IACS Common Structural Rules Knowledge Centre

Bulker Q&As and CIs on the IACS CSR Knowledge Centre
KCID
No.

149

Ref.

7/2.2.2.4

Type

CI

Topic

Date
completedglobalstrengthanalysis

The general case for all primary supporting members of both double hull or
single side bulk carriers shoud be 3 elemnts in height. The case of primary
supporting members in hopper tank and top side tank should be a particularcase, once again for both double hull and single side bulk carriers. Then side
frames in single side bulk carriers are covered in a separate item. Considering
that, we suggest to modify the third and fourth bullets in 2.2.4 as follows: "In FE models for global strength analysis, the number of plate elements on the- webs of primary supporting members are to be divided at least threeheight of primary supporting members is not clear.
2006/10/25
elements height-wise. However, for transverse primary supporting members
In particular, for transverse primary members inside the hopper tank and theinside the hopper tank and top wing tank, in case their web height is smaller
upper wing tank.
than the space between longitudinal ordinary stiffeners, two elements on theheight of primary supporting members are accepted- side shell frames in single side bulk carriers and their end brackets are to bemodeled by using shell elements for web and shell/beam/rod elements forface plate. Webs of side shell frames need not be divided along the directionof the depth"

Question/CI

Attachment

AnswerPage 1 of 12

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

AnswerIn order to have the same relation ship between horizontal shear force andhorizontal bending moment as the one between vertical shear force andvertical bending moment, I suggest introducing the following definition:"The horizontal shear force “Qh” is positive in the case of resulting force
towards portside preceding the ship transverse section, and resulting forces
towards starboard following the ship transverse section, and is negative in the
opposite case"This definition is not mentioned in CSR. Therefore, we will submit the following
modification to Hull Panel.

169

7/2.2.5.4&.
Question
6

horizontal
shear force

2006/9/11

The formulae in 2.5.4 and 2.5.6 deal with horizontal shear force, but there isno sign convention for horizontal shear force.

(1) Chapter 4 Section 1 Figure 1
The symbol “Q” in the figure is amended to “Qs” and “Qwv”..
(2) Chapter 7 Section 2 [2.5.4]
The definition of symbols of “QV_FEM, QH_FEM, MV_FEM, and MH_FE“ areamended as follows.
QV_FEM, QH_FEM, MV_FEM, and MH_FEM: Vertical and horizontal shear
forces and bending moments created by the local loads specified on the FEmodel.
Sign of QV_FEM, MV_FEM and MH_FEM are in accordance with sign
convention defined in Ch.4 Sec.3. Sign of QH_FEM is positive in the case of
resulting force towards portside preceding the shiptransverse section, and resulting forces towards starboard following the shiptransverse section, andis negative in the opposite case.
(3) Chapter 7 Section 2 [2.5.6]
The definition of symbols of “QV_T, QH_T, MV_T, and MH_T“ are amended
as follows. QV_T, QH_T, MV_T and MH_T:Target vertical and horizontal
shear forces and bending moments, defined in Table 3 or Table 4, as thelocation xeq. Sign of QV_T, MV_T and MH_T are in accordance with sign
convention defined in Ch.4 Sec.3.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

170

Ref.

Ch 7 App
2 2.2.2 &
2.2.3

Type

CI

Date
completed

Question/CI

AnswerPSI Factor

2007/6/11

In chapter 7 App2, 2.2.2 and 2.2.3, the formulae to obtain sigma x, sigma y,
psi x and psi y are given for "longitudinal compression" and "transverse
compression". In case the stress are in tension, psi will become bigger thanone, and the associated stress will be the minimum tension stress. According
to the definition of psi in Ch6 Sec3 and the schemes and formulae in Ch6
Sec3 Table 2 doe, psi is supposed to be smaller than one.
One interpretation is to change the formula for sigma and psi in order that psi
is lower than one and sigma is the maximum tension stress.
The other interpretation is to keep the formulae as they are in order to get theminimum tension stress.

As the psi factor will not be used with tension stresses, it seems preferable toretain the minimum tension stress (ie the maximum stress with the sign
convention for stress in the buckling rules) in order to be conservative.
Therefore, the formula for sigma x or sigma y is unchanged, and psi is not
calculated (or limited to one) for tension stress.

Topic

Attachment

197

7/4.3.3

CI

simplified
methodYour understanding is right. The simplified method is applicable to theintersection of inner bottom plate and sloping plate of lower stool as well as
the intersection of inner bottom plate and hopper slant plate. That’s was theoriginal intention of the requirement. In applying the requirement of Ch.7 Sec 4
We understand that the methodology used in the simplified method is[3.3], therefore, the following interpretation is prepared in order to be in line
commonly applicable to the intersection of inner bottom plate and slopingwith the original intention. Common Interpretations for:plate of lower stool as well as bilge knuckle part. Therefore, Common
2006/10/31
Chapter 7/Section 4/3.3Simplified method for the bilge hopper knuckle part
Interpretation should be prepared as soon as possible so that this method can[The text of the Rules] The words “bilge hopper knuckle parts” , “bilge knuckle
be applied to the intersection of sloping plate of lower stool and inner bottom
part” and “hopper slope plate” in the title of [3.3], the text of [3.3.1] and [3.3.3],
plate
the title of Fig.6 and the text in the top of column of the Table 1. Common
Interpretation The requirements of [3.3] are applicable to the knuckle part not
only bilge knuckle part but also lower stool knuckle part such as theintersection of the inner bottom plate and sloping plate of lower stool.

218

7/4.3.2.1

Question

hot spotstress range

2006/11/28

The procedure of obtaining hot spot stress brings very pessimistic results anddiffers from that of JTP.We would like to ask you to reconsider and revise theprocedure as soon as possible.In conjunction with the above, 3.3.2 should bealso reconsidered.

The existing procedure is not modified. However, possible changes will be
subject to the future harmonisation work between CSR for oil tankers and
CSR for bulk carriers.

219

7/4.3.3

Questionconnection

2006/11/8

Please develop and introduce a simplified method for the connection of lower
stool of transverse BHD with inner bottom as soon as possible.

The simplified method is applicable to the intersection of inner bottom plateand sloping plate of lower stool as well as the intersection of inner bottom
plate and hopper slant plate. That’s was the original intention of therequirement.

FE modelExtent of model; The extent of FE model is required to be three cargo holds
and mid one is the target assessment. In handy bulk carriers, loaded
2006/11/30
holds(Nos.1 and 5 holds) are not included in the mid part model(Nos.2-4
holds). Please clarify the FE model for handy bulk carriers with 5 cargo holds.

