hs303

RULES FOR CLASSIFICATION OF

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High Speed, Light Craft and NavalSurface Craft

PART 3 CHAPTER 3

STRUCTURES, EQUIPMENT

Hull Structural Design, Aluminium Alloy

JULY 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

Any comments may be sent by e-mail to [email protected]

If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation tosuch person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided thatthe maximum compensation shall never exceed USD 2 million.In this provision Det Norske Veritas shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalfof Det Norske Veritas.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012Pt.3 Ch.3 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 B501 is amended. Item H300 is deleted. Subsec.I400 is added.

Sec.3 Manufacturing Item A103 is amended.

Sec.5 Plating and Stiffeners Item B302 is amended.

Sec.7 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.3 Contents Page 4CONTENTS

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

A. General ........................................................................................................................................................................... 8A 100 The scantling reduction......................................................................................................................................... 8A 200 Aluminium alloys ................................................................................................................................................. 8

B. Bottom Structures ......................................................................................................................................................... 8B 100 Longitudinal stiffeners .......................................................................................................................................... 8B 200 Web frames ........................................................................................................................................................... 8B 300 Longitudinal girders.............................................................................................................................................. 8B 400 Engine girders ....................................................................................................................................................... 8B 500 Double bottom, if fitted ........................................................................................................................................ 9

C. Side Structure................................................................................................................................................................ 9C 100 Stiffeners ............................................................................................................................................................... 9

D. Deck Structure............................................................................................................................................................... 9D 100 Longitudinal stiffeners .......................................................................................................................................... 9D 200 Bulwarks ............................................................................................................................................................... 9

E. Flat Cross Structure...................................................................................................................................................... 9E 100 Definition .............................................................................................................................................................. 9E 200 Longitudinal stiffeners .......................................................................................................................................... 9

F. Bulkhead Structures ................................................................................................................................................... 10F 100 Transverse bulkheads.......................................................................................................................................... 10F 200 Corrugated bulkheads ......................................................................................................................................... 10

G. Superstructures and Deckhouses............................................................................................................................... 10G 100 Definitions .......................................................................................................................................................... 10G 200 Structural continuity ........................................................................................................................................... 10

H. Structural Design in General ..................................................................................................................................... 11H 100 Craft arrangement ............................................................................................................................................... 11H 200 Soft local transitions ........................................................................................................................................... 11

I. Some Common Local Design Rules ........................................................................................................................... 11I 100 Definition of span ............................................................................................................................................... 11I 200 Effective girder flange ........................................................................................................................................ 12I 300 Sniped stiffeners ................................................................................................................................................. 13I 400 Floating Frames .................................................................................................................................................. 13

J. Support of Equipment and Outfitting Details .......................................................................................................... 13J 100 Heavy equipment, appendages etc. ..................................................................................................................... 13J 200 Minor outfitting details ....................................................................................................................................... 14

K. Structural Aspects not Covered by Rules ................................................................................................................. 14K 100 Deflections .......................................................................................................................................................... 14K 200 Local vibrations .................................................................................................................................................. 14

Sec. 2 Materials and Material Protection ................................................................................................. 15

A. General ......................................................................................................................................................................... 15A 100 Application.......................................................................................................................................................... 15A 200 Material certificates ............................................................................................................................................ 15

B. Structural Aluminium Alloy ...................................................................................................................................... 15B 100 General................................................................................................................................................................ 15B 200 Aluminium grades............................................................................................................................................... 15B 300 Chemical composition ........................................................................................................................................ 15B 400 Mechanical properties......................................................................................................................................... 15

C. Corrosion Protection................................................................................................................................................... 17C 100 General................................................................................................................................................................ 17C 200 For information and approval ............................................................................................................................. 17C 300 Coating................................................................................................................................................................ 17C 400 Cathodic protection............................................................................................................................................. 18C 500 Other materials in contact with aluminium......................................................................................................... 19

D. Other Materials ........................................................................................................................................................... 19D 100 Steel .................................................................................................................................................................... 19DET NORSKE VERITAS AS

D 200 Connections between steel and aluminium......................................................................................................... 19

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Contents Page 5D 300 Fibre Reinforced Plastic (FRP)........................................................................................................................... 19

Sec. 3 Manufacturing.................................................................................................................................. 20

A. General ......................................................................................................................................................................... 20A 100 Basic requirements.............................................................................................................................................. 20

B. Inspection..................................................................................................................................................................... 20B 100 General................................................................................................................................................................ 20B 200 Penetrant testing.................................................................................................................................................. 20B 300 Radiographic testing ........................................................................................................................................... 20B 400 Ultrasonic examination ....................................................................................................................................... 20

C. Extent of Examination ................................................................................................................................................ 20C 100 General................................................................................................................................................................ 20

D. Acceptance Criteria for NDT..................................................................................................................................... 20D 100 Acceptance criteria.............................................................................................................................................. 20

E. Testing .......................................................................................................................................................................... 21E 100 Tanks................................................................................................................................................................... 21E 200 Closing appliances .............................................................................................................................................. 21

Sec. 4 Hull Girder Strength........................................................................................................................ 22

A. General ......................................................................................................................................................................... 22A 100 Introduction......................................................................................................................................................... 22A 200 Definitions .......................................................................................................................................................... 22

B. Vertical Bending Strength.......................................................................................................................................... 22B 100 Hull section modulus requirement ...................................................................................................................... 22B 200 Effective section modulus................................................................................................................................... 22B 300 Hydrofoil on foils................................................................................................................................................ 23B 400 Longitudinal structural continuity ...................................................................................................................... 23B 500 Openings ............................................................................................................................................................. 23

C. Shear Strength............................................................................................................................................................. 24C 100 Cases to be investigated ...................................................................................................................................... 24

D. Cases to be Investigated.............................................................................................................................................. 24D 100 Inertia induced loads ........................................................................................................................................... 24

E. Transverse Strength of Twin Hull Craft................................................................................................................... 24E 100 Transverse strength ............................................................................................................................................. 24E 200 Allowable stresses .............................................................................................................................................. 25

Sec. 5 Plating and Stiffeners....................................................................................................................... 26

