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REGISTRO BRASILEIRO Rules for the Construction and Classification of Ships CONTAINER SHIPS - Title 12

DE NAVIOS E AERONAVES Identified by their Missions – Part II STRUCTURE - Section 2

RGMM18EN CHAPTERS - A, C, E, I

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PART II RULES FOR THE CONSTRUCTION

AND CLASSIFICATION OF SHIPS

IDENTIFIED BY THEIR MISSIONS

TITLE 12 CONTAINER SHIPS

SECTION 2 STRUCTURE

CHAPTERS

A SCOPE

B DOCUMENTS, REGULATIONS AND

STANDARDS

– See Part II, Title 11, Section 2

C MATERIALS AND MANLABOUR

D PRINCIPLES OF CONSTRUCTION


E DESIGN PRINCIPLES OF LOCAL

STRUCTURAL SYSTEMS

F DIMENSIONING OF LOCAL STRUCTURES


G DESIGN PRINCIPLES OF THE SHIP GIRDER


H GLOBAL DIMENSIONING OF THE HULL

GIRDER – SHIPS < 90 METERS


I GLOBAL DIMENSIONING OF THE HULL

GIRDER – SHIPS ≥ 90 METERS




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CONTENTS

CHAPTER A ................................................................... 5 SCOPE ............................................................................. 5

A1. SCOPE ........................................................... 5 100. Application .................................................. 5

CHAPTER C ................................................................... 5 MATERIALS:REQUIREMENTS FOR USE OF

EXTREMELY THICK STEEL PLATES IN

CONTAINER SHIPS .................................................. 5 C1. APPLICATION ............................................. 5

100. General ...................................................... 5 200. Steel Grade ................................................. 5 300. Thickness ..................................................... 5 400. Hull structures (for the purpose of design) . 6

C2. NON-DESTRUCTIVE TESTING (NDT)

DURING CONSTRUCTION ..................................... 6 100. General ....................................................... 6 200. Acceptance criteria of UT ........................... 6

C3. PERIODIC NDT AFTER DELIVERY

(MEASURE NO.2 OF ANNEX 1) .............................. 6 C4. BRITTLE CRACK ARREST DESIGN ......... 6

C5. MEASURES FOR EXTREMELY THICK STEEL

PLATES 8 100. General ....................................................... 8 200. Measures: ................................................... 9

CAPÍTULO E ................................................................. 9 DESIGN PRINCIPLES OF LOCAL STRUCTURAL

SYSTEMS...................................................................... 10 E2. CONFIGURATION AND DESIGN

PRINCIPLES OF THE LOCAL STRUCTURAL

SYSTEMS .................................................................. 10 100. Configuration ............................................ 10 200. Design principles for decks ....................... 13 300. Design principles for side structures

including side tanks ................................................ 14 400. Design principles for transverse bulkhead

structure .................................................................. 14 500. Design principles for double bottom tank

structure .................................................................. 14 600. Design principles for fore end structures.. 15 700. Design principles for aft end structures .... 15 800. Structural continuity ................................. 15

E3. LOADINGS ................................................. 15 100. Scope ......................................................... 15 200. Loads introduced by containers ................ 15 300. Geometry of the forces .............................. 16

CHAPTER I .................................................................. 20 GLOBAL DIMENSIONING OF THE HULL GIRDER

– SHIPS ≥ 90 METERS ................................................ 20 H5. HULL GIRDER STRESSESERRO! INDICADOR

NÃO DEFINIDO. I1. APPLICATION ........................................... 20

100. Scope ......................................................... 20 200. Symbols and definitions ............................ 20 300. S11A.1.3 Corrosion margin and net thickness

21 I2. LOADS ......................................................... 24

100. Sign convention for hull girder loads ....... 24 200. Still water bending moments and shear forces

24 300. Wave loads ................................................ 24 400. Load cases ................................................ 27 500. Hull girder stress ...................................... 28

I3. STRENGTH ASSESSMENT .................... 28 100. General .................................................... 28 200. Stiffness criterion ...................................... 28 300. Yield strength assessment ......................... 28

I4. BUCKLING STRENGTH .......................... 29 100. Application ............................................... 29 200. Buckling criteria ....................................... 29 300. Buckling utilization factor ........................ 29 400. Stress determination ................................ 29

I5. HULL GIRDER ULTIMATE STRENGTH

31 100. General ..................................................... 31 200. Hull girder ultimate bending moments ..... 31 300. Hull girder ultimate bending capacity ...... 31

400. ACCEPTANCE CRITERIA ............................... 31 I6. ADDITIONAL REQUIREMENTS FOR

LARGE CONTAINER SHIPS ................................ 32 100. General .................................................... 32 200. Yielding and buckling assessment ............ 32 300. Whipping .................................................. 32

I7. CALCULATION OF SHEAR FLOW ....... 32 100. General ..................................................... 32 200. Determinate shear flow ............................ 32 300. Indeterminate shear flow .......................... 33 400. Computation of sectional properties ........ 33

I8. BUCKLING CAPACITY ........................... 34 100. Elementary Plate Panel (EPP) ................. 35 200. Buckling capacity of plates ....................... 35 300. Buckling capacity of overall stiffened panel

43 400. Buckling capacity of longitudinal stiffeners

43 I10. FUNCTIONAL REQUIREMENTS ON

LOAD CASES FOR STRENGTH ASSESSMENT

OF CONTAINER SHIPS BY FINITE ELEMENT

ANALYSIS................................................................ 43 100. Application ............................................... 43 200. Principles ................................................. 43 300. Definitions ............................................... 43 400. Analysis .................................................... 43 500. Load principles ......................................... 44 600. Load components ...................................... 44 700. Loading conditions ................................... 44 800. Wave conditions ....................................... 45




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CHAPTER A

SCOPE

CHAPTER CONTENTS

A1. SCOPE

A2. DEFINITIONS

A1. SCOPE

100. Application

101. The present Title 12 Chapter applies to ships are

eligible for the assignment of the Class Notation

“Container Ship”.

102. The requirements of this Chapter are additional to

those of Part II, Title 11, and Section 2.

CHAPTER C

MATERIALS:REQUIREMENTS FOR USE OF

EXTREMELY THICK STEEL PLATES IN

CONTAINER SHIPS

CHAPTER CONTENT

C1. APPLICATION


DURING CONSTRUCTION


C4. BRITTLE CRACK ARREST DESIGN

C5. MEASURES FOR EXTREMELY THICK STEEL

PLATES

C1. APPLICATION

100. General

101. This Chapter is to be complied with for container

ships incorporating extremely thick steel plates having

steel grade and thickness in accordance with C1.200 and

C1.300 respectively.

102. This Chapter identifies when measures for the

prevention of brittle fracture of extremely thick steel

plates are required for longitudinal structural members.

103. This Chapter gives the basic concepts for

application of extremely thick steel plates to longitudinal

structural members in the upper deck and hatch coaming

structural region (i.e. upper deck plating, hatch side

coaming and hatch coaming top).

200. Steel Grade

201. This Chapter is to be applied when any of YP36,

YP40 and YP47 steel plates are used for the longitudinal

structural members.

Note: YP36 YP40 and YP47 refers to the minimum

specified yield strength of steel 355, 390 and 460 N/mm2,

respectively.

202. In the case that YP47 steel plates are used for

longitudinal structural members in the upper deck region

such as upper deck plating, hatch side coaming and hatch

coaming top and their attached longitudinals, the grade of

YP47 steel plates is to be EH47 specified in Part III Title

61 Section 2 Chapter B, B12 and B13 (IACS UR W31).

300. Thickness

301. For steel plates with thickness of over 50mm and

not greater than 100mm, the measures for prevention of

brittle crack initiation and propagation specified in 2, 3

and 4 are to be taken.




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302. For steel plates with thickness exceeding 100mm,

appropriate measures for prevention of brittle crack

initiation and propagation are to be taken in accordance

with each Classification Society’s procedures.

400. Hull structures (for the purpose of design)

401. HT(K) factors (Material factor for YP36, YP40 and

YP47 steel)

a. The HT factor (Material factor of high tensile steel, K)

of YP47 steel for the assessment of hull girder strength

is to be taken as 0.62.

b. For HT factors of YP36 and YP40 refer to Part II, Title

11, Section 2, Subchapter C2 (IACS UR S4).

402. Fatigue assessment

404. Fatigue assessment on the longitudinal structural

members is to be performed in accordance with RBNA’s

procedures.

403. Details of construction design

a. Special consideration is to be paid to the construction

details where extremely thick steel plates are applied as

structural members such as connections between

outfitting and hull structures. Connections details are

to be in accordance with each RBNA’s requirements.

b. Where NDT during construction is required in C5, the

NDT is to be in accordance with C2.201 and C2.202.

Enhanced NDT as specified in C4.301.(e) is to be

carried out in accordance with an appropriate standard.


DURING CONSTRUCTION

100. General

101. Ultrasonic testing (UT) in accordance with Part II,

Title 11, section 2, Subchapter T5 (IACS Rec.20) is to be

carried out on all block-to-block butt joints of all upper

flange longitudinal structural members in the cargo hold

region.

102. Upper flange longitudinal structural members

include the topmost strakes of the inner hull/bulkhead, the

sheer strake, main deck, coaming plate, coaming top plate,

and all attached longitudinal stiffeners. These members are

defined in figure F.C2.102.1.

