rules for the classification of trimarans vi

Rules for theClassification of Trimarans

Volume 1Part 6January 2006

Volume ContentsRULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006

LLOYDS REGISTER 1

VOLUME 1

PART 1 CLASSIFICATION OF TRIMARANS

PART 2 RULES FOR THE MANUFACTURE, TESTING AND CERTIFICATION OF MATERIALS (see Notes)

PART 3 GENERAL REQUIREMENTS AND CONSTRUCTIONAL ARRANGEMENTS (see Notes)

PART 4 ADDITIONAL REQUIREMENTS FOR YACHTS (see Notes)

PART 5 ENVIRONMENTAL LOADS

PART 6 SCANTLING DETERMINATION

Chapter 1 Introduction

Chapter 2 Design Tools

Chapter 3 Global Strength Requirements

Chapter 4 Local Scantling Requirements

VOLUME 2 MACHINERY (see Notes)

VOLUME 3 ADDITIONAL OPTIONAL REQUIREMENTS/OTHER SHIP TYPES AND SYSTEMS (see Notes)

VOLUME 4

PART 1 DIRECT CALCULATION PROCEDURE

Lloyd's Register, 2006. All rights reserved.

Except as permitted under current legislation no part of this work may be photocopied, stored in a retrieval system, published, performed in public,adapted, broadcast, transmitted, recorded or reproduced in any form or by any means, without the prior permission of the copyright owner. Enquiriesshould be addressed to Lloyd's Register, 71 Fenchurch Street, London, EC3M 4BS.

NOTES

The Rules for the Classification of Trimarans are not a complete set of Rules in their own right. Theyare designed to apply in conjunction with the Lloyds Register Rules outlined below (as appropriateto the vessel type):

Rules and Regulations for the Classification of Naval Ships Rules and Regulations for the Classification of Ships Rules and Regulations for the Classification of Special Service Craft

The Trimaran Rules are comprised of the bolded sections highlighted in this Contents Sheet, theremaining sections are NOT included in this set of Rules. General information on the make up ofthe Trimaran Rules can be found in Vol 1, Pt 1, Ch 1.

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ContentsRULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006

Volume 1, Part 6

LLOYDS REGISTER 3

CHAPTER 1 INTRODUCTION

Section 1 Application1.1 General1.2 Equivalents1.3 Symbols and definitions

Section 2 General requirements2.1 General2.2 Plans to be submitted2.3 Enhanced scantlings

CHAPTER 2 DESIGN TOOLS

Section 1 General1.1 General1.2 Rounding policy for Rule plating thickness1.3 Material properties1.4 Higher tensile steel

Section 2 Structural design2.1 General2.2 Effective width of attached plating2.3 Section properties2.4 Convex curvature correction2.5 Aspect ratio correction2.6 Determination of span length2.7 Proportions of stiffener sections2.8 Grillage structures2.9 Detail design

Section 3 Buckling3.1 General3.2 Buckling requirements

Section 4 Fatigue4.1 General

CHAPTER 3 GLOBAL STRENGTH REQUIREMENTS

Section 1 General1.1 Introduction1.2 Application

Section 2 Hull girder strength2.1 Application2.2 Section modulus calculation2.3 Higher tensile steel2.4 Longitudinal bending strength2.5 Minimum hull section modulus2.6 Minimum hull moment of inertia2.7 Shear strength

Section 3 Cross-deck strength3.1 Application3.2 Cross-deck component stresses3.3 Combined stress criteria


ContentsRULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006

Volume 1, Part 6

LLOYDS REGISTER4

CHAPTER 4 LOCAL SCANTLING REQUIREMENTS

Section 1 General1.1 Introduction1.2 Corrosion margin

Section 2 Minimum structural requirements2.1 General2.2 Plate thickness2.3 Stiffener properties

Section 3 Shell envelope3.1 General3.2 Requirements due to design pressures3.3 Additional minimum requirements3.4 Single bottom3.5 Double bottom3.6 Strengthening due to bottom slamming3.7 Slamming above the waterline

Section 4 Wet-deck4.1 General4.2 Requirements due to design pressures4.3 Additional minimum requirements4.4 Slamming above the waterline

Section 5 Weather deck5.1 General5.2 Requirements due to design pressures5.3 Additional minimum requirements

Section 6 Inner bottom6.1 General6.2 Scantlings6.3 Additional minimum requirements

Section 7 Internal decks7.1 General7.2 Minimum requirements

Section 8 Bulkheads and deep tanks8.1 General8.2 Minimum requirements

Section 9 Deckhouses, bulwarks and superstructures9.1 General9.2 Minimum requirements

Section 10 Other structure10.1 General10.2 Pillars and pillar bulkheads10.3 Machinery and raft seating

Section 11 Ice strengthening11.1 General


kg = higher tensile steel factor for global loads, seeCh 2,1.4

l = overall length of stiffener or primary member, inmetres

lch = chord length between stiffeners in mm, seeCh 2,2.4

le = effective span length, in metresnbhd = number of transverse bulkheads in the longitudinal

cross-deck sections = secondary stiffener spacing, in mm

tbhd = cross-deck structure transverse bulkhead platingthickness, in mm

tdk = deck plating thickness in way of cross-deck structure, in mm

tp = plating thickness, in mmx = longitudinal distance, in metres, measured forwards

from the aft end of LR to the position or centre ofgravity of the item being considered

z = vertical distance, in metres, from the hull transverseneutral axis to a position under consideration

zi = section modulus of cross-deck beam, in cm3, seeCh 3,3.2

zm = vertical distance, in metres, from the hull transverseneutral axis to the minimum limit of higher tensilesteel, above or below the neutral axis as appropriate

zB = the vertical distance, in metres, from the transverseneutral axis of the total hull cross-section to the topof the keel

zD = the vertical distance, in metres, from the transverseneutral axis of the total hull cross-section to theuppermost continuous longitudinally effective material

Acd = total vertical shear area of a longitudinal crosssection of the cross-deck structure, extending onlythe length of the side hull, in cm2. Initially onlytransverse bulkheads with breadth including themain hull, side hulls and cross-deck structure willbe considered effective in shear

Awi = shear area of cross deck beam web, in cm2, seeCh 3,3.2

AR = panel aspect ratio= panel length/panel breadth

AT = effective shear area of transverse section, in m2, tobe taken as the net effective sectional area of theside shell plating and the longitudinal bulkheadsafter deductions for openings

E = modulus of elasticity, in N/mm2FB = local scantling reduction factor for hull members

below the neutral axis, see Ch 3,2.3.2FD = local scantling reduction factor for hull members

above the neutral axis, see Ch 3,2.3.2I = moment of inertia, in cm4Ii = moment of inertia of cross deck beam, in cm4, see

Ch 3,3.2Icd = total inertia of a longitudinal cross section of the

cross-deck structure, extending only the length ofthe side hull, in cm4

Mtot = total Rule bending moment, in kNm, given in Pt 5,Ch 4,2.8

MwHog = hogging value of Mw, in kNm, given in Pt 5, Ch 4,2.4

MwSag = sagging value of Mw, in kNm, given in Pt 5, Ch 4,2.4

Section

1 Application

2 General requirements

Section 1Application

1.1 General

1.1.1 This Part of the Rules provides global strengthrequirements and local scantling requirements according tothe loads calculated in Part 5.