A. General ......................................................................................................................................................................... 26A 100 Introduction......................................................................................................................................................... 26A 200 Definitions .......................................................................................................................................................... 26A 300 Allowable stresses............................................................................................................................................... 26

B. Plating .......................................................................................................................................................................... 26B 100 Minimum thicknesses ......................................................................................................................................... 26B 200 Bending............................................................................................................................................................... 27B 300 Slamming ............................................................................................................................................................ 27

C. Stiffeners ...................................................................................................................................................................... 28C 100 Bending............................................................................................................................................................... 28C 200 Slamming ............................................................................................................................................................ 29

Sec. 6 Web Frames and Girder Systems ................................................................................................... 30

A. General ......................................................................................................................................................................... 30A 100 Introduction......................................................................................................................................................... 30A 200 Definitions .......................................................................................................................................................... 30A 300 Minimum thicknesses ......................................................................................................................................... 30A 400 Allowable stresses............................................................................................................................................... 31A 500 Continuity of strength members ......................................................................................................................... 31

B. Web Frames and Girders ........................................................................................................................................... 31B 100 General................................................................................................................................................................ 31B 200 Effective flange................................................................................................................................................... 31B 300 Effective web ...................................................................................................................................................... 32DET NORSKE VERITAS AS

B 400 Strength requirements ......................................................................................................................................... 32

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Contents Page 6B 500 Girder tripping brackets ...................................................................................................................................... 33B 600 Girder web stiffeners........................................................................................................................................... 34

Sec. 7 Pillars and Pillar Bulkheads............................................................................................................ 35

A. General ......................................................................................................................................................................... 35A 100 Introduction......................................................................................................................................................... 35A 200 Definitions .......................................................................................................................................................... 35

B. Pillars............................................................................................................................................................................ 35B 100 Arrangement of pillars ........................................................................................................................................ 35B 200 Cross-section particulars..................................................................................................................................... 35B 300 Pillar scantlings................................................................................................................................................... 35B 400 Pillars in tanks..................................................................................................................................................... 36

C. Supporting Bulkheads ................................................................................................................................................ 37C 100 General................................................................................................................................................................ 37

Sec. 8 Weld Connections............................................................................................................................. 38

A. General ......................................................................................................................................................................... 38A 100 Introduction......................................................................................................................................................... 38A 200 Welding particulars............................................................................................................................................. 38

B. Types of Welded Joints............................................................................................................................................... 38B 100 Butt joints............................................................................................................................................................ 38B 200 Tee or cross joints ............................................................................................................................................... 38

C. Size of Connections ..................................................................................................................................................... 39C 100 Fillet welds, general ............................................................................................................................................ 39C 200 Fillet welds and penetration welds subject to high tensile stresses .................................................................... 39C 300 End connections of girders, pillars and cross ties ............................................................................................... 40C 400 End connections of stiffeners.............................................................................................................................. 40

Sec. 9 Direct Strength Calculations ........................................................................................................... 43

A. General ......................................................................................................................................................................... 43A 100 Introduction......................................................................................................................................................... 43A 200 Application.......................................................................................................................................................... 43

B. Plating .......................................................................................................................................................................... 43B 100 General................................................................................................................................................................ 43B 200 Calculation procedure ......................................................................................................................................... 43B 300 Allowable stresses............................................................................................................................................... 43

C. Stiffeners ...................................................................................................................................................................... 43C 100 General................................................................................................................................................................ 43C 200 Calculation procedure ......................................................................................................................................... 44C 300 Loads................................................................................................................................................................... 44C 400 Allowable stresses............................................................................................................................................... 44

D. Girders ......................................................................................................................................................................... 44D 100 General................................................................................................................................................................ 44D 200 Calculation methods ........................................................................................................................................... 44D 300 Design load conditions........................................................................................................................................ 44D 400 Allowable stresses............................................................................................................................................... 45

Sec. 10 Buckling Control .............................................................................................................................. 46

A. General ......................................................................................................................................................................... 46A 100 Definitions .......................................................................................................................................................... 46

B. Longitudinal Buckling Load ...................................................................................................................................... 47B 100 Longitudinal stresses........................................................................................................................................... 47

C. Transverse Buckling Load ......................................................................................................................................... 47C 100 Transverse stresses.............................................................................................................................................. 47

D. Plating .......................................................................................................................................................................... 47D 100 Plate panel in uni-axial compression .................................................................................................................. 47D 200 Plate panel in shear ............................................................................................................................................. 49D 300 Plate panel in bi-axial compression and shear .................................................................................................... 49

E. Stiffeners in Direction of Compression ..................................................................................................................... 50E 100 Lateral buckling mode ........................................................................................................................................ 50DET NORSKE VERITAS AS

E 200 Torsional buckling mode .................................................................................................................................... 51

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Contents Page 7E 300 Web and flange buckling .................................................................................................................................... 52

F. Stiffeners Perpendicular to Direction of Compression............................................................................................ 52F 100 Moment of inertia of stiffeners ........................................................................................................................... 52

G. Elastic Buckling of Stiffened Panels .......................................................................................................................... 53G 100 Elastic buckling as a design basis ....................................................................................................................... 53G 200 Allowable compression....................................................................................................................................... 53

H. Girders ......................................................................................................................................................................... 54H 100 Axial load buckling............................................................................................................................................. 54H 200 Girders perpendicular to direction of compression............................................................................................. 54H 300 Buckling of effective flange................................................................................................................................ 54H 400 Shear buckling of web ........................................................................................................................................ 55DET NORSKE VERITAS AS

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

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

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

A 200 Aluminium alloys201 The alloy grades are listed in Sec.2 Tables B1 to B4.202 The various formulae and expressions involving the factor f1 may be applied when:

f = yield stress is not to be taken greater than 70% of the ultimate tensile strength.

The material factor f1 included in the various formulae and expressions is given in Sec.2 Tables B1 to B3 forthe un-welded condition and in Table B4 for the welded condition.

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, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals areto be fitted or welds are to be dimensioned accordingly.103 Longitudinal stiffeners are to be supported by bulkheads and web frames.104 Longitudinal stiffeners in slamming areas should have a shear connection to transverse members.

