IACS Common Structural Rules Knowledge Centre

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

220

221

222

223

Ref.

8/1.1.3.1

8/2.2.3.1

8/2.2.3.2

8/5.3.1.1

Type

Topic

Questionfatiguestrengthassessment

Question

Question

Questionfillet weld

fatiguedamagenominalstress range

Datecompleted

Question/CI

Attachment

Answer

The members and locations subjected to fatigue strength assessment
The number of members and locations to be assessed is many.We would like described in Table 1 of Ch 8 Sec 1 are of the members and locations which
2006/11/22 to ask you to reduce the number of locations taking into account damage
the fatigue damage are occurred in the past, even though the number ofexperience and your calculation results.
damages are neglected. Therefore, the fatigue strength assessment should be
carried out for the structural details specified in Table 1.

2006/11/8

There is no category for welded joint of sloped plate and horizontal plate suchas hopper knuckle and lower stool in Table 1.Our understanding is as follows,
because Frank angle of the weld joint is lesser than fillet weld:"Kf=1.25 forwelded joint of sloped plate and horizontal plate"Please confirm the above assoon as possible.

The fatigue notch factor Kf of 1.25 for welded joints of sloped plate andhorizontal plate such as hopper knuckle and lower stool can be applied
because their welded joints are classified with the load carrying full penetration
weld joints as well as butt welded joint. For the non-load carrying full
penetration welded joints between plate, the fatigue notch factor Kf may be
reduced.

The correction factor for mean stress is very complicated and sensitive to
2006/11/28 fatigue damage. Please reconsider and revise the factor to meet ourengineering sense as soon as possible.

According to the fatigue damage experiences, mean stress effect is the mostdominant factor to explain their fatigue damage. Then, the precise procedure
to consider the mean stress effect is mentioned in the text. However, tosimplify the procedure for the mean stress effect without losing the accuracy ofthe present fatigue assessment needs much time, careful discusstion andappropriate ramification study. Therefore, for the time being, the text is kept as
it is.

We understand that the nominal stress range obtained from this formula isbending stress of the cross deck.Thus the stress occurs in athwartshipdirection.In general, the major axis is arranged in longitudinal direction to
reduce the stress concentration due to hull girder bending moment.Therefore
2006/12/22
the explanation of ra and rb is not adequate to use the formula properly.For
example, ra and rb are inner radius and outer radius, respectively.This rulebrings very pessimistic results.In conjunction with the above comment, therules should be revised to obtain reliable results as soon as possible

The requirement on hatch corner fatigue check will be revised as soon as
possible, including a technical background.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

250

Ref.

8/2.2.3.2

Type

Question

Topic

Date
completed

Question/CI

Equivalent hot spot stress range (Corrigenda 1) This item seems to be rulechange. We would like to know the impact of this rule change.

Attachment

AnswerThis revision includes the correction of the factor in the conditional equations
and the alternation of the expression. The correction of the factor in theconditional equations is made for the simple error in writing of the factor in thecondition that the shakedown in compression stress side is occurred. Thiscondition correspond the case that the large mean stress in compression side
is occurred. The effect of this correction on the scantlings of the structuralmember is very small since the fatigue damage in such case is negligible
small. The alternation of the expression is made to clarify the meaning of theconditional equations without changing the conditions.

hot spotstress range

2006/11/10

The bending moments induced on the FE model by local loads are explicitly
taken into account when using superimposition method for yielding andbuckling criteria (Cf Ch 7, Sec 2, [2.5.7]), and it seems necessary to proceed
in the same way for fatigue. Note: Ch 8, Sec 2, [2.2.2] should make reference
to Ch 7, Sec 2, [2.5.7].

251

8/3.2.2.2

Question

FE modelIn Chapter 8 Section 3 / 2.2.2, the calculation of hull girder stresses for thecomputation of fatigue life by direct strength analysis using superimposition
2006/11/10 method does not take into account the hull girder bending moments that exist
in the FE model due to the local loads. Consequently, some of the hull girder
bending stress is considered twice.

253

Fig 8.5.2

Question

Sectionmodulus

When calculating section modulus of the cross deck Wq and moment of
2006/12/20 inertia of the cross deck Iq, how to determine the neutral axis? Is it axis z ?
Please clarify it.

IQ and WQ are to be determined about z-axis. In order to clarify the difinitionof WQ and IQ, the editorial change will be issued as Corrigenda.

It is right that the details 3 and 10 (7/12 and 8/14) are very similar for the case"watertight". An harmonization should be very helpful. More generally, eachdetail should appear only once in the Table with SCF for the two assessed
points, and for both cases "watertight" and "non-watertight". It should beconsidered as a Rule Change

255

Table
8.4.1

Questionwatertight

In Chapter 8 Section 4, Table 1, some details, in the "watertight" cases seems
to be similar (two by two): "3" and "10"; "7" and "12" or "8" and "14". But the
2006/12/11 values of the stress concentration factors differs from a detail to another. An
harmonization of the SCF between these details is needed, in order to apply
the right ones.

256

Table
8.4.1

Questionwatertight2006/11/23

In Chapter 8 Section 4, Table 1, the meaning of "watertight" and "nonA collar plate is not required in all cases."Watertight" means that a full collar
watertight" in the column "collar plate" is not clear: does it mean that a collar
plate is fitted, and "non -watertight" means other cases: no collar plate is fitted
plate is required in any case? Or does it mean that "watertight" is equivalent to or a partial collar plate is fitted.It should be better to replace "watertight" by "fulla full collar plate and "non-watertight" is equivalent to a partial collar plate?|collar plate" and "non-watertight" by "other cases".

