IACS Common Structural Rules Knowledge Centre

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

161

177

204
attc

212

213

Ref.

6/3.4.2.2

6/1/2.5.1

Ch 6

6/1.2.5.1

6/2.2.2.1

Type

Question

QuestionCI

Question

Question

Topic

Stiffeners

weldedshearstrake

Stiffeners

Datecompleted2007/6/11

2006/9/27

2007/6/11

Question/CI

A point is not clear while calculating the bending moment M0.
What must be done when (cf - pz) is negative or null?

2.5.1 Welded sheerstrake
The net thickness of a welded sheerstrake is to be not less than the actual
thicknesses of the adjacent 2m width side plating, taking into account higher
strength steel corrections if needed.
In this item, does the actual thickness mean actual gross thickness or actual
as-built thickness? Is the word 'net' omitted between 'actual' and 'thicknesses'
as 'the actual net thicknesses'?

Sniped stiffeners, requirement to buckling capacity - please see attachment
for full query as it included diagrams and equations.

side shell
plating

There are some cases where the side shell plating adjacent to sheer strake
includes single side part and is increased due to the buckling and hull girder
shear strength.Obviously, its reinforcement is not necessary for sheer strake,
2006/11/22
then please revise the sentence as follows:"...is to be not less than therequired thickness of the adjacent 2 m width side plating, which is calculated
according to Ch.6, Sec.1,..."

hull girder

We consider that this requirement has been introduced taking into accountshear lag.
However, there are some cases where the attached plating is increased dueto the buckling of the plating and hull girder shear strength.
Therefore we would like to ask you to revise the sentence as follows:"The net thickness of the web of ordinary stiffeners, in mm, is to be not lessthan the greater of:・…
・40% of the net required thickness of the attached plating, which is
calculated according to Ch.6, Sec.1."

2007/1/11

Attachment

Answer

The requirement [4.2.3] should be applied both to ordinary stiffeners subjected
or not to the lateral pressure. When this requirement is fullfilled for stiffeners
subjected to lateral pressure, the term (cf-pz) which appears in the calculationof M0 in [4.2.2] becomes greater than 0.
In addition, requirements [4.2.1] and [4.2.2] apply only to ordinary stiffeners
subjected to the lateral pressure.

The actual thickness of the adjacent side plating is to be understand as being
the actual net thickness, equal to (tas built - tc).

a)Section 3 covers buckling of ordinary stiffeners and stiffened panels.
Therefore sniped buckling stiffeners are subject to Ch. 6 Sec. 3 [4].
b)No. Ch.6 Sec. 2[1], [2] and [3] are applicable to ordinary stiffeners and [4] isapplicable to web stiffeners.
Y
Buckling stiffeners as shown are subject to1.Ch. 3 Sec.6 [5.2.1]
2.Ch. 6 Sec.2 [4.1.2]
3.Ch. 6 Sec.3 [4]Generally, when the side shell plating adjacent to sheer strake includes single
side part and is increased due to the buckling and hull girder shear strength, it
is also the case for the sheer strake, which is located above. Consequently,
we see no reason to modify this requirement.

We agree with the modification proposed in the original question:"The net thickness of the web of ordinary stiffeners, in mm, is to be not lessthan the greater of:- t = 3.0 + 0.015L2- 40% of the net required thickness of the attached plating, to be determinedaccording to Ch.6, Sec.1. and is to be less than 2 times the net required
thickness of the attached plating."
We will consider the Rule change proposal.

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6/2.2.3

6/2.3.3.1

6/2.3.4.1

6/2.3.4.2

Type

Question

Question

Topic

Date
completed

PMA

If applying this requirement to longitudinal PMA having wide width, therequired scantlings become to be very heavy. This rule seems to be buckling
requirement. Since at least longitudinal structural members, such as deck
plating, skin plating, longitudinal bulkhead plating, inner bottom plating and2006/12/13
longitudinal stiffeners attached to them, are to be complied with Ch.6, Sec.3“Buckling & Ultimate Strength of ordinary Stiffeners and Stiffened Panels”, it is
not necessary to apply this rule to them. We would like to ask you to revise
the rule taking into account the above.

Such longitudinal PMA having wide width should comply with the requirementof [2.3], where it is applicable considering the configuration of the stiffener. In
case the stiffener should not comply with the requirement of [2.3] or [2.3]should not be applicable to the stiffener, such longitudinal should be modeledby shell elements in FEA and its yielding strength and buckling strength
should be verified as a primary supporting member.