B 200 Web frames201 Web frames are to be continuous around the cross section i.e. floors side webs and deck beams are to beconnected. Intermediate floors may be used.202 In the engine room plate floors are to be fitted at every frame. In way of thrust bearings additionalstrengthening is to be provided.

B 300 Longitudinal girders301 Web plates of longitudinal girders are to be continuous in way of transverse bulkheads.302 A centre girder is normally to be fitted for docking purposes.303 Manholes or other openings should not be positioned at ends of girders without due consideration beingtaken of shear loadings.

B 400 Engine girders401 Under the main engine, girders extending from the bottom to the top plate of the engine seating are to befitted.

s = chosen spacing in m

sr =

a certain stiffener spacing reduction ratio ssr----

basic spacing =2 100 L+( )1000--------------------------- m in general

f1f

240---------=DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 9402 Engine holdingdown bolts are to be arranged as near as practicable to floors and longitudinal girders.403 In way of thrust bearing and below pillars additional strengthening is to be provided.

B 500 Double bottom, if fitted501 Manholes are to be cut in the inner bottom, floors and longitudinal girders to provide access to all partsof the double bottom. The vertical extension of lightening holes is not to exceed one half of the girder height.Centre of lightening holes to be, as close as practicable, to the neutral axes of elements in question. The edgesof the manholes are to be smooth. Manholes in the inner bottom plating are to have reinforcement rings.Manholes are not to be cut in the floors or girders in way of pillars.502 In double bottoms with transverse stiffening, longitudinal girders are to be stiffened at every transverseframe.503 The longitudinal girders are to be satisfactorily stiffened against buckling.

C. Side StructureC 100 Stiffeners101 The craft's sides may be longitudinally or vertically stiffened.

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

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

102 The continuity of the longitudinals is to be as required for bottom and deck longitudinals respectively.

D. Deck StructureD 100 Longitudinal stiffeners101 Decks are normally to be longitudinally stiffened.102 The longitudinals should preferably be continuous through transverse members. If they are to be cut attransverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals areto be fitted.103 The plate thickness is to be such that the necessary transverse buckling strength is achieved, or transversebuckling stiffeners may have to be fitted intercostally.

D 200 Bulwarks201 The thickness of bulwark plates is not to be less than required for side plating in a superstructure in thesame position.202 A strong bulb section or similar is to be continuously welded to the upper edge of the bulwark. Bulwarkstays are to be in line with transverse beams or local transverse stiffening. The stays are to have sufficient widthat deck level. The deck beam is to be continuously welded to the deck in way of the stay. Bulwarks on forecastledecks are to have stays fitted at every frame.Stays of increased strength are to be fitted at ends of bulwark openings. Openings in bulwarks should not besituated near the ends of superstructures.203 Where bulwarks on exposed decks form wells, ample provision is to be made to freeing the decks forwater.

E. Flat Cross StructureE 100 Definition101 Flat cross structure is horizontal structure above waterline like bridge connecting structure between twinhulls, etc.

E 200 Longitudinal stiffeners201 Flat cross structures are normally to be longitudinally stiffened.DET NORSKE VERITAS AS

202 The longitudinals should preferably be continuous through transverse members. If they are to be cut at

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 10transverse members, i.e. watertight bulkheads, continuous brackets connecting the ends of the longitudinals areto be fitted or welds are to be dimensioned accordingly.203 Longitudinal stiffeners are to be supported by bulkheads and web frames.

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 B200.102 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 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.

Fig. 1Corrugated bulkhead

G. Superstructures and DeckhousesG 100 Definitions101 Superstructure is defined as a decked structure on the freeboard deck, extending from side to side of theship 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 Structural continuity201 In superstructures and deckhouses, the front bulkhead is to be in line with a transverse bulkhead in thehull below or be supported by a combination of girders and pillars. The after end bulkhead is also to beeffectively supported. As far as practicable, exposed sides and internal longitudinal and transverse bulkheadsare to be located above girders and frames in the hull structure and are to be in line in the various tiers ofaccommodation. Where such structural arrangement in line is not possible, there is to be other effective support.202 Sufficient transverse strength is to be provided by means of transverse bulkheads or girder structures.203 At the break of superstructures, which have no set-in from the ship's side, the side plating is to extendbeyond the ends of the superstructure, and is to be gradually reduced in height down to the deck or bulwark.The transition is to be smooth and without local discontinuities. A substantial stiffener is to be fitted at the upperedge of plating. The plating is also to be additionally stiffened.204 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. The connection area betweendeckhouse corners and deck plating is to be increased locally.DET NORSKE VERITAS AS

Deck girders are to be fitted below long deckhouses in line with deckhouse sides.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 11205 Deck beams under front and aft ends of deckhouses are not to be scalloped for a distance of 0.5 m fromeach side of the deckhouse corners.206 For deckhouse side stiffeners the scantlings need not be greater than required for tween deck frames withequivalent end connections.207 Casings supporting one or more decks above are to be adequately strengthened.

H. Structural Design in GeneralH 100 Craft arrangement101 Attention is drawn to the importance of structural continuity in general.102 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 strongwebs web or pillar rings in engine room twin hull connections access for inspection superstructures and deckhouses:

direct support transitions

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

103 Structural details in spaces that will be coated are to be designed in such way that a sound layer of coatingcan be achieved everywhere.

H 200 Soft local transitions201 Gradual taper or soft transition is specially important in high speed aluminium vessels, to avoid:

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

202 End brackets, tripping brackets etc. are not to terminate on unsupported plating.Brackets are to extend to the nearest stiffener, or local plating reinforcement is to be provided at the toe of thebracket.