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KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer

257

Table
8.4.1

Questionwatertight

In Chapter 8 Section 4, Table 1, for details 1 to 8, stress concentration factors
are indicated for both cases 'watertight' and 'weathertight' for one of the
2006/11/18 assessed point and for case 'watertight' only for the other assessed point.
What are the values to consider the stress concentration factors in case 'nonwatertight' for this later point?

258

Table
8.4.1

Questionwatertight

In Chapter 8 Section 4, Table 1, a detail is missing: the one corresponding
2006/12/13 with detail 1, but without vertical stiffener. What are the values to consider forthe stress concentration factors for such a detail?

For a detail corresponding to detail 1, but without vertical stiffener nor bracket,
SCFs should be developed.

259

Table
8.4.1

Aft & Fore

|In Chapter 8 Section 4, Table 1, the meaning of "Aft" and "Fore" is not clear:
2006/11/23 does it mean aft and fore ends of the ship, or aft and fore ends of the stiffenerconsidered, or is it only a way to identify both sides of the detail?

"Aft" and "Fore" does not mean aft anf fore part of the ship. They are to beunderstood as being one side and the other side of the considered detail. It
should be better to give a name to the two assessed points, i.e. "Point A" and"Point B", and to modify the schemes accordingly ("A" and "B" instead of "a"anf "f", and delete "Aft" and "Fore".

277

8/2.2.3.2

Question

Questionconditional
equations

2006/11/23

This item seems to be rule change.We would like to know the impact due tothis change.

In the case 'non-watertight', the missing stress concentration factors for one of
the two points leads to less severe results in fatigue. That is the reason why
the values of the SCF are not indiciated. However, our point of view is to add
these values in the Table in order to be coherent.

This revision includes the correction of the factor in the conditional equations
and the alternation of the expression. The correction of the factor in theconditional equations is made for the simple error in writing of the factor in thecondition that the shakedown in compression stress side is occurred. Thiscondition correspond the case that the large mean stress in compression side
is occurred. The effect of this correction on the scantlings of the structuralmember is very small since the fatigue damage in such case is negligible
small. The alternation of the expression is made to clarify the meaning of theconditional equations without changing the conditions.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

286

342
attc

355

Ref.

Type

8/1.1.3.1 &Table
Question
8.1.1

8/4.2.3.6

8/5.2.1.1

Question

QuestionTopicfatiguestrengthassessment

Transverse
BHD

Parameter
correction

Datecompleted

Question/CI

List of locations subject to fatigue strength assessment:a) For ships having length L of 150 m or above, are there any circumstances
under which fatigue assessment of the locations listed in the Table can bewaived?
2006/12/13b) Is each detail to be assessed for location in homogeneous hold, ore holdand ballast hold? (This question is based on actual cases of different Class
giving different opinions of the locations requiring fatigue assessment basedon actual designs in progress.)

Attachment

Answera)No in general. The members and locations subjected to fatigue strength
assessment described in Table 1 of Ch 8 Sec 1 are of the members andlocations which the fatigue damage are occurred in the past, even though thenumber of damages are neglected. Therefore, the fatigue strength
assessment should be carried out for the structural details specified in Table 1.
b)If the arrangement and scantling of the detailed to be assessed in holds aredifferent, each detail should be assessed.

The relative deflection for double bottom is defined as follows.
(1) On the bottom
The base line is defined as the line between connecting points of the floors tobottom in way of fore and aft of lower stools. The relative deflection is definedas the deflection of the connecting points of the adjacent floors to bottom
measured from the base line.
(2) On side shell
The case 2 as shown in your attached document is correct.

2007/5/22

Relative displacement of transverse BHD.
See the attached question.

2007/3/20

In Chapter 8 Section 5,[2.1.1], the following parameters needs to be more
1) The shear area "AQ" is the effective shear area of the whole section shownspecific:in figure 2 with respect to the ship's longitudinal direction. For the deternination
1) "AQ" is the shear area of the cross deck: does it includes the shear area ofof the effective shear area the consideration of only the plate elements is
all plates and of all ordinary stiffenerd, as shown on Figure 2 ?
sufficient, and the stiffeners can be neglected.
2)"bS" is the breadth of the remaining deck strip beside the hatch opening: is it2) "bs" is only the reamaining deck strip on one side, so it is identical to "b" in
the total breadth on both sides or is it only on one side? If it is the latest case,[3.1.1]it should be identical to "b" defined in [3.1.1].
3) This is an editorial typo: "C" should be as an index in "LC".
3) "LC" is the length of the cargo area, it should be noted LC, with "C" as andAlso Included in Corrigenda 5
index.

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KCID
No.

Ref.