FIGURE F.C2.102.1 - UPPER FLANGE

LONGITUDINAL STRUCTURAL MEMBERS

200. Acceptance criteria of UT

201. Acceptance criteria of UT are to be in accordance

with IACS Rec.20 or each Classification Society’s

practice.

202. The acceptance criteria may be adjusted under

consideration of the appertaining brittle crack initiation

prevention procedure and where this is more severe than

that found in IACS Rec.20, the UT procedure is to be

amended accordingly to a more severe sensitivity.


Where periodic NDT after delivery is required, the NDT

is to be in accordance with C3.101, C3.102 and C3.103.

100. General

101. The procedure of the NDT is to be in accordance

with Part II, Title 11, Section 2, Subchapter T5 (IACS

Rec.20).

200. Timing of UT

201. Where UT is carried out, the frequency of survey

is to be in accordance with RBNA’s requirements.

300. Acceptance criteria of UT

300. Where UT is carried out, acceptance criteria of UT

are to be in accordance with Part II, Title 11, Section 2,

Subchapter T5 (IACS Rec.20).

C4. BRITTLE CRACK ARREST DESIGN

100. General

101. Measures for prevention of brittle crack

propagation, which is the same meaning as Brittle crack

arrest design, are to be taken within the cargo hold region.

102. The approach given in this section generally

applies to the block-to-block joints but it should be noted

that cracks can initiate and propagate away from such




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joints. Therefore, appropriate measures should be

considered in accordance with C3.201 (b) (ii).

103. Brittle crack arrest steel is defined below. Only for

the scope of this Chapter, the definition also applies to

YP36 and YP40 steels.

Guidance

For the purpose of this Chapter, brittle crack arrest steel is

defined as steel plate with measured crack arrest properties

at manufacturing approval stage,

Kca at (-10) degree C ≥6,000 N/mm3/2

or other methods based on the determination of Crack

Arrest Temperature (CAT).

Note 1: The Crack Arrest Fracture Toughness Kca is to be

determined by the ESSO Test or other alternative method.

Crack Arrest Temperature (CAT) may also be determined

by the Double Tension Wide Plate Test or equivalent. The

use of small scale test parameters such as the Nil Ductility

Test Temperature (NDTT) may be considered provided that

mathematical relationships of NDTT to Kca or CAT can be

shown to be valid.

Note 2: Where the thickness of the steel exceeds 80 mm the

required Kca value or alternative crack arrest parameter

for the brittle crack arrest steel plate is to be specifically

agreed with RBNA.

End of Guidance

200. Functional requirements of brittle crack arrest

design

201. The purpose of the brittle crack arrest design is

aimed at arresting propagation of a crack at a proper

position and to prevent large scale fracture of the hull

girder.

a. The point of a brittle crack initiation is to be

considered in the block-to-block butt joints both of

hatch side coaming and upper deck.

b. Both of the following cases are to be considered:

i. where the brittle crack runs straight along the butt

joint, and

ii. where the brittle crack initiates in the butt joint but

deviates away from the weld and into the plate, or

where the brittle crack initiates from any other

weld (see the figure below for definition of other

welds) and propagates

c. “Other weld areas” includes the following (refer to

Figure F.C4.201.1):

FIGURE F.C4.201.1 – OTHER WELD AREAS

Legend:

1. Fillet welds where hatch side coaming plating,

including top plating meet longitudinals;

2. Fillet welds where hatch side coaming plating,

including top plating and longitudinals, meet attachments.

(e.g., Fillet welds where hatch side top plating meet hatch

cover pad plating.);

3. Fillet welds where hatch side coaming top plating

meets hatch side coaming plating;

4. Fillet welds where hatch side coaming plating meet

upper deck plating;

5. Fillet welds where upper deck plating meets inner

hull/bulkheads;

6. Fillet welds where upper deck plating meets

longitudinal; and

7. Fillet welds where sheer strakes meet upper deck

plating.

300. Concept examples of brittle crack arrest design

301. The following are considered to be acceptable

examples of brittle crack arrest-design.

302. The detail design arrangements are to be submitted

for RBNA approval. Other concept designs may be

considered and accepted for review by RBNA.

303. Brittle crack arrest design for C4.201.(b)(ii):




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a. Brittle crack arresting steel is to be used for the upper

deck plating along the cargo hold region in a way

suitable to arrest a brittle crack initiating from the

coaming and propagating into the structure below.

304. Brittle crack arrest design for C4.201.(b)(i):

a. Where the block to block butt welds of the hatch side

coaming and those of the upper deck are shifted, this

shift is to be greater than or equal to 300mm. Brittle

crack arrest steel is to be provided for the hatch side

coaming plating.

b. Where crack arrest holes are provided in way of the

block-to-block butt welds at the region where hatch

side coaming weld meets the deck weld, the fatigue

strength of the lower end of the butt weld is to be

assessed. Additional countermeasures are to be taken

for the possibility that a running brittle crack may

deviate from the weld line into upper deck or hatch

side coaming. These countermeasures are to include

the application of brittle crack arrest steel in hatch side

coaming plating.

c. Where Arrest Insert Plates of brittle crack arrest steel

or Weld Metal Inserts with high crack arrest toughness

properties are provided in way of the block-to-block

butt welds at the region where hatch side coaming weld

meets the deck weld, additional countermeasures are to

be taken for the possibility that a running brittle crack

may deviate from the weld line into upper deck or

hatch side coaming. These countermeasures are to

include the application of brittle crack arrest steel in

hatch side coamings plating.

d. The application of enhanced NDT particularly time of

flight diffraction (TOFD) technique using stricter

defect acceptance in lieu of standard UT technique

specified in C2 can be an alternative to (b), (c) and (d).

C5. Measures for Extremely Thick Steel Plates

100. General

101. The thickness and the yield strength shown in the

following table apply to the hatch coaming top plating and

side plating, and are the controlling parameters for the

application of countermeasures.

102. If the as built thickness of the hatch coaming top

plating and side plating is below the values contained in

the table, countermeasures are not necessary regardless of

the thickness and yield strength of the upper deck plating.




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TABLE T.C5.101.1 – MEASURE OF EXTREMELY THICK STEEL PLATES

200. Measures:

201. NDT other than visual inspection on all target block

joints (during construction) See C2 of UR S33.

202. Periodic NDT other than visual inspection on all

target block joints (after delivery) See C3 of UR S33.

203. Brittle crack arrest design against straight

propagation of brittle crack along weldline to be taken

(during construction) See C4.301 (b), (c) or (d) of UR S33.

204. Brittle crack arrest design against deviation of brittle

crack from weldline (during construction) See C4.301 (a)

of UR S33.

205. Brittle crack arrest design against propagation of

cracks from other weld areas*** such as fillets and

attachment welds. (during construction) See C4.301 (a) of

UR S33.

Symbols:

(a) “X” means “To be applied”.

(b) “N.A.” means “Need not to be applied”.

(c) Selectable from option “A” and “B”.




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CAPÍTULO E

DESIGN PRINCIPLES OF LOCAL STRUCTURAL

SYSTEMS

CHAPTER CONTENTS

E1. DIRECT CALCULATION

- See Part II, Title 11, Section 2, E1.

E2. CONFIGURATIONS AND DESIGN PRINCIPLES

OF THE LOCAL STRUCTURAL SYSTEMS

E3. LOADING CONDITIONS

E4. GENERAL EQUATIONS FOR THICKNESSESS

AND FOR STRENGTH MODULUS

E5. SELECTING THE SCANTLINGS TO USE

- See Title 11

E2. CONFIGURATION AND DESIGN

PRINCIPLES OF THE LOCAL

STRUCTURAL SYSTEMS

[Based on IACS Rec 84]

100. Configuration

101. Figures F.E2.101.1 to F.E2.101.3 show typical

structural configurations for a container ship.

FIGURE T.E2.101.1 TYPICAL CARGO HOLD CONFIGURATION FOR A CONTAINER SHIP




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FIGURE T.E2.101.2 NOMENCLATURE FOR TYPICAL TRANSVERSE SECTION IN WAY OF CARGO HOLD




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FIGURE T.E2.101.3 NOMENCLATURE FOR TYPICAL TRANSVERSE BULKHEADS FOR A CONTAINER SHIP

102. In general, container ships have double hull side

structure in the cargo hold area. The double hull is used as

deep tanks, i.e. ballast tanks, heeling tanks or fuel oil tanks.

In most cases, the upper part of the double hull is used as a

passageway. Smaller container ships (and the foremost

cargo hold in the case of larger container ships) may have a

single side structure, at least in the upper part. Stringer

decks (raised tanks) may be arranged in the foremost and

aft cargo holds to provide additional space for container

stacks.

103. In addition to contributing to the shear strength of

the hull girder, the side structure forms the external

boundary of a cargo hold and is naturally the first line of

defence against ingress or leakage of sea water when the

ship’s hull is subjected to wave and other dynamic

loading in heavy weather.




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104. Two different types of transverse bulkheads are

found in the cargo holds of container ships: watertight

bulkheads and non-watertight bulkheads.

105. The transverse bulkheads are located at the end of

each cargo hold and are commonly constructed as plane

double plated bulkheads with internal stiffening. In general

every second transverse bulkhead is watertight i.e. with

watertight plating on one side and with large cut-outs on the

opposite side.

