Common Structural Rules for
Bulk Carriers, January 2006

Background Document
CHAPTER 6 – HULL SCANTLINGS

NOTE:- This TB is published to improve the transparency of CSRs and increase theunderstanding of CSRs in the industry.
- The content of the TB is not to be considered as requirements.
- This TB cannot be used to avoid any requirements in CSRs, and in cases
where this TB deviates from the Rules, the Rules have precedence.
- This TB provides the background for the first version (January 2006) of theCSRs, and is not subject to maintenance.

COMMON STRUCTURAL RULES FOR BULK CARRIERS − BACKGROUND DOCUMENT
PAGE 2 – CHAPTER 6: HULL SCANTLINGS© IACS - the International Association of Classification Societies and theInternational Association of Classification Societies Limited
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COMMON STRUCTURAL RULES FOR BULK CARRIERSCOMMON STRUCTURAL RULES FOR BULK CARRIERS − BACKGROUND DOCUMENT
PAGE 3 – CHAPTER 6: HULL SCANTLINGSTABLE OF CONTENTS:
SECTION 1 – PLATING...................................................................................................................... 5
1.

GENERAL.................................................................................................................................... 5
1.1
1.2
1.3
1.4
1.5

2.

GENERAL REQUIREMENTS ..................................................................................................... 5
2.1
2.2
2.3
2.4
2.5
2.6
2.7

3.

Application.............................................................................................................................. 5
Net thicknesses........................................................................................................................ 5
Pressure combination scantlings ............................................................................................. 5
Elementary plate panel............................................................................................................ 5
Load calculation point............................................................................................................. 5
Corrugated bulkhead .............................................................................................................. 5
Minimum net thicknesses........................................................................................................ 6
Bilge plating ............................................................................................................................ 6
Keel plating ............................................................................................................................. 6
Sheerstrake .............................................................................................................................. 6
Stringer plate ........................................................................................................................... 7
Inner bottom loaded by steel coils on a wooden support ....................................................... 7

STRENGTH CHECK OF PLATING SUBJECTED TO LATERAL PRESSURE .......................... 7
3.1
3.2

Load model ............................................................................................................................. 7
Plating thickness...................................................................................................................... 8

SECTION 2 – ORDINARY STIFFENERS ........................................................................................... 91.

GENERAL.................................................................................................................................... 9
1.1
1.2
1.3
1.4

2.

GENERAL REQUIREMENTS ..................................................................................................... 9
2.1
2.2
2.3
2.4
2.5
2.6
boat

3.

Application.............................................................................................................................. 9
Net scantlings .......................................................................................................................... 9
Pressure combination scantlings ............................................................................................. 9
Load calculation point............................................................................................................. 9
Corrugated bulkhead .............................................................................................................. 9
Minimum net thicknesses of webs of ordinary stiffeners........................................................ 9
Net dimensions of ordinary stiffeners................................................................................... 10
Struts connecting ordinary stiffeners .................................................................................... 10
Ordinary stiffeners of inner bottom loaded by steel coils on a wooden support .................. 10
Deck ordinary stiffeners in way of launching appliances used for survival craft or rescue
11

YIELDING CHECK ................................................................................................................... 11
3.1
Load model ........................................................................................................................... 11
3.2
Strength criteria for single span ordinary stiffeners other than side frames of single side bulk
carriers............................................................................................................................................... 12
3.3
Strength criteria for side frames of single side bulk carriers ................................................. 12
3.4
Upper and lower connections of side frames of single side bulk carriers ............................. 16
3.5
Strength criteria for multi-span ordinary stiffeners .............................................................. 18

4.

WEB STIFFENERS OF PRIMARY SUPPORTING MEMBERS ................................................ 18
4.1

Net scantlings ........................................................................................................................ 18

SECTION 3 – BUCKLING & ULTIMATE STRENGTH OF STIFFENERS AND STIFFENEDPANELS ............................................................................................................................................. 20
1.

GENERAL.................................................................................................................................. 20
1.1 ...................................................................................................................................................... 20

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PAGE 4 – CHAPTER 6: HULL SCANTLINGS2.

APPLICATION .......................................................................................................................... 21
2.1
2.2

3.

BUCKLING CRITERIA OF ELEMENTARY PLATE PANELS ................................................. 21
3.1
3.2
3.3

4.

Plates...................................................................................................................................... 21
Verification of elementary plate panel within FEM analysis................................................. 22
Webs and Flanges .................................................................................................................. 26

BUCKLING CRITERIA OF PARTIAL AND TOTAL PANELS ................................................ 26
4.1
4.2
4.3

5.

Load model for hull transverse section analysis.................................................................... 21
Application ............................................................................................................................ 21

Longitudinal and transverse stiffeners .................................................................................. 26
Ultimate strength in lateral buckling mode........................................................................... 26
Torsional buckling ................................................................................................................. 28

EFFECTIVE WIDTH OF ATTACHED PLATING..................................................................... 28
5.1
5.2

Ordinary stiffeners ................................................................................................................ 28
Primary supporting members ............................................................................................... 29

6. TRANSVERSE VERTICALLY CORRUGATED WATERTIGHT BULKHEAD IN FLOODEDCONDITIONS................................................................................................................................... 29
6.1

General .................................................................................................................................. 29

SECTION 4 – PRIMARY SUPPORTING MEMBERS....................................................................... 30
1.

GENERAL.................................................................................................................................. 30
1.1
1.2
1.3
1.4
1.5

Application ............................................................................................................................ 30
Primary supporting members for ships less than 150 m in length (L)................................... 30
Primary supporting members for ships of 150 m or more in length (L)................................ 30
Net scantlings ........................................................................................................................ 30
Minimum net thickness of webs of primary supporting members ....................................... 30

2. SCANTLING OF PRIMARY SUPPORTING MEMBERS FOR SHIPS OF LESS THAN 150 M
IN LENGTH (L) ................................................................................................................................. 31
2.1
2.2
2.3
2.4
2.5
2.6

Load model............................................................................................................................ 31
Center girders and side girders ............................................................................................. 31
Floors ..................................................................................................................................... 31
Stringer of double side structure ........................................................................................... 31
Transverse web in double side structure............................................................................... 31
Primary supporting member in bilge hopper tanks and topside tanks and other structures 31

3. ADDITIONAL REQUIREMENTS FOR PRIMARY SUPPORTING MEMBERS OF BC-A AND
BC-B SHIPS ....................................................................................................................................... 32
3.1
4.

Evaluation of double bottom capacity and allowable hold loading in flooded conditions... 32

PILLARS .................................................................................................................................... 32
4.1

Buckling of pillars subjected to compressive axial load ........................................................ 32

APPENDIX 1 – BUCKLING & ULTIMATE STRENGTH................................................................. 33

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PAGE 5 – CHAPTER 6: HULL SCANTLINGSSECTION 1 – PLATING
1. GENERAL
1.1

Application

1.1.1
1.1.1.a

1.2

This Section applies for the strength check of plating subjected to lateral pressure
and, for plating contributing to the longitudinal strength, to in-plane hull girder
normal stress.