BWE

The net required section modulus [3.2.3] of side frames in holds intended tocarry ballast water is excessive than our experience and approximately twice
the value required by [3.3.1].The cause of the above is the difference inposition to be assessed.In [3.3.1], the position to be assessed is the mid spanof side frame. And the position to be assessed in [3.2.3] is the fixed
ends.According to [3.3.3], the required section modulus at ends of side frame
is to be twice of the required section modulus at mid span.Therefore we would
like to ask you to revise the rule as follows:Case A - [3.2.3] "m=20 for side
frames of single side bulk carrier"orCase B - [3.3.1]To add the following:"...thenet section modulus at lower and upper bracket"

We conclude that there is no need to change the rule formula according to thefollowing reason. With our calculations, we have not seen this ratio of 2
between the application of [3.2.3] for side frames in holds intended to carryballast water and [3.3.1].It would be interesting to have more detailed
information on the comparative calculation to check that all parameters arecorrectly taken into account, and in particular the span, which is not the same
in both requirements. In [3.2.3], the span is defined in Ch 3, Sec 6, [4.2], i.e.
by considering reduction of span due to brackets; and, In [3.3.1], the span isdefined in Ch 3, Sec 6, Fig 19, i.e. by considering no reduction of span due tobrackets.Therefore, the text is kept as it is.

2006/12/8

Question/CI

Questionpressure
formulaThe required scantlings by this rule is excessive than our experience. In theformula, counter pressures acting on side longitudinals, hopper / top side
longitudinals and backing brackets are ignored. Thus the rule brings heavy
2006/11/22
scantlings. We would like to ask you to revise the formula in which counterpressures are taken into account. If it is difficult, an alternative analysis suchas direct calculation should be permitted.

Question

directcalculation

The required scantling and the material by this requirement are excessive
2006/11/23 than our experience.An alternative analysis such as direct calculation shouldbe permitted.

Attachment

Answer

The pressures to be considered in this formula are the pressures at mid-spanof the side frame. In addition, the differential pressures, if any, are to beconsidered. Also Included in Corrigenda 5

From our experience, we have not seen excessive scantlings. We would liketo have more information on this "excessive" values. In addition, to accept thatalternative analysis such as direct calculation are permitted is a generalquestion for the totality of CSR (oil or bulk). This should be discussed as a
general matter.

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KCID
No.

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Type

Topic

268
6/3.3.1.2

Question

FEM
buckling

Datecompleted

Question/CI

The author requests changes and defines e3 & ky as equal to 1. As far as weconcern both kx (for longitudinally loaded plating) and ky (for transversely
2006/11/30 loaded plating) is defined in Tables 2 & 3(for curved plating) and e3 is welldefined in Table 4. IACS's proposed additional definition confuses the issue.
Propose to leave text as it was prior to errata

Reference is made to: Additional information according to "Corrigenda 1, May
2006", Ch 6, Sec 3, [3.1.2]:
The following three lines are the original text: Each term of the above
conditions must be less than 1.0. The reduction factors kx and ky are given in
Tab 2 and/or Tab 3. The coefficients e1, e2 and e3 are defined in Tab 4. This
was the Add. inf.: For the determination of e3, ky is to be taken equal to 1 incase of longitudinally framed plating and kx is to be taken equal to 1 in case oftransversely framed plating. We added this additional information due toseveral requests from other classification societies, how to calculate e3,
because in the buckling assessment of a plate field in a transverse section
analsys only hull girder bending and shear stress have to be taken into
account (Ch6, Sec3, 3.1.2). Therefore the kappa parameter of a load normal
to the hull girder bending stress has to be set to "1" to calculate e3 according
Table 4. In case of a pressure loaded bilge plate, the pressure induced
circumferential stress has to be neglected for a transverse section analysis. In
a FEM based buckling analysis this stress has to be taken
into consideration and the complete interaction formula of 3.2.4 has to be
used. The
additional information, given in "Corrigenda 1, May 2006", is kept because thisiscomplete interaction formula of 3.2.4 has to be used. The additional
information, given in "Corrigenda 1, May 2006", is kept because this isuniversally valid for the transverse section analysis.
From our experience, we have not seen excessive scantlings. We would liketo have more information on this "excessive" values.It would be interesting tohave more detailed information on the comparative calculation to check thatall parameters are correctly taken into account.
There may be various arrangement of pillars and other supporting structures.
Then supporting area should be determined on a case by case basis.