106. The non-watertight bulkhead is constructed as plane

double plated bulkhead with large cut-outs in the plating on

both sides. Normally cell guides are fitted at the bulkheads

in order to guide the containers during loading and

unloading as well as to support the containers during the

voyage.

107. Cell guides are strong vertical structures constructed

of metal installed into a ship's cargo holds. These structures

guide containers into well-defined rows during the loading

process and provide some support for containers against the

ship's rolling at sea.See figures F.E2.107.1 and F.E2.107.2.

FIGURE F.E2.107.1 – CELL GUIDES IN A

CONTAINER SHIP’S HOLD

FIGURE F.E2.107.2 – CELL GUIDE TOP IN A

CONTAINER SHIP’S HOLD

200. Design principles for decks

201. In calculating the deck structure by the Rules or by

direct calculation methods, the following factors are to be

taken into consideration:

a. Due to the large hatch openings for loading and

unloading of containers the hull structure is very

flexible showing considerable elastic deformations

in a seaway as well as high longitudinal stresses.

b. Normally containerships meet only hogging still

water bending moment conditions of the hull

causing high tensile stresses in the continuous

longitudinal deck structures such as longitudinal

hatch coamings, upper deck plating and

longitudinals.

c. The range of these higher bending stresses is

extended over the complete cargo hold area.

Particular areas of the deck may also be subjected

to additional compressive stresses in heavy

weather, caused by slamming or bow flare effect at

the fore part of the ship. Longitudinal deck

girders, even though in general not completely

effective for the longitudinal hull girder strength,

are also subject to high longitudinal stresses.

d. In particular in case of the use of higher tensile

steel in such high stressed areas special attention is

to be paid to the detail design of the structure.




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e. The cross deck structure between cargo hatches is

subjected to transverse compression from the sea

pressure on the ship sides and in-plane bending due

to torsional distortion of the hull girder under wave

action.

f. The area around the corners of a main cargo hatch

can be subjected to high cyclical stresses due to the

combined effect of hull girder bending moments,

transverse and torsional loads.

g. Cargo hatch side coamings can be subjected to stress

concentrations at their ends.

h. Considerable horizontal frictional forces in way of

the hatch cover resting pads can result from the

elastic deformation of the deck structure in

combination with the hatch covers which are

extremely rigid against horizontal in-plane loads.

The magnitude of these frictional forces depends on

the material combination in way of the bearing.

i. The marine environment and the high temperature

on deck and hatch cover plating due to heat from the

sun may result in accelerated corrosion of plating

and stiffeners making the structure more vulnerable

to the exposures described above. Therefore, due

consideration is to be given to a corrosion margin.

202. Local reinforcements are to be fitted under container

corners.

203. The width of the hatch coamings is to be such as to

accommodate the hatch covers and their securing

arrangements.

204. The connections of the deck longitudinal girders in

way of the holds and in way of the machinery space

structure and aft and fore part structures is to be designed in

such a manner as to ensure proper transmission of stresses.

205. Cross decks: transverse deck strips between the

hatches are subject to a shear force induced by the overall

torsion of the ship. The adequate strength of these strips

is to be verified taking this factor into account.

300. Design principles for side structures including

side tanks

301. In calculating the side structures including tanks by

the Rules or by direct calculation methods, the following

factors are to be taken into consideration:

a. Due consideration if to be given to the ship side

structure, which is prone to damage caused by

contact with the quay during berthing and impacts

of cargo and cargo handling equipment during

loading and unloading operations.

b. In longitudinally stiffened areas the side shell is

more prone to damage due to action of fenders and

tugs. A careful positioning of reinforced parts of

the side shell structure in these areas, using the

service experience of the owner, can reduce any

damage.

c. In some cases cell guides are fitted at the

longitudinal bulkheads in order to guide containers

during loading and unloading as well as to support

the containers during the voyage.

d. The structure in the transition regions at the fore

and aft ends of the ship is subject to stress

concentrations due to structural discontinuities.

e. The side shell plating in the transition regions is

also subject to panting.

f. The lack of continuity of the longitudinal structure,

and the increased slenderness and flexibility of the

side structure, makes the structure at the transition

regions more prone to fracture damage.

400. Design principles for transverse bulkhead

structure

401. The bulkheads serve as main transverse strength

elements in the structural design of the ship. Additionally

the watertight bulkhead serves as a subdivision to prevent

progressive flooding in an emergency situation.

402. Reinforcements in way of cell guides: where cell

guides are fitted on transverse or longitudinal bulkheads

which for boundaries of the holds, such structures are to

be adequately reinforced taking into account the loads

transmitted by the cell guides.

500. Design principles for double bottom tank

structure

501. In calculating the bottom tank structure by the

Rules or by direct calculation methods, the following





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a. In addition to contributing to the longitudinal

bending strength of the hull girder, the double

bottom structure provides support for the cargo in

the holds.

b. The tank top structure is subjected to impact forces

of containers during loading and unloading

operations. The bottom shell at the forward part of

the ship may sustain increased dynamic forces

caused by slamming in heavy weather

c. Normally, on container ships, a strict observance of

a maintenance programme in the cargo holds could

be difficult due to the fact that cargo holds are very

seldom completely empty. Therefore, the tank top

and the adjacent areas of bulkheads are prone to

increased corrosion and need particular attention.

502. The double bottom spacing of the floors is to be

such as to provide support for the container corner fittings.

Girders are to be fitted in way of the container corners.

600. Design principles for fore end structures




a. In general container ships have a high power main

engine and are operated to a tight schedule.

Therefore, ships can proceed in comparatively heavy

weather at a relatively high speed. In particular in

the case of larger bow flare high local pressure due

to bow flare slamming as well as increased global

bending moments and shear forces in the fore end of

the ship can cause hull damage such as deformations

and fractures.

b. Deformation can be caused by contact which can

result in damage to the internal structure leading to

fractures in the shell plating.

c. Fractures of internal structure in the fore peak tank

and spaces also result from wave impact load due to

slamming and panting.

d. The forecastle structure is exposed to green water

and can suffer damage such as deformation of deck

structures, deformation and fracture of bulwarks and

collapse of masts, etc. Bulwarks are provided for

the protection of the crew and of the anchor and

mooring equipment. Due to the bow flare effect

bulwarks are subject to impact forces which result in

alternating tension and compression stresses which

can cause fractures and corrosion at the bulwark

bracket connections to the deck. These fractures

may propagate to the deck plating and cause serious

damage.

e. The shell plating around the anchor and hawse pipe

may suffer corrosion, deformation and possible

fracture due to the movement of an improperly

stowed and secured anchor, especially in the case of

an unsheltered position as the same high

hydrodynamic impact forces act on the anchor as

on the hull structure, influencing the motion of the

anchor in the hawse pipe.

700. Design principles for aft end structures




a. Deformation can be caused by contact or wave

impact action from astern (which can result in

damage to the internal structure leading to

fractures in the shell plating).

b. Fractures to the internal structure in the aft peak

tank and spaces can also result from main engine

and propeller excited vibration.

800. Structural continuity

801. In double side skin ships where the machinery

space is located between two holds the inner side is, in

general, to be continuous within the machinery space.

Where the machinery space is situated aft, the inner side

is to extern as far aft as possible and be tapered at the

ends.

E3. LOADINGS

100. Scope

101. The present Subchapter E3 is related to loads on

the ship’s structure introduced by the containers.

200. Loads introduced by containers

201. The loads transmitted by the cargo to the container

fittings, lashing and securing are to be calculated in

addition to the structural loads as per Part II, Title 11,

Section 2.

202. The determination of the loads takes into account:

a. The maximum weight of the containers;

b. The ship’s movements; and

c. Environmental conditions (wind, wave impact,

etc.).

203. The loads introduced by the container cargo are to

be applied at the centre of gravity of the container or

container stack according to the factors given in nest

topics, for the determination of the forces at the supports.




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300. Geometry of the forces

FIGURE F.E3.301 – INERTIAL AND WIND FORCES

UPRIGHT SHIP CONDITION

301. Still water forces to a container unit

𝐹 𝑝 = 𝑚 ∗ 𝑔

302. External dynamic forces to a container unit in

longitudinal, transversal and vertical direction should be

obtained by the formula:

𝐹 𝑥 = 𝑚 ∗ 𝑎𝑥 + 𝐹𝑤𝑥 + 𝐹𝑠𝑥

𝐹 𝑦 = 𝑚 ∗ 𝑎𝑥𝑦 + 𝐹𝑤𝑦 + 𝐹𝑠𝑦

𝐹 𝑧 = 𝑚 ∗ 𝑎𝑧

where

F(x, y, z) = longitudinal, transverse and vertical forces

m = unit mass of the container

a(x, y, z) = longitudinal, transverse and vertical accelerations

(see table T.E3.301.1.)