1.1.2 In addition to the requirements of this Part mandatory structural strength analysis and verification is to becarried out for all Trimarans, see Vol 4, Pt 1, Ch 2.

1.2 Equivalents

1.2.1 Alternative scantlings and arrangements may beaccepted as equivalent to the Rule requirements. Details ofsuch proposals are to be submitted for consideration.

1.3 Symbols and definitions

1.3.1 The symbols and definitions for use throughout thisPart are as follows:

b = actual breadth of plating, in mm, of the load bearingplating which is defined as one-half the sum of thespacings between parallel adjacent members orequivalent supports

be = effective breadth of attached plating, see Ch 2,2.2cI = inertia coefficient dependent on the loading model

assumption, see Fig 4.2.1cA = web area coefficient dependent on the loading

model assumption, see Fig. 4.2.1cZ = section modulus coefficient dependent on the

loading model assumption, see Fig. 4.2.1dcd = depth of cross-deck structure, in metres, see

Ch 3,3.2dch = the distance, in mm, measured perpendicularly

from the chord length, lch, (i.e. spacing in mm) tothe highest point of the curved plating arc betweenthe two supports, see Ch 2,2.4

far = panel aspect ratio correction factor as defined inCh 2,2.5

fcurv = convex curvature correction factor as defined in Ch 2,2.4.1

fhts = high tensile steel factor, defined in Ch 2,1.4f = limiting stress coefficient for local plate bending for

the plating area under consideration given in Table 4.2.2 in Chapter 4

fhg = limiting hull bending stress coefficient, see Ch 3,2.4fws = limiting working stress coefficient, see Ch 3,2.5

kl = higher tensile steel factor for local loads, seeCh 2,1.4

Introduction RULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006

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Introduction

Pdes = design pressure, in kN/m2, for structural item underconsideration, as calculated according to Pt 5, Ch 5

S = primary stiffener spacing, in metresSbhd = spacing of transverse bulkheads in the cross-deck

structure, in metresZcdb = section modulus at the bottom, or wet deck, of a

longitudinal section of the cross-deck structure,extending only the length of the side hull, in cm3

Zcdt = section modulus at the top, typically the main deck,of a longitudinal section of the cross-deck structure, extending only the length of the side hull,in cm3

Zcurv = section modulus, in cm3, of transverse main andtween deck frames, corrected for convex curvature

Zi = actual section modulus at structural element beingconsidered, in cm3

Zi = section modulus of general stiffening member, incm3

B = maximum hull vertical bending stress at keel inN/mm2, see Table 3.2.1 in Chapter 3

D = maximum hull vertical bending stress at strengthdeck in N/mm2, see Table 3.2.1 in Chapter 3

p = permissible combined stress in N/mm2, seeCh 3,2.4.3

sph = direct stress on transverse primary member due tohog splitting load, in N/mm2

sps = direct stress on transverse primary member due tosag splitting load, in N/mm2

tt = direct stress on transverse primary member due totransverse torsional moment, in N/mm2

yd = guaranteed minimum yield strength of the materialin N/mm2

ydMild = minimum yield strength of mild steel in N/mm2u = ultimate tensile strength of the material in N/mm2

ws = hull girder bending stress range in N/mm2, seeCh 3,2.4

sp = shear stress induced by the splitting shear force, inN/mm2

tt = shear stress induced by the transverse torsionalmoment, in N/mm2

yd = shear strength of the material in N/mm2

=

Section 2General requirements

2.1 General

2.1.1 Limitations with regard to the application of thisPart are indicated in the individual Chapters.

yd

3

2.2 Plans to be submitted

2.2.1 Plans are to be of sufficient detail for plan approvalpurposes. For all areas of structure listed below the submitted plans are to show all plating thickness, stiffenerssizes and spacings, bracket arrangements and connections.Where appropriate, the plans should clearly show theallowance for corrosion margin or Owner's extra. Welding,constructional arrangements and tolerances are also to besubmitted and this may be in the form of a booklet.

2.2.2 In general all items of steel structure are to beshown except where they are ineffective in supporting hullgirder and local loads and do not impinge on such structure.

2.2.3 Equipment seating and supports are to be shownwhere they require additional stiffening and support to beincorporated in items of hull structure. In such cases the loading on the seating is also to be supplied. Generally totalcombined equipment weights on seating less than 0,5 tonnesneed not be considered.

2.2.4 Normally the plans for each item will be able to becontained on a few sheets. Unit or production drawings willnot be accepted.

2.2.5 Plans and calculations are to be submitted asrequired in the Complementary Rules and are to include allappropriate structure in the side hulls, centre hull and crossdeck structure.

2.2.6 The details of the cross deck structure connec-tions, forward and aft, to the main and centre hulls must eitherbe included within the required plans or be provided as aseparate plan.

2.2.7 Plans are to be supplied to the ship as required inthe Complementary Rules.

2.3 Enhanced scantlings

2.3.1 An enhanced scantling notation may be applied asdescribed in the Complementary Rules.

RULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006

Volume 1, Part 6, Chapter 1Sections 1 & 2

LLOYDS REGISTER2


fhts is as follows:

1.4.3 Normally, this allowance is included in the appropri-ate scantling requirements. Where this is not the case, thefollowing correction factors may be applied:

(a) Plating thickness factor = kl for local loads

= kg for global loads

(b) Section modulus and cross sectional area factor = kl.

1.4.4 The designer should note that there is no increasein fatigue performance with the use of higher tensile steels.

1.4.5 Local scantlings which are to be calculated according to the Complementary Rules are to use the hightensile steel factor as defined in the Complementary Rules.This local factor, having the same values as in the TrimaranRules, is named as follows in the Complementary Rules:

kl = ks Rules and Regulations for the Classification ofNaval Ships (hereinafter referred to as the Rules forNaval Ships)

= ks Rules and Regulations for the Classification ofSpecial Service Craft (hereinafter referred to as theRules for Special Service Craft)

= k Rules and Regulations for the Classification ofShips (hereinafter referred to as the Rules forShips).

Section 2Structural design

2.1 General

2.1.1 This Section gives the basic principles to beadopted in determining the Rule structural requirements givenin Chapter 3 and Chapter 4.

2.1.2 For derivation of scantlings of stiffeners, beams,girders, etc., the formulae in the Rules are normally based onelastic or plastic theory using simple beam models supportedat one or more points and with varying degrees of fixity at theends, associated with an appropriate concentrateddistributed load.