Net thicknesses

1.2.1
1.2.1.aThis requirement specifies that all thicknesses are determined in net value, andspecify how to obtain the gross thickness.

1.2.2
1.2.2.a

The applicability of net scantling approach to platings is specified.

1.3

Pressure combination scantlings

1.3.1

Elements of the outer shell

1.3.1.a

The way to combine the loads to be considered is specified.

1.3.2

Elements other than those of the outer shell

1.3.2.a

The way to combine the loads to be considered is specified.

1.4

Elementary plate panel

1.4.1
1.4.1.a

1.5

The definition of what is an Elementary Plate Panel is indicated.

Load calculation point

1.5.1
1.5.1.aThe determination of the point at which pressures and stresses are calculated isspecified, depending on the type of framing.

2. GENERAL REQUIREMENTS
2.1

Corrugated bulkhead

2.1.1
2.1.1.a

The parameters for the determination of the thickness of a corrugated bulkhead as
Elementary Plate Panel are specified.
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PAGE 6 – CHAPTER 6: HULL SCANTLINGS

2.2

Minimum net thicknesses

2.2.1
2.2.1.a

2.3

This requirement specifies minimum net thickness, adapted from BV Rules for Steel
Ships (Ch 7, Sec 1).

Bilge plating

2.3.1
2.3.1.aThis requirement is based on 2.3.1 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.3.2
2.3.2.aThis requirement is based on 2.3.2 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.3.3
2.3.3.a

2.4

This requirement is based on 2.3.3 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

Keel plating

2.4.1
2.4.1.aThis requirement specifies the thickness of the keel in respect to the thickness of theadjacent bottom plating.

2.5

Sheerstrake

2.5.1

Welded sheerstrake

2.5.1.aThis requirement is based on 2.5.1 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.5.2

Rounded sheerstrake

2.5.2.aThis requirement is based on 2.5.2 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.5.3

Net thickness of the sheerstrake in way of breaks of long superstructures

2.5.3.aThis requirement is based on 2.5.3 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.5.4

Net thickness of the sheerstrake in way of breaks of short superstructures

2.5.4.aThis requirement is based on 2.5.4 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

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PAGE 7 – CHAPTER 6: HULL SCANTLINGS

2.6

Stringer plate

2.6.1

General2.6.1.aThis requirement is based on 2.6.1 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.6.2

Net thickness of the stringer plate in way of breaks of long superstructures

2.6.2.aThis requirement is based on 2.6.2 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.6.3

Net thickness of the stringer plate in way of breaks of short superstructures

2.6.3.aThis requirement is based on 2.6.3 of Part B, Chapter 7, Section 1 of BV Rules for
Steel Ships.

2.7

Inner bottom loaded by steel coils on a wooden support

2.7.1

General2.7.1.aThis requirement is based on NK Rules.

2.7.2

Inner bottom plating

2.7.2.aThis requirement is based on NK Rules.

2.7.3

Hopper sloping plate and inner hull plating

2.7.3.aThis requirement is based on NK Rules.

2.7.4
2.7.4.aThis requirement is based on NK Rules.

3. STRENGTH CHECK OF PLATING SUBJECTED TO LATERAL PRESSURE
3.1

Load model

3.1.1

General3.1.1.a

The loads to be considered are specified in 3.1.2 to 3.1.4. The basic concepts
considered related to loads are static loads and wave loads corresponding to 8 loadcases, induced by the sea and various type of cargoes. The loads in flooded (i.e.
damaged) condition and testing condition are also considered.

3.1.2

Lateral pressure in intact conditions

3.1.2.a

The lateral pressures (i.e. the local pressure applied normally to the plating) in intact
condition are specified. They are static and wave loads, induced by the sea or by thevarious type of cargoes.

3.1.3

Lateral pressure in flooded conditions

3.1.3.a

The lateral pressure in the specific case of flooded condition is specified and refers
to Ch 4, Sec 6.
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PAGE 8 – CHAPTER 6: HULL SCANTLINGS

3.1.4

Lateral pressure in testing conditions

3.1.4.a

The lateral pressure in testing condition are specified and refers to Ch 4, Sec 6. The
draught T1 at which the testing is carried out may be taken into account, if known.
These lateral pressures apply to the platings subjected to testing, as defined in Ch 11,
Sec 3.

3.1.5

Normal stresses

3.1.5.aThis requirement specifies the normal stress to be considered for the strength checkof plating contributing to the hull girder longitudinal strength. It is defined for the 8load cases, and is taken as the maximum value between sagging and hogging
conditions.

3.2

Plating thickness

3.2.1

Intact conditions

3.2.1.aThis requirement specifies the thickness required under intact condition. It is to be
noted that the formula is in line with CSR for Oil Tankers.

3.2.2

Net thickness under flooded conditions excluding corrugations oftransverse vertically corrugated bulkhead separating cargo holds

3.2.2.aThis requirement specifies the thickness required under flooded condition for
plating which constitutes the boundary of compartments not intended to carryliquids (excluding bottom plating and side shell plating), and excluding
corrugations of transverse vertically corrugated bulkhead separating cargo holds,
which is covered under 3.2.3.

3.2.3

Net thickness of the corrugations of transverse vertically corrugatedwatertight bulkheads separating cargo holds for flooded conditions

3.2.3.aThis requirement specifies the thickness required under flooded condition for
plating of transverse vertically corrugated watertight bulkheads separating cargoholds. This regulation is in accordance with IACS UR S18 (S18.4.7).

3.2.4

Testing conditions

3.2.4.aThis requirement specifies the thickness required under testing condition for
platings subjected to testing.

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PAGE 9 – CHAPTER 6: HULL SCANTLINGSSECTION 2 – ORDINARY STIFFENERS
1. GENERAL
1.1

Application

1.1.1
1.1.1.a

1.2

This Section applies for the yielding check of ordinary stiffeners subjected to lateralpressure and, for ordinary stiffeners contributing to the hull girder longitudinalstrength, to hull girder normal stresses.

Net scantlings

1.2.1
1.2.1.a

The applicability of net scantling approach to ordinary stiffeners is specified.

1.3

Pressure combination scantlings

1.3.1

Elements of the outer shell

1.3.1.a

The way to combine the loads to be considered is specified.

1.3.2

Elements other than those of the outer shell

1.3.2.a

The way to combine the loads to be considered is specified.

1.4

Load calculation point

1.4.1

Horizontal stiffeners

1.4.1.aThe determination of the point at which pressures and stresses are calculated, incase of horizontal stiffeners, is specified.

1.4.2

Vertical stiffeners

1.4.2.aThe determination of the point at which pressures and stresses are calculated, incase of vertical stiffeners, is specified.

2. GENERAL REQUIREMENTS
2.1

Corrugated bulkhead

2.1.1
2.1.1.a

The parameters for the determination of the section modulus of corrugation of acorrugated bulkhead, if any, are specified.

2.2

Minimum net thicknesses of webs of ordinary stiffeners

2.2.1

Ordinary stiffeners other than side frames of single side bulk carriers

2.2.1.aThis requirement specifies minimum net thickness of web, based on the ones
indicated in CSR for Oil Tankers. In addition, some ratio between web thickness of
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PAGE 10 – CHAPTER 6: HULL SCANTLINGS

ordinary stiffener and thickness of attached plating is specified to allow an easy
weldability.