Fw(x,y) = longitudinal and transverse forces by wind

pressure

Fs(x, y) = longitudinal and transverse forces by sloshing




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303. The basic acceleration data is presented in table

T.E3.303.1

TABLE T.E3.303.1 – BASIC ACCELERATION DATA

Transverse acceleration ayinm/s2 Longitudinal

acceleration

ax in m/s2

On

deck,

high

7,1 6,9 6,8 6,7 6,7 6,8 6,9 7,1 7,4 3,8

On

deck,

low

6,5 6,3 6,1 6,1 6,1 6,1 6,3 6,5 6,7 2,9

‘tween

deck

5,9 5,6 5,5 5,4 5,4 5,5 5,6 5,9 6,2 2,0

Lower

hold

5,5 5,3 5,1 5,0 5,0 5,1 5,3 5,5 5,9 1,5

% L 0 10 20 30 40 50 60 70 80 90 % L

Vertical accelerationazinm/s2

7,6 6,2 5,0 4,3 4,3 5,0 6,2 7,6 9,2

304. The given transverse acceleration figures include

components of gravity, pitch and heave parallel to the

deck.

305. The given vertical acceleration figures do not

include the static weight component.

306. The basic accelerations considered are valid under

the following operating conditions:

a. Operation in unrestricted area

b. Operation during the whole year

c. Duration of the voyage 25 days

d. Length of ship 100 meters

e. Service speed 15 knots

f. B/GM ≥ 13

307. For ships under of a length other than 100 m, the

figures should be corrected by a factor given in Table

T.E3.307.1

TABLE T.E3.307.1 – CORRECTION TABLE FOR SHIP’S LENGTH

Length (m)

Speed( kn)

50 60 70 80 90 100 120 140 160 180 200

9 1,20 1,09 1,00 0,92 0,85 0,79 0,70 0,63 0,57 0,53 0,49

12 1,34 1,22 1,12 1,03 0,96 0,90 0,79 0,72 0,65 0,60 0,56

15 1,49 1,36 1,24 1,17 1,07 1,00 0,89 0,80 0,73 0,68 0,63

18 1,64 1,49 1,37 1,27 1,18 1,10 0,98 0,89 0,82 0,76 0,71

21 1,78 1,62 1,49 1,38 1,29 1,21 1,08 0,98 0,90 0,83 0,78

24 1,93 1,76 1,62 1,50 1,40 1,31 1,17 1,07 0,98 0,91 0,85

308. For length/speed combinations not directly

tabulated, the following formula may be used to obtain the

correction factor with v = speed in knots and L = length

between perpendiculars in metres:

Correction factor = (0,345) ∗𝑣

√𝐿)+ (58,62 ∗ 𝐿 −

1034,5)/𝐿2




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TABLE T.E3.309.1 – CORRECTION FACTORS FOR B/GM

B/GM 7 8 9 10 11 12 13

or

above

On deck, high 1,56 1,40 1,27 1,19 1,11 1,05 1,00

On deck, low 1,42 1,30 1,21 1,14 1,09 1,04 1,00

1tweendeck 1,26 1,19 1,14 1,09 1,06 1,03 1,00

Lower hold 1,15 1,12 1,09 1,06 1,04 1,02 1,00

310. Notes:

a. In cases of roll resonance with amplitudes ≥ 30º,

the given values of transverse acceleration may be

exceeded;

b. In case of heading into the seas at high speed with

marked slamming, the figures of vertical and

longitudinal acceleration may be exceeded;

c. In case of running before large or quartering seas,

large rolling motions are to be expected with the

figures of transverse accelerations exceeded;

d. Forces by wind and sea to cargo units above the

weather deck should be accounted for by a simple

approach:

e. Forces by wind pressure = 1 kN per m2

f. Forces by sea sloshing = 1 kN per m2

g. Sea sloshing forces need only to be applied to a

height of deck cargo up to 2 metresabove the

weather deck or hatch top.

h. For voyages in restricted sea areas, sloshing forces

may be neglected.

311. The still water and inertial forces applied to one

container at level “i” is as per Table T.E3.3111.1 below.

312. The forces applied to a container stack containing

“n” containers, and the reactions at each of the container

corner are as per Table T.E3.312.1 below.

TABLE T.E3.311.1 – STILL WATER AND DYNAMIC FORCES ACTING ON A SINGLE CONTAINER UNIT “I”

Ship condition Still water and dynamic forces acting on a

single container unit “I”

Still water Fp= m * g

Upright heave motion Up to 2 meters from weather deck:

𝐹 𝑥𝑖 = 𝑚 ∗ 𝑎𝑥𝑖 + 𝐹𝑤𝑥𝑖 + 𝐹𝑠𝑥𝑖 𝐹 𝑧𝑖 = 𝑚 ∗ 𝑎𝑧𝑖

More than 2 meters from weather deck:

𝐹 𝑥𝑖 = 𝑚 ∗ 𝑎𝑥𝑖 + 𝐹𝑤𝑥𝑖 𝐹 𝑧𝑖 = 𝑚 ∗ 𝑎𝑧𝑖

Inclined roll motion Up to 2 meters from weather deck:

𝐹 𝑦𝑖 = 𝑚 ∗ 𝑎𝑦𝑖 + 𝐹𝑤𝑦𝑖 + 𝐹𝑠𝑦𝑖

𝐹 𝑧𝑖 = 𝑚 ∗ 𝑎𝑧𝑖

More than 2 meters from weather deck:

𝐹 𝑦𝑖 = 𝑚 ∗ 𝑎𝑦𝑖 + 𝐹𝑤𝑦𝑖

𝐹 𝑧𝑖 = 𝑚 ∗ 𝑎𝑧𝑖




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TABLE T.E3.312.1 – STILL WATER AND DYNAMIC FORCES ACTING ON EACH CONTAINER STACK

Ship condition Still water force Fs, inertial and wind force

Fw, in kN, acting on each container stack

Vertical still water force Rs

and inertial and wind force

Rw, in kN, transmitted at the

corners of each container stack

Still water 𝐹𝑠 = ∑ 𝐹𝑠,𝑖

𝑁

𝑖=1

𝑅𝑠 =𝐹𝑠

4

Upright heave motion

In x direction:

𝐹 𝑊,𝑋 = ∑(𝐹𝑊,𝑋,𝑖 + 𝐹𝑋,𝑤𝑖𝑛𝑑,𝑖)

𝑁

𝑖=1

In z direction:

𝐹 𝑊,𝑍 = ∑ 𝐹𝑊,𝑍,𝑖

𝑁

𝑖=1

𝑅𝑊,1 =𝐹𝑊,𝑍

4+

𝑁𝐶ℎ𝐶𝐹𝑊,𝑋

4ℓC


4−

𝑁𝐶ℎ𝐶𝐹𝑊,𝑋

4ℓC

Inclined roll motion

In y direction:

𝐹 𝑊,𝑌 = ∑(𝐹𝑊,𝑌,𝑖 + 𝐹𝑌,𝑤𝑖𝑛𝑑,𝑖)

𝑁

𝑖=1

In z direction:

𝐹 𝑊,𝑍 = ∑ 𝐹𝑊,𝑍,𝑖

𝑁

𝑖=1


4+

𝑁𝐶ℎ𝐶𝐹𝑊,𝑌

4bC


4−

𝑁𝐶ℎ𝐶𝐹𝑊,𝑌

4bC




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CHAPTER I

GLOBAL DIMENSIONING OF THE HULL GIRDER

– SHIPS ≥ 90 METERS

CHAPTER CONTENTS

I1. APPLICATION

I2. LOADS

I3. STRENGTH ASSESSMENT

I4. BUCKLING STRENGTH


I6. ADDITIONAL REQUIREMENTS FOR LARGE

CONTAINER SHIPS

I7. CALCULATION OF SHEAR FLOW

I8. BUCKLING CAPACITY

I9. HULL GIRDER ULTIMATE BENDING

CAPACITY

I10. FUNCTIONAL REQUIREMENTS ON LOAD

CASES FOR STRENGTH ASSESSMENT OF

CONTAINER SHIPS BY FINITE ELEMENT

ANALYSIS

I1. APPLICATION

100. Scope

101. This Chapter I applies to the following types of

steel ships with a length L of 90 m and greater and

operated in unrestricted service:

a. Container ships

b. Ships dedicated primarily to carry their load in

containers.

102. The wave induced load requirements apply to

monohull displacement ships in unrestricted service and

are limited to ships meeting the following criteria:

a. Length 90 m ≤ L ≤ 500 m

b. Proportion 5 ≤ L/B ≤ 9; 2 ≤ B/T ≤ 6

c. Block coefficient at scantling draught 0.55 ≤ CB ≤ 0.9

103 For ships that do not meet all of the aforementioned

criteria, special considerations such as direct calculations

of wave induced loads may be required by the

Classification Society.

104. Longitudinal extent of strength assessment

a. The stiffness, yield strength, buckling strength and

hull girder ultimate strength assessment are to be

carried out in way of 0.2L to 0.75L with due

consideration given to locations where there are

significant changes in hull cross section, e.g. changing

of framing system and the fore and aft end of the

forward bridge block in case of two-island designs.

b. In addition, strength assessments are to be carried out

outside this area. As a minimum assessments are to

be carried out at forward end of the foremost cargo

hold and the aft end of the aft most cargo hold.

Evaluation criteria used for these assessments are

determined by the RBNA.