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 on Fig.1. It is assumed that brackets are effectively supportedby the adjacent structure. For stiffeners, see also Fig. 2 or Sec.5.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 12Fig. 2Span points

I 200 Effective girder flange201 For girders with curved face plate, e.g. web frames, the effective area of the flange is given by:

Ae= k tf bf (mm2)

b = 0.5 (bf tw) for symmetrical free flanges

bf = total face plate breadth in mmk = flange efficiency coefficient, see also Fig. 3

=

= 1.0 maximum

k1 =

for symmetrical and unsymmetrical free flange

=

for girder flange with two webs

=

for box girder flange with multiple webs

=

l

l

23

b

l

b

STIFFENERS GIRDERS

R S

23 R

23 b

S

b

k1rtfb

----------

0.643 sinh cosh sin cos+( )h 2sin 2sin+

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

0.78 sinh sin+( ) cosh cos( )h 2sin 2sin+

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

1.56 cosh cos( )sinh sin+-------------------------------------------------

1.285brtf

----------------- (rad)DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 13 = bf for unsymmetrical free flanges

= s tw for box girder flangess = spacing of supporting webs for box girder (nun)tf = face plate thickness in general (mm) = tw (maximum) for unsymmetrical free flangestw = web plate thickness (mm)r = radius of curved face plate (mm)

Fig. 3Effective width of curved face plates for alternative boundary conditions

202 The effective width of curved plate flanges, or effective width of plate at knuckles, is to be speciallyconsidered.

I 300 Sniped stiffeners301 Stiffeners with sniped ends may be allowed where dynamic loads are small and vibrations considered tobe of small importance.

I 400 Floating Frames401 Floating frames are considered beams supporting extruded panels (plating and stiffeners together).402 Profiles that may be used for floating frames are double flanged profiles (e.g. I or C profiles). Singleflanged profiles (e.g. T profiles) are not acceptable.403 Floating frames may be used in Decks, Bulkheads, Side Shell Aft, etc., generally in low stress area andwhere only static loads are foreseen. 404 Floating frames cannot be used in Hull Bottom, Side Fore Body Area, etc., generally in highly stressedareas and / or areas where dynamic loads are foreseen.405 Attached panels cannot be considered participating in strength of floating frames. Section properties offloating frames to be calculated only for bare profile.406 Allowable stresses as stipulated in Sec.6 A400 and Sec.9 D400 may be increased by 5% after specialconsiderations.

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 system (taking into account hull stresses already existing) until forces are safely carried to craft's side orbulkheads.102 Doublers should be avoided normal to a tensile force.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.1 Page 14J 200 Minor outfitting details201 Generally connections of outfitting details to the hull are to be such that stress-concentrations areminimized and welding to high stressed parts are avoided wherever possible.Connections are to be designed with smooth transitions and proper alignment with the hull structure elements.Terminations are to be supported.202 Connections to topflange of girders and stiffeners are to be avoided if not well smoothened. Preferablysupporting of outfittings are to be welded to the stiffener web.

K. Structural Aspects not Covered by RulesK 100 Deflections101 Requirements for minimum moment of inertia or maximum deflection under load are limited to structurein way of hatches and doors and some other special cases.102 Deflection problems in general are left to designer's consideration.

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

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

a) impair the integrity of structure during the anticipated service life of the craft or the service life agreedwith the Administration;

b) hinder normal functioning of machinery and equipment; andc) impair the ability of the crew to carry out its duties.


Upon request such evaluation may be undertaken by the Society.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.2 Page 15SECTION 2 MATERIALS AND MATERIAL PROTECTION

A. GeneralA 100 Application101 The rules in this chapter apply to wrought aluminium alloys for objects classified or intended forclassification with the Society.

A 200 Material certificates201 Rolled and extruded wrought aluminium alloys, glass reinforced plastic and core materials for hullstructures and rolled steel are normally to be supplied with DNV material certificates.202 For class certificate requirement for chemical composition, mechanical properties, heat treatment andrepair of defects, see Pt.2 Ch.2.203 Particular attention is to be given to aluminium hull materials specification in Pt.2 Ch.2.204 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. Structural Aluminium AlloyB 100 General101 Aluminium alloy for marine use may be applied in hulls, superstructures, deckhouses, hatch covers andsundry items.

B 200 Aluminium grades201 Aluminium alloys are to have a satisfactory resistance to corrosion in marine environments. Grades forwelded structures are to be weldable, applying one of the welding methods approved by the Society.202 For major hull structural components, alloys with temper H116/H321 for rolled products, and alloys withtemper T5/T6 for extruded products, are normally to be used. The use of 0- or F temper must be agreed withthe Society.203 The use of 6000 series aluminium alloys in direct contact with sea water may be restricted depending onapplication and corrosion protection system. The use of these alloys are to be agreed with the Society.204 In weld zones (HAZ) of rolled or extruded products, the factor f1 given in Table B4 may in general beused as basis for the scantling requirements.205 Welding consumables are to be chosen according to Table C2 in Pt.2 Ch.3 Sec.2. The consumable chosenare to have minimum mechanical properties not less than specified for the parent alloy in the welded condition.

B 300 Chemical composition301 The chemical composition is to satisfy the requirements in Pt.2 Ch.2. Other alloys or alloys which do notfully comply with Pt.2 Ch.2, may be accepted by the Society after consideration in each particular case. Specialtests and/or other relevant information, e.g. which confirm a satisfactory corrosion resistance and weldability,may be required.

B 400 Mechanical properties401 Requirements to mechanical properties for different delivery conditions are given in Tables B1 and B2for wrought products, extruded products and rivet bars/-rivets, respectively. Other delivery conditions withrelated mechanical properties may be accepted by the Society after consideration in each particular case.

Table B1 Factor f1 for wrought aluminium alloy sheets, strips and plates, t: 2 mm t 40 mmDNV Designation Temper f1

NV-5052 H32 H34

0.61 0.69

NV-5154A 0, H111 0.35NV-5754 H24 0.69NV-5454 H32 0.73 DET NORSKE VERITAS AS

H34 0.79

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.2 Page 16V-5086 H116, H32 H34

0.80 0.88

NV-5083 H116, H321 0.89NV-5383 H116, H34 0.89

Note: For tempers 0 and H111, the factor f1 is to be taken from Table B4.

Table B2 Factor f1 for extruded aluminium alloy profiles, rods and tubes, t: 2 mm t 25 mmDNV

DesignationTemper f1

NV-6060 T5 0.55NV-6061 T4

T5/T60.46 0.76

NV-6063 T5 T6

0.44 0.60

NV-6005A T5/T6 0.76NV-6082 T4

T5/T60.46 0.90

Note: Table B2 only applies when the main loading direction is logitudinal to the extrusion, see also Table B3.