248

7/2.2.1.1

Question

The FEA assessment of cargo holds is restricted to the midship area by the
CSR.However, assessment of holds of both ends is left to the responsibility ofeach Society – this may be an extrapolation schema, a specific FE analysis, a
FEA provided by the ship designer,…Furthermore, it should be noticed that
this problem is also relevant in the CSR for Oil Tankers.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

278

Ref.

7/App.2,Fi
g2

Type

Question

7/4.3.3.3 &Table
Question
287
7.4.1

Topic

FE

Date
completed2006/11/22

colum plate
thickness

2006/12/18

Attachment

Question/CI

AnswerMy only comment is that the Amendment for Ch7, App 2, [2.2.3], Fig 2 is still
not clear to me.

The numbers 1 to 8 in Fig. 2 indicate the diplacement nodes number of theshell element of FE. The numbers 1 to 6 in bold style in Fig.2 indicate thestress calculation points number of panel which is obtained from the transform
matrix using the displacement of the node numbers 1 to 8.The figure may be
splited into two figures in a next revision of the CSR: one for the displacement
points and the other for the stress calculation points.

Is the column plate thickness, t column, based on the gross inner bottom
plate?

The requirement of 1.4.1, Ch 7 Sec 1 mentions as follows. “Direct strength
analysis is to be based on the net scantling approach according to Ch 3 Sec
2.” According to this requirement, the thickness in Table 1 of Ch.7 Sec 4[3.3.3] is “Net thickness” in FEA. In order to clarify this, the text modification
will be proposed as "Corrigenda".
Also Included in Corrigenda 5288

7/4.3.3.3 &Table
Question
7.4.2

Radius Ra) Yes, it is correct.
a) The radius R is believed measured to the radius on upper surface of hopper b) No, it is not correct. The thickness t is always the “Net thickness” in FEA.
knuckle is that correct.
c) Yes. It is typo. The “Corrigenda” will be issued soon.
b) The thickness t is assumed to be the plate thickness in way of radiusd) Noted. The text of Note (2) should be revised as follows. “In using the
knuckle. t is assumed gross thickness. Is that correct?
correction factor K3 for bend type knuckle, the members should be arranged
2006/12/20 c) K2 in Note 2 should read K3
such that the bending deformation of the radius part is effectively suppressed.”d) Note 2 only applies to radius knuckle, therefore the text “For bend typeThis revise will be issued soon as “Corrigenda”
knuckle ...” should be insertede) Yes, it is recommended to be the same thickness as inner bottom platee) Does it mean that the insert plate in the floor web is to be the same
where the fatigue assessment is carried out by simplified method. However,thickness as inner bottom plate?
where the fatigue assessment is carried out by very fine FEA, the thickness ofinsert plate is to be determined based on the results of fatigue assessment.

289

7/4.3.3.3 &QuestionFig.7.4.7

longitudinalrib

2006/12/21

290

291
attc

7/4.3.3.3
Fig 7.4.8

7/4.3.3.3
Table
7.4.2

Question

Question

longitudinalribsintersection

Is there a maximum distance for the position of the single longitudinal rib
required by Table 2 Note (2)?

No, there isn’t. This figure is just example. The distance for the position of thesingle longitudinal rib is determined by case by case basis but the single
longitudinal rib is recommended to fit near of knuckle part as far aspracticable.

2007/1/8

The figure shows two longitudinal ribs, and indicates a distance of 500mm
from the margin girder to the second rib. Is this correct?

Yes, it is correct that Figure 8 shows two longitudinal ribs, and indicates a
distance of 500mm from the margin girder to the second rib.
However, in order to clarify the arrangement of transverse rib, longitudinal rib
and extent of local reinforcement, we will consider the rule change proposal of
Figures 7 and 8 in future.

2007/1/11

Regarding the simplified method, IACS Q&A (no 11) in the official
spreadsheet, indicates that simplified method is applicable to intersection of
inner bottom plate and sloping plate of lower stool as well.
For this connection with longitudinally framed inner bottom and verticallystiffened lower stool, K2 is understood = 0.9, and K4 =0.9. Is that correct?
It is assumed that Note 3 i.e. insert plate in web, is only applicable to hopper
knuckle connection.

In our point of view, if the simplified method is applicable to intersection of
inner bottom plate and sloping plate of transverse lower stool, the correction
coefficients K2 and K4 should be considered in the following way:
- K2 equal to 0,9 should be considered when there is a thickness increment of
longitudinal girder web, up to the thickness of the inner bottom plating,- K4 equal to 1.0 in general and equal to 0.9 when longitudinal ribs are fitted.

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KCID
No.

292
attc

Ref.

7/4.3.2.2

Type

Question

Topic

Radius R

Datecompleted

Answer

Attachment

2007/1/31

Please find the attached PDF describes our implementation for Lambda as
follows. Could you check it if our interpretation is correct?
(a) welded intersection between plane plates apply to;- Bilge Hopper plane part to Hopper Transring.
- Side Girder to Hopper Transring and Floor.
- Inner Bottom to Floor.
- Side Girder to Inner Bottom.
b) welded intersection between bent plate and plane plate apply to;- Bilge Hopper bent part (between R.ENDs) to Hopper Transring.

Your interpretation is correct, however, the parts indicated in the question are
not required to carry out the fatigue assessment. The fatigue assessment is tobe carried out for the members and locations described in Table 1 Ch 8 Sec 1.

Y

Surface stress is used for hot spot stress evaluation. Figure 3 shows thelocations of stress evaluation points to define the hot spot stress. In order toclarify used stresses, we will consider the editorial correction of the second
sentence of the first paragraph as follows. “The surface stress located at 0.5
times and 1.5 times the net plate thickness are to be linearly extrapolated at
the hot spot location, as described in Fig. 3 and Fig. 4.”

Question/CI

293

7/4.3.2.1

Questiongeometric
stress2007/1/23

The principal stress in the 4th line is a surface stress (at top or bottom of theelement? or a membrane stress (at neutral axis of the element? According to[3.1.1], the hot spot stress is defined as the structural geometric stress on thesurface at a hot spot. However, in figure 3, it seems a membrane stress.
Could you tell us which is correct?

294

7/4.3.3.2

Questionnominalstress range

2007/1/31

The second and third words "nominal stress" is not consistent withterminology used in 3.2.1 is "nominal stress" a principal stress? or normal
stress?

The word “normal stress” instead of “nominal stress” is correct. This revision
will be issued as “Corrigenda”.

334

7/2.3.4

Question

Measurements

2007/3/9

Would you please confirm which direction is the maxium relative deflectiondelta_ max between the double bottom and the afterward (forward) transvers
bulk head? Z or the reluctant?

The maximum relative deflection has to be measured normal to a line, whichconnects the adjacent bulkheads at Bottom / CL.