200. Symbols and definitions

201. Symbols

L Rule length, in m, as defined in UR S2

B Moulded breadth, in m

C Wave parameter, see I2.301

T Scantling draught in m

CB Block coefficient at scantling draught

Cw Waterplane coefficient at scantling draught, to be

taken as:

𝐶𝑊 = 𝐴𝑊

(𝐿𝐵)

Aw Waterplane area at scantling draught, in m2

ReH Specified minimum yield stress of the

material, in N/mm2

k Material factor as defined in UR S4 for

higher tensile steels, k=1.0 for mild steel having a

minimum yield strength equal to 235 N/mm2

E Young’s modulus in N/mm2 to be taken as E

= 2.06*105 N/mm2 for steel

MS Vertical still water bending moment in

seagoing condition, in kNm, at the cross section under

consideration

MSmax, MSmin Permissible maximum and minimum

vertical still water bending moments in seagoing condition,

in kNm, at the cross section under consideration,

see I2.202

MW Vertical wave induced bending moment, in

kNm, at the cross section under consideration

FS Vertical still water shear force in seagoing

condition, in kN, at the cross section under consideration

FSmax, FSmin Permissible maximum and minimum still

water vertical shear force in seagoing condition, in kN, at

the cross section under consideration, see I2.200.




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F Vertical wave induced shear force, in kN, at

the cross section under consideration

qv Shear flow along the cross section under

consideration, to be determined according to I7.

fNL-Hog Non-linear correction factor for hogging, see

I2.302

fNL-Sag Non-linear correction factor for sagging, see

I2.302

fR Factor related to the operational profile, see

I2.3022

tnet Net thickness, in mm, see I1.301.

tres Reserve thickness, to be taken as 0.5mm

Inet Net vertical hull girder moment of inertia at

the cross section under consideration, to be determined

using net scantlings as defined in I1.300, in m4

σ HG Hull girder bending stress, in N/mm2, as

defined in I2.500

τ HG Hull girder shear stress, in N/mm2, as

defined in I2.500

x Longitudinal co-ordinate of a location under

consideration, in m

z Vertical co-ordinate of a location under

consideration, in m

zn Distance from the baseline to the horizontal

neutral axis, in m.

202. Fore end and aft end

a. The fore end (FE) of the rule length L, see Figure 1, is

the perpendicular to the scantling draught waterline at

the forward side of the stem.

b. The aft end (AE) of the rule length L, see Figure 1, is

the perpendicular to the scantling draught waterline at

a distance L aft of the fore end (FE).

FIGURE F.I1.202.1: ENDS OF LENGTH L

203. Reference coordinate system: The ships geometry,

loads and load effects are defined with respect to the

following righthand coordinate system (see Figure

F.H4.203.1):

a. Origin: At the intersection of the longitudinal plane of

symmetry of ship, the aft end of L and the baseline.

b. X axis: Longitudinal axis, positive forwards.

c. Y axis: Transverse axis, positive towards portside.

d. Z axis: Vertical axis, positive upwards.

FIGURE F.I1.203.1: REFERENCE COORDINATE

SYSTEM

300. Corrosion margin and net thickness

301. Net scantling definitions

a. The strength is to be assessed using the net thickness

approach on all scantlings.




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b. The net thickness, tnet, for the plates, webs and flanges

is obtained by subtracting the voluntary addition

tvol_add and the factored corrosion addition tc from the

as built thickness tas_built, as follows:

tnet = tas_built − tvoladd− αtc

where α is a corrosion addition factor whose values are

defined in Table T.I1.301.1.

c. The voluntary addition, if being used, is to be clearly

indicated on the drawings.

TABLE T.I1301.1: VALUES OF CORROSION ADDITION FACTOR

Structural requirement Property / analysis type α

Strength assessment

I3

Section properties 0,5

Buckling strength

I4

Section properties (stress

determination)

0,5

Buckling capacity 1,0

Hull girder ultimate strength

I5

Section properties 0,5

Buckling / collapse capacity 0,5

302. Determination of corrosion addition

a. The corrosion addition for each of the two sides of a

structural member, tc1 or tc2 is specified in Table

T.I1.302.1. T he total corrosion addition, tc, in mm,

for both sides of the structural member is obtained by

the following formula:

tnet = tas_built − tvoladd− αtc

b. The corrosion addition of a stiffener is to be

determined according to the location of its connection

to the attached plating.

TABLE T.I1.302.1: CORROSION ADDITION FOR

ONE SIDE OF A STRUCTURAL MEMBER

Compartment type One side corrogin

addition

tc1 or tc2

Exposed to sea water 1,0

Exposed to atmosphere 1,0

Ballast water tank 1,0

Void and dry spaces 0,5

Fresh water, fuel oil and lube oil

tank

0,5

Accommodation spaces 0,0

Container holds 1,0

Compartments not mentioned

above

0,5

303. Determination of net section properties

a. The net section modulus, moment of inertia and shear

area properties of a supporting member are to be

calculated using the net dimensions of the attached

plate, web and flange, as defined in Figure F.I1.303.1.

The net cross-sectional area, the moment of inertia

about the axis parallel to the attached plate and the

associated neutral axis position are to be determined

through applying a corrosion magnitude of 0.5 αtc

deducted from the surface of the profile cross-section.




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FIGURE F.I1.303.1.a: NET SECTIONAL PROPERTIES OF SUPPORTING MEMBERS

FIGURE F.I1.303.1.b: NET SECTIONAL PROPERTIES OF SUPPORTING MEMBERS

FIGURE F.I1.303.1.c: NET SECTIONAL PROPERTIES OF SUPPORTING MEMBERS




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FIGURE F.I1.303.1.d: NET SECTIONAL PROPERTIES OF SUPPORTING MEMBERS

I2. LOADS

100. Sign convention for hull girder loads

101. The sign conventions of vertical bending moments

and vertical shear forces at any ship transverse section are

as shown in Figure 4, namely:

102. The vertical bending moments MS and MW are

positive when they induce tensile stresses in the strength

deck (hogging bending moment) and negative when they

induce tensile stresses in the bottom (sagging bending

moment).

103. The vertical shear forces FS, FW are positive in the

case of downward resulting forces acting aft of the

transverse section and upward resulting forces acting

forward of the transverse section under consideration. The

shear forces in the directions opposite to above are

negative.

FIGURE F.I2.401.1 FIGURE 4: SIGN

CONVENTIONS OF BENDING MOMENTS AND

SHEAR FORCES

200. Still water bending moments and shear forces

201. Still water bending moments, MS in kNm, and still

water shear forces, FS in kN, are to be calculated at each

section along the ship length for design loading conditions

as specified in I2.202 below.

202. In general, the design cargo and ballast loading

conditions, based on amount of bunker, fresh water and

stores at departure and arrival, are to be considered for the

MS and FS calculations.

203. Where the amount and disposition of consumables

at any intermediate stage of the voyage are considered

more severe, calculations for such intermediate conditions

are to be submitted in addition to those for departure and

arrival conditions. Also, where any ballasting and/or de-

ballasting is intended during voyage, calculations of the

intermediate condition just before and just after ballasting

and/or de-ballasting any ballast tank are to be submitted

and where approved included in the loading manual for

guidance.

204. The permissible vertical still water bending

moments MSmax and MSmin and the permissible vertical still

water shear forces FSmax and FSmin in seagoing conditions at

any longitudinal position are to envelop:

a. The maximum and minimum still water bending

moments and shear forces for the seagoing loading

conditions defined in the Loading Manual.

b. The maximum and minimum still water bending

moments and shear forces specified by the designer

The Loading Manual should include the relevant

loading conditions, which envelop the still water hull

girder loads for seagoing conditions, including those

specified in Part II, Section 1, Chapter J, J.7 (UR S1

Annex 1).

300. Wave loads

301. Wave parameter: The wave parameter is defined

as follows:

𝐶 = 1 − 1,50 (1 − √𝐿

𝐿𝑟𝑒𝑓

)

2,2

𝑓or L ≤ Lref




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C = 1 − 0,45 ( √L

Lref

− 1)

1,7

for L > Lref

where:

Lref Reference length, in m, taken as:

Lref = 315 Cw−1,3

for the determination of vertical wave

bending moments according to I2.302

Lref = 330 Cw−1,3

for the determination of vertical wave

shear forces according to I2.303

302. Vertical wave bending moments: The distribution

of the vertical wave induced bending moments, MW in

kNm, along the ship length is given in Figure F.I2.302.2,

where:

MW−Hog = +1,5 fRL3C CW(B

L)0,8 fNL−Hog

MW−Sag = −1,5 fRL3C CW(B

L)0,8 fNL−Sag

where:

fR: Factor related to the operational profile, to be taken as:

fR = 0.85

fNL-Hog: Non-linear correction for hogging, to be taken as:

not to be taken greater than 1.1

fNL-Sag: Non-linear correction for sagging, to be taken as:

not to be taken less than 1.0

fBow: Bow flare shape coefficient, to be taken as:

ADK: Projected area in horizontal plane of uppermost deck,

in m2 including the forecastle deck, if any, extending

from 0.8L forward (see Figure 5). Any other

structures, e.g. plated bulwark, are to be excluded.