276

6/2.3.3

Questionside frames

The requirement of this rule for side frame seems to be excessive. The
2006/11/22
section modulus of side frame of CSR is about twice of URS25.

311
attc

6/4.4.1.1

Questionve stress

How to determine the supporting area of the pressure to calculate the
2006/12/21 compressive stress? If the CSR Bulker Rules has not described, the proposal
in the attached file could be taken into consideration.

6/3.3.2.4

In the first formula in Ch 6, Sec 3, 3.2.4, we are worried about the effect of thethird term with B factor which makes the buckling ratio higher in case when
Question buckling ratio 2006/12/21
We confirm that the formula is correct, with B factor defined in Table 4.
one side is in tension than in case when both sides are in compression.Could
you confirm that the formula is correct?

318

319
attc

6/2.3.4.2

Question

brackets

2007/1/12

The value of the net connection area of upper and lower brackets to the ithlongitudinal stiffener supporting the bracket, obtained from Ch 6, Sec 2,[3.4.2]) may be 2 times the actual value.
Such a large increase may imply the following risks:- Uselessly reinforce bracket thickness.
- Uselessly ask for web stiffener connected to longitudinals.
- Uselessly extend brackets which could interfer with the PMA arrangement.
Please forward us the background of formula in [3.4.1] and [3.4.2].

Attachment

AnswerThis requirement is coming from work of IACS WP/S at the time of fourth
revision of UR S12, in 2002/2003. A Technical Background explaining theformulae of Ch 6, Sec 2 , [3.4] of CSR for bulk carriers is herewith enclosed.
The calculation is on the conservative side (i.e. higher part of the end-fixing
moments is transferred by transverse supporting webs), but not unduly, andwe really don't think a change is technically justified.
The only interpretation that could safely be done looking at the derivation of
the formula in [3.4.2] is to replace the provided net section modulus wi by its
minimum required value to comply with [3.4.1].

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6/2.4.1.3

Type

CI

6/1.2.7.4 &Question6/2.2.5.4

3/6.5.2
6/2.2.2
6/2.2.3
6/4.1.5

Question

Datecompleted

Question/CI

2007/1/22

Regarding the internal inertial pressure p due to liquid to be applied, ourundestanding is that such pressure are those of:- Double Bottom pressure alone acting on bottom longitudinal. Pleaseconfirm?
- Topside tank ballast pressure alone acting on side and deck longitudinal.
Please confirm?
- Balance of Double Bottom pressure and Deep Tank ballast pressure actingon Inner Bottom longitudinal of Deep tank. Please confirm?
- Balance of Top side tank ballast pressure and Deep Tank ballast pressure
acting on top side sloping plate longitudinal. Please confirm?
In addition, in no case pressure p acting on watertight floors of double is not tobe considered, neither should it be considered for watertight part of bulkheads
belonging to wing tanks. Please confirm?

uniformloads

2007/1/12

In [2.7.4] of Ch 6, Sec 1 for plating and in [2.5.4] of Ch 6, Sec 2 for ordinary
stiffeners, for steel coil load with dunnage more than 5, it is stated that the
inner bottom may be considered as loaded by a uniform distributed load.
But CSR has no definition for uniform loads.
So such definition of uniform loads should be introduced CSR.