2.2.2

Side frames of single side bulk carriers

2.2.2.aThis requirement is based on requirement S12.5 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003.

2.3

Net dimensions of ordinary stiffeners

2.3.1

Flat bar

2.3.1.aThis requirement covers a buckling check of a flat bar. It is based on 1.4.1 of Part B,
Chapter 7, Section 2 of BV Rules for Steel Ships.

2.3.2

T-section

2.3.2.aThis requirement covers a buckling check of a T-section. It is based on 1.4.2 of Part B,
Chapter 7, Section 2 of BV Rules for Steel Ships.

2.3.3

Angle

2.3.3.aThis requirement covers a buckling check of an angle profile. It is based on 1.4.3 ofPart B, Chapter 7, Section 2 of BV Rules for Steel Ships.

2.4

Struts connecting ordinary stiffeners

2.4.1
2.4.1.aThis requirement applies to the scantlings of struts , as defined in Ch 3, Sec 6, [4.2.3].
It is based on 2.3.1 of Part B, Chapter 7, Section 2 of BV Rules for Steel Ships.

2.5

Ordinary stiffeners of inner bottom loaded by steel coils on a wooden
support2.5.1

General2.5.1.aThis requirement is based on NK Rules.

2.5.2

Ordinary stiffeners located on inner bottom plating

2.5.2.aThis requirement is based on NK Rules.

2.5.3

Ordinary stiffeners located on hopper sloping plate or inner hull plating

2.5.3.aThis requirement is based on NK Rules.

2.5.4
2.5.4.aThis requirement is based on NK Rules.

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PAGE 11 – CHAPTER 6: HULL SCANTLINGS

2.6

Deck ordinary stiffeners in way of launching appliances used for survival
craft or rescue boat

2.6.1
2.6.1.aThis requirement is based on 2.3.1 of Part B, Chapter 7, Section 2 of BV Rules for
Steel Ships.

2.6.2
2.6.2.aThis requirement is based on 2.3.2 of Part B, Chapter 7, Section 2 of BV Rules for
Steel Ships.

2.6.3
2.6.3.aThis requirement is based on 2.3.3 of Part B, Chapter 7, Section 2 of BV Rules for
Steel Ships.

3. YIELDING CHECK
3.1

Load model

3.1.1

General3.1.1.a

The loads to be considered are specified in 3.1.2 to 3.1.4. The basic concepts
considered related to loads are static loads and wave loads corresponding to 8 loadcases, induced by the sea and various type of cargoes. The loads in flooded (i.e.
damaged) condition and testing condition are also considered.

3.1.2

Lateral pressure in intact conditions

3.1.2.a

The lateral pressures (i.e. the local pressure applied normally to the attachedplating) in intact condition are specified. They are static and wave loads, induced by
the sea or by the various type of cargoes.

3.1.3

Lateral pressure in flooded conditions

3.1.3.a

The lateral pressure in the specific case of flooded condition is specified and refers
to Ch 4, Sec 6.

3.1.4

Lateral pressure in testing conditions

3.1.4.a

The lateral pressure in testing condition are specified and refers to Ch 4, Sec 6. The
draught T1 at which the testing is carried out may be taken into account, if known.
These lateral pressures apply to the ordinary stiffeners subjected to testing, as
defined in Ch 11, Sec 3.

3.1.5

Normal stresses

3.1.5.aThis requirement specifies the normal stress to be considered for the strength checkof ordinary stiffeners contributing to the hull girder longitudinal strength. It isdefined for the 8 load cases, and is taken as the maximum value between sagging
and hogging conditions.

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3.2

Strength criteria for single span ordinary stiffeners other than side frames ofsingle side bulk carriers

3.2.1

Boundary conditions

3.2.1.aThe scantlings of ordinary stiffeners in 3.2 to 3.5 are indicated for ordinary stiffeners
considered as being clamped at both ends, except otherwise specified. The yielding
check for other boundary conditions is not covered.

3.2.2

Groups of equal ordinary stiffeners

3.2.2.aThis requirement indicates a practical criteria to check scantlings of ordinary
stiffeners gathered in group having the same actual scantlings.

3.2.3

Net section modulus and net shear sectional area of single span ordinary
stiffeners under intact conditions

3.2.3.aThis requirement indicates section modulus and shear area of ordinary stiffeners
and it is based on elastic design under lateral pressures in intact conditions.

3.2.4

Net section modulus of corrugated bulkhead of ballast hold for ships
having a length less than 150m

3.2.4.aThis requirement applies to corrugated bulkhead of ballast hold for ships having alength less than 150m. It indicates the section modulus of corrugation and it is basedon NK Rules.

3.2.5

Net section modulus and net shear sectional area of single span ordinary
stiffeners under flooded conditions excluding corrugations of transverse
vertically corrugated bulkhead separating cargo holds

3.2.5.aThis requirement indicates section modulus and shear area of ordinary stiffeners
and it is based on elastic design under lateral pressures in flooded conditions.

3.2.6

Bending capacity and shear capacity of the corrugations of transverse
vertically corrugated watertight bulkheads separating cargo holds forflooded conditions

3.2.6.aThis requirement specifies the bending capacity and the shear capacity ofcorrugations of transverse vertically corrugated watertight bulkheads separatingcargo holds under flooded conditions. This requirement is in accordance with IACS
UR S18 (S18.4.2).

3.2.7

Net section modulus and net shear sectional area of single span ordinary
stiffeners under testing conditions

3.2.7.aThis requirement indicates section modulus and shear area of ordinary stiffeners
and it is based on elastic design under lateral pressures in testing conditions.

3.3

Strength criteria for side frames of single side bulk carriers

3.3.1

Net section modulus and net shear sectional area of side frames

3.3.1.aThis requirement is based on requirement S12.4.1 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003.
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PAGE 13 – CHAPTER 6: HULL SCANTLINGSThis draft text consider the net section modulus and the minimum net web
thickness under the following forms:
Net section modulus : Z = C 3

Net web thickness : t w =m m Pframe h
σF1000 Cs Pframe h − 2h B⋅
d b sin φ τahThese formulae have been then expressed in terms of symbols specific to CSR for
bulk carriers:(pS + p W )sl 2 103



Net section modulus : w = 1.125α mNet shear sectional area : A sh = 1.1αSmλ S R Y

5(pS + p W )sl ⎛ l − 2l B ⎞⎜⎟τ a sin φ ⎝l ⎠The technical background is given below:
The shear force at the lower end of the side frame span is obtained, by assumingthat the sum of the still water and wave pressures is uniform along the span. It isalso assumed that the percentage of total lateral force on the frame that is carried by
the lower end support is equal to:60%, in general,

66%, for the side frames of holds specified to be empty in ships assignedwith the BC-A notation, as defined in UR S25. This greater value is due tothe effect of the hopper tank rotation induced by the sea pressure on the
double bottom, not counterbalanced by any internal cargo (see below).