2007/7/2

1. Your understanding that is the local plate bending is neglected is correct.
2. In principle stress levels of all elements should be within the allowable
According to Ch.7 Sec.2 [3.2.3] “The reference stresses in FE model that does
criteria. However, the averaged stress among smaller elements (e.g., quarter
not include orthotropic elements, as specified in [2.2.4] are not to exceed
size or smaller) can be used when deemed reasonable by the Society.
235/k N/mm2 (..)” We have 3 multiple questions. See the attached.
3. All elements over the height of the girder should be within the allowable
criteria when the difference of size of all elements in girder is relative small.

340
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7/2.3.2.3

Question Stress Levels

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YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer
1a. Your understanding is correct.
1b. Your understanding is correct.

341
attc

7/2.3.2.3

QuestionStressAssessment

2007/7/2

2. According to 2.1.1 of Ch 7 Sec 3, as the refined areas are limited to theSection 3 Detailed stress assessment.
locations listed in Table 1 of Ch 7, Sec 3 and the stresses thereof obtained by
Item [2.1.1] “Where the global cargo hold analysis of Sec.2 is carried out usingcoarse mesh FEA in Ch 7 Sec 2 exceed 95% of the allowable stress, thea model complying with the modelling criteria of [2.2.4], the areas listed in Tab
enlarged area to create the refine mesh is not required to the locations where
1 are to be refined at the locations whose calculated stresses exceed 95% of
the stresses obtained by coarse mesh FEA is below 95% of allowable stress.
the allowable stress as specified in Sec 2,[3.2.3]. Please review following
Therefore, The example given in "b" of your questionary document as
related questions (see the attached).
attached is correct.

Y

3. The example given in "a" of your questionary document as attached iscorrect.

343
attc

393

411

484

7/2.2.3.1

7/2.2.3.1

7/2.2.5

7/2.3.3

Boundary
Question conditions for
FE analysis

Question

Question

Longitudinal
Items

Horizontal
Bending
MomentBuckling andUltimate
Questionstrengthassessment

2009/9/4

FE analysis of cargo hold structures - boundary conditions
See the attached question

Your comments have been noted and we can advise that the boundary
conditions have been changed accordingly in RCN No.1-5 to the July 2008
Rules.

2007/6/11

1. Normally at neutral axis on centreline, there are no longitudinal items
present,so to which "independent point" are the nodes on longitudinal
members at both end sections to be linked ?
2. to which node is the total moment (still water & wave) to be applied ?
3. are boundary conditions to be applied only to the master node of coupling
equations & not at all end nodes of longitudinal items ?

In general “independent point” does not locate in any members of the FEmodel but shall be produced additionally near the cross point of centerline andneutral axis. The nodes on the longitudinal members at the end shall be rigidly
linked to the “independent point”. It might be common way to use the bulk
data card “MPC” (Multi-Point-Constraint) in case of MSC/NASTRAN. The total
moments (enforced moment for BM/SF adjustment) and boundary conditions
are to be applied to the independent point only.

2007/6/12

Handling of horizontal moment induced by P1-Loadcase: Loading conditions
with load case P1 create horizontal bending moments, which increases from
"0" at one model side to a maximum value at the other side. We adjust thesehorizontal bending moments with counter shear forces and bending moments
at the model ends analog to the horizontal bending moment in the R1 loadcase. The target value for the horizontal bending moment in P1 load case is"0" at mid of cargo hold model.Please confirm.

2007/7/2

Regarding buckling and ultimate strength assessment in a global strength
analysis, an increase in thickness of each panel satisfying requirements will beobtained by iteration. As there is no clear process in the current rules, it is
CSR only requires that the results of DSA are to comply with the strength
considered appropriate that the stress may be used as it is with no reductions
criteria in Chapter 7. There is no need to specify the iteration procedure toassociated with thickness ratios in each iteration step. Is this correct?
confirm the reinforcement of structure in CSR because it is considered that the
If not correct, some known approches are considered available, for example,
responsibility of reinforcement of structure which does not comply with the(i) all component stresses are reduced with thickness ratios,
strength criteria is up to designers not classification societies. Classification(ii) the same as (i) but stresses in the global X direction are not reduced,
society only confirms that the results of DSA carried out for the given(iii) only the stress due to local loads is reduced with thickness ratios and thescantlings of structure comply with the strength criteria specified in the Rules.
stress due to hull girder loads is not reduced.
Please advise a common process to apply proper stresses for required
thickness calclations.

We confirm that the target value for the horizontal bending moment in P1 loadcase is “0” at the mid of cargo hold model.

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YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

AnswerWhilst an answer has been given in IACS KC484 to the question on thickness
iteration procedure for buckling strength assessment, it is still requested that acommon iteration procedure or a Rule stipulation be specified.
Question: Regarding buckling and ultimate strength assessment in a global
strength analysis, an increase in thickness of each panel satisfying
requirements will be obtained by iteration. As there is no clear process in thecurrent rules, it is considered appropriate that the stress may be used as it is The report of the FE analysis has to demonstrate that the ship structure haswith no reductions associated with thickness ratios in each iteration step. Is
been designed according CSR-BC.
this correct? If not correct, some known approaches are considered available,
for example, (i) all component stresses are reduced with thickness ratios, (ii)the same as (i) but stresses in the global X direction are not reduced, (iii) only
the stress due to local loads is reduced with thickness ratios and the stressdue to hull girder loads is not reduced. Please advise a common process toapply proper stresses for required thickness calculations.

542

571
attc

7/2.3.3

Ch4 App3
and Ch7
sec 4

RCP

QuestionThicknessiteration
procedure for2007/10/24
buckling
strength
Answer: CSR only requires that the results of DSA are to comply with theassessment
strength criteria in Chapter 7. There is no need to specify the iteration
procedure to confirm the reinforcement of structure in CSR because it isconsidered that the responsibility of reinforcement of structure which does notcomply with the strength criteria is up to designers not classification societies.
Classification society only confirms that the results of DSA carried out for the
given scantlings of structure comply with the strength criteria specified in theRules.
As in CSR-DHOT 9/2.1.2.1 in respect of submission of results stipulating that'(m) proposed amendments to structure where necessary, including revised
assessment of stresses, buckling and fatigue properties showing compliancewith design criteria", it is considered necessary for CSR-BC to implement a
harmonised iteration process for determining amended scantlings by
thickness iteration.

fatiguestrengthassessment

2008/8/9

Please answer to the attached question for fatigue of Bulker CSR.