2.1.3 The stiffener, beam or girder strength is defined bya section modulus and moments of inertia requirements. Inaddition there are local requirements for web thickness andflange thickness.

Section

1 General

2 Structural design

3 Buckling

4 Fatigue

Section 1General

1.1 General

1.1.1 The guidance notes, information and formulaecontained within this Chapter are to be used when calculatingthe global strength requirements (Chapter 3) and the requiredscantlings due to local loads (Chapter 4).

1.2 Rounding policy for Rule plating thickness

1.2.1 Where plating thicknesses as determined by theRules require to be rounded then this is to be carried out tothe nearest full or half millimetre, with thicknesses 0,75 and0,25 being rounded up.

1.3 Material properties

1.3.1 The basic grade of steel used in the determinationof the Rule scantling requirements is taken as mild steel withthe following mechanical properties:(a) Yield strength (minimum), yd = 235 N/mm2(b) Tensile strength, u = 400 490 N/mm2(c) Modulus of elasticity, E = 200 x 103 N/mm2.

1.4 Higher tensile steel

1.4.1 Steels having a yield stress not less than 265 N/mm2 are to be regarded as higher tensile steels.

1.4.2 Where higher tensile steels are to be used, dueallowance is given in the determination of the Rule require-ment for plating thickness, stiffener section modulus, inertiaand cross-sectional area by the use of higher tensile steelcorrection factors kl and kg or fhtswhere

kl =

kg =235

yd fhts

235yd

Design Tools RULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006


LLOYDS REGISTER 1

yd

235

265

315

355

>390

fhts

1,00

0,964

0,956

0,919

0,886390yd


2.5 Aspect ratio correction

2.5.1 The thickness of plating as determined by the Rulesmay be reduced when the panel aspect ratio is taken intoconsideration. In such cases a panel aspect ratio correctionfactor may be applied:

fAR = AR (1 0,25AR) for AR 2= 1 for AR > 2

wherefAR and AR are defined in Ch 1,1.3.

2.6 Determination of span length

2.6.1 The effective length, le, of a stiffening member isgenerally less than the overall length, l, by an amount whichdepends on the design of the end connections. The spanpoints, between which the value of le is measured are to bedetermined as follows:(a) For rolled or built secondary stiffening members:

The span point is to be taken at the point where thedepth of the end bracket, measured from the face of themember, is equal to the depth of the member. Wherethere is no end bracket, the span point is to bemeasured between primary member webs. For doublebottom construction the span may be reduced by thedepth of primary member web stiffener, see Fig. 2.2.2.

(b) For primary support members:The span point is to be taken at a point distant from theend of the member,where

be = bb 1 , see Fig. 2.2.2.dwdb

Design Tools

2.2 Effective width of attached plating

2.2.1 For stiffening members, the geometric properties ofrolled or built sections are to be calculated in association withan effective area of attached load bearing plating of thickness,tp, in mm and an effective breadth, tp in mm.

2.2.2 The effective breadth of attached plating tosecondary stiffener members be, in mm, is to be taken as thelesser of:(a) The actual spacing of the stiffeners, b, and(b) The greater of 40tp and 600 mm(c) The effective breadth of attached plating to primary

support members (girders, transverses, webs, etc.) is tobe taken as follows:

be = 300S2/3

mm( )but is not to exceed SS and l are defined in Ch 1,1.3.

2.3 Section properties

2.3.1 The effective geometric properties of rolled or builtsections are to be calculated directly from the dimensions ofthe section and associated effective area of attached plating.Where the web of the section is not normal to the actual plating, and the angle exceeds 20, the properties of thesection are to be determined about an axis parallel to theattached plating.

2.3.2 If applicable, idealised section properties may becalculated as described in the Complementary Rules.

2.4 Convex curvature correction

2.4.1 The thickness of plating as determined by the Rulesmay be reduced where significant curvature exists betweenthe supporting members. In such cases a plate curvaturecorrection factor may be applied:

fcurv = 1 , see Fig. 2.2.1

wherefcurv, dch and lch are defined in Ch 1,1.3.

2.4.2 The required section modulus of transverse mainand tween deck frames, which have reasonably constantconvex curvature over their entire length, may be corrected forcurvature as follows:

Zcurv = Z cm3

whereZcurv, Z, dch and lch are defined in Ch 1,1.3.

1

cosh2 dch

lch

dchlch

lS



LLOYDS REGISTER2

dch

lch

Fig. 2.2.1 Convex curvature


Design Tools

2.7 Proportions of stiffener sections

2.7.1 Requirements for the proportions of stiffenersections are to be calculated according to the followingsections of the Complementary Rules:

Vol 1, Pt 6, Ch 2,2.9 of the Rules for Naval ShipsPt 6, Ch 3,1.18 of the Rules for Special Service CraftPt 3, Ch 10,4.5 of the Rules for Ships.

2.8 Grillage structures

2.8.1 For complex girder systems, a complete structuralanalysis using numerical methods may have to be performedto demonstrate that the stress levels are acceptable whensubjected to the most severe and realistic combination ofloading conditions intended.

2.8.2 General or special purpose computer programs orother analytical techniques may be used provided that theeffects of bending, shear, axial load and torsion are properlyaccounted for and the theory and idealisation used can bejustified.



LLOYDS REGISTER 3

Span points

ds

ds

Span point

Span point

ds

ds

Span point

db

be

bb

dw

l

Span point

Span point

db

be

bb dw

l

Fig. 2.2.2 Definition of span points


Design Tools

2.8.3 In general, grillages consisting of slender girdersmay be idealised as frames based on beam theory providedproper account of the variations of geometric properties istaken. For cases where such an assumption in not applicable, finite element analysis or equivalent methods mayhave to be used.

2.9 Detail design

2.9.1 Items such as details of end connections andscantlings of end brackets are to be in compliance with theComplementary Rules.

Section 3Buckling

3.1 General

3.1.1 In general, all areas of the structure are to meet thebuckling requirements for the design stresses calculatedaccording to Pt 5, Ch 3.

3.2 Buckling requirements

3.2.1 Requirements for buckling are to be calculatedaccording to the following sections of the ComplementaryRules:

Vol 1, Pt 6, Ch 2,4 of the Rules for Naval ShipsVol 1, Pt 6, Ch 5,3 of the Rules for Naval ShipsPt 6, Ch 7,4 of the Rules for Special Service CraftPt 3, Ch 7,7 of the Rules for ShipsAdditional requirements for specific ship types are alsoto be complied with.

Section 4Fatigue

4.1 General

4.1.1 For guidance on evaluation of structural models forfatigue aspects, see the Fatigue Design Assessment (FDA) Structural Detail Design Guide.


Volume 1, Part 6, Chapter 2Sections 2, 3 & 4

LLOYDS REGISTER4


2.2.3 In general, sections are to be evaluated along thelength of the ship to adequately represent structural transitions. If portions of the side hull and decks outside thebreadth of the main hull are considered longitudinally effectiveaccording to 2.2.2, additional sections are to be calculated atamidships of the side hull, at side hull terminations, and at anyother appropriate sections to capture the transitions of theside hulls.