Table B3 Factor f1 for extruded aluminium alloy profiles, rods and tubes, t: 2 mm t 25 mm, transverse to extruding direction

DNVDesignation

Temper f1

NV-6060 T5 0.51NV-6061 T4

T5/T60.46 0.71

NV-6005A T5/T66 < t < 10

10 < t < 250.760.67

NV-6082 T5 / T6 0.85Note: Table B2 only applies when the main loading direction is logitudinal to the extrusion

Table B4 Factor f1 in the welded conditionDNV

DesignationTemper Filler f1

NV-5052 0, H111, H32, H34 5356 0.27NV-5154A 0, H111 5356-5183 0.35NV 5754 0, H111, H24 5356-5183 0.33NV 5454 0, H111, H32, H34 5356-5183 0.35NV-5086 0, H111, H116, H32, H34 5356-5183 0.42NV-5083 H116, H321

H116, H3215356 5183

0.531) 0.601)

NV-5383 H116, H34 5183 0.642)NV-6060 T5 5356-5183 0.27NV-6061 T4

T5/T65356-5183 0.48

0.48NV-6063 T5

T65356-5183 0.27

NV-6005A T5/T6 5356-5183 0.48NV-6082 T4

T5/T65356-5183 0.46

0.481) The utilisation of the material is higher than given by the f1 factor as given in Sec. 1 A. This is due to extended

utilisation in Rules for HS, LC and NSC, f1=(1/240) x 1.102) The utilisation of the material is higher than given by the f1 factor as given in Sec. 1 A. This is due to extended

utilisation in Rules for HS, LC and NSC, f1=(1/240) x 1.10

Table B1 Factor f1 for wrought aluminium alloy sheets, strips and plates, t: 2 mm t 40 mm (Continued)DNV Designation Temper f1DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.2 Page 17C. Corrosion ProtectionC 100 General101 Loss of structural strength due to corrosion is not acceptable.102 All surfaces that are not recognised as inherently resistant to the actual marine environment are to beadequately protected against corrosion.

Guidance note:In these rules, corrosion is defined as degradation of material due to environmental influence.


C 200 For information and approval201 Specifications for corrosion protection, i.e. for coating, if applied, see 301, and for cathodic protection(including calculations), see 403, are to be submitted for information. The specifications are basis for approvalof drawings of the cathodic protection system.202 Drawings of cathodic protection system, e.g. fastening, numbers and distribution of anodes and referenceelectrodes (if impressed current), are subject to approval.203 Selection and combination of materials for exposure to sea water and/or marine atmosphere are subjectto approval.

C 300 Coating301 If coating is applied, the specification is to be submitted for information.

Guidance note:Coating of aluminium hulls is normally not required (see B200). However, hulls normally need to be coated for anti-fouling purposes. When coating is applied, it will influence the corrosion resistance of the hull, and constitute a basisfor cathodic protection design. The coating system including surface preparation before coating should therefore besubmitted for information.The following is normally included in a specification for coating:

metal surface cleaning and preparation before application of the primer coat, including treatment of edges andwelds

build-up and application of coating system with individual coats curing times and over-coating intervals acceptable temperatures of air and metal surface and dryness or humidity conditions during the above mentioned

operations (normally, the metal surface is minimum 3 C above the dew point and the relative humidity is below85%)

thickness of individual coats and final coating system resistance to cathodic disbonding (for coatings to be used in connection with impressed current).


302 A sound anti-corrosion coating should always be combined with the anti-fouling coating on the externalhull.303 Anti-corrosion coating is not to contain copper or other constituents that may cause galvanic corrosionon the aluminium hull.304 Hull integrated water ballast tanks and other tanks holding corrosive liquids are to be coated. Allstiffeners and frames in these tanks are to be welded to plating with double continuous welding, see Sec.8 B202.305 In other internal compartments of the hull where corrosive water is likely to occur, the lower 0.5 m ofthe internal bottom surface, measured along the plate on each side of the keel, and the corresponding sectionof the bulkheads, is normally to be coated. The preparation of surfaces including welds and edges shall be suchthat the coating can be properly applied.

Guidance note:The use of 6000 alloys containing more than 0.15% Cu in internal compartments without coating may be restricted.Stagnant, chloride-containing water in internal compartments, e.g. condensation water, may cause corrosion onaluminium alloy plates and structures. Corrosion attacks will usually be of localised type, e.g. in the form of pitting.Corrosion attacks of galvanic type may also occur, see also 500, e.g. if equipment made of other metal alloy remainsin electrical contact with aluminium alloy material.Corrosion attacks of the above mentioned types can be reduced by means of e.g.:

coating applied as described above regular cleaning, drying and inspection of the actual compartment electrical isolation of any other metallic part from aluminium alloy plates and structuresDET NORSKE VERITAS AS

use of dehumidifying equipment in a closed compartment

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.2 Page 18 ventilation holes (minimum 2) drainage holes hot air fans.


C 400 Cathodic protection401 Cathodic protection of aluminium hulls can be obtained with aluminium or zinc sacrificial anodes orimpressed current. Magnesium based sacrificial anodes are not to be used, and impressed current is not to beused in internal hull compartments.402 Cathodic protection is normally to be applied to aluminium hull craft due to electrical connection of thealuminium with another metals (in propeller, water jet, etc.), which may initiate galvanic corrosion, and toprotect the hull against local corrosion and damage that normally will occur in protective coatings.403 The following is normally to be included in a cathodic protection specification:

areas to be protected (m2) for hull and attached metallic components such as water jet unit and water jet duct stipulated protective current density demand (mA/m2) for coated and not coated surfaces of hull and

attached components, respectively total current demand (A) target design life of cathodic protection system anode material and manufacturer for sacrificial anodes; calculation of anode mass, distribution, total number for impressed current systems; current capacity of rectifiers and anodes for impressed current systems; reference electrodes, system control and monitoring arrangement, cabling

and procedures for exchange or renewal of components target protective potential difference to be obtained drawings of cathodic protection systems, showing anode types, mass, distribution, location and attachment

details (for sacrificial anodes or impressed current anodes with reference electrodes) cathodic protection system drawings shall be in compliance with the specification and calculations for the

same.