A1. For fatigue strength assessment, the cargo density used is to be as much“realistic” as possible. Therefore, the cargo density according to Ch 4 App.3
should be used for fatigue strength assessment not only by direct analysis
specified in Ch 8 Sec 3 but also simplified method specified in Ch 8 Sec 4.
We will consider the rule change proposal accordingly
A2. We think that Ch 7 Sec 4 3.3.2 referred in the question is Ch 7 Sec 4 3.2.2
correctly. The the definition of lamda for "welded intersection between plane
plates" is applicable for intersection of two plates and intersection of plating
and bracket.
A3 The correction factor of Ch 7 Sec 4 [3.2.2] is applicable to the case where
the stress at the 0.5 t from the hot spot is slightly greater than the stress at the
1.5 t from the hot spot.

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YIACS Common Structural Rules Knowledge Centre

KCID
No.

636

Ref.

7/2.2.3.1

Type

RCP

Topic

High Stressof Cross
Deck

Datecompleted2008/3/26

Question/CI

Attachment

AnswerRegarding the draft answer for "PH7101_: High Stress of Cross Deck obtainedby DSA (KC ID No.343)", we would like to offer following suggestions to havea feasible conclusion for this issue before the wording of the draft answer issettled.
1. It is noted that the problem has happened in the DSA using a FE cargo hold1.We will consider the rule change proposal regarding the boundary condition
model under the load cases of R1, R2, P1 and P1, where dynamic pressureson rotational restriction about x-axis in order to avoid the unreasonableinduced will be unsymmetrical to the ship centre line. As described in Table 2stresses due to unexpected and unreasonable warping of FE model.
of Ch. 7, Sec. 2, Para. 2.3.1 of the CSR for BC, the cargo hold model is simply
2. The examination regarding the stress assessment of hatch corner has been
supported at both ends through the independent point for vertical bending andcarried out by IACS another PT separately.
horizontal bending whilst relevant bending moments are applied at both ends
to achieve the target values, however, the rotation around x axis at the fore
end is constrained in addition to the warping, i.e., fully fixed at the fore end for
torsion, whilst those are free at the aft end. Under such boundary conditions, if
there is any local pressure in it unsymmetrical to the centre line, the cargohold model is naturally twisted without any control.

Relevant boundary conditions may need to be added to the aft end and willprobably be well modified the wave-induced torsional moment and warping.
2. It is understood that the load cases of R1, R2, P1 and P2 correspond to
beam sea since hydrodynamic pressures are independent of x coordinate as
shown in Ch. 4, Sec. 5, Paras. 1.4 and 1.5. Wave-induced torsional momentsin the load cases may, therefore, be relatively small as compared with thoseinduced in oblique sea which may be given in Ch. 4, Sec. 3, Para. 3.4,
however, the torsional moments are not available in any part of the Rules.

3. Warping may be calculated at any position using the formula in Ch. 8, Sec.
5 if relevant wave induced torsional moment is available, whilst the formula isinsufficient from the following points of view;
3.1. The rate of twisting is calculated by pure torsion, i.e., St. Venant's torsion
only. The secondary torque induced as a result of the constraint of warping is
ignored. (Note: Warping is proportional to the rate of twisting.) 3.2. The hull
section is treated as closed section and hatch openings is taken into accountby introduction of deck opening coefficient without any theoretical background.
The hull section is to be an open section and the cross deck is to be treatedas a spring resisting the torsion.
4. The control of the boundary conditions is quite complicated and difficult for
torsion, then, the rotation is to be constrained even at the aft end under theload cases of R1, R2, P1 and P2, i.e., Rx is to be fixed at the aft end. This
may give a reasonable solution for the cargo hold model apart from thetorsion.
5. The cross deck bending due to torsion is to be examined in oblique sea
separately, if necessary.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

637
attc

Ref.

7/2.2.1.1

Type

RCP

Topic

The extent of
FE ModelDatecompleted2008/5/12

Question/CI

Attachment

AnswerWhilst an answer has been given in IACS KC248 to the question forassessment of holds of both ends, the procedure is not clarified but left to the
responsibility of each Society.
Question ID: 248 Approved: 30/11/06
Rule Ref.: Text 7/2.2.1.1 (bulker)
Question: Extent of model The extent of FE model is required to be three
We appreciate the questioner's effort to provide the disccusion material on thiscargo holds and mid one is the target assessment. In handy bulk carriers,
matter.
loaded holds(Nos.1 and 5 holds) are not included in the mid part model(Nos.2We will ask the Hull Panel to resolve this matter and we will submit this
4 holds). Please clarify the FE model for handy bulk carriers with 5 cargo
proposal tp the Hull Panel as a support material for discussion.
holds.
Answer: The FEA assessment of cargo holds is restricted to the midship areaby the CSR. However, assessment of holds of both ends is left to the
responsibility of each Society – this may be an extrapolation schema, aspecific FE analysis, a FEA provided by the ship designer,… Furthermore, it
should be noticed that this problem is also relevant in the CSR for Oil Tankers.

However, it is considered necessary to provide a common procedure todecide scantlings subject to Common Structural Rules. Furthermore, the local
strength and hull shear strength in way of the foremost and aftermost cargoholds should be assessed by the direct strength analysis using the FE cargohold models to confirm the structural adequacy and suitability in way.
1) Local strength aspect
Due to the hull form change, the double bottom shape will become slender
toward the fore end of the foremost cargo hold and the aft end of theaftermost cargo hold respectively. Consequently bottom girder/floor
arrangements in way will differ from those amidships and transmission ofloads on the double bottom to the girders and floors will differ from thatamidships. Furthermore, the sectional shape of the hopper tank will becomecrescent toward the fore and aft ends whilst it is triangular amidships.
Application of the outcome of the direct strength

analysis for the cargo holds amidships is very difficult for such different
structural configuration and not relevant. The direct strength analysis should
be carried out for the foremost and aftermost cargo holds to assess the load
supporting capability of the bottom girders/floors and the transverse webs inthe hopper tank.
2) Hull shear strength aspect
Under alternate loading conditions, very high hull girder shear forces will be
induced at the aft transverse bulkhead of the foremost cargo hold and at thefore transverse bulkhead of the aftermost cargo hold and those will becorrected by a factor which is derived taking into account load transmission to
the transverse bulkhead through the bottom girders on the assumption thatthe double bottom shape is rectangular whilst it is not rectangular in way. The
hull shear strength is critical at both transverse bulkheads, however, it deeply
depends upon accuracy of the factor. To avoid uncertainties in derivation of
the factor, the hull shear strength should be assessed by the direct strength
analysis.
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KCID
No.

637
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Ref.