2.2.4 In addition to meeting the requirement of 2.2.2, inorder for the full breadth of the deck structure to be effectivein longitudinal bending, the taper ratio, as depicted in Fig. 3.2.1, is to be 3:1 or greater.

2.2.5 Deck and side hull plating located forward of theposition on the side hull corresponding to the 3:1 taper ratiois to be considered ineffective, see Fig. 3.2.2.

Section

1 General

2 Hull girder strength

3 Cross-deck strength

Section 1General

1.1 Introduction

1.1.1 This Chapter contains information regarding thederivation of global strength requirements that are to be usedin conjunction with the global design loads calculated according to Pt 5, Ch 4.

1.2 Application

1.2.1 The requirements for longitudinal and transverseglobal strength are contained within this Chapter.

1.2.2 The requirements of this Chapter are to be applied inlieu of the corresponding requirements of the ComplementaryRules.

Section 2Hull girder strength

2.1 Application

2.1.1 The requirements for longitudinal strength oftrimarans are contained within this Section.

2.1.2 Longitudinal strength calculations are to be carriedout for all vessels, covering the range of load and ballastconditions proposed, in order to determine the required hullgirder strength. Still water, static wave and dynamic bendingmoments and shear forces are to be calculated for bothdeparture and arrival conditions.

2.2 Section modulus calculation

2.2.1 In general, the effective sectional area of continuous longitudinal strength members, after deduction ofopenings, is to be used for the calculation of the midshipsection modulus.

2.2.2 Initially, the side hulls and deck structure extendingoutside the breadth of the main hull may only be consideredeffective if the cross-deck length is greater than 0,4L.Additional structure may be incorporated into the sectionmodulus calculations if proven effective by a global finiteelement analysis. This analysis must be submitted to andapproved by LR.

Global Strength RequirementsRULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006


LLOYDS REGISTER 1

3

1

Fig. 3.2.1Taper ratio of cross-deck connecting main hull

to side hull

3

1

= ineffective plating

1,5

Fig. 3.2.2Ineffective plating for lower taper ratios

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2.2.15 Where calculating deduction-free openings, theopenings are assumed to have longitudinal extensions asshown by the shaded areas in Fig. 3.2.3. The shadow area isobtained by drawing two tangent lines to an opening angle of30. The section to be considered is to be perpendicular tothe centreline of the ship and is to result in the maximumdeduction in each transverse space.

2.2.16 Isolated openings in longitudinals or longitudinalgirders need not be deducted if their depth does not exceed25 per cent of the web depth or 75 mm, whichever is thelesser.

2.2.17 Openings are considered isolated if they arespaced more than 1 m apart.

2.2.18 A reduction for drainage holes and scallops inbeams and girder, etc., is not necessary so long as the globalsection modulus at deck or keel is reduced by no more than0,5 per cent.

Global Strength Requirements

2.2.6 Structural members which contribute to the overallhull girder strength are to be carefully aligned so as to avoiddiscontinuities resulting in abrupt variations of stresses andare to be kept clear of any form of opening which may affecttheir structural performance.

2.2.7 In general, short superstructures or deckhouses willnot be accepted as contributing to the global longitudinal ortransverse strength of the ship. However, where it is proposedto include substantial, continuous stiffening members, specialconsideration will be given to their inclusion on submission ofthe designer's/builder's calculations.

2.2.8 Where continuous deck longitudinal or deck girdersare arranged above the strength deck, special considerationmay be given to the inclusion of their sectional area in thecalculation of the hull section modulus.

2.2.9 Adequate transition arrangements are to be fitted atthe ends of effective continuous longitudinal strengthmembers in the deck and bottom structures.

2.2.10 Structural material which is longitudinally continuous but which is not considered to be fully effective forlongitudinal strength purposes will need to be speciallyconsidered. The global longitudinal strength assessment musttake into account the presence of such material when it canbe considered effective. The consequences of failure of suchstructural material and subsequent redistribution of stressesinto or additional loads imposed on the remaining structuremust be considered.

2.2.11 In particular, all longitudinally continuous materialwill be fully effective in tension whereas this may not be so incompression due to a low buckling capability. In this case, itmay be necessary to derive and apply different hull girdersection moduli to the hogging and sagging bending momentcases.

2.2.12 Openings in decks, longitudinal bulkheads andother longitudinal effective material having a length in the foreand aft directions exceeding 0,1B m or 2,5 m or a breadthexceeding 1,2 m or 0,04B m whichever is the lesser, are in allcases to be deducted from the sectional areas used in thesection modulus calculation. B is as defined in Pt 1, Ch 1,5.2.

2.2.13 Openings smaller than stated in 2.2.9, includingmanholes, need not be deducted provided they are isolatedand the sum of their breadths or shadow area breadths, see2.2.14, in one transverse section does reduce the sectionmodulus at deck or bottom by more than 3 per cent.

2.2.14 The expression 0,06 (B1 b1), where B1 equals thebreadth of the ship at the section considered and equals thesum of the breadths of deductible openings, may be used fordeck openings in lieu of the 3 per cent limitation of reductionof section modulus in 2.2.13.



LLOYDS REGISTER2

b3

b2

b1

X

X

Tran

sver

se

Tran

sver

se

Total equivalent breadth of small openingsbo = b1 + b2 + b3 at position xx

30

Fig. 3.2.3 Isolated openings



2.3 Higher tensile steel

2.3.1 Higher tensile steel may be used for both deck andbottom structures or deck structure only. Where fitted forglobal strength purposes, it is to be used for the whole of thelongitudinally continuous material for the following verticaldistances:(a) zhtd below the line of deck at side

zhtd = 1 zD

(b) zhtb above the top of keel

zhtb = 1 zB

whereFD and FB are not to be taken as less than kg and are definedin 2.3.2zD , zB and kg and are defined in Ch 1,1.3.

2.3.2 Where the maximum hull vertical bending stress atthe deck or keel is less than the permissible combined stress,p, reductions in local scantlings within to 0,3LR to 0,7LRmay be permitted. The reduction factors are defined asfollows:

(a) For hull members above the neutral axis FD =

(b) For hull member below the neutral axis FB =

whereD, B and ws are defined in Ch 1,1.3.1.

2.3.3 In general, the values of D and B to be used arethe greater of the sagging or hogging stresses. FD and FB arenot to be taken as less than 0,67 for plating and 0,75 forlongitudinal stiffeners.

2.3.4 Where higher tensile steel is used in the hull structure, the values of FD and FB for the mild steel part are tobe taken as not less than z/zmwhere

z and zm are defined in Ch 1,1.3.1.