Type

8/4.2.3.4,
359 8/4.2.3.5 & Question
4.3.3.4

Topic

FatigueCalculations

Datecompleted2007/7/2

Question/CI

Attachment

Answer

A1 The same loading condition should be applied to both direct strength
analysis and prescriptive requirement for fatigue check.
Please review the below questions related to Fatigue calculations.
(a) rho_c = MH/VH and filling to upper deck may be applied to.
Q1: Loading conditions and assumptions. Fatigue calculation is performed in (b) Fuel oil is always filled to half the height of FOT.
the following 4 load condition; Homogenous, Alternate, Ballast and Heavy
A2: Tanks other than Water Ballast Tanks are considered as being filled atballast. The design loading condition for FEM is listed in Ch. 4 App.3. Are
50%. All Water Ballast Tanks are considered either full or empty. Even thoughthese conditions also applicable for prescriptive calculation of stiffenersuch WBT are intended to be partially filled at the standard loading condition,connection according to Ch. 8 Sec. 4? Following differences are fond between the partial filling of such tanks is not considered for fatigue check.
Ch.8 Sec. 4 and Ch. 4 App. 3: a.Filling height and density for Homogenous
A3:
condition. According to Ch. 8 Sec. 4 [2.3.5] the definition of Ch.4 Sec. 6 [1.3](a) Yes, actual still water bending moment in the Loading Manual for theshould be applied. That is = max(MH/VH,1) and filling to main deck.
respective loading conditions may be used for fatigue strength assessment.
According to Ch.4App.3 the = MH/VH with filling height to main deck.
(b) The requirement of Chapter 4 Section 3, 2.2.1 mentions that “The designb.Heavy fuel oil tanks(HFO). According to Ch.8 Sec.4 [2.3.4] the filling height still water bending moment, MSW,H and MSW, S, at any hull transverseof HFO tanks may be taken as “half height of the tank”. According to Ch.4
section are the maximum still water bending moment calculated, in hogging
App.3 the HFO tanks is full. Q2: Partially filled ballast tanks. Please advice if
and sagging condition, respectively, at that hull transverse section for the
all ballast tanks are 100% for the purpose of fatigue calculations?
loading conditions, as defined in 2.1.1.”.
Q3: Still water bending moment We assume the actual still water bending
Therefore, the loading condition is to be used which gives the maximum still
moment in the Loading Manual for the respective loading conditions may bewater bending moment among the considered loading conditions, i.e.,
used for the fatigue calculations. Please confirm. Please also clarify which
departure, arrival and intermediate conditions specified in Loading Manual.
conditions to use, departure, arrival or max./average? Q4: Partially filled
A4:
Heavy fuel oil tanks. According to Ch. 8 Sec. 4 [2.3.4] the HFO tanks are(a) Yes, the equation in Ch.4 Sec.6 [2.2.1] may be used as is, provided; indicated as half full when calculating CNI factor. Please advise on the
Liquid surface level at mid-height of the tank may be assumed to remain
following related items: a.The dynamic pressure is calculated according tounchanged relative to tank geometry even when hull motion should occur, Ch.4 Sec.6 [2.2.1]. The equation is, as far as we can see, developed based
Ztop may be taken as the Z-coordinate, in m, of the Liquid surface level at
on a full tank. How is this modified to account for filling height? Can thismid-height of the tank, and - xB, yB and zB may be taken on the Liquid
equation be used as is with respect to Ztop and reference point (xB,yB,zB). ? surface level at mid-height of the tank.
b.Mean stress and still water pressure according to Ch.8 Sec.4 [3.3.4]. The(b) Ztop may be taken as mentioned in (a).
static pressure is calculated according to Ch.4 Sec.6 [2.1]. This still water(c) We confirm that ballast exchange operation is not applicable. Please notepressure is assuming PBS = Lg(zTOP-z+0.5dAP) or Lg(zTOP-z)+100PPV that Min.25kN/m2 is not applicable to fatigue strength assessment.
whichever is greatest. Minimum 25kN/m2. How is this modified to treat
partially filled tanks? c.We assume ballast exchange operation is not applicabledoing fatigue calculations? Please confirm.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

375

385
attc

Ref.

8/App.1,
1.3.1

8/5/3.1.1

Type

Question

Question

Topic

Calculation
ChangeElliptic
Corners

Datecompleted2007/3/9

2007/3/9

Question/CI

Attachment

Answer1) That is right: the stiffeners are not to be considered in the calculation of theproperties of the cross section. Only the plates are to be considered as "partialarea" (defined in [1.1.1]).
2) The parameter "yS" which appears in the calculation of "Iz" for symmetric
In Chapter 8, Appendix 1, [1.3.1], the following items needs some clarification: cross section should be considered equal to zero. By defining it in the same1) it is understood that the stiffeners are not considered in the calculation of
way as for asymmetric cross section, it comes equal to zero, as "Sz" should be
the properties of the cross section. Please confirm?
equal to zero for such symmetric cross secton.
2) In table 1.4, for symmetric cross section, the parameter "yS" appears in the 3) We agree that using twice the same symbol for different definitions is
calculation of "Iz", but is not defined. What is the definition of "yS" in such a
confusing, It should be corrected. However, your understanding is correct: thecase?
parameter "Iwy" used in the definition of "Iw" is also the one defined in Table3) in table 1.4, for symmetric cross section, it is understood that the
1.4.
parameters "Iwy" and "Iz" which appears in the definition of "zM" are4) That is right, this is a typo: in Table 1.4, for symmetric cross section, in thethoseparameters defined just above in the table, and not those defined in the definition of " Iw", "zm" should be understood as "zM".
beginning of [1.3.1]. Please confirm? Using twice the same symbol for5) in the statement "S, Iw are to be computed with relation to shear centre M",
different definitions is confusing. The same understanding is considered for"S" is to be understood as being "Sy", "Sz" and "Sw" in the list of formulae at
the parameter "Iwy", used in the definition of "Iw".
the beginning of [1.3.1], and "Iw" is to be understood as being "Iw", "Iwy" and4) In Table 1.4, for symmetric cross secton, in the definitionof "Iw", it should be Iwz". It means that in such expressions the coordinates "yk", "yi", "zk" and "zi""zM" instead of "zm".
are to be considered also in reltion with the shear centre M.
5) Below Table 1.4, it is stated that "S, Iw are to be computed with relation to 6) We agree that the formula giving "Delta w" is not clear. The formula should
shear centre M". What are the meaning of "s" and "Iw" in this statement? 6)
be replaced by: "Delta wi = zM * yi". In order to clarify all symbols in Chapter
The formula giving "Deltaw" is not clear. Please explain?
8 Appendix 1, we will consider the rule change proposal.the coordinates "yk","yi", "zk" and "zi" are to be considered also in reltion with the shear centre M.