Web
Stiffener(1) Primary supporting member are defined as: members of the beam, girderof stringer type which ensure the overall structural integrity of the hullenvelope and tank boundaries, e.g double bottom floors and girders,
Web stiffeners of primary supporting members:
transverse side structures, web frames/diaphragms in hopper side tanks,(1) Because there is no definition for “primary supporting member”, themeaning of “web stiffener of primary supporting member” itself is unidentified. topside tanks, lower stools and upper stools, side stringers, horizontal
girders/transverse web frames, hatch side/end coaming.
Please clarify the definition of “primary supporting members”.
(2) The requirements in Ch 6, Sec2, [2.2] adn [2.3] are not applicable to web(2) Please see the attached summary table about rule applications for web
stiffeners but to ordinary stiffeners, The only requirements applicatle to web
stiffeners of primary supporting members based on our understanding. It
stiffeners in CSR for bulk carriers are the following ones:- Ch 3, Sec6 [5.2.1]
shows that which requirements should be applied to web stiffeners. Please
for the net thickness of such stiffeners, which refers to the minimum net
confirm.
2006/12/18
thickness of the primary members on which they are fitted, i.e. to Ch 6, Sec 4,(3) We also would like to confirm that whether the web stiffeners fitted onwatertight girders, e.g. watertight centre girder and floors, should be applied to [1.5.1], and - Ch 6, Sec 2 [4] for the net scantlings of web stiffeners of primary
the both requirements for primary supporting members of Chapter6/Section4 supporting members.
(3) The same requirements as stated in (2) above apply to web stiffeners fitted
and for ordinary stiffeners of Chapter6/Section2 or not.
on(4) If there is any needs to satisfy both requirements for primary supportingwatertight side girders, centre girders and floors, i.e. Ch 3, Sec 6, [5.2.1]for themembers and for members subject to lateral pressure, I would like to know
net thickness of such stiffeners ( and so Ch 6, Sec 4, [1.5.1] and Ch 6, Sec 2,
whether the web stiffeners fitted on the watertight bulkheads in the topside[4].
tanks and bilge hopper tanks are treated the same or not.
(4) See our comment in (1) as we consider that stiffeners on these bulkheads
are considered as ordinary stiffeners and not as web stiffeners.

Topicinertialpressure

Attachment

Answer

Our interpretation is that the pressure to be considered should be only internal
inertial pressure acting on the longitudinal.
For better understanding, we will consider the editorial correction of thedefinition of p in [4.1.3].
Also Included in Corrigenda 5

A definition of uniform loads on inner bottom will be included in CSR for bulk
carriers.

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Date
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Question/CI

Attachment

Answer

2007/5/14

The current requirement is only considering the buckling strength from thelocal bending stress as it is only taken the maximum vertical stress without
shear component. Therefore, the panel size is only taken as b times b for faceplate and 2b times b for web plate. However it should be noted that thebuckling strength should be considered not only from the local bending stress If a FE analysis derives signifcant shear stress in face plates of corrugated
but from the global bending and shear stress. It is expected that the higher
bulkheads you may take this stress into consideration according case b),
shear stress would be induced at the connection of corrugated bulkhead todescribed in 1.3.4.
side shell, hence the shear buckling should also be taken into account. To
assess the shear buckling, the panel size should be taken separately fromabove, i.e. full length panel from top of lower stool to bottom of upper stool
and the shear stress to be taken as mean shear stress of the large panel.

QuestionThe
Maximum
Verticalstress2007/7/2

The current requirement states that “the maximum vertical stress in theelementary plate panel is to be considered in applying the criteria”. This
results the severe requirement when the quality of the mesh was poor at theedge of corrugation where the connection of other structures to corrugation isrelatively complex. To apply the maximum vertical stress to the “elementary
plate panel” is considered unrealistic. This should be enhanced to be morepractical.

Assuming a b x b or 2b x b buckling field (depending on the considered area)
you may derive the vertical stress as an average value of elements inside thisarea. Lower part of the web plates prone to include bad shaped elements or
triangular elements may be neglected. Each area with a different thickness is
to be considered and checked separately.

Chp 6/
346 Appendix1 Question/1.3.4The Edge
constraint
factor

2007/3/9

The current requirement, the edge constraint factor, F1 = 1.1. This should be
1.0.

As the correction factor F1 is not used for the buckling load cases 1 and 5, thelines "F1=1.1 is to be used" in (a) and (b) of 1.3.4 are not necessary. We willconsider the editorial correction.

344

345

Ch.6,
Appendix
1/1.3.4

Text 6/
Appendix
1/1.3.4

Question

Corrugated
BHD

356
attc

6/2.3.3.1

Question

Modulus2007/3/16

Questions on the requirement for mid-span sectional modulus. See theattached.

(a) Yes, ps and pw in the formulas in Ch.6 Sec.2 [3.3] are pressures in intact
condition.
(b) Yes, Ch.6 Sec.2 [3.2.3] is to be applied to side frame only in way of ballast
hold in heavy ballast condition.
(c) Q1: The required section modulus by the formula in Ch.6 Sec.2 [3.2.3]
should be applied to whole span of side frame. Please note that while thespan l in Ch.6 Sec.2 [3.3.1] is to be determined without consideration to end
brackets according to Ch.3 Sec.6 Fig.19, the span l in Ch.6 Sec.2 [3.2.3] may
be with consideration to end brackets as specified in Ch.3 Sec.6 [4.2]. (d) Q2:
The required net section modulus at end brackets is to be not less than twice
the greater of the net section moduli required for the frame mid-span area
obtained from Ch.6 Sec.2 [3.3.1] and Ch 6 Sec.2 [3.2.3] for ballat hold.