2.4 Longitudinal bending strength

2.4.1 The effective geometric properties of all criticalsections along the length of the ship are to be calculateddirectly from the dimensions of the section using only effectivematerial elements which contribute to the global longitudinalstrength irrespective of the grades of steel incorporated in theconstruction, see 2.2.

2.4.2 Where higher tensile steel is fitted to satisfy globalstrength requirements, the extent of higher tensile steel is tobe as specified in 2.3. Where a mix of steel grades is used forplating and associated stiffeners, then the lower of the steelgrades is to be used for the derivation of permissible stresses.

Bp

Dp

kgFB

kgFD

2.4.3 The longitudinal strength of the ship is to satisfy thefollowing criteria for the hogging and sagging conditions:

B < pD < pws < fws ydMild

wherep = fhg fhts yd

fhg = 0,75 from 0,3L to 0,7L

= 0,319 + 2,311 2,974 2

for continuous( )structural members aft of 0,3L and forward of 0,7L

fws = limiting working stress coefficient= 1,2

Note that the ws criteria may be relaxed if it can be demon-strated that either: A continuous fatigue monitoring system is to be adopted

for the in-service life of the ship, or A fatigue design assessment procedure is applied which

demonstrates that a higher limiting working stress coefficient, fws, may be applied.

B, D and p are given in Table 3.2.1fhts, fhg, fws, MwHog, MwSag, Mtot, yd, ydMild and x aredefined in Ch 1,1.3.

L is defined in Pt 1, Ch 1,5.2.

2.4.4 The design stress due to hull girder bending, hg,for each structural member is given by:

hg = N/mm2

whereMtot is defined in Pt 5, Ch 1,1.4

Zi is defined in Ch 1,1.3.

Mtot1000Zi

xL

xL



LLOYDS REGISTER 3

Table 3.2.1 Longitudinal component stresses

Component stress type Nominal stress, N/mm2

Hull girder bending stress at strength deck, see Note 1 D =

Hull girder bending stress at keel, see Note 1 B =

Hull girder bending stress range, see Note 2 ws =

NOTES1. The hogging and bending moments are to be considered.2. The stress range at the keel or other longitudinally effective

material should be used if it is greater than the stress range atthe strength deck.

MwHog MwSag1000ZD

Mtot1000ZB

Mtot1000ZD



2.4.5 Where different grades of steel are used then itshould be ensured that the design stress in each structuralmember is less than the permissible hull vertical bendingstress, i.e.

hg < p N/mm2

wherehg and p are defined in Ch 1,1.3.

2.5 Minimum hull section modulus

2.5.1 The hull midship section modulus about the transverse neutral axis, at the deck or the keel, is to be notless than:

Zmin = 0,95kg Mo x 105 m3

wherekg is defined in Ch 1,1.3

Mo is defined in Pt 5, Ch 4,2.4.1.

2.6 Minimum hull moment of inertia

2.6.1 The hull midship section moment of inertia aboutthe transverse neutral axis is to be not less than the followingusing the maximum total bending moment, sagging orhogging:

Imin = x 105 m4

whereMtot is defined in Pt 5, Ch 3,2.9.1

L is defined in Pt 1, Ch 1,5.2.

2.7 Shear strength

2.7.1 The shear strength of the vessel at any positionalong its length is to satisfy the following criteria:

103 p

whereQtot is defined in Pt 5, Ch 1,1.4

A is defined in Ch 1,1.3p = 0,72ydyd is defined in Ch 1,1.3.

Section 3Cross-deck strength

3.1 Application

3.1.1 The requirements for transverse strength oftrimarans are contained within this Section.

QtotA

3,0L Mtot175

3.1.2 Transverse strength calculations are to be carriedout for all vessels. If the vessel's transverse deadweight distribution varies significantly over the range of load andballast conditions proposed, then transverse hog and sag stillwater conditions must be specified to be applied in conjunction with the hogging and sagging wave splittingmoments. If the transverse deadweight distribution remainsfairly constant, one transverse still water distribution may beused.

3.2 Cross-deck component stresses

3.2.1 The primary stiffening members of the cross-deckstructure are to provide sufficient strength to satisfy the stresscriteria in Table 3.3.1.

3.2.2 When calculating the stresses due to the transversetorsional moment Mtt the following is assumed:(a) The cross-deck structure is a series of 'beams' formed

by transverse bulkheads and decks.(b) Transverse bulkheads are equally spaced.(c) The beams are treated as built-in at each hull, i.e. the

hulls have much greater stiffness than the cross-deck.(d) The cross-deck is symmetrical forward and aft of a

transverse axis at its mid-length.(e) The hulls move vertically only, rotating about their pitch

axis, but do not rotate about their own longitudinal axis.

3.2.3 Cross-deck designs other than those described in3.2.2 may require an alternative analysis to demonstratecompliance with the combined stress criteria.

3.2.4 Section properties are to be calculated using aneffective breadth of plating to be determined in accordancewith Ch 2,2.2.

3.2.5 Zcdt, Zcdb and Acd, defined in Ch 1,1.3, are to becalculated using the effective section at the appropriate loadcalculation point, see Fig. 3.3.1.

3.3 Combined stress criteria

3.3.1 The total stresses are to be evaluated for four different load cases (a) to (d) as given in Table 3.3.2.



LLOYDS REGISTER4




LLOYDS REGISTER 5

z

y

x

AP

A

A

A-A Section to be used for calculation of Zcdb and Zcdt

Fig. 3.3.1 Cross-deck section

Table 3.3.1 Cross-deck component stresses

Component stress type

Direct stress induced by the sag splitting moment, Msps, and the hog splitting moment Msph, as defined in Pt 5, Ch 4,3.1

Shear stress induced by the splitting shear force, Qsps and Qsph, as defined in Pt 5, Ch 4,3.2

Bending stress induced by the transverse torsional moment, Mtt, as defined in Pt 5, Ch 4,3.3

Shear stress induced by the transverse torsional moment, Mtt, as defined in Pt 5, Ch 4,3.3

Nominal stress (N/mm2)

sps = 103

sph = 103

sps =

sph =

tt =

tt = + 38k Mtt (yo yI)2

2Sbhd nbhd (nbhd2 1) Ii

60Mtt Sbhd nbhd (nbhd + 1) Awi

3000 (yo yI) Mtt Sbhd nbhd (nbhd + 1) zi

5QsphAcd

5QspsAcd

MsphZcd

MspsZcd

k =

where

K =

R = 2tdk Sbhd dcd for the deckR = 2tbhd Sbhd dcd for the transverse bulkhead

Zcd = is to be taken as the lesser of Zcdb and Zcdtsps, sph, Zcdb, Zcdt, tt, nbhd, Sp, sps, sph, Acd, tt, dcd, Awi, zi, Ii, tdk and tbhd are defined in Ch 1,1.3Msps, Msph, Mtt, yo, yI, Qsps and Qsph are defined in Pt 5, Ch 1,1.4.