We have some doubts on the correction factor for elliptic corners whichappears in the formula of the stress concentration factor in Ch 8, Sec 5,[3.1.1]. We see on the knowledge centre under the answer to question 223
Having considered your attached document, it seems effectively that “ra” andthat "The requirement on hatch corner fatigue check will be revised as soon“rb” are not defined correctly. We will consider it at the time of revision of thisas possible, including a technical background". However, to help for thisrequirement.
revision, we would like to ask you to consider the attached document. It showsthat some misunderstanding has occurred between "ra" and "rb". Pleaseconsider this proposal?

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KCID
No.

386
attc

452

Ref.

8/5.3.1.1

Table
8.1.1 &
8/1.1.3.1

Type

Question

RCP

Topic

Formula"Kgh"fatiguestrengthassessment

Datecompleted

Question/CI

Attachment

Answer

2007/4/25

It is right, there is a mistake in the formula of “Kgh”. See the technicalbackground attached, in which it is clearly shown on figure 1(b) that “b” should
It seems that there is a mistake in the definition of the term “b” in the formula
be twice the distance from the edges of hatch opening to the ship’s side. So,
defining “Kgh”. We think that “b” should be twice the distance from the edge ofthe definition of “b” may remains the same as it is, but the formula of “Kgh”
hatch opening to the ship’s side. Please confirm our interpretation?
should be modified accordingly by replacing the term “b” by “2b”.
Also Included in Corrigenda 5

2009/10/6

It is requested from interpretation point of view that the members andlocations to be assessed for fatigue strength can be waived with a proviso. It
is considered unnecessary to assess fatigue strength by FEM analysis forevery location in Table 1 in particular any taken as less significant. Fatigue
assessment by FEM should be streamlined to be more practical to focus on
critical locations such as lower hopper corners and lower stool connections
with inner bottom considering selective cargo holds.

Y

We noted your comment and this issue has been addressed in RCN No.3
(issued September 2008).

The matter leads to a rule change proposal. As a result of our detailed fatigue
strength calculation based on simplified method for lower hopper corners andlower stool connections with inner bottom of a panamax bulk carrier, it is foundthat the fatigue life of these locations is impractically too short. Moreover, it isfound that the fatigue life calculated for lower hopper corners in the empty
hold is shorter than that in the ballast hold in both cases of bent and welded
corners, which is in serious contradiction of the ubiquitous fact of experience.
The least fatigue life calculated is only a few years at a lower stool connectionin the ore hold for which no way of designing to achieve the prescriptive
fatigue life of 25 years could be possible.

603
8/4.2.3.6
attc

635
attc

Table
8.4.1

CI

Displacemen
t oftransverse
bulkhead.

CI

Stressconcentration
factors

2008/4/18

JBP rules Chapter 8,Section 4.2.3.6 Stress due to relative displacement oftransverse bulkhead. There are 3 questions:
Q1. Is the relative displacement an absolute value or with a sign?
Q2. If it is not absolute value, how to decide the sign of them?
Q3. We understand that this additional stress is only applied at thetransververse bulkhead. This additional stress is not required for the rings
adjacent to the transverse bulkhead.

2008/3/26

Regarding the stress concentration factors given in the Rules Chapter 8,
Section 4, Table 1, it is understood that where values are given only forYour understanding is correct.
connections with watertight collar plates fitted, these are also applicable forconnections with non-watertight collar plate or no collar plate fitted. NK Bulletin
We will consider the rule change proposal in order clarify this.
No.276, 2006 refers. (in Japanese)
Please confirm.

Regarding the requirement in Ch 8, Sec 4, [2.3.6], please find our answers.
A1: The relative displacements are not absolute value. They should be
calculated with signs (+ or -);A2: The signs of the displacements are decided as per the rules in theattachment;
A3: Your understanding is correct and comfirmed.

Y

Y

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IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

688 8/4.2.3.3

Type

Question

Topic

Fatigure of
stiffener end
connection

Datecompleted2008/5/28

Question/CI

Attachment

Answer

Reference is made to Ch.8 Sec.4 [2.3.3] – Fatigue of stiffener end connection– Stress due to wave pressure
Design pressure in the formula is CNE x pw.
The statement of Ch 4 Sec 5, [1.1.1] is not valid when calculating sea
pw should be calculated according to Ch. 4 Sec. 5 [1.3], [1.4], [1.5]
pressure according to Ch 8 Sec 4, [2.3.3]. Becasue Ch 8 Sec 4, [2.3.3] is
Ch. 4 Sec.5 [1.1.1] is generally valid for Section 5. Quote “The total pressure p concerned only the hydrodynamic pressure, not the static pressure.
at any point of the hull, in kN/m2, to be obtained from the following formula is The statement of Ch4 Sec5[1.1.1] is only applicable to the one wave state.
not to be negative: p=pS+pw.” Unquote
When a wave, which has a certain wave height, is acting on the ship's side,
It is unclear whether or not [1.1.1] is valid for pressure calculation for Ch.8
wave pressure has to be corrected so as not to generate negative pressure.
Sec.4 [2.3.3].
Therefore the degree of correction is different by the wave height although the
Please note that if no correction to the dynamic pressure is made, the total
correction procedure is the same.
dynamic pressure for side longitudinals right below the water line is larger than The statement of Ch8 Sec4[2.3.3] is introduced to obtain the expected wave
the static pressure at the same location, that is Ps+(CNE x pw) < 0. This is in condition considering the stochastic nature of wave height so as to evaluate
contraddiction to the general statement in Ch.4 Sec.5 [1.1.1]
stress range for fatigue assessment.
Q1: Is the statement of Ch.4 Sec. 5 [1.1.1] valid when calculating sea
pressure for Ch.8 Sec.4 [2.3.3]?
Q2: If yes, it is assumed that Ch.4 Sec.5 [1.6.2] should be used for correcting
the dynamic sea pressure. Please advice how to apply [1.6.2]:
a.No correction according to [1.6.2] is made for pw when calculating CNE?
b.Correction of dynamic pressure according to [1.6.2] for the total dynamic
pressure
pw = CNE x pw(uncorrected)?