Guidance note:The current density demand will vary dependent upon the speed of hull, the speed of propeller, and the type of metallicmaterial to be protected (aluminium, stainless steel, etc.).The target protective potential difference for aluminium alloy surfaces may be minus 950 mV versus the Ag/AgCl/seawater reference electrode, with an acceptable potential difference range of minus 800 mV to minus 1150 mV, i.e.approximately as for carbon steel and stainless steel. Due concern must be given to the possibility of detrimentaloverprotection of aluminium.Stainless steel surfaces in water jet units of high speed craft may need a current density of up to about 300 mA/m2 tobe protected, while values as high as 500 mA/m2 may give overprotection problems.


404 For documentation of instrumentation and automation, including computer based control andmonitoring, see Pt.4 Ch.9 Sec.1.405 The designed (target) service life of a cathodic protection system is normally to be at least as long as theexpected time interval between dockings.406 With impressed current cathodic protection systems, precautions are to be taken to avoid:

1) overprotection or excessive negative potential differences locally, especially on aluminium surfaces(implying transpassive corrosion) as well as

2) loss of protection,

by means of anode screens, automatic voltage control, overprotection alarm, or similar. The protective potentialdifference is to be kept within a specified and agreed range, see Guidance note to 403.407 Direct voltage stray currents may impose rapid electrolytic corrosion damage to hulls and is to beavoided.

Guidance note:Stray D.C. sources may be shore connections (e.g. ramps, cranes, cables, etc.), not properly grounded weldingmachines, etc. Special precautions should be taken if welding is carried out with the craft afloat, or if the craft isconnected to electrical power in port.

---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.3 Sec.2 Page 19C 500 Other materials in contact with aluminium501 If other metallic materials are used in propellers or impellers, piping, pumps, valves, etc. and are incontact with the aluminium hull, provisions are to be made to avoid galvanic corrosion. Acceptable provisionsare either one of or a combination of:

coating of water or moisture exposed surfaces electrical isolation of different materials from each other cathodic protection.

Guidance note:Full electrical isolation of e.g. propeller or impeller from hull is usually difficult. Contact will be established when thepropeller is idle.Wooden material, cloth, debris, non-adherent coating or other organic material remaining in durable contact withaluminium may cause under-deposit corrosion on aluminium due to local oxygen deficiency at the surface.


D. Other MaterialsD 100 Steel101 Structural steel may be used in sundry items such as rudders, foils, propeller shaft brackets, etc.102 For requirements for chemical composition, mechanical properties, heat treatment, testing and repair ofdefects, see Pt.2.103 The material factor f1 = 1 for ordinary ship quality steel.104 All steel surfaces are to be protected against corrosion by paint of suitable composition or other effectivecoating.105 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 Register of Approved Manufacturers and Register of Type Approved Products.106 Coating systems are to be suitable for use on any previously applied shop primer.The coating and the assumed application conditions must have been approved by the Society. Such approvalwill normally be given as a Type approval.The shipbuilders are to present a written declaration stating that the coating has been applied as specified.

Guidance note:Upon request approval programs for coating systems may be obtained from the Society.


D 200 Connections between steel and aluminium201 If there is risk of galvanic corrosion, provisions are to be made, see C500.202 Aluminium plating connected to a steel boundary bar is wherever 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 hot galvanized steel. The bolts are ingeneral to be fitted with sleeves of insulating material.

D 300 Fibre Reinforced Plastic (FRP)301 FRP materials, core materials and fillers are to be approved according to Sec. 3.302 Other reinforcement and plastic materials may be approved on the basis of relevant documentation andtesting in each individual case.DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.3 Page 20SECTION 3 MANUFACTURING

A. GeneralA 100 Basic requirements101 Welding of hull structures, machinery installations and equipment are to be carried out by approvedwelders, with approved welding consumables and at welding shops recognised by the Society. See Sec.2.102 Shot blasting, priming and coating are to be carried out under indoor conditions. For coatingspecification and documentation, see Sec.2.103 For all craft a non-destructive testing (NDT) plan is to be submitted for approval to the surveyor.

B. InspectionB 100 General101 Welds are to be subject to visual survey and inspection as fabrication proceed. NDT is to be performedaccording to established procedures and if required, qualified for the work.102 All examinations are to be carried out by competent personnel. The NDT operators are to be qualifiedaccording to a recognised certification scheme accepted by the Society. The certificate is clearly to state thequalifications as to which examination method and within which category the operator is qualified.

B 200 Penetrant testing201 Penetrant testing is to be carried out as specified in the approved procedures.

B 300 Radiographic testing301 Radiographic testing is to 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 are to be free from imperfections due to development processing.

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

C. Extent of ExaminationC 100 General101 All welds are to be subject to visual examination. In addition to the visual examination, at least 2 to 5%of total welded length are to be examined by penetrant examination and/or radiographic examination. Forhighly stressed areas the extent of examination may be increased.102 If defects are detected, the extent of examination is to be increased to the surveyors satisfaction.

D. Acceptance Criteria for NDTD 100 Acceptance criteria101 All welds are to show evidence of good workmanship. The quality is normally to comply with ISO 10042quality 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.3 Sec.3 Page 21E. 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 Unless otherwise agreed, all tanks are to be tested with a water head equal to the maximum pressure towhich the compartment may be exposed. The water is in no case to be less than to the top of the air pipe or toa level h0 above the top of the 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/m2. The nozzle should be held ata distance of maximum 1.5 m from the item during the test.Alternative methods of tightness testing may be considered.203 All weathertight or 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.3 Sec.4 Page 22SECTION 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.

A 200 Definitions201 Moulded deck line, Rounded sheer strake, Sheer strake and Stringer plate are as defined in Fig.1.