The shear force at section b) is assumed to be equal to that at section a) multiplied
by a factor. The factor is equal to the frame span “h” minus twice the length of thelower bracket divided by “h” (it is assumed here that the upper and the lower
brackets have the same length).
The minimum net web thickness of the side frame is evaluated at the section b),
considering the angle of the inclination of the web to the shell plating.
The bending moment acting on the side frame is obtained by multiplying the totallateral force on the frame by the frame span and by coefficients “mm”, that gives
the factor of the maximum bending moment along the side frame span.
The “mm” values depend on the loading condition of the hold to which the frame
under consideration belongs. Finite element calculations have shown that the
maximum bending moment for the side frames of ore holds is at the mid-span; forempty holds the maximum bending moment is at the lower end.
On the basis of finite element calculations, “mm” values are assumed to be 70 for
BC-A ships, as defined in UR S25, and 60 for other cases; the value of 70 for the
loaded holds of BC-A ships is equivalent to the bending moment of the frame
assumed simply supported inside the brackets.
For the empty holds of BC-A ships, an higher values of the coefficient “mm” hasbeen included considering that in non-homogeneous loading conditions (i.e. at the
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PAGE 14 – CHAPTER 6: HULL SCANTLINGS

maximum draft) the sea pressure acting on the double bottom is notcounterbalanced by internal cargo. This induces significant rotation of the hoppertanks and hence of the side frame lower ends, that increases the bending moment at
the lower end.
The required net section modulus of the side frame is evaluated in the elastic
domain; a reduction of 20 per cent, incorporated using coefficient C3 equal to 0,83,
was included in the formula for the required modulus to permit some plastic
behaviour under extreme loads.

3.3.2

Supplementary strength requirements

3.3.2.aThis requirement is based on requirement S12.4.2 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003,as follows:
Service record of bulk carriers and other type of ships reports that vertical crack
occurs on side shell plating along the line of collision bulkhead. In case wherebrackets are fitted on side shell between collision bulkhead and a hold frame abaft
the bulkhead, those brackets crack or side shell plating cracks along the hold frame
abaft the brackets fitted.
It is considered that deformation of hold frame due to repeated wave load induces
bending of side shell plating between collision bulkhead and the hold frame
thereafter and this bending of side shell plating induces fatigue crack on side shell
plating along the line of collision bulkhead. Cracks of brackets or of side shell
plating abaft brackets are considered to occur for the same reason.
A formula to require a moment of inertia of hold frame is specified to control thedeformation of the frame within 3/1000*(frame space) at its mid span where a sea
pressure force, Pframe, acts on the side shell plating.

3.3.3

Lower bracket of side frame

3.3.3.aThis requirement is based on requirements S12.6 and S12.8 of the draft text of IACS
UR S12 Rev.4 agreed at the WP/S meeting of 8-10 April 2003,as follows:First, the relevant requirements in UR S12 Rev. 3 have been written in terms of the
net scantlings, considering a corrosion of 25 %. This corrosion is consistent with thecorrosion additions considered for the frame webs.
Secondly, limit values for the web depth to thickness ratio are introduced for lower
brackets, in addition to those already specified in UR S12 Rev.3, which are valid forthe side frames.
The limits for the web depth to thickness ratio of lower brackets take into accountthat, in order to comply with the requirements for the section modulus of thebrackets in S12.6, the web depth increases more in the lower bracket than the shear
force, with respect to the corresponding value at the top of the lower bracket. As aconsequence, the shear stresses in the lower bracket are lower than in the span (thehighest shear stress values occur at the top of the lower bracket).
When calculating the web depth to the thickness ratio, the web depth of the lower
bracket may be measured from the intersection between the sloped bulkhead of thehopper tank and the side shell plate, perpendicularly to the face plate of the lower
bracket.
COMMON STRUCTURAL RULES FOR BULK CARRIERSCOMMON STRUCTURAL RULES FOR BULK CARRIERS − BACKGROUND DOCUMENT
PAGE 15 – CHAPTER 6: HULL SCANTLINGS

The thickness td/t, which satisfies the web dept to thickness ratio, can be reduced to3

t’d/t =

t d / t 2 t w for the frames immediately abaft the collision bulkheads, which

are often oversized for the purpose of providing a smooth stiffness transition
between the fore peak structure and the hold side structures. For these frames,
when the required minimum net web thickness tW is such that the side frame web
works in the elastic domain, the formula for t’d/t accounts for the fact that theworking shear stress is lower than the admissible one.
The formula for t’d/t is derived as reported in the following:
The relationship between critical shear stresses and the web plate thickness is givenby the formula (1)
2

π2 E

⎛t⎞
τ cr = K= Sf τ a2 ⎜b⎟12(1 − υ ) ⎝ ⎠(1)

where:t=
td/t, web thickness satisfying the required shear buckling criteria
corresponding to the assumed allowable shear stress τa with safety factor.
τa=allowable shear stress (= 0,5 σy )Sf=safety factor

In case where working shear stress τwork is less than the allowable shear stress τa thecorresponding critical shear stress τcr', while maintaining the same safety factor, isgiven by2

π2 E

⎛ t'd / t ⎞τ cr ' = K= Sf τ work
2 ⎜ b ⎟
12(1 − υ ) ⎝⎠(2)

where, t’d/t is the web plate thickness giving the critical shear stress τcr'
On the other hand, the working shear stresses τwork is given by formula (3)twτat' d / tτ work =(3)

where, tW is as given in S12.4.1 or in S12.5, whichever is the greater.
The following equation is obtained by substituting τwork in formula (2) by that offormula (3):

K

2

π2 E

t
t
⎛ t'd / t ⎞= Sf w τ a = Sf τ a w
2 ⎜ b ⎟
t'd / tt'd / t12(1 − υ ) ⎝⎠(4)

Combining equations (1) and (4) give the following relationship between td/t andt’d/t:
2t ⎛t ⎞⎛ t'd / t ⎞⎜⎟ = w ⎜ d/t ⎟t'd / t ⎝ b ⎠
⎝ b ⎠

2

(5)

Equation (5) gives t’d/t as follows:

t'd / t =3

t d2 / t t w(6)

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PAGE 16 – CHAPTER 6: HULL SCANTLINGS

t’d/t given by the formula (6) gives the web thickness for side frames and lower
brackets satisfying the shear buckling criteria corresponding to the working shear
stresses, where td/t is greater than tw.
The formula for t’d/t is based on the formulation of the elastic shear buckling stress,
1⋅ σ F , that is 0,29 of the material
which is valid for shear stress lower than2⋅ 3
yielding. As tW is based on the admissible shear stress equal to 0,5 of the material
yielding, when the thickness td/t is greater than 0,5/0,29 of tW, that is 1,73 tw, the side
frame web works in the elastic domain and t’d/t will be obtained by the following
formula:t’d/t =

3

td / t2t w

Furthermore, in the requirements for asymmetrically flanged frames the higher
strength steel k factor has been removed, as the same UR S12 allows such frames tobe adopted only if made in normal strength steel.

3.3.4

Upper bracket of side frame

3.3.4.aThis requirement is based on requirements S12.6 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003: the relevant requirements in
UR S12 Rev. 3 have been written in terms of the net scantlings, considering a
corrosion of 25 %. This corrosion is consistent with the corrosion additions
considered for the frame webs.