742
attc

Table
8.1.1

QuestionFEA

A-1 Structural members can be evaluated by the simplified method according
to the specification in Ch 7 Sec 4 [3.3] if applicable, except for the following
members: hold frames of single side bulk carriers, connections between
corrugations and stools and ordinary stiffeners in double side space at theconnection of transverse stiffeners with stringer or similar. Where the fatigue
assessment is carried out by the very fine mesh FEA, all cargo holds should
See the attached Question. It has multiple questions, however, for the sake of
2008/10/10
be evaluated. If the structural details in cargo holds other than heavy ballast
easy reference, they are grouped as one Question.
hold are the same as those in heavy ballast hold and the evaluated results of
those in heavy ballast hold are satisfactory, the very fine FEA for cargo holds
other than heavy ballast hold can be omitted.
A-2 The transverse BHD connection with vertical lower stool and upper stool
as well as sloping ones should be checked.
A-3. Only representative locations should be checked.

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743

Figure
8.5.2

812

854

8/4.2.3.2

Type

Topic

Date
completed

Question

Co-ordinate"Y"

2008/7/2

Ch 8 Sec 5 Figure 2 indicates coordinates. Is the co-ordinate "Y" typo? Should
Yes, it is typo. We will consider a rule change.
it be "X" ? .

2009/3/3

Geometrical stress concentration factor for stress due to lateral pressure,
K_gl, is permitted to be evaluated directly by FEM according to Ch8 Sec4,
2.3.3. However, no indications of direct evaluation by FEM are found in the
The geometrical stress concentration factor for stress due to hull girder
definition of geometrical stress concentration factor for stress due to hull girder moments, K_gh is also be able to evaluated directly by FEM. This is included
moments, K_gh, in Ch8 Sec4, 2.3.2.
in RCP 4 which has been reviewed according to PR 32.
Please confirm whether geometrical stress concentration factor for stress due
to hull girder moments, K_gh, can be evaluated directly by FEM.

2009/3/10

Table 1 of Ch8, Sec1 defines the members and locations to be analysed in
fatigue assessments. Each mentioned connection of primary supporting
members is analysed in only one direction. We see the necessity to evaluate
a connection from both sides. This question focus' on the connection of inner
bottom and lower stool.. Summary of experience with fatigue assessment ofheavy ballast cargo holds: + The connection of the inner bottom to thevertical/sloping plate of the lower stool is the most critical loaction + The
deformation of the double bottom and the transverse bulkhead expand thiswelding connection due the large internal dynamic pressures . + The global
bending stress plays not a dominant role. Stress ranges of the inner bottom
and the stool plating are of a comparable size + Typically the initial calculated
damages of the inner bottom AND the stool plate are considerably larger than
1. + Counter measures in one member, e.g inserted plates in inner bootom,
decrease the damage of this member, but increase the damage of the othermember.

StressQuestion concentration
factors

8/1.1.3.1 &Table
Question
8.1.1

Primary
SupportMembers

Question/CI

Attachment

AnswerThis is already under discussion at the Hull Panel. The conclusions will beendorsed by PT1. UPDATED ANSWER AGREED 11 SEPT 2009: "Regarding Tab
1 in Ch 8, Sec 1 of CSR-BC, the intent at the time of development of the CSRBC was not to check the inner bottom only, but the whole connection of inner
bottom with sloping and/or vertical plate of lower stool, which includes all theplates. The whole connection means the connection of plating members of
inner bottom, side of lower stool, girders and floors in DB and diaphragms inlower stool. In addition, it is to be noted that, when making fatigue assessmentof such connection, if fatigue problems are found in any of the above plating
members, then reinforcements are to be considered for all the concerned
plating members. It means that Table 1 should be understood as considering
all the plating members involved in the inner bottom/lower stool connection
and not only the inner bottom plating. Table 1 will be modified accordingly at afuture date."

As an example, the reduction of the damage of the inner bottom from 4 to 1
may increase the damage of the sloping plate up to 6 or more. The
deformation and stresses of the considered structure and the damage results
indicate clearly that this fatigue problem is a 3D-problem, where measures in
one member directly affects the other member. If we follow the definition ofmembers, to be assessed (Table 1), only the inner bottom need to comply
with the fatigue requirements, whatever the calculated damage of the stool
plating is. It seems, there are two options: 1) Assess the inner bottom - lower
stool connection from both sides. 2) Assess only the inner bottom In case of
option 1, we need a modification of the table and we need an instruction, how
to deal with approved vessels (MOU, TOCA), where no fatigue assessment
have been performed for the stool plating. In case of option 2, it has to be
demonstrated, why the damage results of the lower stool plating can beneglected.