Fig. 1Deck corners

B. Vertical Bending StrengthB 100 Hull section modulus requirement101

M = the longitudinal midship bending moment in kNm from Ch.1 Sec. 3 = sagging or hogging bending moment = hollow landing or crest landing bending moment = maximum still water + wave bending moment for high speed displacement craft and semi-planing craft

in the displacement mode = maximum total moment for hydrofoil on foils = 175 f1 N/mm2 in general.

Guidance note:Simultaneous end impacts over a hollow are considered less frequent and giving lower moments than the crestlanding.Need not be investigated if deck buckling resistance force is comparable to that of the bottom.


B 200 Effective section modulus201 Where calculating the moment of inertia and section modulus of the midship section, the effectivesectional area of continuous longitudinal strength members is in general the net area after deduction of

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

openings.

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.4 Page 23Superstructures 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.2, i.e. inside tangents at an angle of 30 to each other. Example for transverse section III:

bIII = b' + b + b203 For twin hull vessels the effective breadth of wide decks without longitudinal bulkhead support will beconsidered separately.

B 300 Hydrofoil on foils301 For hydrofoils in addition to the calculation for the midship section, the sections in way of the foils arerequired to be checked.

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.

Fig. 2Effect of openings

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 wherever practicable. Any necessary openings in the bilge plate are to be kept clearof a bilge keel.502 Openings in strength deck are wherever practicable to be located well clear of the 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 craft's centreline as practicable.504 For corners with rounded shape the radius is not to be less than:

r = 0.025 Bdk (m)

B = breadth of strength deck.DET NORSKE VERITAS AS

dk

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.4 Page 24r need 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 Sec. 5 B.505 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 craft's side, the required sectional area of the remaining side plating will bespecially considered.102 If rows of windows are arranged below strength deck, sufficient horizontal shear area must be arrangedto carry down the midship tension and compression.103 In these and other locations with doubtful shear areas, allowable shear stress may be taken as:

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

FL= al (kN)al = maximum surge acceleration, not to be taken less than:

The distribution of stresses will depend on instantaneous forward immersion and on location of cargo.102 Bottom structure in way of thrust bearings may need a check for the increased thrust when vessel isretarded 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 whensubject to the collision load as given in the International Code of Safety for High-Speed Craft, paragraph 4.3.3(see Ch.7 Sec.1 B300).

Guidance note:Inertia forces from the collision deceleration should be considered for shear and buckling in the foreship area, and forthe forces 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 bending stress

3-----------------------------------------------------------=

0.4 g for VL

------- 5

0.2 g for VL

------- 3

linear interpolaton of al for 3V

l----- 5<

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.4 Page 25connecting structure, the effective sectional area of transverse strength members is in general to be taken as thenet area with effective flange after deduction of openings.The effective shear area of transverse strength members is in general to be taken as the net web area afterdeduction of openings.

E 200 Allowable stresses 201 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.3 Sec.5 Page 26SECTION 5 PLATING AND STIFFENERS

A. GeneralA 100 Introduction101 In this section the general requirements for plate thicknesses and local strength of panels of aluminiumalloy are given.102 Buckling strength requirements are related to longitudinal hull girder stresses. Panels subjected to othercompressive, shear or biaxial stresses will be specially considered.

A 200 Definitions201 Symbols:

t = rule thickness of plating in mmZ = rule section modulus of stiffener in cm3s = stiffener spacing in m, measured along the platingl = stiffener span in m, measured along the top flange of the member.

The depth of stiffener on crossing panel may be deducted when deciding the span.For curved stiffeners l may be taken as the chord length

p = design pressure in kN/m2 as given in Ch.1 Sec.2 = nominal allowable bending stress in N/mm2 due to lateral pressure (see Table A1)f1 = see Sec.l A202 = nominal allowable shear stress in N/mm2.

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

B. PlatingB 100 Minimum thicknesses101 The thickness of structures is in general not to be less than:

Table A1 Allowable bending stressesItem Plate Stiffener

(N/mm2)Bottom, slamming load 200 f1 180 f1Bottom, sea load 180 f1 160 f1Side 180 f1 160 f1Deck 180 f1 160 f1Flat cross structure, slamming load 200 f1 180 f1Flat cross structure, sea load 180 f1 160 f1Bulkhead, collision 180 f1 160 f1Superstructure/deckhouse front 160 f1 140 f1Superstructure/deckhouse side/deck 180 f1 160 f1Bulkhead, watertight 220 f1 200 f1Tank bulkhead 180 f1 160 f1

f =

f = yield stress in N/mm2 at 0.2% offset for unwelded alloy.

tt0 kL+

f----------------- s

sR----- (mm)=

f240---------DET NORSKE VERITAS AS

f is not to be taken greater than 70% of the ultimate tensile strength

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.5 Page 27t0 and k according to Table B1.

B 200 Bending201 The general requirement for thickness of plating subject to lateral pressure is given by:

C = correction factor for aspect ratio (= s/l) of plate field and degree of fixation of plate edges given in Table B2.

202 The thickness requirement for a plate field clamped along all edges and with an aspect ratio 0.5:

B 300 Slamming301 The bottom plating is to be strengthened according to the requirements given in 302 to 303.

302 The thickness of the bottom plating is not to be less than:

s = actual stiffener spacing (m)sR = basic stiffener spacing (m)

=

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

Table B1 Values of t0 and kItem t0 k

Shell platingBottom, bilge and side to loaded water line 4.0 0.03Side above loaded water line 3.5 0.02Bottom aft in way of rudder, shaft brackets etc. 10.0 0.10

Deck and inner bottom plating

Strength deck weather part forward of amidships 3.0 0.03Strength deck weather part aft of amidships 2.5 0.02Inner bottom 3.0 0.03Car deck 4.0 0.03Accommodation deck 2.0 0.02Deck for cargo 4.0 0.03Superstructure and deckhouse decks 1.0 0.01

Bulkhead plating

Collision bulkhead 3.0 0.03Tank bulkhead 3.0 0.03Other watertight bulkheads 3.0 0.02Superstructure and deckhouse front 3.0 0.01Superstructure and deckhouse sides and aft 2.5 0.01

Other structures Foundations 3.0 0.08Structures not mentioned above 3.0 0

ka = correction factor for aspect ratio of plate field= (1.1 0.25 s/l)2= maximum 1.0 for s/l = 0.4= minimum 0.72 for s/l = 1.0

kr = correction factor for curved plates

2 100 L+( )1000

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

ssR------

t s Cp

-------------- (mm)=

t 22.4s p

--------------------- (mm).=

t22.4krkas Psl

sl------------------------------------ (mm)=

DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.5 Page 28303 Above the slamming area the thickness may be gradually reduced to the ordinary requirement at side.For craft with rise of floor, however, reduction will not be accepted below the bilge curvature or chine.