7/2.2.1.1

Type

RCP

Topic

The extent of
FE ModelDatecompleted2008/5/12

Question/CI

Attachment

Answer

The procedure of the direct strength analysis is proposed for the foremost andaftermost cargo holds as shown in the attachment which is basically in linewith those for the cargo holds amidships.
(Refer to the former page)
Please specify the procedure for assessment of holds of both ends on therules and provide the procedure of the direct strength analysis for the foremostand aftermost cargo holds.

Y

Reference is made to Chapter 7 Section 2 3.2.1

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7/2.3.2.1

RCP

FE Model2008/5/28

Quote
Where the effects of openings are not considered in the FE model, thereference stresses in way of the openings are to be properly modified withadjusting shear stresses in proportion to the ration of web height and opening
height.
UnqouteWe will consider the Rule change considering the proposal.

Y

There is no clear definition in the rule on how to make this correction. We
know this is done differently between different customers. Definitions known to
DNV are the “Vertical” and “CSR Tank” procedure as illustrated in attachment.
Please conclude on a procedure to be used for CSR Bulk and include in Ch. 7
Sec. 2 or in Appendix to Ch. 7 as found appropriate.

675

7/2.3.2.3

Question

doublebottomgirders

2009/5/27

1) Is it suitable to evaluate the equivalent stress of the coarse mesh of adouble bottom longitudinal girder (3 elements over the height and loaded withbending), if the element size of the upper and lower element is 1.2 x frame
spacing? What is the maximum allowable element size and/or number in
relation to the girder height in order to consider the bending stress in theequivalent stress criteria?
2) Please confirm that is not necessary to model a dummy truss element at
the connection of the double bottom girder to adjacent plating in order toevaluate the bending stress of the girder!
3) If a girder is built with a flange instead of connecting two PSM, the axial
stress of the flange is to be evaluated and has to be within the design limits(S_axial<=235/R_eH)?

1. The girders such as the 1/3 of its height are 1.2 time of longitudinal frame
spacing should be divided into 4 or more elements height-wise. In general,mesh height of girder is expected less than spacing of longitudinal stiffeners
according to Ch.7 Sec.2 2.2.4.
2.Such dummy element is not required from CSR requirements.
3. The axial stress of the flange should be less than the design limit (235/k).
This is the same as the axial stress of flange of trans. rings in bilge hoppertanks and top side tanks should be less than design limit according to Ch.7
Sec.2 3.2.1.

Page 10 of 12

IACS Common Structural Rules Knowledge Centre

KCID
No.

718

719

Ref.

7/2.3.3

7/A2

Type

CI

CI

Topic

Change ofelement
thickness &material in
EPP buckling
check

Displacemen
t bucklingcheck basedon DSA

Date
completed2008/7/31

Question/CI

Chapter7_Sec2_[3.3] Change of element thickness & material in EPP
buckling check
Regarding the EPP, which consist of elements with different thickness and/or
material yielding strength, it would better provide a practicable approach forbuckling check based on DSA reults. Currently, there would be three options ,1) The weighted average thickness, along with the minimum material yieldstrength will be used
2) The weighted average thickness, along with the weighted average material
yield strength will be used
This issue is still under investigation. An interpretation will be prepared.
3.1) When the plate thickness changes within the field breadth b, bucklingstrength may be checked for an equivalent plate field axb' by using the smaller
thickness t1, whereb' = b1 + b2 * ( t1 / t2) ** 1.5.
In this case b1 is the breadth with the smaller thickness t1 and b2 is thebreadth with the larger thickness t2 within the total breadth b..
3.2) When the plate thickness of an elementary panel varies over the length""a"", the minimum plate thickness will be used.
3.3) Anyway, for elements with different material yield strengths, the minimum
material yield strength is generally to be used.
Please be kindly request to provide clarification or confirmation.

Chapter7_Appendix2 Displacement buckling check based on DSA
JBP rule provides a displacement method to obtain the reference stress forbuckling check of EPP. However, following issues would still need to beclarified,
2008/7/31

Attachment

Answer1)The conditions, under which the displacements method is to be used
compulsively.

A1 The displacement method for evaluating the stresses of panel is notcompulsively.
A2 Yes, the displacement method is optional.

2)Does the displacement method is just optional ? Therefore, we could use
stress method only for any EPP buckling check.

738

7/1.1.2.1

Question

Strength
Assessmentof theprimary
supporting
members

2008/7/2

In Ch 7, Sec 1, relevant to direct strength assessment of the primary
supporting members, the requirement [1.2.1] states that: "Computer programsfor FE analysis are to be suitable for the intended analysis. Reliability of
unrecognized programs is to be demonstrated to the satisfaction of theSociety prior to the commencement of the analysis."
The meaning of "unrecognized" programs needs to be clarified.

In this context, a "recognized" program is a FEA program well known andwidely used in the shipbuilding industry, which has been proven its reliability.
"Recognized " program in this context doesn't mean that such program shoud
be recognized by a specific procedure from Class Society or IACS.

Page 11 of 12

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer822

7/3.2.1.1

Questionares to berefined2009/3/3

Ch.7 Sec.3 2.1 Areas to be refined : For the end brackets of hatch side
coaming and hatch end beam, they are not listed in the Table 1. Thus, could
we understand these areas are not required to be refined even if theYes, the structural members not listed in Table 1 of Ch 7 Sec 3 are notcalculated stresses exceed 95% of the allowable stress as specified in Sec
required to be refined even if the stresses calculated by coarse mesh analysis
2,[3.2.3]? We suspect that there should be some technical background forexceed 95% of the allowable stress.
such brackets since the deck plating in way of the most stressed hatch
corners is listed in the Table 1. In general, the high stressed elements may befound at the end bracket of hatch side coaming.

846

7/2.2

Question

openings in
PSM

2009/9/28

Ch.7 Sec.2 [2]Please provide guidelines on how to represent openings in PSM webs in the
FE cargo hold model, similar to CSR Tanker rules App. B 2.2.1.15

The representation of openings in PSM for finite element hold models will be
addressed by the harmonisation process.

2009/7/28

For the current CSR/BC rules and current practice of the class societies, withregard to the fine mesh FEM model of the transverse set of Primary Support
Members mentioned in the second figure in 7/3 Tab 1, is the portion of themodel representing the single side skin frame to be modeled by deducting
1.0Tc or 0.5Tc?

Regarding the fine mesh FEM model of the transverse set of Primary Support
Members mentioned in the second figure in 7/3 Tab 1, the portion of themodel representing the single side skin frame to be modeled by deducting
0.5tc.