AWL: Waterplane area, in m2, at draught T, extending from

0.8L forward

Zf: Vertical distance, in m, from the waterline at draught

T to the uppermost deck (or forecastle deck),

measured at FE (see Figure F.I2.302.1. Any other

structures, e.g. plated bulwark, are to be excluded

FIGURE F.I2.302.1. PROJECTED AREA ADK AND VERTICAL DISTANCE ZF




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FIGURE F.I2.302.2: DISTRIBUTION OF VERTICAL WAVE BENDING MOMENT MW ALONG THE SHIP

LENGTH

303. Vertical wave shear force :The distribution of the

vertical wave induced shear forces, FW in kN, along the

ship length is given in Figure F.H4.404.1, where:

FW HogAft = +5,2fRL2CCW (

B

L)

0,8

(0,3 + 0,7fNL−Hog)

FW HogFore = +5,7fRL2CCW (

B

L)

0,8

fNL−Hog

FW SagAft = +5,2fRL2CCW (

B

L)

0,8

(0,3 + 0,75fNL−Sag)

FW SagFore = +5,7fRL2CCW (

B

L)

0,8

(0,25 + 0,7fNL−Sag)

FMid = +4,0fRL2CCW (B

L)

0,8




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FIGURE F.I2.404.1: DISTRIBUTION OF VERTICAL WAVE SHEAR FORCE FW ALONG THE SHIP LENGTH

400. Load cases

401. For the strength assessment, the maximum hogging

and sagging load cases given in Table T.I2;501;1 are to be

checked. For each load case the still water condition at

each section as defined in I2.200 is to be combined with

the wave condition as defined in I2.300, refer also to

Figure F.I2.501.1.

TABLE T.I2.501.1: COMBINATION OF STILL WATER AND WAVE BENDING MOMENTS AND SHEAR

FORCES

Load case Bending Moment Shear force

MS MW FS FW

Hogging MSmax MWH FSmax for x ≤ 0,5L FWmax for x ≤ 0,5L

FSmin for x >0,5L FWmin for x >0,5L

Sagging MSmin MWS FSmin for x ≤ 0,5L FWmin for x ≤ 0,5L

FSmax for x > 0,5L FWmax for x > 0,5L

FIGURE F.I2.501.1: LOAD COMBINATION TO DETERMINE THE MAXIMUM HOGGING AND SAGGING

LOAD CASES AS GIVEN IN TABLE T.H4.501.1




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MWH: Wave bending moment in hogging at the cross section under consideration, to be taken as the positive value of MW as

defined in Figure F.I2.302.2.

MWS: Wave bending moment in sagging at the cross section under consideration, to be taken as the negative value of MW as

defined Figure F.I2.302.2.

FWmax: Maximum value of the wave shear force at the cross section under consideration, to be taken as the positive value of

FW as defined Figure F.I2.404.1.

FWmin: Minimum value of the wave shear force at the cross section under consideration, to be taken as the negative value of

FW as defined Figure F.I2.404.1

500. Hull girder stress

501. The hull girder stresses in N/mm2 are to be

determined at the load calculation point under

consideration, for the “hogging” and “sagging” load cases

defined in 2.4 as follows:

Bending stress:

𝜎𝐻𝐺 = 𝛾𝑠𝑀𝑆+𝛾𝑊𝑀𝑊

𝐼𝑛𝑒𝑡 (𝑍 − 𝑍𝑛)1

Shear stress:

𝜏𝐻𝐺 = 𝛾𝑠𝐹𝑆+𝛾𝑊𝐹𝑊

𝑡𝑛𝑒𝑡𝑞𝑣

103

where:

γ s , γ W : Partial safety factors, to be taken as:

γ s = 1.0

γ W = 1.0

I3. STRENGTH ASSESSMENT

100. General

101. Continuity of structure is to be maintained

throughout the length of the ship. Where significant

changes in structural arrangement occur adequate

transitional structure is to be provided.

200. Stiffness criterion

201.The two load cases “hogging” and “sagging” as listed

in 2.4 are to be checked. The net moment of inertia, in

m4, is not to be less than:

300. Yield strength assessment

301. General acceptance criteria: The yield strength

assessment is to check, for each of the load cases

“hogging” and “sagging” as defined in 2.4, that the

equivalent hull girder stress σ eq , in N/mm2, is less than

the permissible stress σ perm, in N/mm2, as follows:

Where:

γ1 : Partial safety factor for material, to be taken as:

𝛾1 = 𝐾𝑟𝐸ℎ

235

γ 2 : Partial safety factor for load combinations and

permissible stress, to be taken as:

γ 2 = 1.24, for bending strength assessment

according to 3.3.2.

γ 2 = 1.13, for shear stress assessment

according to 3.3.3.




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302. Bending strength assessment:

a. The assessment of the bending stresses is to be carried

out according to I3.301 at the following locations of

the cross section:

i. At bottom

ii. At deck

iii. At top of hatch coaming

iv. At any point where there is a change of steel

yield strength

b. The following combination of hull girder stress is to

be considered:

303. Shear strength assessment: The assessment of

shear stress is to be carried out according to I3.301 for all

structural elements that contribute to the shear strength

capability. The following combination of hull girder stress

is to be considered:

I4. BUCKLING STRENGTH

100. Application

101. The present requirements apply to plate panels and

longitudinal stiffeners subject to hull girder bending and

shear stresses.

102. Definitions of symbols used in the present

Subchapter I4 are given in Subchapter I8 “Buckling

Capacity”.

200. Buckling criteria

201. The acceptance criterion for the buckling

assessment is defined as follows:

ηact ≤ 1

where:

ηact: Maximum utilization factor as defined in I4.300

below.

300. Buckling utilization factor

301. The utilization factor, act η , is defined as the

inverse of the stress multiplication factor at failure c γ , see

figure F.I4301.1.

𝜂𝑎𝑐𝑡 = 1

𝛾𝑐

302. Failure limit states are defined in:

I8.200 for elementary plate panels,

I8.300 for overall stiffened panels,

I8.400 for longitudinal stiffeners.

303. Each failure limit state is defined by an equation,

and γc is to be determined such that it satisfies the

equation.

304. Figure F.I4.301.1 illustrates how the stress

multiplication factor at failure γc , of a structural member is

determined for any combination of longitudinal and shear

stress.

Where:

σx, τc : Applied stress combination for buckling given in

I4.401

σc, τ: Critical buckling stresses to be obtained according to

Subchapter I8 for the stress combination for buckling σx

and τ .

FIGURE F.I4.301.1: EXAMPLE OF FAILURE LIMIT

STATE CURVE AND STRESS MULTIPLICATION

FACTOR AT FAILURE

400. Stress determination

401. Stress combinations for buckling assessment:

The following two stress combinations are to be

considered for each of the load cases “hogging” and

“sagging” as defined in I2.400. The stresses are to be

derived at the load calculation points defined in I4.200




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a. Longitudinal stiffening arrangement:

Stress combination 1 with:

σx = σHG

σy = 0

τ = 0,7τHG


σx = 0,7 σHG

σy = 0

τ = τHG

b. Transverse stiffening arrangement:


σx = 0

σy = σHG

τ = τHG


σx = 0

σy = σHG

τ = τHG

402. Load calculation points: the hull girder stresses

for elementary plate panels (EPP) are to be calculated at

the load calculation points defined in Table T.I4.402.1

TABLE T.I4.402.1: LOAD CALCULATION POINTS (LCP) COORDINATES FOR PLATE BUCKLING

ASSESSMENT

LCP coordinates Hull girder benring stress Hull girder shear stress

Non horizontal plating Horizontal platin

x coordinate Mid length on the EPP

y coordinate Both upper and lower ends

of the EPP

(pointes A1 and A2 in Figure

F.I4.402.1

Outboard and inboard ends

of the EPP

(points A1 and A2 in Figure

F.I4.402.1)

Mid point of EPP

(pont B in Figure F.I4.402.1)

z coordinate Corresponding to x and y values

FIGURE F.I4.402.1: LCP FOR PLATE BUCKLING – ASSESSMENT, PSM STANDS FOR PRIMARY

SUPPORTING MEMBERS

403. The hull girder stresses for longitudinal stiffeners

are to be calculated at the following load calculation point:

at the mid length of the considered stiffener.

at the intersection point between the stiffener and

its attached plate.




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100. General

101. The hull girder ultimate strength is to be assessed

for ships with length L equal or greater than 150m.

102. The acceptance criteria, given in I5.400 are

applicable to intact ship structures.

103. The hull girder ultimate bending capacity is to be

checked for the load cases “hogging” and “sagging” as

defined in I2.400.

200. Hull girder ultimate bending moments

201. The vertical hull girder bending moment, M in

hogging and sagging conditions, to be considered in the

ultimate strength check is to be taken as:

𝑀 = γsMs + γwMw

where:

Ms = Permissible still water bending moment, in kNm,

defined in 2.4

Mw = Vertical wave bending moment, in kNm, defined in

I2.400.

γ s = Partial safety factor for the still water bending

moment, to be taken as:

γ s = 1.0

γ w = Partial safety factor for the vertical wave

bending moment, to be taken as:

γ w = 1.2

300. Hull girder ultimate bending capacity

301. General: The hull girder ultimate bending moment

capacity, MU is defined as the maximum bending moment

capacity of the hull girder beyond which the hull structure

collapses.

302. Determination of hull girder ultimate bending

moment capacity: The ultimate bending moment

capacities of a hull girder transverse section, in hogging

and sagging conditions, are defined as the maximum

values of the curve of bending moment M versus the

curvature χ of the transverse section considered (MUH for

hogging condition and MUS for sagging condition, see

Figure F.I5.302.1). The curvature χ is positive for hogging

condition and negative for sagging condition.