2tdk tbhd Sbhd2 dcd2

Sbhd tbhd + dcd tdk

K

R




LLOYDS REGISTER6

Stress type Component stressesAllowable stress

level, N/mm2

Total direct stress, cd (a) sps(b) sph 0,72fhts yd(c) tt + 0,6sps(d) tt + 0,6sph

Total shear stress, cd (a) sps(b) sph 0,72fhts yd(c) tt + 0,6sps(d) tt + 0,6sph

Equivalent stress, eq cd2 + 3cd2 0,90fhts yd(see Note 1)

NOTES1. When calculating equivalent stress, the component stresses

for direct and shear stress are to correspond to the load case

considered, i.e. for load case (a) eq = sps2 + 3sps2

2. fhts is defined in Ch 2,1.4.

Table 3.3.2 Cross-deck primary member stresscriteria


2.1.3 The remaining scantlings not listed in 2.1.2 and2.1.3 are to be determined directly from the ComplementaryRules as defined in Sections 7 to 11.

2.2 Plate thickness

2.2.1 The requirements for the thickness of plating, tp, isin general to be in accordance with the following:

tp = 22,4s fcurv far x 103 mm

wheref is defined in Table 4.2.2s, fcurv, far, Pdes and yd are defined in Ch 1,1.3.1.

2.3 Stiffener properties

2.3.1 Primary stiffening members. The requirements forsection modulus, inertia and web area of primary stiffeningmembers subjected to pressure loads are, in general, to be inaccordance with the following:Section Modulus:

Z = 103 cm3

Inertia:

I = 105 cm4

Web area:

Aw = cm2

wheref is a structural element type factor and is 0,5 in general, forprimary stiffening membersf factors are listed for specific structural items in Table 4.2.1cA, cZ and cl are coefficients defined in Fig. 4.2.1f, f, f are defined in Table 4.2.2Pdes, S, le ,yd, yd and E are defined in Ch 1,1.3.1.

2.3.2 Secondary stiffening members. The require-ments for section modulus, inertia and web area of secondarystiffening members subjected to pressure loads are, ingeneral, to be in accordance with the following:Section Modulus:

Z = cm3

Inertia:

I = cm4

Web area:

Aw = cm2

wheref is a structural element type factor and is 0,8 in general, forsecondary stiffening membersf factors are listed for specific structural items in Table 4.2.1

cA f Pdes s le100 f o

100 cI f Pdes s le2f E

cZ f Pdes s le2f yd

10cA f Pdes S lef yd

cI f Pdes S le2f E

cZ f Pdes S le2f yd

Pdesf yd

Section

1 General

2 Minimum structural requirements

3 Shell envelope

4 Wet-deck

5 Weather deck

6 Inner bottom

7 Internal decks

8 Bulkheads and deep tanks

9 Deckhouses, bulwarks and superstructures

10 Other structures

11 Ice strengthening

Section 1General

1.1 Introduction

1.1.1 This Chapter contains local scantling requirementsfor the structural elements of a trimaran.

1.1.2 Where plating or stiffening contributes to the globalstrength of the ship, the scantlings are not to be less than thatrequired to satisfy the global strength requirements detailed inChapter 3.

1.2 Corrosion margin

1.2.1 The local scantling requirements are calculated inthe Rules using a net scantling approach, see Vol 1, Pt 1, Ch 1,3.2.

Section 2Minimum structural requirements

2.1 General

2.1.1 This Section gives the basic principles to beadopted in determining the Rule structural requirements.

2.1.2 The equations given in this Section are to be usedto determine the scantling requirements for shell envelope,wet-deck, weather deck and inner bottom, see Sections 4 to 7.

Local Scantling RequirementsRULES FOR THE CLASSIFICATION OF TRIMARANS, January 2006


LLOYDS REGISTER 1


cA, cZ and cl are coefficients defined in Fig. 4.2.1f, f and f are defined in Table 4.2.2Pdes, s, le ,yd, o and E are defined in Ch 1,1.3.1.



LLOYDS REGISTER2

Fig. 4.2.1 Section modulus, inertia and web area coefficients for different load models

Position (i)Web area

SectionLoad

(i) coefficientmodulus Inertia coefficient Application

Model 1 2 3CA

coefficient CIEnd Midspan End CZ

1 1/2 1/2 Primary and other members where the end

(A) 2 1/24 1/384 fixity is considered encastre and the pressure

3 1/2 1/12 is uniformly distributed

1 1/2 1/10 Local, secondary and other members where

(B) 2 1/10 1/288 the end fixity is considered to be partial and the

3 1/2 1/10 pressure is uniformly distributed

1 7/20 1/20 Fully fixed and the pressure is a linearly

(C) 2 1/764 varying distribution

3 3/20 1/30

1 1 1/2 1/8 Cantilever and uniformly distributed pressure

(D) 2

3

1 1/2 Simply supported and uniformly distributed

(E) 2 1/10 5/384 pressure

3 1/2

Fully fixed and a single 1 point load anywhere on

the span

(F) 2

3

1 1/2 1/8 Fully fixed and a single point load at the centre

(G) 2 1/8 1/192 of the span

3 1/2 1/8

Simply supported and a 1 single point load

anywhere on the span3/2

(H) 2 ( )3

1 1/2 Simply supported and a single point load at the

(J) 2 1/4 1/48 centre of the span

3 1/2

a

l

l2 a2

3

a

3l4a (l a)2

l2

(l a)

l

a2 (l a)2

l3a2 (3l 2a)

l3

2a3 (l a)2

3l3 (l + 2a)22a2 (l a)2

l4

a (l a)2

l3(l a)2 (l + 2a)

l3

p

p

l

a F

l

Fl/2

a F

l

l

Fl/2




LLOYDS REGISTER 3

Structural element f

Shell envelope

Main hull bottom and bilge longitudinalsMain hull side longitudinals

0,8Side hull bottom and bilge longitudinalsSide hull side longitudinals

Main hull bottom transverse framesMain hull side frames

0,8Side hull bottom transverse framesSide hull side frames

Bottom girdersSide stringersFloors 0,5Bottom transverse web framesSide transverse web frames

Wet deck

Wet-deck longitudinalsWet deck transverse frames

0,8

Wet-deck transverse web framesWet-deck girders

0,5

Weather and exposed decks

Deck longitudinalsDeck beams

0,8

Deck girdersDeck transverses 0,5Deck deep beams

Inner bottom

Inner bottom longitudinals 0,8

Inner bottom transverse frames 0,5

Table 4.2.1 Stiffening type factors




LLOYDS REGISTER4

Table 4.2.2 Acceptance criteria (see continuation)