3.4

Upper and lower connections of side frames of single side bulk carriers

3.4.1
3.4.1.aThis requirement is based on requirements S12.7 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003.
This draft text consider the relation ship between net section modulus and distances
under the following form:∑ (Zi ⋅ a i ) ≥n1000 C t Pframe h l 2l
16 s σ FThis formula have been then expressed in terms of symbols specific to CSR for bulk
carriers:
∑nw i d i ≥ αT

(pS + p W )l 2 l 12
16R Y

The technical background is given below:
The section modulus of the longitudinals is required to have sufficient bending
strength to support the end fixing moment of the side frame about the intersection
point of the sloping bulkhead and the side shell.

COMMON STRUCTURAL RULES FOR BULK CARRIERSCOMMON STRUCTURAL RULES FOR BULK CARRIERS − BACKGROUND DOCUMENT
PAGE 17 – CHAPTER 6: HULL SCANTLINGSThe end fixing moment of the side frame is that induced by the external sea
pressure acting on the side frame (end brackets excluded) and the deflection androtation of the end support due to the loading on the hopper and the double bottom.
The sea pressure loading on the end brackets is not included because the sea
pressure loading on this and on the connecting structure of the hopper and topsidetank are assumed to cancel.
The end fixing moment, Mef, in Nm, of the side frame about the intersection point of
the sloping bulkhead and the side shell in Nm is given as:

M ef = 1000 ⋅ Pframe ⋅ h ⋅ C m + h B ⋅ 1000⋅ Pframe ⋅ Cs ⋅h − 2h B
hwhere:
Cm is the bending moment coefficient at the lower end or at the upper end of theside frame;
Cs is the fraction of the total sea pressure force, which is carried by the lower end or
the upper end of the side frame.
The end fixing moment, Mef, gives rise to the line loads, qef, in N/m, on thelongitudinals of the side shell and sloping bulkhead, that support the lower andupper connecting brackets, given as:

q ef =

M ef
1000 Pframe h ⎛h h − 2h B⎞
Cs ⎟=⎜ Cm + B ⋅
s a
s a
h
h
⎠
⎝

The line load, qef, gives rise to the plastic bending moments, Mc, in Nm, in thelongitudinals, that support the lower and upper connecting brackets, given as:

Mc =q ef l 2l1000 Pframe h l 2l ⎛h h − 2h B⎞=
Cs ⎟⎜ Cm + B ⋅16
16 s ahh⎝⎠Hence, assuming an allowable stress equal to yield, the section modulus
requirement for a connected side or sloping bulkhead longitudinal in cm3 becomes:

Z =Mc
1000 Pframe h l 2l ⎛h h − 2h B⎞
Cs ⎟=⎜ Cm + B ⋅16 s a σ F ⎝
h
h
σF
⎠

The above expression assumes a single connected longitudinal. For more than one
connected longitudinal, the plastic bending moment Mc is to be supported by thesum of the connected longitudinals and the requirement becomes:∑ (Zi ⋅ a i ) =n1000 Pframe h l 2l ⎛h h − 2h B⎞
Cs ⎟⎜ Cm + B ⋅16 s σ Fhh⎝⎠h h − 2h B⎛⎞
The above expression, assuming CT = ⎜ C m + B ⋅Cs ⎟ , becomes:hh⎝⎠∑ (Zi ⋅ a i ) =n1000 Pframe h l 2l
CT
16 s σ F

On the basis of the finite element calculations, Cm is assumed equal to 0,07 for the
lower end and 0,02 for the upper end.

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PAGE 18 – CHAPTER 6: HULL SCANTLINGS

For a lower bracket length of 0,125 the side frame span, considering the value for CS
h h − 2h B
equal to 0,66, as defined in S12.4.1, the term B ⋅Cs is, conservativelyhhassumed equal to 0,08 for the lower brackets; hence CT is assumed equal to 0,15 forthe longitudinal stiffeners supporting the lower connecting brackets.
Assuming that the shear force supported by the upper end is 2/3 of that supported
h h − 2h B
Cs is, conservatively equal to 0,05 for theby the lower end, the term B ⋅hhupper brackets, hence CT is assumed equal to 0,075 for the longitudinal stiffeners
supporting the upper connecting brackets.

3.4.2
3.4.2.aThis requirement is based on requirements S12.7 of the draft text of IACS UR S12
Rev.4 agreed at the WP/S meeting of 8-10 April 2003: this draft text consider aspecified requirement to ensure that the brackets have a sufficient net connection
area to the longitudinals supporting the brackets. This net connection area Ai of thebracket to the i-th longitudinal stiffener supporting the bracket is given under thefollowing form:Ai = 0,4 Zi s kbkt/(li2 klong,i)This formula have been then expressed in terms of symbols specific to CSR for bulk
carriers:

A i = 0.4

w i s k bkt
l 2i k lg, i

3.5Strength criteria for multi-span ordinary stiffeners

3.5.1

Checking criteria

3.5.1.aThis requirement indicates the admissible normal and shear stresses to consider inintact, flooded or testing condition for the check of stresses in a multi-span ordinary
stiffener.

3.5.2

Multi-span ordinary stiffeners

3.5.2.aThis requirement specifies the parameters to take into account for the determinationof normal and shear stresses in a multi-span ordinary stiffener.

4. WEB STIFFENERS OF PRIMARY SUPPORTING MEMBERS
4.1

Net scantlings

4.1.1
4.1.1.aThis requirement is based on 4.7.2 of Part B, Chapter 4, Section 3 of BV Rules for
Steel Ships.

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PAGE 19 – CHAPTER 6: HULL SCANTLINGS

4.1.2
4.1.2.aThis requirement is based on 4.7.3 of Part B, Chapter 4, Section 3 of BV Rules for
Steel Ships.

4.1.3

Connection ends of web stiffeners

4.1.3.aThis requirement is based on NK Rules.

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PAGE 20 – CHAPTER 6: HULL SCANTLINGSSECTION 3 – BUCKLING & ULTIMATE STRENGTH OF
STIFFENERS AND STIFFENED PANELS
1. GENERAL
1.1
1.1.1
1.1.1.a

The buckling strength requirements are based on the DIN-standard 18800,“Structural steelwork, Part 1 to 4” [DIN] amended in 1990 which is based on theultimate strength concept. Part 2 contains “Analysis of safety against buckling of
linear members and frames” and Part 3 “Analysis of safety against buckling ofplates”. Comments are given in “Beuth – Kommentare Stahlbauten, 1. Auflage 1993,
J. Lindner, J. Scheer, H. Schmidt“ [LIN]. The calculation procedures are based on
experimental and analytical buckling and ultimate strength data.
In order to improve the practical application the calculation procedure has been
simplified in some areas and has been adapted to specific conditions of hull
structures of ships as described in “Background Information for Users of the New
Requirements of Germanischer Lloyd for Proof of Buckling Strength, 1997” [BCK].
The main difference of the CSR-Buckling procedure to the procedure used atGermanischer Lloyd is the net thickness concept. Therefore the following
adjustments were necessary:•