FIGURE F.I5.302.1: BENDING MOMENT M

VERSUS CURVATURE Χ

303. The hull girder ultimate bending moment capacity

MU is to be calculated using the incremental-iterative

method as given in I8.200 or using an alternative method

as indicated in I8.300.

400. Acceptance criteria

401. The hull girder ultimate bending capacity at any

hull transverse section is to satisfy the following criteria:

M ≤ MU

γMγDB

where:

M = Vertical bending moment, in kNm, to be obtained as

specified in I5.200.

MU = Hull girder ultimate bending moment capacity, in

kNm, to be obtained as specified in I5.300.

γM = Partial safety factor for the hull girder ultimate

bending capacity, covering material, geometric and

strength prediction uncertainties, to be taken as:

γM = 1.05

γ DB = Partial safety factor for the hull girder ultimate

bending moment capacity, covering the effect of double

bottom bending, to be taken as:

For hogging condition: γ DB = 1.15

For sagging condition: γ DB = 1.0

402. For cross sections where the double bottom breadth

of the inner bottom is less than that at amidships or where

the double bottom structure differs from that at amidships

(e.g. engine room sections), the factor γ DB for hogging

condition may be reduced based upon agreement with the

RBNA.




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I6. ADDITIONAL REQUIREMENTS FOR

LARGE CONTAINER SHIPS

100. General

The requirements in I6.200 and I6.300 are applicable, in

addition to requirements in I.3 to I5, to container ships

with a breadth B greater than 32.26 m.

200. Yielding and buckling assessment

201. Yielding and buckling assessments are to be carried

out in accordance with the Rules of the RBNA, taking into

consideration additional hull girder loads (wave torsion,

wave horizontal bending and static cargo torque), as well

as local loads. All in-plane stress components (i.e. bi-axial

and shear stresses) induced by hull girder loads and local

loads are to be considered.

300. Whipping

301. Hull girder ultimate strength assessment is to take

into consideration the whipping contribution to the vertical

bending moment according to the RBNA procedures.

I7. CALCULATION OF SHEAR FLOW

100. General

101. This Subchapter I7 describes the procedures of

direct calculation of shear flow around a ship’s cross

section due to hull girder vertical shear force. The shear

flow qv at each location in the cross section, is calculated

by considering the cross section is subjected to a unit

vertical shear force of 1 N.

102. The unit shear flow per mm, qv, in N/mm, is to be

taken as:

qv = qD + ql

where:

qD : Determinate shear flow, as defined in I7.200.

ql : Indeterminate shear flow which circulates around the

closed cells, as defined in I7.300.

103. In the calculation of the unit shear flow, qD, the

longitudinal stiffeners are to be taken into account.

200. Determinate shear flow

201. The determinate shear flow, qD, in N/mm at each

location in the cross section is to be obtained from the

following line integration:

qd(s) = − 1

106Iy−net

∫ (z − zn)s

0

tnetds

where:

s : Coordinate value of running coordinate along the cross

section, in m.

Iy-net : Net moment of inertia of the cross section, in m4.

tnet : Net thickness of plating, in mm.

zn : Z coordinate of horizontal neutral axis from baseline,

in m.

202. It is assumed that the cross section is composed of

line segments as shown in Figure F.I7.202.1: where each

line segment has a constant plate net thickness.

FIGURE F.I7.202.1 – DEFINITION OF THE

SEGMENT




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203. The determinate shear flow is obtained by the

following equation:

qDk = − tnet l

2 ∗ 106IY−net

(zk + zi − 2zn) + qDi

qDk, qDi : Determinate shear flow at node k and node i

respectively , in N/mm.

ℓ : Length of line segments, in m.

yk, yi : Y coordinate of the end points k and i of line

segment, in m, as defined in Figure F.I7.202.1.

zk, zi : Z coordinate of the end points k and i of line

segment, in m, as defined in Figure F.I7.202.1.

204. Determinate shear flow at bifurcation points is to be

calculated by water flow calculations, or similar, as shown

in Figure F.I7.204.1.

FIGURE F.I7.204.1 – PLACEMENT OF VIRTUAL

SLITS AND CALCULATION OF DETERMINATE

SHEAR FLOW AT BIFURCATION POINTS

300. Indeterminate shear flow

301. The indeterminate shear flow around closed cells of

a cross section is considered as a constant value within the

same closed cell. The following system of equation for

determination of indeterminate shear flows can be

developed. In the equations, contour integrations of several

parameters around all closed cells are performed.

where:

Nw : Number of common walls shared by cell c and all

other cells.

c&m : Common wall shared by cells c and m

qIc, qIm : Indeterminate shear flow around the closed cell c

and m respectively, in N/mm.

302. Under the assumption of the assembly of line

segments shown in Figure F.I6.202.1 and constant plate

thickness of each line segment, the above equation can be

expressed as follows:

where:

Nc : Number of line segments in cell c.

Nm : Number of line segments on the common wall shared

by cells c and m.

qDi : Determinate shear flow, in N/mm, calculated

according to I8, I9.

303. The difference in the directions of running

coordinates specified in I8, I9 and in this section has to be

considered.

FIGURE F.I6.303.1 – CLOSED CELLS AND

COMMON WALL

400. Computation of sectional properties

401. Properties of the cross section are to be obtained by

the following formulae where the cross section is assumed

as the assembly of line segments:




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where:

anet, Anet: Area of the line segment and the cross section

respectively, in m2.

sy-net, sy-net: First moment of the line segment and the cross

section about the baseline, in m3.

iy0-net, Iy0-net: Moment of inertia of the line segment and the

cross section about the baseline, in m4.

402. The height of horizontal neutral axis, zn, in m, is to

be obtained as follows:

403. Inertia moment about the horizontal neutral axis, in

m4, is to be obtained as follows:

I8. BUCKLING CAPACITY

Symbols

x axis : Local axis of a rectangular buckling panel parallel

to its long edge.

y axis : Local axis of a rectangular buckling panel

perpendicular to its long edge.

σx : Membrane stress applied in x direction, in N/mm2.

σy : Membrane stress applied in y direction, in N/mm2.

τ : Membrane shear stress applied in xy plane, in N/mm2.

σa : Axial stress in the stiffener, in N/mm²

σb : Bending stress in the stiffener, in N/mm²

σw : Warping stress in the stiffener, in N/mm²

σcx,σcy,τc : Critical stress, in N/mm2, defined in [2.1.1] for

plates.

ReH_S : Specified minimum yield stress of the stiffener, in

N/mm²

ReH_P : Specified minimum yield stress of the plate, in

N/mm²

a : Length of the longer side of the plate panel as shown in

Table 2, in mm.

b : Length of the shorter side of the plate panel as shown in

Table 2, in mm.

d : Length of the side parallel to the axis of the cylinder

corresponding to the curved plate panel as shown in Table

3, in mm.

σE : Elastic buckling reference stress, in N/mm2 to be

taken as:

For the application of plate limit state according

to [2.1.2]:

• For the application of curved plate panels

according to [2.2]:

ν : Poisson’s ratio to be taken equal to 0.3

𝑡𝑝 : Net thickness of plate panel, in mm

𝑡𝑤 : Net stiffener web thickness, in mm

𝑡𝑓 : Net flange thickness, in mm




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𝑏𝑓 : Breadth of the stiffener flange, in mm

ℎ : Stiffener web height, in mm

𝑒𝑓 : Distance from attached plating to centre of flange, in

mm, to be taken as:

ef = ℎ𝑤 for flat bar profile.

ef = ℎ𝑤 – 0.5 tf for bulb profile.

ef = ℎ𝑤 + 0.5 tf for angle and Tee profiles.

𝛼 : Aspect ratio of the plate panel, to be taken as 𝛼 = 𝑎

𝑏

𝛽 : Coefficient taken as β = 1 −ψ

α

𝜓 : Edge stress ratio to be taken as ψ = σ1

σ2

𝜎1 : Maximum stress, in N/mm²

𝜎2 : Minimum stress, in N/mm²

R : Radius of curved plate panel, in mm

ℓ : Span, in mm, of stiffener equal to the spacing between

primary supporting members

s : Spacing of stiffener, in mm, to be taken as the mean

spacing between the stiffeners of the considered stiffened

panel.

100. Elementary Plate Panel (EPP)

101. Definition: An Elementary Plate Panel (EPP) is the

unstiffened part of the plating between stiffeners and/or

primary supporting members. All the edges of the

elementary plate panel are forced to remain straight (but

free to move in the in-plane directions) due to the

surrounding structure / neighbouring plates (usually

longitudinal stiffened panels in deck, bottom and inner-

bottom plating, shell and longitudinal bulkheads).

102. EPP with different thicknesses: Longitudinally

stiffened EPP with different thicknesses.

103. In longitudinal stiffening arrangement, when the

plate thickness varies over the width, b, in mm, of a plate

panel, the buckling capacity is calculated on an equivalent

plate panel width, having a thickness equal to the smaller

plate thickness, t1.

1043. The width of this equivalent plate panel, beq, in mm,

is defined by the following formula:

𝑏𝑒𝑞 = 𝑙1 + 𝑙2 (𝑡1

𝑡2

)1,5

where:

ℓ1 : Width of the part of the plate panel with the smaller

plate thickness, t1, in mm, as defined in Figure F.I8.104.1.