Structural item Limiting criteria

Longitudinally effective structure Bending stress Stiffener web Stiffener Buckling factor,shear stress deflection Compressive

ratio stressesSee Note 3

Stress descriptor f f f

Plating See Note 5 See Note 1

Main hull bottom shell f2 0,00125 1,0Main hull side shell f2 0,00125 1,0Side hull bottom shell 0,9f2 0,00125 1,0Side hull side shell 0,9f2 0,00125 1,0Wet-deck 0,9f2 0,00125 1,0Weather deck, outboard the line of openings f2 0,00100 1,0Inner bottom 1,4f2 0,00125 1,0

Secondary stiffeners See Note 1

Main hull bottom and bilge longitudinals f2 0,65 0,00125 1,1Main hull side longitudinals f2 0,65 0,00125 1,1Side hull bottom and bilge longitudinals f2 0,65 0,00125 1,1Side hull side longitudinals f2 0,65 0,00125 1,1Wet-deck longitudinals f2 0,65 0,00125 1,1Main hull bottom transverse frames 0,65 0,65 0,00125 1,1Main hull side frames 0,65 0,65 0,00125 1,1Side hull bottom transverse frames 0,65 0,65 0,00125 1,1Side hull side frames 0,65 0,65 0,00125 1,1Wet-deck transverse frames 0,65 0,65 0,00125 1,1Weather deck longitudinals f2 0,65 0,00100 1,1Weather deck beams 0,65 0,65 0,00100 1,1Inner bottom longitudinals f2 0,65 0,00125 1,1

Primary stiffeners See Note 2

Single bottom girders 0,75 0,65 0,00100 1,0Double bottom girders 0,75 0,80 0,00100 1,0Side stringers 0,75 0,65 0,00100 1,0Floors 0,75 0,65 0,00100 1,0Bottom transverse web frames 0,65 0,65 0,00100 1,0Side transverse web frames 0,65 0,65 0,00100 1,0Wet-deck transverse web frames 0,65 0,65 0,00100 1,0Wet-deck girders 0,75 0,65 0,00100 1,0Deck girders 0,75 0,65 0,00100 1,0Deck transverses 0,65 0,65 0,00100 1,0Deck deep beams 0,65 0,65 0,00100 1,0Wet-deck transverse frames 0,65 0,65 0,00100 1,0Weather deck girders 0,75 0,65 0,00100 1,0Weather deck transverses 0,65 0,65 0,00100 1,0Weather deck deep beams 0,65 0,65 0,00100 1,0

Symbols

f2 is applicable to stiffeners and plating subjected to global hull girder bending stresses and local bending stresses and is to be taken as follows:

f2 = 0,9 183 but not greater than 0,95. Note that for initial design assessment f2 may be taken as 0,75.( )wherehg is the stress due to hull girder bending in the appropriate structural item, see Ch 3,2.4.4a is the lower of allowable hull girder stress, p, given in Ch 3,2.4.3

is the buckling factor for this itemcr is the critical buckling stress, see Note 4.

cr

hga


Local Scantling Requirements

Section 3Shell envelope

3.1 General

3.1.1 This Section contains local scantling requirementsapplicable to the shell envelope. Each applicable sub-Sectionis to be evaluated to determine the governing scantlingrequirement as follows: All shell envelope structure over the length of the ship is

to be evaluated according to 3.2 and 3.3. All bottom structure in way of a single bottom is to be

evaluated against the requirements of 3.4. All bottom structure in way of a double bottom is to be

evaluated against the requirements of 3.5. Where applicable, bottom and side shell structure below

the waterline is to be evaluated against the slammingrequirements in 3.6.

Side shell above the waterline is to be evaluated againstthe requirements of 3.7.

3.2 Requirements due to design pressures

3.2.1 The scantlings of plating and stiffeners on the shellenvelope are to be determined from the general equationsgiven in Section 2, using the design pressures calculatedaccording to Pt 5, Ch 5,3.

3.3 Additional minimum requirements

3.3.1 In addition to complying with 3.1.1, scantlingrequirements are to be assessed according to 3.3.2 to 3.3.4.

3.3.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in: Pt 3, Ch 5 and Ch 6 of the Rules for Ships. Pt 4, Ch 1 of the Rules for Ships and the appropriate

Chapter for the particular ship type.

3.3.3 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Table 3.2.1 in Vol 1, Pt 6, Ch 3 ofthe Rules for Naval Ships.

3.3.4 If the Complementary Rules are the Rules forSpecial Service Crafts then the scantlings of plating and stiffeners are not to be less than those given in Table 3.2.1 in Pt 6, Ch 3 of the Rules for Special Service Craft.

3.4 Single bottom

3.4.1 The requirements of this sub-Section are applicableto the bottom structure of vessels having a single bottom.

3.4.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in: Pt 3, Ch 5 and Ch 6 of the Rules for Ships, Pt 4, Ch 1 of the Rules for Ships and the Chapter

appropriate for the ship type.

3.4.3 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 3, Ch 2,3.5 of the Rulesfor Naval Ships.

3.4.4 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are not to be less than those given in Pt 6, Ch 4,5 ofthe Rules for Special Service Craft.

3.5 Double bottom

3.5.1 The requirements of this sub-Section are applicableto the bottom structure of vessels having a double bottom.

3.5.2 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 3, Ch 2,3.6 of the Rulesfor Naval Ships.

3.5.3 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in: Pt 3, Ch 5 and Ch 6 of the Rules for Ships. Pt 4, Ch 1 of the Rules for Ships and the Chapter appro-

priate for the ship type.




LLOYDS REGISTER 5

NOTES1. Deflection ratio for secondary stiffeners, expressed as a ratio of the stiffener's span, i.e. f x span where is the deflection2. Deflection ratio for secondary stiffeners, expressed as a ratio of the stiffener's span, i.e. f x span where is the deflection3. Buckling factor of safety to be applied to the compressive stress due to global longitudinal stresses4. If the Complementary Rules are the Rules and Regulations for the Classification of Naval Ships (hereinafter referred to as the Rules for Naval

Ships) then see Vol 1, Pt 5, Ch 2,7 of the Rules for Naval Ships. If the Complementary Rules are the Rules and Regulations for theClassification of Ships (hereinafter referred to as the Rules for Ships) then see Pt 3, Ch 4,7 of the Rules for Ships. If the ComplementaryRules are the Rules and Regulations for the Classification of Special Service Craft (hereinafter referred to as the Rules for Special ServiceCraft) then see Pt 6, Ch 7,4 of the Rules for Special Service Craft.

5. If the Complementary Rules are the Rules for Special Service Craft then for bottom, bow and wet-deck slamming f2 is to be taken as 0,85.

Table 4.2.2 Acceptance criteria (conclusion)



3.6 Strengthening due to bottom slamming

3.6.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 6, Ch 3,14 of the Rulesfor Naval Ships using the pressure, IPbi, calculated accordingto Pt 5, Ch 5,2.4. Note that for calculation of hs according toVol 1, Pt 6, Ch 3,14.2.8 of the Rules for Naval Ships:

hs = 0,1fDLF IPbi m

wherefDLF is to be taken as 1,0.

3.6.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in Pt 3, Ch 5,1.5 of the Rules for Ships.