C. StiffenersC 100 Bending101 The section modulus of longitudinals, beams, frames and other stiffeners subjected to lateral pressure isnot to be less than:

m = bending moment factor depending on degree of end constraints and type of loading, see also Sec. 6Table B2.

The m-values are normally to be as given in Table C 1.The m-values may have to be increased after special consideration of rotation/deflection at supports or variationin lateral pressure.The m-values may be reduced, provided acceptable stress levels are demonstrated by direct calculations.102 The requirement in 101 is to be regarded as a requirement about an axis parallel to the plating. As anapproximation, the requirement for standard section modulus for stiffeners at an oblique angle with the platingmay be obtained if the formula in 101 is multiplied by the factor:

= angle between the stiffener web plane and the plane perpendicular to the plating.

For -values less than 12 corrections are normally not necessary.103 When several members are equal, the section modulus requirement may be taken as the averagerequirement for each individual member in the group. However, the requirement for the group is not to be takenless than 90% of the largest individual requirement.104 Front stiffeners of superstructures and deckhouses are to be connected to deck at both ends with aconnection area not less than:

=

r = radius of curvature in mPsl = as given in Ch.1 Sec.2sl = 200 f1 (N/mm2).

Table B2 Values of CDegree of fixation of plate edges Aspect ratio < 0.5 Aspect ratio = 1.0

l s x y l s x yClamped along all edges 500 342 75 250 310 310 130 130Longest edge clamped, shortest edge simply supported

500 0 75 250 425 0 140 200

l = stress at midpoint of longest edge.s = stress at midpoint of shortest edge.x = maximum field stress parallel to longest edge.y = maximum field stress parallel to shortest edge.

1 0.5sr--

Z m l2sp

---------------- cm3( )=

1cos

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

a 0.07f1-----------lsp= cm2( )DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.5 Page 29Side and after end stiffeners in the lowest tier of erections are to have end connections.

C 200 Slamming201 The section modulus of longitudinals or transverse stiffeners supporting the bottom plating is not to beless than:

m = 85 for continuous longitudinals = 100 for transverse stiffenerspsl = slamming pressure as given in Ch.1 Sec. 2sl = 180 f1 (N/mm2).

The shear area is not to be less than:

sl = 90 f1 (N/mm2).

Table C1 Values of mItem mContinuous longitudinal members 85Non-continuous longitudinal members 100Transverse members 100Vertical members, ends fixed 100Vertical members, simply supported 135Bottom longitudinal members 85Bottom transverse members 100Side longitudinal members 85Side vertical members 100Deck longitudinal members 85Deck transverse members 100Watertight bulkhead stiffeners, fixed ends 65Watertight bulkhead stiffeners, fixed one end (lower) 85Watertight bulkhead stiffeners, simply supported ends 125Watertight bulkhead horizontal stiffeners, fixed ends 85Watertight bulkhead stiffeners, fixed one end (upper) 75Watertight bulkhead horizontal stiffeners, simply supported 125Tank cargo bulkhead, fixed ends 100Tank cargo bulkhead, simply supported 135Deckhouse stiffeners 100Casing stiffeners 100

Zm l2s psl

sl---------------------- cm3( )=

AS6.7 l s( )s psl

sl----------------------------------- cm2( )=DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.6 Page 30SECTION 6 WEB FRAMES AND GIRDER SYSTEMS

A. GeneralA 100 Introduction101 In this section the general requirements for simple girders and procedures for the calculations of complexgirder systems are given.

A 200 Definitions201 Symbols:

s = girder span in m. The web height of in-plane girders may be deductedb = breadth of load area in m (plate flange) b may be determined from Table A1p = design pressure in kN/m2 according to Ch. 1 Sec.2P = design axial force in kN = nominal allowable bending stress in N/mm2 due to lateral pressure = nominal allowable shear stress in N/mm2c = critical buckling stress in N/mm2el = ideal elastic buckling stress in N/mm2Z = rule section modulus in cm3AW = rule web area in cm2A = rule cross-sectional area in cm2tw = web thickness in mmhw = web height in mmbf = flange breadth in mm.

A 300 Minimum thicknesses301 The thickness of structures are in general not to be less than:

t0 and k according to Table A2.

f =

f = yield stress in N/mm2 at 0.2% offset for unwelded alloy. f is not to be taken greater than 70% of the ultimate tensile strength. For unwelded material, f may be taken as f1 in Sec.2 Tables B1 to B3.

s = actual stiffener spacing in msR = basic stiffener spacing in m

=

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

Table A1 Breadth of load areaFor ordinary girders b = 0.5 (l1 + l2 (m)

l1 and l2 are the spans in m of the supported stiffenersFor hatch side coamings b = 0.2 (B1 - b2) (m)

B1 = breadth of craft in m measured at the middle of the hatchwayb2 = breadth of hatch in m measured at the middle of the hatchway

For hatch end beams b = 0.4 b3 (m)b3 = distance in m between hatch end beam and nearest deep transverse girder or transverse bulkhead

tt0 kL+

f----------------- s

sR----- mm( )=

f240---------

2 100 L+( )1000

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

ssR------DET NORSKE VERITAS AS

Rules for High Speed, Light Craft and Naval Surface Craft, July 2012 Pt.3 Ch.3 Sec.6 Page 31A 400 Allowable stresses401 Maximum allowable bending stresses and shear stresses in web frames and girders are to be accordingto Table A3.

For watertight bulkheads (excluding the collision bulkhead), allowable stresses may be increased to 200 f1, 100f1 and 220 f1 for bending, shear and equivalent stresses, respectively.

A 500 Continuity of strengt

hs303

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