Page 9 of 10

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

858 8/2.3.2.1

875
attc

999
attc

Table
8.2.2

8/4.2.3.4

Type

Question

Question

Topic

shape
parameter

fatiguestrength

Calculationof stress due
Question
to liquidpressure

Datecompleted

Question/CI

Answer

2009/2/11

In CSR BC Ch.8 Sec.2 [3.2.1], the Weibull shape parameter is taken to 1.0. In
CSR OT App. C/2.4.1.2, this parameter is a linear function of the rule length L.
Using in CSR BC the same definition of Weibull shape parameter as in CSR
OT leads to longer fatigue life duration. As the approach used in CSR OT isalso used in BV rules and in other societies, it is therefore requested toreconsider the value of in 1.0 for this parameter in CSR BC.

Originally, the Weibull shape parameter, which is the function of L, wasdefined for the wave bending moment in the IACS Recommendation No.56 in
1999. Strictly, it depends on the RAO of the object member and consideredload environments. In the CSR-B, the Weibull shape parameter was set as 1.0
for the simplification and the effect of such treatment is confirmed being small.
The point you mentioned should be the harmonization issue and will be
discussed in the forthcoming harmonization team on fatigue.

In practice, there are some bulk carriers without heavy ballast condition. Howis fatigue strength checked? Especially, how is the coefficient αj determinedwhich is defined in Ch8, /Sec 2, /Table 2? Is it practical to incorporate αj inheavy ballast condition into that in normal ballast condition as the following
table (as attached)?

Normal ballast condition and heavy ballast condition are required for all
vessels with CSR Bulk Carrier notation for providing sufficient draught and trim
to prevent damages during navigation in Ch.4 Sec.7 [2.2.1]. In case that abulk carrier does not have a ballast hold and has only one loading condition
carrying ballast water and that the loading condition complies with the both
requirements of normal ballast condition and heavy ballast condition in Ch.4
Sec.7 [2.2.1], the loading condition may be treated as normal ballast conditionand heavy ballast condition stipulated in Ch.8 Sec.2, Table 2. Coefficientalpha_j in Ch.8 Sec.2, Table 2 should be applied accordingly.

Y

A1 "the tank top longitudinals" in Ch.8/Sec.4/[2.3.4] mean the longitudinals on
With respect to Ch.8 Sec.4 [2.3.4]
the top structure of the tank.
1. Please specify the definition of the tank top longitudinals in the sentence “…
no inertial pressure is considered for the tank top longitudinals…”.
A2 For the half-filled tanker, when calculating the inertial liquid pressure
2. When calculate the inertial liquid pressure pBW,ij(k),SF for full-filled tank or
pBW,ij(k), z=z_SF, y=y coordinate of the calculation point of the longitudinalhalf-filled tanker, the coordinates of the calculation point taken at the liquid
stiffener.
surface should be clarified.
xB, yB and zB are considered in A4 of KC #359

Y

2009/9/3

Attachment

Page 10 of 10

Page 1 of 4

KC#342
Gil-Yong Han
From:

Johnston, Alex [Alex.Johnston@lr.org]

Sent:

08 January 2007 12:20

To:

Johnston, Alex

Subject: FW: CSR-BC Relative displacement of transverse bulkhead
1. Could you forward our question below to IACS PT with respect to JBP Ch 8 Sec 4 2.3.6 for fatigue analysis
of longitudinals in way of T.BHD.

2. Relative displacement G_A, G_F;
Example displacement in alternate condition is shown below with undeformed shape. We haveconsidered how to treat this relative displacement and some ideas are illustrated. Could you confirm whichinterpretation (Case 1 ~ 3) is correct?
2.1. On bottom shell;
Case 1 Measured in global Z coordinate (vertical direction);

Case 2; Measured from parallel line at the location considered;

09/01/2007

Page 2 of 4

Case 3; Measured from parallel line joining intersection of adjacent floors;

2.2. On side shell;
Case 1 Measured in global Y coordinate (transverse direction);

09/01/2007

Page 3 of 4

Case 2 Measured from normal line at the location considered;
However, it seems difficult to make the normal line as there are no connecting point such as inner bottom asshown above.

Case 3 Measured from parallel line joining intersection of adjacent transverse webs;

09/01/2007

Page 4 of 4

3. This interpretation is urgently requested .
We very much appreciate your kind support,
Best Regards,
A Fukushima
Surveyor
Hull Structures Group
Yokohama Design Support & Plan Approval Department (YDSPAD)
Lloyd’s Register Asia Tel No. +81 (0) 45 682 5270 Fax No. +81 (0) 45 682 5279

09/01/2007

KC#385
COMMON STRUCTURAL RULES FORBULK CARRIERS
Stress concentration factor for the hatch corners

Doubts in the CSR bulk formula (Kgh)
COMMON STRUCTURAL RULES FORBULK CARRIERS
Chapter 8 - Fatigue check of structural details
Section 5 – STRESS ASSESSMENT OF HATCH CORNERS

Correction factor for elliptic corners
In the bulk formula, ra is used for rounded corners (the radius in major axis) as a basis for
elliptic corners. They attribute a correction factor to take into account the influence of elliptic
shape.
Here is the equivalence between the two shapes:

2 rb

ra

2 ra

with the following correction factor to apply to get the elliptic stress concentration factor fromthe rounded one:

fc

1 2rb

3 3ra

Here follow the original text describing the correction factor:
This correction factor gives the ratio of stress concentration for the tension of an infinite
width thin element with an elliptic hole to that with a circular hole. In this equation, ra denotes
the radius in major axis and rb denotes the radius in minor axis. This correction factor can beapplied to the stress concentration factor for the fillet shoulder with circular arc shape ofradius ra .