Adjustment of safety factors•

Change of formula for degree of fixation of torsional buckling check

The buckling check is valid for structures which comply with IACS Rec. 47 [I47] orrecognized national shipbuilding quality standards.
To afford a complete overview about the background of the buckling and ultimate
strength concept used in CSR for Bulk Carriers, reference is made to the following
literature:[DIN]DIN 18800, “Structural steelwork”, Part 1 to 4, Beuth Verlag, Berlin, 1993
[LIN] J. Lindner, J. Scheer, H. Schmidt, „Beuth – Kommentare Stahlbauten“, 1993
[BCK]M. Böckenhauer, H.-J. Schulte, “Background Information for Users of the
New Requirements of Germanischer Lloyd for Proof of Buckling Strength”,
Germanischer Lloyd, Hamburg, 1997
[BLE] Bleich, “Buckling strength of metal structures”, Mc Graw-Hill Book Complex,
New York, Toronto, London, 1952
[I47] IACS Recommendation No.47 “Shipbuilding and Repair Quality Standard”,
2006

1.1.2
1.1.2.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers , is necessary to explain the background.

1.1.3
1.1.3.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers , is necessary to explain the background.
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PAGE 21 – CHAPTER 6: HULL SCANTLINGS

2. APPLICATION
2.1

Load model for hull transverse section analysis

2.1.1

General2.1.1.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers , is necessary to explain the background.

2.1.2

Normal stress σn2.1.2.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers , is necessary to explain the background.

2.1.3

Shear stress2.1.3.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers , is necessary to explain the background.

2.1.4

Lateral pressure

2.1.4.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

2.2

Application

2.2.1
2.2.1.a

The application of the buckling and ultimate strength criterion is described in App1of Ch06 Sec03 of the CSR for Bulk Carriers.

3. BUCKLING CRITERIA OF ELEMENTARY PLATE PANELS
3.1

Plates3.1.1

General3.1.1.aTaking into account that the maximum values of the normal stresses resulting fromglobal bending of the hull and the maximum value of shear stress resulting fromhull girder shear forces are not acting simultaneously a stress combination isdefined.

3.1.1.b

The ratio between normal and shear stress is based on GL-Rules and the long-term
experience of Germanischer Lloyd applying the buckling assessment.

3.1.2

Verification of elementary plate panel in a transverse section analysis

3.1.2.a

The verification criteria given in this section are a simplification of the generalcriterion (interaction formulation) given in [3.2.4] taking into account normal
stresses in ships longitudinal direction and shear stresses. The criteria areformulated with respect to framing system (longitudinally or transverse framed
plating). For the determination of e3, κy is to be taken equal to 1 in case of
longitudinally stiffened plating and κX is to be taken equal to 1 in case oftransversely stiffened plating.

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PAGE 22 – CHAPTER 6: HULL SCANTLINGS

3.2

Verification of elementary plate panel within FEM analysis

3.2.1

General3.2.1.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

3.2.2

Stresses

3.2.2.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

3.2.3

Poisson effect3.2.3.a

The membrane stresses σx and σy are either resulting from a calculation based on
simple beam theory or from a FE analysis. In the latter case, the stress share due tothe suppression of transverse contraction (Poisson-effect) is already included in the
result, while this is not the case for the simple beam theory. In order to bring theresults to a comparable level, the FE stresses are to be transformed to beam stresses
as described in the rules. The stress correction has to be carried out after thesummation of stresses due to global and local loads. Furthermore both of the stresscomponents (longitudinal and transverse) are to be compressive stresses. Reference
is made to [BCK].

3.2.3.b Results obtained with the CSR buckling strength checks are based on stresses
resulting from calculations using simple beam theory (e.g. conventional longitudinalstrength calculations). If the results are instead to be based on stresses resulting froma finite element calculation, then the stress share due to the Poisson effect is alreadyincluded in the result. This is not the case if the simple beam method is applied. Inorder to bring the results of both calculation procedures to a comparable level, thestresses obtained from a calculation procedure which already incorporates the
Poisson effect may be reduced. One reason for this procedure is that the load carrying
capacity of a plate field with the Poisson effect (longitudinal edges non-displaceable
in the plate level) is at least equal or greater than the capacity of a plate field withlongitudinal edges which can freely move. Shear stresses have no effect on the
reduction of the finite element stresses, but they must of course be included in thesubsequent buckling strength assessment.
It should be noted that the stress reduction is a ‘may’ condition, i.e. it should not beapplied when the smaller compressive stress is less than 0.3 times the larger since anunrestrained elongation at the unloaded plate edge does not produce a stress acting in
the direction of the loaded plate edge. Accordingly, if both σx* and σy* arecompressive stresses, then the reduced stresses σx and σy as input data for a bucklingstrength calculation are derived as follows:σ x * = σ x + νσ y→

σ x = σ x * −νσ y

→

σx =

σ x * −νσ y *1 −ν 2where σy* ≥ 0.3 σx*. If σy* < 0.3 σx*, then σy = 0 and σx = σx*.
and

COMMON STRUCTURAL RULES FOR BULK CARRIERS(Eq. 1)

COMMON STRUCTURAL RULES FOR BULK CARRIERS − BACKGROUND DOCUMENT
PAGE 23 – CHAPTER 6: HULL SCANTLINGS

σ y * = σ y + νσ x→

σ y = σ y * −νσ x

→

σy =

σ y * −νσ x *1 −ν 2(Eq. 2)where σx* ≥ 0.3 σy*. If σx* < 0.3 σy*, then σx = 0 and σy = σy*.
Finally, since it cannot be guaranteed that both stress components are always acting
simultaneously (e.g. if they develop from separate loads), stresses containing the
Poisson effect are not permitted to exceed the ultimate strength of the plate under auniaxial stress (i.e. σx* ≤ κx ReH and σy* ≤ κy ReH).

yb =875mm

3.2.3.c Example: Elementary plate panel (EPP) with uniform stresses (τ = 0 N/mm²) – Figure1.

t=21.0,t=21.0,t=21.0,t=21.0,a =3680mm
x
Figure 1

Boundary correction factor F1 = 1.00. Load correction factor c1 = (1-F1/α) ≥ 0. Safety
factor S = 1.0.
To illustrate the relationship between stress combinations with and without the
Poisson effect, Figure 2 shows the capacity curve of stress combinations which include
the Poisson effect (upper curve) and the capacity curve of those which exclude it(lower curve - κx = 0.979, κy = 0.462). Stress combinations from the upper curve would
generally come from finite element analyses and the stress combinations from thelower curve would be those used in the buckling strength assessment. As can be seen,
the capacity curve of stress combinations which include the Poisson effect (upper
curve) is divided into four segments. The first segment is that in which σx ≤ 0.3 σy andso σx = 0 and σy = σy*. Similarly, the fourth segment is that in which σy ≤ 0.3 σx and so
σy = 0 and σx = σx*. In the second segment, stresses containing the Poisson effect arelimited by the ultimate strength of the plate under a uniaxial stress in the y-direction(i.e. σy* ≤ κy ReH). Finally, in the third segment the relationship between stresscombinations with and without the Poisson effect are as described in Eq. 1 and Eq. 2.
3.2.3.d In the examples which follow, it is assumed that the stated stresses already include
the foregoing correction for Poisson effect.

