200 Allowable stresses201 The equivalent stress is defined as:

x = total normal stress in x-directiony = total normal stress in y-direction = total shear stress in the xy-plane

By total stress is meant the arithmetic sum of stresses from hull girder and local forces and moments.202 The following total stresses are normally acceptable:

Normal stress: = 160 f1 (N/mm2) Mean shear stress: = 90 f1 (N/mm2) Equivalent stress: e = 180 f1 (N/mm2)

c x2 y

2 xy 32

+( )+=DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.5 Page 28SECTION 5 STEEL PLATING AND STIFFENERS

A. GeneralA 100 Introduction101 In this section the general requirements for plate thicknesses and local strength of stiffeners in single skinpanels are given.102 For buckling control, see Sec.10.

A 200 Definitions201 Symbols:L, B, D, T, CB, see Ch.1 Sec.1.

t = rule thickness in mm of platingZ = rule section modulus in cm3 of stiffenerss = stiffener spacing in m, measured along the plating

for corrugations, see Sec.1 Dfor wash bulkhead section modulus calculations s may be reduced according to size and locationof openings

sr = basic stiffener spacing= 2 (240 + L) (mm) in general

= 760 mm for watertight bulkheads, cargo hold bulkheads and superstructure and deckhousebulkheads

l = stiffener span in m, measured along the topflange of the member. For definition of span point, seeSec.1 F100. For curved stiffeners l may be taken as the cord length

= nominal allowable bending stress in N/mm2. due to lateral pressurep and psl = design pressure in kN/m2 as given in Ch.1 Sec.2. To be calculated at load point as defined in Ch.1

Sec.2 AZA = midship section modulus in cm3 as built at deck or bottom, respectivelyZR = rule midship section modulus in cm3.

A 300 Allowable stresses301 Maximum allowable bending stresses in plates and stiffeners are to be according to Table A1.

Table A1 Allowable bending stressesItem Plate Stiffener

Within 0.4 L Within 0.1 Lfrom AF/FP

Within 0.4 L Within 0.1 Lfrom AP/FP

(N/mm2)Bottom, slamming loads 160 f1 150 f1Bottom, sea load: 120 f1 160 f1 160 f1- longitudinals, ZA = ZR 1) 95 f1- longitudinals, ZA 2 ZR 1) 160 f1- transverse beams 160 f1Side, slamming load 160 f1 160 f1Side, sea load:Longitudinal stiffening 180 f1 160 f1- at neutral axis 2) 180 f1- at deck or bottom 2) 120 f1- 0.25 D above and below neutral axis 2) 160 f1Transverse stiffening, 160 f1 160 f1- at neutral axis 2) 160 f1- at deck or bottom 2) 120 f1Deck:Longitudinal stiffening 120 f1 180 f1 160 f1DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.2 Sec.5 Page 29B. PlatingB 100 Minimum thickness101 The thickness of the structures is in general not to be less than:

t0 and k according to Table B1

B 200 Formulae201 The thickness requirement corresponding to lateral pressure or impact is given by:

- ZA = ZR 1) 95 f1- ZA 2 ZR 1) 160 f1Transverse stiffening 120 f1 160 f1 160 f1Flat cross structure longitudinal bulkhead: 160 f1 150 f1Longitudinal stiffening 160 f1- at neutral axis 2) 160 f1- at deck or bottom 2) 120 f1Transverse stiffening 160 f1 160 f1- at neutral axis 2) 140 f1- at deck or bottom 2) 120 f1Transverse tank bulkhead 160 f1 160 f1Collision bulkhead 160 f1 160 f1Watertight bulkhead 220 f1 220 f1Watertight doors 135 f1Superstructure/deckhouse, side/front 160 f1 160 f1Superstructure/deckhouse deck 160 f1Shell doors 135 f11) For ZR < ZA < 2 ZR -values may be varied linearly.2) Between specified regions -values may be varied linearly.

Table B1 Values of t0 and kItem t0 kShell plating: Keel 1) 7.0 0.05

Bottom, bilge, side, sea inlets and other openings 2) 5.0 0.04Strength deck Weather and cargo decks 4.5 0.025

Accommodation deck 4.5 0.025Plating of decks below strength deck Cargo deck 4.0 0.02

Accommodation deck 4.0 0.02Plating of decks above strength deck Weather exposed parts of first tier superstructure

decks and deckhouse tops4.0 0.02

Accommodation 4.0 0.02Bulkhead plating Tank bulkheads and watertight bulkheads 5.0 0.025

First tier of superstructure ends and exposed sides 5.0 0.01Other structures Structure not mentioned above 2.51) The thickness of the keel plate is in no case to be less than that of the adjacent bottom plate.2) The thickness of the bilge plate is not to be less than that of the adjacent bottom and side plates whichever is the greater.

Table A1 Allowable bending stresses (Continued)Item Plate Stiffener

Within 0.4 L Within 0.1 Lfrom AF/FP

Within 0.4 L Within 0.1 Lfrom AP/FP

(N/mm2)

t t0 kL+( )ssr---- mm( )=

ssr---- is not to be taken less than 0.5 or greater than 1.0.

t15 8, s p or p s l-------------------------------------- (mm)=DET NORSKE VERI

hs302_2012-07

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