2010/1/27

With regard to fatigue assessment for welded intersection between bent plate
and plane plate, KC292 said that " the parts indicated in the question are notrequired to carry out the fatigue assessment".
Howerver, CSR in Bulk Carrier says that the correction factor λ at 7.4.3.2.2
and (K2, K3) correction coefficient at 7.4.3.3.3 is considered for bent type. (i.e.
bilge hopper to floor)
Please clarify the applied spots among structure. relative sentences are to bedeleted if intersection for bent type is not required to carry out the fatigue
assessment.

2009/6/26

According to CH7, Sec1, 1.5.1 the most severe loading regime shall be usedin FEA. We noticed during the work in PT3 that several Societies use deckloads according to CH4, Sec5, 2. in FEA. From our point of view thenegotiation of deckloads causes a more severe situation, because theupwards directed deformation of the TWT in full load condition is reduced bydeck loads. This can be judged comparing the buckling strength of the sloped
plate of the TWT with and without deck loads. Another aspect of the definitionof deck loads makes the usage in FEA disputable. In hogging and sagging
condition and for all drafts are the "dynamic" deck loads the same. We
request a clear advise of the application of deck loads in FEA (Yield, bucklingand Fatigue check) for different loading conditions and load cases.

2010/1/18

Rule Ref.: Text 7/4.3.2 (bulker)
The method to obtain hot spot stress by linear interpolation will be considered
How to obtain the hot spot stress by a linear extrapolation method is notduring the Harmonization process between CSR OT and CSR BC. In thespecified in the CSR BC. We find that there are several methods, as shown inmean time it may be left to the discretion of the individual class society
the attachment. Please confirm which one should be adopted.

7/3.2.1.1 &
892
Table
question
7.3.1

corosiondeduction

7/4.3.2.2 &Question
3.3

Fatigueassessment
for weldedintersection
betweenbent plate
and plane
plate

919

928

1006
attc

Text
7/1.1.5.1

7/4.3.2

question

FEA

Question

Hot spotstress bylinearinterpolation

Fatigue cracks are found on bilge hopper knuckle part of bend type,accordingly, fatigue strength assessment on bilge hopper knuckle part of bend
type should be carried out.
At the bilge hopper knuckle part of bend type, fatigue crack mainly occurs fromweld toe of transverse web welding, and penetrates the knuckled connection
between hopper plate and inner bottom plate. Therefore the most importantstress in fatigue strength assessment is the longitudinal stress on the knuckled
connection between hopper plate and inner bottom plate. It is necessary toassess the stress in fatigue assessment.

This question is now relevant to the harmonisation between CSR BC and CSR
OT and will be submitted to the relevant project team. In the meantime, theloads to consider on the deck for FEA calculations are defined in Ch.4 Sec.5[2].

Page 12 of 12

YKC#291ClassNK
Stress Concentration Factor for Knuckle Part
(Stool Structure, Bilge Hopper Structure, etc.)

1. Basic SCF
Stress condition around the knuckle part is generally depending on the angle of knuckle part and on the distancefrom knuckle point. According to the Williams’ solution (R.William and Soutas-Little, “Elasticity”, Dover publishing,1998), stress on the plate surface around knuckle part is given by the equation below:
Ac
Vr
(1)
O 2
r
r
; Distance from the knuckle point to the evaluated point
where
O 2
; Parameter which shows the degree of the effect of singular point depending on
the angle to the horizontal of sloped plate, T 
Ac; Coefficient
Since the value of O  2 is depending on T , the equation which gives the approximate to a strict solution ofO  2 was examined. Then the simplified approximate equation is obtained as below. Table 1 shows the comparison
between the strict solution and the approximation.
O  2 0.2  0.0028  T(2)Table 1 Comparison between the strict solution and the approximation
T (deg.)O 2
0.2  0.0028  T
90
75
60
45
30
20

0.4556
0.42610.38400.32650.24800.18130.45200.41000.36800.32600.28400.2560According to the equation (1), the value Vr is asymptotic in a certain value when r becomes around 300mm to500mm. If an asymptotic value is assumed to be a nominal stress, the stress concentration factor can be defined as
below.

Vr

r

Ac

A

O 2

O 2

r

V n

K0 V nA ºª
« K 0 { O 2 »
r
¬
¼

(3)

When the stress around the knuckle part is evaluated by the FE analysis, coefficient A is expressed as below.
A(r )V r O 2r
Vn

V FEM ( r )Vnr O 2(4)

Although the coefficient A is originally depending on the distance from the knuckle point, the coefficient A isevaluated as the mean value around the knuckle part to generalize the stress concentration factor. In order to evaluate
the value of coefficient A , FE analyses of stool and bilge hopper structures of bulk carriers and bilge knuckle structuresof tankers were made. The obtained results are shown in Fig.1. Since the value of coefficient A shows strong
dependency on the angle, the approximated equation of A with the angle is obtained as below.
A

0.14 T  1.15  0.0033 T(5)

On the other hand, from an engineering viewpoint, the stress concentration factor is defined as the ratio of the hot
spot stress evaluated by the FE analysis to the nominal stress as below.

1

K0 {

V hot spot

(6)

Vn
14
12

Mean of A(r)108
6
Inn.Btm.Plate

4

Sloped Plate

2

approximated equation

0
0

20

40

60

80

100

Knuckle Angle ( deg. )Fig. 1 Evaluated Value of Coefficient ‘A’
In general, the hot spot stress is obtained by the linear extrapolation based on the stresses at the points where 0.5t and1.5t part from the hot spot position. Table 2 shows the evaluated stress at the points 0.5t and 1.5t part from the hot spot
position and the extrapolated hot spot stress. According to the results shown in Table 2, the calculated stress according
to the approximated equation at a point 0.5t part from the knuckle point is almost same as the extrapolated stress basedon the FE analysis.
Therefore, the stress concentration factor for the knuckle part can be defined as the equation below.

K0 {

r

A

0.14T  1.15  0.0033TO 2

0.5  t 0.2 0.0028TT (deg.)
45
45
45
45
60
60
75
75
75
75
90
90
45
45
48
48
42
42

> V hot

K 0 uV n @Table 2 Comparison of the hot spot stress
0.5 t
1.5 t
hot spot
FEM(a) formula(b) FEM(c) formula(d) FEM(e) formula(f)
18.6
18.9
14.3
13.2
20.8
21.8
20.6
24.7
16.8
17.6
22.5
28.2
12.4
13.4
9.5
9.4
13.9
15.4
14.4
15.2
11.9
10.6
15.7
17.5
12.0
13.8
9.1
9.2
13.5
16.1
14.6
19.3
12.2
12.9
15.8
22.5
14.0
15.4
10.3
9.8
15.9
18.2
16.8
23.2
13.4
14.8
18.5
27.4
7.9
9.1
5.8
5.8
9.0
10.8
10.2
13.6
8.3
8.7
11.2
16.1
9.7
10.1
7.0
6.2
11.1
12.1
12.1
16.5
9.4
10.0
13.5
19.8
24.2
25.7
19.9
18.0
26.4
29.6
20.7
24.2
17.8
16.9
22.2
27.9
19.6
20.9
15.4
14.5
21.7
24.1
15.9
18.0
13.9
12.5
16.9
20.8
9.9
8.0
7.5
5.6
11.1
9.2
10.7
11.7
8.8
8.3
11.7
13.4
2