We test the correction factor with ANSYS 9.0 finite element software. We used shellelements of 10 mm thickness. We model plates of 2 by 6 meters with holes in the middle andimpose displacements of 20 mm in the small direction as shown in the figure below. We use
a 206000 MPa Young modulus and a 0.3 Poisson ratio.

10 mm2000 mm

10 mm
We compare six different shapes to the circular one.

Dimensions of the compared ellipses
Shape
Arm length in x axis
200
Circular hole
Ellipse 1
50
Ellipse 2
75
Ellipse 3
100
Ellipse 4
200
Ellipse 5
200
Ellipse 6200

Arm length in y axis
200
200
200
200
250
300
400

Ellipse shapes 4, 5 and 6 are other kind of ellipse shape that those used for bulk formula.
The reference axis is the minor one.

ra

2 rb

2 rb
y

x

ra

Ellipse shape based on
major axis (bulk

2 rb
Ellipse shapebased on minor

Measuresx

Mean stress

The mean stress is calculated as follow for a simple tensile test without any hole:V mean E H
H 0.01
V mean 2060 MPa
xMaximum stressThis is the greatest principal stress read in the model as shown on the following pictures.

2 ra

ANSYS 9.0 tests

Rounded corner
Sig max = 5731 MPa

Elliptic corner (200x300)
Sig max = 4386 MPa

Elliptic corner (75x200)
Sig max = 3538 MPa

Models usedResults
Comparison between Kt eval (fc) and Kt real (ANSYS software) for the different ellipses
Kt eval /Kt
Shape
dimensions
Maximum
Kt real (MaxCorrection Kt evaluated(2.78* fc)
realstressstress/2060)
factor fc
Circular hole 200x200
5731
2.78
1
Ellipse 1
50x200
3057
1.48
0.5
1.39
0.94
Ellipse 2
75x200
3538
1.72
0.58
1.62
0.94
Ellipse 3
100x200
4009
1.95
0.67
1.85
0.95
Ellipse 4
200x250
4928
2.39
0.87
2.42
1.01
Ellipse 5
200x300
4386
2.13
0.78
2.17
1.02
Ellipse 6
200x400
3702
1.8
0.67
1.85
1.03
We can see that rb radius is a more conservative basis than ra to evaluate the influence of anelliptic shape. The error is a bit less than for ra and the Kt obtained is over evaluated (rbbasis) instead of being under evaluated (ra).

ra

2 rb

2 rb
y

2 rb
Ellipse shapebased on minorxraEllipse shape based on
major axis (bulk

2 raKC#386
Stress Concentration around Hatch Corner of Bulk Carrier

1㧚 Simplified Fillet Shoulder Model of Hatch Corner
When evaluating a stress concentration around hatch corner of bulk carrier subject to the longitudinal stress due tovertical hull girder bending moment, that is illustrated in Fig.1(a), the shaded area in cross deck is the area where thelongitudinal stress is not worked. Therefore, in order to evaluate the stress concentration around hatch corner of bulk
carrier, the simplified fillet shoulder model shown in Fig.1(b) can be used.
The height of fillet shoulder depend on the degree of disturbance of longitudinal stress flow occurred due to thestructural discontinuity around hatch corner.

H

b

B

h

r

I

h

b/2

L

b/2

L

Fig. 1(a) Hatch Opening of Bulk Carrier

Fig. 1(b) Simplified Fillet Shoulder Model

2㧚 Stress Concentration Factor
2.1 Experimental Formula
The stress concentration factor for the stepped flat tension bar with fillet shoulder was given by Heywood[ Heywood, R. B., “Photo-elasticity for Designers”, Pergamon, New York, 1969 ] as below.

b
H b ·¸© 2.8 H  2b 2r ¹§

D 1 ¨

0.65

b
h·
§
1 ¨
¸
© 5.6h  0.8b r ¹

0.65

§
b
L tan I ·¸¸
1  ¨¨© 2.8L tan I  0.8b 2r ¹

0.65

The above formula can be applied in evaluating the stress concentration factor to the nominal hull girder verticalbending stress which acts on the ship’s side part of upper deck. The above formula gives the stress concentration factor
for the hatch corner of circular arc shape. Although an elliptic arc shape is often used to decrease stress concentration in
the actual design, there are no analytical nor experimental results regarding on the stress concentration for the fillet
shoulder with elliptic arc shape.
Here, following simple correction factor for the elliptic arc shape is assumed. This correction factor gives the ratio ofstress concentration for the tension of an infinite width thin element with an elliptic hole to that with a circular hole. In
this equation, ra denotes the radius in major axis and rb denotes the radius in minor axis. This correction factor can beapplied to the stress concentration factor for the fillet shoulder with circular arc shape of radius ra .
fc

1 2rb

3 3ra

1

2.2 Disturbance of stress flow

As shown in Fig. 1(a), the disturbance of longitudinal stress flow is occurred at the opening corner due to thestructural discontinuity around hatch corner. This disturbance of stress flow causes stress concentration and the degreeof stress concentration depends on the angle of disturbed stress flow ‘ I ’ and the length of shoulder. According to thephotoelasticity experimental results, it is said that the angle of disturbed stress flow was about 10 to 30 degree.
According to the results of FE analysis of bulk carrier made by NK, the angles of disturbed stress flow around hatch
corner were about 15 to 30 degree as shown in Table 1.
Table 1 Angle of disturbed stress flow to the longitudinal direction
Location
Opening at mid part
Foremost opening

Angle to the longl. Direction.
16.5 㨪 28.9
23.0

2.3 Shape of Hatch Opening of Bulk Carrier

The degree of stress concentration at hatch corner is also depending on the shape of hatch opening on the upper
deck. Table 2 shows the results of the survey of existing bulk carriers.
According to the Table 2, the ratio of ‘H’ to ‘b’ is about 1.1 to 1.3. And the ratio of ‘ ra ’ to ‘b’ is about 0.05 to 0.07.