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PAGE 24 – CHAPTER 6: HULL SCANTLINGS

200
Including Poisson EffectExcluding Poisson Effect150

0,0; 145,4

43,6; 145,4

223,0; 145,42

σx < 0,3 * σy2σy [N/mm ]

1

3

100

308,3; 92,5
197,1; 86,3

σy < 0,3 * σx50

4308,3; 0,0

0
0

50

100

150

200

250

300

350

2

σx [N/mm ]Figure 2

3.2.4

Checking Criteria

3.2.4.a

The CSR buckling strength checks of elementary plate fields require proof of
sufficient ultimate strength capacity. The checks require proof for membranestresses acting in the x- and y-direction and for shear stresses acting in the x-y plane.
Lateral loads may be neglected in the buckling strength check. The capacity ofelementary plate panels subjected to lateral loads is regulated by separate strength
criteria in other sections of the CSR.
The proof of single plate fields for stresses acting in the x- and y-direction and forshear stresses acting in the xy-plane has to satisfy the following interaction
condition considering the net thickness.
⎛ σx S ⎞⎜⎟⎜ κ x ReH ⎟⎝⎠e1⎛ σy S ⎞⎟+ ⎜⎜⎜ κ y ReH ⎟⎟⎝⎠e2⎛ σ xσ y S 2 ⎞ ⎛ τ S 3 ⎞
⎟+⎜
⎟
− B⎜
⎜ R2
⎟ ⎜ κ τ ReH ⎟
eH
⎠
⎝
⎠ ⎝

e3

≤ 1.0

The symbols in the above condition have the following meaning:

σx, σy=membrane stresses in the x- or y-direction (compression ispositive) [N/mm2]

τ=

shear stress in the x-y plane of the plate field [N/mm2]S=

safety factor

ReH=

minimum yield stress of the material [N/mm2]

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PAGE 25 – CHAPTER 6: HULL SCANTLINGS

κx, κy, κt=

reduction factors which, in principal, depend on the reference
degree of slenderness

e1, e2, e3, B=

functions of the reduction factors κx, κy and κt

3.2.4.b

Each individual term of the above interaction condition shall not be greater than 1,0.
In accordance with DIN 18800 lateral loads are neglected. The strength of plane
plate fields subjected to lateral loads is regulated by other sections of the CSR for
Bulk Carriers.

3.2.4.c

The interaction condition exemplarily is illustrated for a quadratic plate field for
different effective widths of platings.

Interaction condition for• α = 1,0 (quadratic plate field)• S = 1,0
• τ = 0,0
• κx = κy = κ = 1,0; 0,8; 0,6v. Mises ellipse

Figure 3:

Interaction condition of a quadratic plate field for different effective widths

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PAGE 26 – CHAPTER 6: HULL SCANTLINGS

3.2.4.d

For a fully effective width, i.e. a stocky plate with κ=1,0 the interaction condition
results in the von Mises ellipse.

3.2.4.e

For wide plate fields a large part of the plate field behaves like a single beam(column buckling) which reduces the load bearing capacity of the plate field. Thiseffect is included in the formulations for wide plate fields.

3.2.4.f

According to the DIN 18800 the interaction condition applies to single plate fields
and to partial and total plate fields. In the GL-Rules this condition is only used forsingle plate fields.

3.2.4.g

An analysis of the interaction condition indicated that the results in the 2nd and 4th
sector, indicated in Figure 3 (σx or σy is a tension stress), are very conservative. If theinteraction condition of the DIN 18800 should be incorporated into the CSR for Bulk
Carrier in principle and should remain valid in all sectors, only the 3rd term could
be modified. Therefore the κp-values for σx and σy in this term are set to 1.0 for thesectors 2, 3 and 4. This implies that in the CSR for Bulk Carrier the factor B is set to
1.0 in these three sectors.

3.2.4.h

The reference degree of slenderness results from the degree of slenderness of theplate field

λp =πstress λ a = π

λ=

3.3

λp
=
λa

E
K ⋅σ eand from the degree of slenderness related to the yieldE
as follows:
ReH

ReH
,
K ⋅σ eWebs and Flanges

3.3.1
3.3.1.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

4. BUCKLING CRITERIA OF PARTIAL AND TOTAL PANELS
4.1

Longitudinal and transverse stiffeners

4.1.1
4.1.1.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

4.2

Ultimate strength in lateral buckling mode

4.2.1

Checking Criteria

4.2.1.a

In addition to the buckling analysis for single plate fields stiffeners must havesufficient strength against lateral and torsional buckling.

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PAGE 27 – CHAPTER 6: HULL SCANTLINGS

4.2.1.b

Proof of sufficient safety against lateral buckling is made by applying 2nd ordertheory. Thereby the following loads are to be considered:•Compressive stresses in stiffener direction•

Compressive stresses perpendicular to the stiffener direction•

Shear stresses in the plate plane•

External lateral loads•

Calculated loads resulting from pre-deformations are considered in accordancewith the buckling curve b of DIN 18800, Part 2 [DIN]. These are valid, until thestructure complies with IACS Rec. 47 (Shipbuilding and Repair Quality
Standard) or recognized national shipbuilding standards.

4.2.1.c

According to DIN 18800, Part 2 [DIN] it is assumed that the in-plane stresses σx, σyand τxy with regard to the pre-deformation are applied by equivalent lateral loads toobtain correct bending stresses in the stiffener. Here the cross section values of
stiffener with attached plating are determined using the effective width of 2ndorder.

4.2.1.dThe sum of the axial compression stress and the resultant bending stresses of allload components is checked with a required safety factor against yield stress. The
following figure illustrates the procedure.

p=lateral load
σa

σa
w0
w
a

beff.= κx*b

σa +σb
Axial compression stress

ReH

S ≤1

Bending Stress due to• lateral Load
• In-plane loads (σ , σ ,τ)xyFigure 4: Lateral Buckling, check against a required safety factor to yield stress

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PAGE 28 – CHAPTER 6: HULL SCANTLINGS

4.2.2

Evaluation of the bending stress σb4.2.2.a

The calculation of the bending stress σb is in detail described in [BCK]. Initialdeflections are considered in accordance with the buckling curve b of DIN 18800
Part 2 [DIN].

4.2.3

Equivalent criteria for longitudinal and transverse ordinary stiffeners not
subjected to lateral pressure

4.2.3.a

The formulas to check the strength of stiffeners not subjected to lateral pressure aretaken from GL-Rules. The formulations are based on 2nd Order Theory considering
imperfections and are checked against the yield strength applying an appropriate
safety factor.

4.3

Torsional buckling

4.3.1

Longitudinal stiffeners

4.3.1.a

Stiffeners subjected to compressive stresses are to be examined for their ability to
σx ⋅Sresist torsional buckling. The basic condition is:≤ 1.0
κ τ ⋅ ReH

4.3.1.b

The calculation procedure of the reduction factor κτ follows the buckling curve a of
DIN 18800, Part 2 [DIN].