(7)

(e) / (b)
1.10
0.91
1.03
1.03
0.97
0.82
1.03
0.80
0.98
0.82
1.09
0.82
1.03
0.92
1.04
0.94
1.39
1.00

2. Correction coefficient for SCF
2.1 Influence Factors on Stress Concentration

When the stress concentration factor of an actual structure is evaluated, it is necessary to correct the basic stressconcentration factor because this value is the one evaluated based on the solution to two dimensional plane problem.
The following correction coefficients will be necessary if the difference between an actual structure and the idealization
model, which is the base of K 0 .
Kt

K 0 u K1 u K 2 u K 3 u K 4
K0
K1
K2
K3
K4

where

; SCF depending on the dimensions of the considered structure (Eqn.(7) & Table 2); Correction factor depending on the plate bending process; Correction factor depending on the thickness increment of the web plate; Correction factor depending on the insertion of horizontal gusset or longitudinal rib; Correction factor depending on the insertion of transverse rib

In order to evaluate the above mentioned correction factors, a number of FE analyses were made as shown in Table 3.
According to the results of FE analyses, following values were evaluated as the correction factors.
Table 3 FEM Analyses

part of structural

knuckle typelongitudinal rib

transverse rib

VLCC
Lower knuckle

R=120 - 800
weld type
R=60 - 120
weld type
R=120 - 800
weld typenone / attachednone / attachednone / attachednone / attached
none
none

none / attachednone / attachednone / attachednone / attached
none
none

Bulk Carrier
Bilge knuckle
VLCC
Upper knuckle
2.1 Correction Factor

Figure 2 shows the evaluated value of correction factor K 1 according to the FE analyses for weld type structuresand bend type structures. The correction factor K 1 for weld type structure does not depend on the plate thickness but
K 1 for bend type structure depends on the radius of bend part and the plate thickness. According to the results, thecorrection factors K 1 for weld type and bend type could be obtained as below:
㪊㪅㪇㪇

㪋㪅㪇㪇

㪉㪅㪌㪇

㪊㪅㪇㪇

㪢㪈

㪢㪈

㪉㪅㪇㪇

㪈㪅㪌㪇
㪉㪅㪇㪇
㪈㪅㪇㪇

㪇㪅㪌㪇
㪈㪅㪇㪇
㪇㪅㪇

㪇㪅㪇㪇
㪇

㪌

㪈㪇

㪈㪌

㪉㪇

㪉㪌

㪊㪇

㪈㪅㪇

㪉㪅㪇

㪊㪅㪇

㪋㪅㪇

㪌㪅㪇

㪍㪅㪇

㪩㪆㫋

(a) weld type(b) bend typeFig. 2 Evaluated Value of Correction Factor K1

3

㪎㪅㪇

㪏㪅㪇

㪐㪅㪇

K 1 , weld

1.7

K 1 , bend

; R t4­1.75°
®0.2625  R t  0.7 ; 4 d R t d 8°2.80; 8 R t¯

The difference of SCF between weld type and bend type is the effect of bending stress due to cross bending
occurred in bend type knuckle part. It is noted that the location of hot spot point is different between both structures. If
the cross bending is controlled effectively, SCF for bend type becomes almost same as the SCF for weld type.
According to the results of FE analyses, K 3 0.9 was obtained as the average value for weld type, which shows theeffect of stress reduction due to the longitudinal rib. And the correction factor K 3 was so determined that theK 1 u K 3 for bend type becomes same as one for weld type. Then the correction factors K 3 for weld type and bend
type could be obtained as below:
K 3 , weld

0.9

K 1 , bend

; R t4­0.85°
®1.15  0.075  R t ; 4 d R t d 8°0.55; 8 R t¯

According to the results of FE analyses, K 2of the difference of knuckle type.

0.9 and K 4

0.9 were obtained as the average values regardless

3. Summary
The geometrical stress concentration factor for the bilge hopper knuckle is giving by the following equation.
Kt

K 0 u K1 u K 2 u K 3 u K 4
K0
K1
K2
K3
K4

;
;
;
;
;

SCF depending on the dimensions of the considered structure
Correction factor depending on the plate bending process
Correction factor depending on the thickness increment of the web plate
Correction factor depending on the insertion of horizontal gusset or longitudinal rib
Correction factor depending on the insertion of transverse rib
Table 4 Stress concentration factor K0

Plate thickness
(mm)
16
18
20
22
24
26
28
30

Angle of hopper slope plate to the horizontal (deg.)
40
45
50
90
3.0
3.2
3.4
4.2
2.9
3.1
3.3
4.0
2.8
3.0
3.2
3.8
2.7
2.9
3.1
3.6
2.6
2.8
3.0
3.5
2.6
2.7
2.9
3.4
2.5
2.7
2.8
3.3
2.4
2.6
2.7
3.2

Note: Values for intermediate plate thickness and angle may be interpolated from the values
given in the table.

4

Table 5 Correction Coefficients
Type of knuckle

K1

Weld Type

1.7

Bend Type1.75 ;
2.80 ;R t4
R t !8

K2

K3

K4

0.9
0.9

0.85 ;
0.55 ;R t4
R t !80.9

Notes :
(1) When evaluating K 1 and K 3 between 4 d R t d 8 , the linear interpolation is applied“R” denotes the radius of bend part and “t” denotes the plate thickness(2) In using the correction coefficients K 2 , the increase in web thickness is taken based on the plate
thickness of the inner bottom plating.
(3) In using the correction coefficients K 3 and K 4 , the members should be arranged such that thebending deformation of the radius part is effectively suppressed.

5

KC#292

KC#340

KC ID #340 Question
Chapter 7 Direct strength assessment
Section 2 Global Strength FE analysis of cargo hold structures.
According to Ch.7 Sec.2 [3.2.3] “The reference stresses in FE model that does not include
orthotropic elements, as specified in [2.2.4] are not to exceed 235/k N/mm2 (..)”
Q1: We assume item [3.2.3] is referring to membrane stress only. That is, local plate bendingis neglected. Please confirm.
Q2: We assume the acceptance criteria of Ch. 7 Sec. 2 [3.2.3] is related to an element size of
S x S. That is:a. all elements with size equal to the representative stiffener spacing S x S (asspecified in sec. 2 [2.2.4]) is to be within the limit specified in [3.2.3]
b. smaller elements when averaged over the representative stiffener spacing are to bewithin the limit specified in 3.2.3
Please advice
Q3: A typical connection of a longitudinal girder to the lower stool is shown in the figure
below. A typical utilization for yield in a heavy ballast cargo hold is indicated Veq/Vaccetp.[3.2.3].