ℓ2 : Width of the part of the plate panel with the greater

plate thickness, t2, in mm, as defined in Figure F.I8.104.1.

FIGURE F.I8.203.1 - PLATE THICKNESS CHANGE

OVER THE WIDTH

105. Transversally stiffened EPP with different

thicknesses: In transverse stiffening arrangement, when an

EPP is made of different thicknesses, the buckling check

of the plate and stiffeners is to be made for each thickness

considered constant on the EPP.

200. Buckling capacity of plates

201. Plate panel

Plate limit state: The plate limit state is based on the

following interaction formulae:

a. Longitudinal stiffening arrangement:

b. Transverse stiffening arrangement:

where:

σ x, σ y : Applied normal stress to the plate panel in N/mm²,

as defined in I4.400, at load calculation points of the

considered elementary plate panel.

τ : Applied shear stress to the plate panel, in N/mm², as

defined in I4.400, at load calculation points of the

considered elementary plate panel.

σ cx : Ultimate buckling stress in N/mm² in direction

parallel to the longer edge of the buckling panel as defined

in 2.1.3

σ cy : Ultimate buckling stress in N/mm² in direction

parallel to the shorter edge of the buckling panel as defined

in 2.1.3




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τ c :Ultimate buckling shear stress, in N/mm² as defined in

2.1.3

β p : Plate slenderness parameter taken as:

202. Reference degree of slenderness

The reference degree of slenderness is to be taken as:

K : Buckling factor, as defined in Table 2 and Table 3.

203. Ultimate buckling stresses

a. The ultimate buckling stress of plate panels, in

N/mm², is to be taken as:

𝜎𝑐𝑥 = 𝐶𝑥𝑅𝑒𝐻_𝑃

𝜎𝑐𝑦 = 𝐶𝑦𝑅𝑒𝐻_𝑃

b. The ultimate buckling stress of plate panels subject to

shear, in N/mm², is to be taken as:

where:

Cx, Cy, Cτ : Reduction factors, as defined in Table

T.I8.203.1

c. The boundary conditions for plates are to be

considered as simply supported (see cases 1, 2 and 15

of Table T.I8.203.1). If the boundary conditions differ

significantly from simple support, a more appropriate

boundary condition can be applied according to the

different cases of Table T.I8.203.1 subject to the

agreement of the RBNA.

204. Correction Factor Flong

The correction factor Flong depending on the edge stiffener

types on the longer side of the buckling panel is defined in

T.I8.204.1. An average value of Flong is to be used for

plate panels having different edge stiffeners. For stiffener

types other than those mentioned in T.I8.204.1, the value

of c is to be agreed by the RBNA. In such a case, value of

c higher than those mentioned in Table t.i8.204.1 can be

used, provided it is verified by buckling strength check of

panel using non-linear FE analysis and deemed appropriate

by the RBNA.




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TABLE T.I8.203.1 - : BUCKLING FACTOR AND REDUCTION FACTOR FOR PLANE PLATE PANELS




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TABLE T.I8.203.1 - : BUCKLING FACTOR AND REDUCTION FACTOR FOR PLANE PLATE PANE (CONT.)




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TABLE T.I8.204.1 – CORRECTION FACTOR Flong

Structural element types Flong c

Unstiffened panel 1,0 N/A

Stiffened

Panel

Stiffener not fixed at both ends 1,0 N/A

Stiffener

fixed at

both

ends

Flat bar (1)

0,10

Bulb profile 0,30

Angle profile 0,40

T profile 0,30

Girder of high

rigidity (e.g. bottom

transverse)

1,4 N/A

(1) tw is the net web thickness, in mm, without the correction defined in 4.3.5

205. Curved plate panels

This requirement for curved plate limit state is applicable

when R/tp ≤ 2500. Otherwise, the requirement for plate

limit state given in 2.1.1 is applicable.

The curved plate limit state is based on the following

interaction formula:

where:

σax : Applied axial stress to the cylinder corresponding to

the curved plate panel, in

N/mm². In case of tensile axial stresses, σax=0.

Cax, Cτ : Buckling reduction factor of the curved plate

panel, as defined in Table 3.

The stress multiplier factor γ c of the curved plate panel

needs not be taken less than the

stress multiplier factor γ c for the expanded plane panel

according to 2.1.1.




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300. Buckling capacity of overall stiffened panel

301. The elastic stiffened panel limit state is based on

the following interaction formula:

where Pz and cf are defined in 4.4.3.

400. Buckling capacity of longitudinal stiffeners

401. Stiffeners limit states: The buckling capacity of

longitudinal stiffeners is to be checked for the following

limit states:

a. Stiffener induced failure (SI).

b. Associated plate induced failure (PI).

402. Lateral pressure: The lateral pressure is to be

considered as constant in the buckling strength assessment

of longitudinal stiffeners.

403. Stiffener idealization:

a. Effective length of the stiffener ℓeff: The effective

length of the stiffener ℓeff, in mm, is to be taken equal

to:

I10. FUNCTIONAL REQUIREMENTS ON LOAD

CASES FOR STRENGTH ASSESSMENT OF

CONTAINER SHIPS BY FINITE ELEMENT

ANALYSIS

100. Application

101. This UR applies to container ships and ships

dedicated primarily to carry their cargo in containers.

200. Principles

201. The requirements in this UR are functional

requirements on load cases to be considered on finite

element analysis for the structural strength assessment

(yielding and buckling).

202. The procedure for yielding and buckling assessment

are to be in accordance with the Rules of the Classification

Society.

203. All in-plane stress components (i.e. bi-axial and

shear stresses) induced by hull girder loads and local loads

as specified in this UR are to be considered.

204. All aspects and principles not mentioned explicitly

in this UR are to be applied according to the procedures of

the Classification Society.

300. Definitions

301. Global Analysis: A Global Analysis is a finite

element analysis, using a full ship model, for assessing the

structural strength of global hull girder structure, cross

deck structures and hatch corner radii.

302. Cargo Hold Analysis: A Cargo Hold Analysis is a

finite element analysis for assessing the structural strength

of the cargo hold primary structural members (PSM) in the

midship region.

303. Primary Structural Members (PSM): Primary

structural members are members of girder or stringer type

which provide the overall structural integrity of the hull

envelope and cargo hold boundaries, such as:

a. double bottom structure (bottom plate, inner bottom

plate, girders, floors)

b. double side structure (shell plating, inner hull,

stringers and web frames)

c. bulkhead structure

d. deck and cross deck structure

400. Analysis

401. Global Analysis: A Global Analysis is to be carried

out for ships of length 290 m or above. Hull girder loads

(including torsional effects) are to be considered in

accordance with the procedures of the Classification

Society.




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The following methods may be used for Global Analysis:

a. Method 1: Analysis where hull girder loads only

(vertical bending moment, horizontal bending moment

and torsional moment) are directly applied to the full

ship finite element model

b. Method 2: Analysis where direct loads transferred

from direct load analysis are applied to the full ship

finite element model

402. Cargo Hold Analysis: Cargo Hold Analysis is to

be carried out for ships of length 150 m or above. Local

loads such as sea pressure and container loads as well as

hull girder loads are to be considered in accordance with

the procedures of the Classification Society.

500. Load principles

501. Wave environment: The ship is to be considered

sailing in the North Atlantic wave environment for

yielding and buckling assessments. The corresponding

vertical wave bending moments are to be in line with UR

S11A and the other hull girder loads are to be taken in

accordance with the Rules of the Classification Society.

The corresponding local loads are to be taken in

accordance with the Rules of the Classification Society.

502. Ship operating conditions: Seagoing conditions

are to be considered. Harbour conditions and special

conditions such as flooded conditions, tank testing

conditions may be considered in accordance with the Rules

of the Classification Society.

600. Load components

601. Global Analysis: The load components to be

considered in Global Analysis are shown in Table

T.I10.601.1.

TABLE T.I10.601.1: LOAD COMPONENTS TO BE CONSIDERED IN GLOBAL ANALYSIS

602. Cargo Hold Analysis: The load components to be

considered in Cargo Hold Analysis are defined in

TableT.I10.602.1.

TABLE T.I10.602.1: LOAD COMPONENTS TO BE CONSIDERED IN CARGO HOLD ANALYSIS

700. Loading conditions

701. Global Analysis: Loading conditions to be

considered for the Global Analysis are to be in accordance

with the Loading Manual and with the Rules of the

Classification Society.

702. Cargo Hold Analysis: The minimum set of loading

conditions is specified in Table T.I10.702.1. In addition,

loading conditions from the Loading Manual are to be

considered in the Cargo Hold Analysis where deemed

necessary.




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TABLE T.I10.702.1: MINIMUM SET OF LOADING CONDITIONS FOR CARGO HOLD ANALYSIS

800. Wave conditions

801. Global Analysis: Wave conditions presumed to

lead to the most severe load combinations due to vertical

bending moment, horizontal bending moment and

torsional moment are to be considered.

802. Cargo Hold Analysis: The following wave

conditions are to be considered:

a. Head sea condition yielding the maximum hogging

and sagging vertical bending moments.

b. Beam sea condition yielding the maximum roll

motion. This condition may be disregarded for some

loading conditions defined in Table 3 where deemed

not necessary.

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