3.6.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are to be determined from the general equationsgiven in Section 2, using the design pressures calculatedaccording to Pt 5, Ch 5,2.5.

3.7 Slamming above the waterline

3.7.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 6, Ch 3,15 of the Rulesfor Naval Ships using the pressure, IPwi, calculated accordingto Pt 5, Ch 5,2.5. Note that for calculation of hs according toVol 1, Pt 6, Ch 3,15.2.2 of the Rules for Naval Ships:

hs = 0,1fDLF IPwi m

wherefDLF is to be taken as 1,0.

3.7.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in Pt 3, Ch 5,1.6, Pt 4, Ch 2 and Pt 4, Ch 8of the Rules for Ships, depending on the particular ship type,using the pressure, IPwi, calculated according to Pt 5, Ch 5,2.5. Note that for calculation of hs according to Pt 4, Ch 2 of the Rules for Ships:

hs = 0,1IPwi m

3.7.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are to be determined from the general equationsgiven in Section 2, using the design pressures calculatedaccording to Pt 5, Ch 5,2.5.

Section 4Wet-deck

4.1 General

4.1.1 This Section contains local scantling requirementsapplicable to the wet-deck. Each applicable sub-Section is tobe evaluated to determine the governing scantling requirement as follows:

All wet-deck structure is to be evaluated according to4.2 and 4.3.

Where applicable, wet-deck structure above the waterline is to be evaluated against the requirements of4.4.


4.2.1 The scantlings of plating and stiffeners on the wet-deck are to be determined from the general equationsgiven in Section 2, using the design pressures calculatedaccording to Pt 5, Ch 5,4.


4.3.1 The scantlings of plating and stiffeners are not to beless than those required for the main hull side shell, as in 3.3.

4.4 Slamming above the waterline

4.4.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 6, Ch 3,15 of the Rulesfor Naval Ships using the pressure, IPwi, calculated accordingto Pt 5, Ch 5,4.3. Note that for calculation of hs according toVol 1, Pt 6, Ch 3,15.2.2 of the Rules for Naval Ships, fDLF is tobe taken as 1,0.

4.4.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in Pt 3, Ch 5,1.6, Pt 4, Ch 2 and Pt 4, Ch 8of the Rules for Ships depending on the particular ship type,using the pressure, IPwi, calculated according to Pt 5, Ch 5,2.5.

4.4.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are not to be less than those given in Section 2using the pressure calculated according to Pt 5, Ch 5,2.5.

Section 5Weather deck

5.1 General

5.1.1 This Section contains local scantling requirementsapplicable to the weather-deck. All weather deck structure isto be evaluated according to 5.2 and 5.3.


5.2.1 The scantlings of plating and stiffeners on theweather deck are to be determined from the general equations given in Section 2, using the design pressurescalculated according to Pt 5, Ch 5,5.1.



LLOYDS REGISTER6




5.3.1 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in Pt 3, Ch 5 and Ch 6 of the Rules for Ships. Pt 4, Ch 1 of the Rules for Ships and the appropriate


5.3.2 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Table 3.2.1 in Vol. 1, Pt 6, Ch 3, ofthe Rules for Naval Ships.

5.3.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are not to be less than those given in Table 3.2.1 inPt 6, Ch 3 of the Rules for Special Service Craft.

Section 6Inner bottom

6.1 General

6.1.1 This Section contains local scantling requirementsapplicable to the inner bottom. All inner bottom structure is tobe evaluated according to 6.2 and 6.3.

6.2 Scantlings

6.2.1 The scantlings of plating and stiffeners on the innerbottom are to be determined from the general equations givenin Section 2, using the design pressures calculated accordingto Pt 5, Ch 5,6.1.


6.3.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Table 3.2.1 in Vol 1, Pt 6, Ch 3 ofthe Rules for Naval Ships.

6.3.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in: Pt 3, Ch 5 and Ch 6 of the Rules for Ships Pt 4, Ch 1 of the Rules for Ships and the appropriate



Section 7Internal decks

7.1 General

7.1.1 This Section contains local scantling requirementsapplicable to the internal decks. All internal decks are to beevaluated according to 7.2.

7.2 Minimum requirements

7.2.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are to be inaccordance with Vol 1, Pt 3, Ch 2,3.7 of the Rules for NavalShips.

7.2.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are to be in accordance with Pt 4, Ch 1,9 of the Rules for Ships.

7.2.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are to be in accordance with Pt 6, Ch 3,7 of theRules for Special Service Craft.

Section 8Bulkheads and deep tanks

8.1 General

8.1.1 This Section contains local scantling requirementsapplicable to bulkheads and deep tanks. All bulkheads anddeep tanks are to be evaluated according to 8.2.


8.2.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are to be inaccordance with Vol 1, Pt 3, Ch 2,4.1 of the Rules for NavalShips.

8.2.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are to be in accordance with Pt 4, Ch 1,9 of the Rules for Ships.

8.2.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of plating and stiffeners are to be in accordance with Pt 6, Ch 3,7 of theRules for Special Service Craft.


Volume 1, Part 6, Chapter 4Sections 5 to 8

LLOYDS REGISTER 7



Section 9Deckhouses, bulwarks andsuperstructures

9.1 General

9.1.1 This Section contains local scantling requirementsapplicable to deckhouses, bulwarks and superstructures. Alldeckhouses, bulwarks and superstructures are to be evaluated according to 9.2.


9.2.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of plating and stiffeners are not tobe less than those given in Vol 1, Pt 3, Ch 2,7 of the Rules forNaval Ships.

9.2.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of plating and stiffeners are not to be lessthan those given in Pt 3, Ch 8 of the Rules for Ships.


Section 10Other structure

10.1 General

10.1.1 This Section contains local scantling requirementsapplicable to other local structure as given in 10.2 and 10.3.

10.2 Pillars and pillar bulkheads

10.2.1 If the Complementary Rules are the Rules for NavalShips then the scantlings of pillars are to be in accordancewith the requirements of Vol 1, Pt 3, Ch 2,8 of the Rules forNaval Ships.

10.2.2 If the Complementary Rules are the Rules for Shipsthen the scantlings of pillars are to be in accordance with therequirements of Pt 4, Ch 1,4.4 of the Rules for Ships and theappropriate Chapter for the particular ship type.

10.2.3 If the Complementary Rules are the Rules forSpecial Service Craft then the scantlings of pillars are to be inaccordance with the requirements of Pt 6, Ch 4,9 of the Rulesfor Special Service Craft.

10.3 Machinery and raft seating




Section 11Ice strengthening

11.1 General

11.1.1 This Section contains local scantling requirementsfor ice strengthening.






LLOYDS REGISTER8


Lloyds Register, 2006Published by Lloyds Register

Registered office71 Fenchurch Street, London, EC3M 4BS

United Kingdom

Printed by Butler and Tanner,Frome, Somerset

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