0.60

1.10

0.80

0.70

0.75

0.70

0.60

0.45

0.45

Assuming all 3 elements are equally sized over the height of the double bottom as indicatedon the figure. What is the correct application of [3.2.3]?:

a. Each individual element over the height has to be within the requirement of[3.2.3]. That is, the red element has to be reinforced until the utilization is < 1. ?
orb. The results may be averaged over a typical stiffener spacing, SxS, in the double
bottom as indicated with grey in the below figure. The averaged utilization shouldbe <1?

Assuming the 3 elements are slightly different is size. What is the correct application of[3.2.2]?

c. Each individual element over the height has to be within the requirement of[3.2.3]. That is, the red element has to be reinforced until utilization is < 1.?
ord. The results may be averaged over a typical stiffener spacing, SxS, in the double
bottom. The averaged utilization should be <1?
ore. The results may be averaged based on an element size = HdblBottom/3?

KC#341Q
KC ID# 341 Questions

Q1: According to Ch.7 Sec.3 [2.1.1] “(..)the areas listed in Tab 1 are to be refined at thelocations whose calculated stresses exceed 95%(..)“What is the correct interpretation of thisitem?
a.
We assume that only areas covered by Table 1 need to be refined if theutilization according to section 2 (coarse mesh model) is above 95%. Areas
not given in table 1 are not subject to refined mesh analysis according tosection 3 even if the stress level is above 95%. Please advice.
b.
If all areas mentioned in Table 1 have utilization below 95% according to theanalysis in section 2 (coarse mesh model), no refined mesh is required.
Please advice.
Q2: Example:
A refined mesh analysis is made for one location in table 1 where peak stresses in the global
analysis (coarse mesh model) according to section 2 is above 95% of allowable limit.
The refined model will cover an area of the (coarse mesh model) model where stress levelaccording to section 2 (coarse mesh model) range from 80-99% of allowable limits.
In the refined mesh analysis according to chapter 3 the allowable stress levels are above 280/k
in a large area. That is, high stressed elements are identified at locations where the global
analysis according to section 2 show stresses below 95%. What is the correct application of
the CS Rules?
a. Where the stress level according to section 2 (coarse mesh model) is below 95% of
acceptable limit no reinforcement will be required by the analysis of section 3.
orb. Where stress level according to section 3 is above the acceptable limit of section 3,
reinforcements are required. This is regardless of result in coarse mesh analysis in
section 2.
Q3: Example: The uppermost element in the web of a double bottom girder at the connection
to hopper tank or stool plating has a utilization of 1.1 against yield according to the coarse
mesh model of section 2. Ref. situation in Q3 above. The fine mesh model according tosection 3 is made of the area and stress levels are found to be within the limits of section 3.
What is the correct application of the CS Rules?
a. Coarse mesh analysis according to section 2 has to be satisfied before doing fine meshanalysis according to section 3. Both requirements shall be fulfilled.
orb. If the results of the fine mesh analysis of section 3 are within rule limits of section 3, itis acceptable that the coarse mesh analysis according to section 2 is above the limits ofsection 2.
orc. The results may be accepted based on fine mesh analysis if:
I: The criteria of section 2 [3.2.3] is satisfied for the fine mesh analysis when stresses
are averaged over an area, SxS, equal to the representative stiffener spacing.
and
II: The criteria of section 3 [3.1.1] is satisfied for the fine mesh analysis.

Please note that alternative c. is in line with the procedure in the CSR for Tankers.

KC#343
Ch

Sec

Para

Comment

7

2

2.3.1

The required thickness for cross deck shown below is obtained by the buckling
analysis of global strength assessment for P’max BC.
4CH(Ball)
3CH(Ore)2CH(Emp)5CH-4CH
4CH-3CH
3CH-2CH
2CH-1CH
Upper Deck 25.0AH36
23.0AH36
21.0AH36
15.0AH32
Cross Deck 16.5AH32
18.0AH32
19.5AH32
22.5AH32
As a result, it is found that the required thickness for cross deck tends to be thicker
than that of upper deck. This phenomenon is more remarkable towards the forward
end of the three hold model where the sectional modulus is lesser. In this respect,
following reasons are considered.
1. The current boundary condition is that the both ends of model are simply
supported and Rx at fore end is fixed and Rx at aft end is free which results themodel to deform too softly.
2. The subjected Load case is Full Load condition and applied design wave is P1,
hence torsional moment induces.
3. As such, the maximum stress occurs around hatch corners, which may be due tothe combination of longitudinal stress due to hull girder bending and twisting under
torsional loads, in line with the large local deformation of the elements in the area.
To obtain the feasible required thickness for cross deck, it is suggested that that Dx
for Independent point on aft end of model to be fixed as forward end of the model.

1/1

KC#571

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KC#637

Procedure of Direct Strength Analysis for Foremost and Aftermost Cargo Holds

Bow

Coll.Bhd

E/R Bhd

A.P.Bhd

A.P.
Rule Aft End

idlingForemost
Cargo
Hold

F.P.

AftmostCargo
HoldEngineRoom

Extent of model(1+1+D cargo holds and three T.Bhds are to be covered.
The idling extent D is to be decided by the designer.
D
1
1
1
1

D

idlingBoundary conditions
Both ends of model are to be simpliy supported according to Tab 1 and Tab 2 in Ch 7 Sec 2.

Fix

Hull Girder loads
Target BM is to be applied at 1/3 cargo hold length in mid-hold.

1/3 CH length from T.Bhd
1/3 CH length from T.Bhd
1/3 CH length from T.Bhd
1/3 CH length from T.Bhd

Standard Loading Conditions
Loading Pattern
for Aftmost CH
Mfull

Loading Pattern
for Foremost CH
Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

MHD+

MHD+

0.1MH

0.1MH

MHD+

MHD+

0.1MH

0.1MH

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

MHD+

MHD+

0.1MH

0.1MH

Loading Pattern
for Aftmost CH
Mfull

Loading Pattern
for Foremost CH
Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

Mfull

KC#650
Procedures to correct for effective web area in way of openings
CSR Tank procedure

“Vertical method”
Shear area is adjusted based on the ratio hw/(hn1+hn2) measured vertically.

KC#1006
1.

2.

3.

4.

4.

5.