4.3.1.c

The reference degree of slenderness uses the critical torsional buckling stress σKiT
derived by Bleich, ”Buckling Strength of Metal Structures” [BLE].

4.3.2

Transverse stiffeners

4.3.2.a

It is considered that for this topic, no information in addition to that shown in the
CSR for Bulk Carriers, is necessary to explain the background.

5. EFFECTIVE WIDTH OF ATTACHED PLATING
5.1

Ordinary stiffeners

5.1.1
5.1.1.aTwo different approaches were used for the determination of the effective width of
the attached plating for ordinary stiffeners. The minimum value determined for thetwo approaches have to be used for further calculations. The first approach
multiplies the reduction factor κx or κy with the distance between the stiffeners a orb for longitudinal or transverse stiffeners respectively. The reduction factor for thisapproach is based on the plate buckling assessment for elementary plate panels. For
the second approach (shear lag effect) a reduction factor κs is multiplied with the
distance between the stiffeners s. The calculation of the reduction factor κs isdependent of an effective length of the stiffener leff (dependent from supporting
conditions or moment distribution along the length of the stiffener). The calculation
gives results similar to table 6 of CSR CH06, Sec03 [5.2] with the assumption, that
ordinary stiffeners are loaded by uniformly distributed loads (equivalent to em1 oftable 6).

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PAGE 29 – CHAPTER 6: HULL SCANTLINGS

5.2

Primary supporting members

5.2.1
5.2.1.a

In difference to the beam theory the normal stress in wide plate flanges of beams is
not uniformly distributed in reality. To simplify the calculations acc. to the beam
theory an effective width is obtained such that the resulting force of the stresses
acting on the real plate flange is equal to the force of the uniformly distributed
normal stresses acting on the plate flange of the effective width.

5.2.1.b

The effective width is dependent of the moment distribution alongside the girder,
resulting from boundary conditions and the applied forces as well as of the ratio
between the length of the girder and the width of the supported plating (shear lag
effect).

5.2.1.c

Based on a plane stress state, effective width can be calculated for varying ratios
between the length of the girder and the supported width and the moment
distribution caused by boundary conditions and applied loads. Results for suchcalculations are given in table 6 of CSR Ch06 Sec03 [5.2] with respect to uniformly
distributed loads and single loads.

6. TRANSVERSE VERTICALLY CORRUGATED WATERTIGHT BULKHEAD IN
FLOODED CONDITIONS
6.1

General

6.1.1

Shear buckling check of bulkhead corrugation webs

6.1.1.a

The proof of the shear buckling strength of bulkhead corrugation webs follows themethod of IACS UR S18.

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PAGE 30 – CHAPTER 6: HULL SCANTLINGSSECTION 4 – PRIMARY SUPPORTING MEMBERS
1. GENERAL
1.1

Application

1.1.1
1.1.1.a

1.2

Primary supporting members are assessed by direct strength calculation for ships oflength 150 m and greater, except for double bottom strength in the flooded
condition incorporating IACS UR S20. For primary supporting members in ships oflength below 150 m, strength formulae are specified with the focus on shear
strength.

Primary supporting members for ships less than 150 m in length (L)

1.2.1
1.2.1.a

It is considered that for this topic, no information in addition to that shown in theRules, is necessary to explain the background.

1.2.2
1.2.2.a

1.3

It is considered that for this topic, no information in addition to that shown in theRules, is necessary to explain the background.

Primary supporting members for ships of 150 m or more in length (L)

1.3.1
1.3.1.a

1.4

It is considered that for this topic, no information in addition to that shown in theRules, is necessary to explain the background.

Net scantlings

1.4.1
1.4.1.a

1.5

Half the corrosion addition is considered in direct strength calculation, but in therule formulae, 100% of the corrosion addition is considered because primary
supporting members are assessed locally.

Minimum net thickness of webs of primary supporting members

1.5.1
1.5.1.a

Net thickness was taken as 0.6 L considering empirical values.

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PAGE 31 – CHAPTER 6: HULL SCANTLINGS

2. SCANTLING OF PRIMARY SUPPORTING MEMBERS FOR SHIPS OF LESS
THAN 150 M IN LENGTH (L)
2.1

Load model

2.1.1

General2.1.1.aThe same regulation as for plating in Section 1, Chapter 6 has been set.

2.1.2

Lateral pressure in intact conditions

2.1.2.aThe same regulation as for plating in Section 1, Chapter 6 has been set.

2.1.3

Elements of the outer shell

2.1.3.aThe same regulation as for plating in Section 1, Chapter 6 has been set.

2.1.4

Elements other than those of the outer shell

2.1.4.aThe same regulation as for plating in Section 1, Chapter 6 has been set.

2.1.5

Normal stresses

2.1.5.aThe same regulation as for plating in Section 1, Chapter 6 has been set.

2.2

Center girders and side girders

2.2.1

Net web thickness

2.2.1.aThis regulation is based on NK Rules.

2.3

Floors

2.3.1

Net web thickness

2.3.1.aThis regulation is based on NK Rules.

2.4

Stringer of double side structure

2.4.1

Net web thickness

2.4.1.aThis regulation is based on NK Rules.

2.5

Transverse web in double side structure

2.5.1

Net web thickness

2.5.1.aThis regulation is based on NK Rules.

2.6

Primary supporting member in bilge hopper tanks and topside tanks andother structures

2.6.1

Load calculation point

2.6.1.aThe same regulation as for plating in 1.4.1, Section 2, Chapter 6 has been set.

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PAGE 32 – CHAPTER 6: HULL SCANTLINGS

2.6.2

Boundary conditions

2.6.2.a

2.6.3

Net section modulus, net shear sectional area and web thickness underintact conditions

2.6.3.a

3. ADDITIONAL REQUIREMENTS FOR PRIMARY SUPPORTING MEMBERS OF
BC-A AND BC-B SHIPS
3.1

Evaluation of double bottom capacity and allowable hold loading in flooded
conditions

3.1.1

Shear capacity of the double bottom

3.1.1.aThis regulation is in accordance with IACS UR S20.

3.1.2

Floor shear strength

3.1.2.aThis regulation is in accordance with IACS UR S20.

3.1.3

Girder shear strength

3.1.3.aThis regulation is in accordance with IACS UR S20.

3.1.4

Allowable hold loading

3.1.4.aThis regulation is in accordance with IACS UR S20.

4. PILLARS
4.1

Buckling of pillars subjected to compressive axial load

4.1.1

General4.1.1.aCompressive stress acting in pillars is required to be less than the critical column
buckling stress.

4.1.2

Critical column buckling stress of pillars

4.1.2.aThis requirement is based on the BV Rules.

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PAGE 33 – CHAPTER 6: HULL SCANTLINGSAPPENDIX 1 – BUCKLING & ULTIMATE STRENGTH“The Appendix 1 shows the sample applications of Chapter 6 Section 3.
Therefore, it is considered that for this topic, no information in addition to thatshown in the CSR for Bulk Carriers, is necessary to explain the background.

COMMON STRUCTURAL RULES FOR BULK CARRIERS