S. No.

Lpp

B

BC1
BC2
BC3
BC4
BC5
BC6
BC7

179.80185.00215.00279.00279.00279.20290.20

31.00
32.26
32.20
45.00
45.00
45.00
50.00

Table 2 Shape of Hatch Opening of Typical Bulk Carriers
Length WidthLb
H(15) H(20) H(25)

H(30) major r minor r

20.80
20.47
17.85
16.32
14.72
15.47
15.76

18.02
18.80
22.04
30.94
30.37
30.78
32.86

17.60
18.60
14.58
20.16
21.00
20.00
23.40

8.00
8.90
7.65
10.56
11.04
10.01
10.84

13.40
13.66
17.62
24.84
24.00
25.00
26.60

15.54
16.04
19.67
27.67
26.96
27.68
29.50

16.31
16.90
20.40
28.68
28.02
28.64
30.54

17.13
17.81
21.19
29.76
29.15
29.67
31.65

0.90

0.45

1.22

0.61

1.36

0.78

2.4 Examples of Stress Concentration Factor

Figure 2(a) and 2(b) show the results of evaluated stress concentration factor for the hatch corner where a circular
arc shape and an elliptic arc shape are applied respectively. In these figures, x ra b and p H b .
When an elliptic arc shape is applied to the hatch corner, the stress concentration becomes sufficiently small.
2.5

2.5

x=0.05

2.25

2.25

2

p=1.3

2

x=0.07

1.75
1.5

1.75
1.5

x=0.06

1.25
1

1.05

1.1

1.15
p

p=1.1
p=1.2

1.25
1.2

1.25

1.3

0.05

0.06

0.07

x

0.08

Fig. 2(a) Stress Concentration Factor when the Corner is Circular Arc Shape

2

0.09

0.1

1.8

1.8

1.6

1.6

x=0.05

1.4

p=1.3

1.4

x=0.07

1.2

1.2

p=1.1

x=0.06
1

1.05

1.1

1.15
p

1.2

p=1.2
1.25

1.3

0.05

0.06

0.07

x

0.08

0.09

Fig. 2(b) Stress Concentration Factor when the Corner is Elliptic Arc Shape3㧚 Proposed Formula of Stress Concentration Factor

The stress concentration factor for the hatch corner is proposed as below.

Dªmax «1.0,«¬

where ra0.65 ºra  2rb ­° §b
0.22 L · ½°»¸ ¾
 ®1  ¨¨¸3ra°̄ © 1.23L  0.8b ra ¹ °¿»¼

; radius in major axis

rb

; radius in minor axis ( if the shape of corner is a circular arc, rb is to be equal to ra )L

; length of cross deckb

; distance from the edge of hatch opening to the ship’s side3

0.1

KC#603 )RUERWWRPVWUXFWXUH
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KC#635

KC#742

KC Question ID 742, 28 April 2008 (from LR)
The members and locations subjected to fatigue analysis are described in Table 1 of Ch 8,
Section 1 of CSR bulk carrier Rule (see below table). Could you please clarify following
queries:Members
Inner bottom plating
Inner side plating
Transverse bulkhead
Hold frames of single sidebulk carriers
Ordinary stiffeners in doubleside space
Ordinary stiffeners in upperand lower wing tankOrdinary stiffeners in double
bottomHatch corners

Details
Connection with sloping and/or vertical plate of lower stool
Connection with sloping plate of hopper tankConnection with sloping plate of hopper tankConnection with sloping plate of lower stool
Connection with sloping plate of upper stool
Connection to the upper and lower wing tankConnection of longitudinal stiffeners with web frames andtransverse bulkhead
Connection of transverse stiffeners with stringer or similar
Connection of longitudinal stiffeners with web frames andtransverse bulkhead
Connection of longitudinal stiffeners with floors in way oftransverse bulkheadFree edge of hatch corners(1) The fatigue performance of members and loactions in red font in above table need to beevaluated using very fine mesh FE model, the other parts can be evaluated using
simplified method.
For very fine mesh analysis, which cargo hold should be done? Heavy ballast hold,
Heavy cargo hold or Light cargo hold?
(2) The transverse BHD connection with sloping lower stool and upper stool should bechecked, but how about transverse BHD connection with vertical lower stool and upperstool? Should it be checked as well or just ignored it?
(3) Which locations should be checked, for example:(3-1)Inner bottom plating/connection with sloping and/or vertical plate of lower stool
Centreline or full breath?
(3-2)Inner bottom plating/ Connection with sloping plate of hopper tank Mid-hold or fulllength of hold?
(3-3)Inner side plating/ Connection with sloping plate of hopper tank Mid-hold or fulllength of hold?
(3-4)Transverse bulkhead/ Connection with sloping plate of lower stool Centreline or full
breath?
(3-5)Transverse bulkhead/ Connection with sloping plate of upper stool Centreline or full
breath?
(3-6) Hold frames of single side bulk carriers/ Connection to the upper and lower wing tankMid-hold or full length of hold?

END

Page 1 of 1

KC#875
CSR KC ID 875, Question

Loading Conditions

BC-A

BC-BǃBC-C

Homogeneous
L<200m Alternate
Normal ballast

0.6
0.1
0.3

0.7
--0.3

HomogeneousḺ200m Alternate
Normal ballast

0.25
0.25
0.5

0.5
--0.5

KC#999(y, Zsf)

Calculated Point