357

6/2.4.1.1

QuestionWeb
Stiffener

2007/5/14

Which value of k1 is to be used for a web stiffener on watertight primary
supporting member ?

For a web stiffener on watertight primary supporting member, i.e. with fullcollar plate, k1 is to be taken equal to 0.2.

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367

Ref.

Table
6.3.2

Type

Topic

Question Rule Change

Flooding
6/1.3.1.5 &Question Requirement
6/2.3.1.5sDatecompleted

Question/CI

2007/7/1

Ch6 Sec3 We get different results for LC5 in Table 2 depending on whether
we denote the longer side b and the shorter side alpha*b, or vice versa. Thisis an unexpected result. We suspect this is caused by an inaccurate definitionof b. The definition of b should be similar to the definition of la in CSR Tank.
We propose the following definition, which is in line with CSR Tank:
b: length in mm, of the shorter side of the plate panel for Cases 1 and 2, or
length in mm, of the side of the plate panel as defined for Cases 3-10.
Further we suspect the formula for reference stress sigma_e in the List ofErrata of April 2006 is incorrect. b, as defined above, should be used for the
calculation, not b'. This means the formula as printed in the Rules of January
2006 is correct.
By making the above described modifications we avoid the problem for LC5,
and we are also in line with CSR Tank. Please comment.

2009/9/4

The definition of sig-x is unclear for longitudinal members in flooding
condition. The MSW,F in Ch 4 Sec 3 [2.4] assumes flooding of individualcargo hold and is required only for BC-A and BC-B ships. Does the same
MSW,F apply to any dry compartment, for instance, inner side and duct keel
in double bottom space? How do we apply MWH,F and any of the load
combination factors?

Attachment

AnswerYour conclusions are right. We will prepare a rule change proposal as follows:
Definitions in Symbols
a: Length in mm of the longer side of the partial plate field ingeneral or length in mm of the side of the partial plate fieldaccording Table 2, BLC 3 - 10
b: Length in mm of the shorter side of the partial plate field ingeneral or length in mm of the side of the partial plate fieldaccording Table 2, BLC 3 - 10
In accordance with these definitions of a and b the definition of the reference
stress S_e of the CSR for Bulk Carrier 2006 is correct. We will reject thedefinition, given in the Corrigenda 1. "Note: IACS Council expediated therrule change required as a result of this question and on 19 July 2007 agreed
that the correction in the attached file should be made to Ch.6, Sec.3
Symbols."
Also Included in Corrigenda 5

1) When hold flooding is considered for local scantlings check of a plate or a
stiffener, MSW,F, MWV,F and MWH,F are to be used in lieu of MSW,MWV
and MWH respectively for calculating sigma_x by the formulas in Ch.6 Sec.1[3.1.5] and Ch.6Sec.2 [3.1.5], where MWH,F=0.8MWH. However in this casethe same load combination factors CSW, CWV and CWH as those for intact
condition are to be used.
Notwithstanding the above, for a ship of length Ls <150m the sigma_x is to be
calculated by the same formula as that in Ch.6 Sec.1 [3.1.5] or Ch.6 Sec.2[3.1.5], as applicable."2) When flooding of the compartment other than a hold is considered,sigma_x is to be calculated by the same formula as that in Ch.6 Sec.1 [3.1.5]
or Ch.6 Sec.2 [3.1.5], i.e, only intact conditions should be used to determine
Sigma_x, as applicable.
This interpretation will be included in the Rules at a future revision.

368

Ch 6
Sec1.3.1.5
Question&
Sec2.3.1.5

Calculation

2007/3/20

In order to calculate sig-x for BC-C ships and ships with length less than 150
m, do we have to calculate MSW,F by flooding individual cargo holds which is Sigma x for intact condition is used.
not required for longitudinal strength?

369

Ch 6 Sec
1.3.2.2
and Sec
2.3.2.5

corrugatedBHD

2007/3/20

We assume that these requirements apply to stools of corrugated bulkheads
with the design load as given in Ch 4 Sec.6 [3.2.1]. Flooding load given in[3.3] does not apply to the bulkhead stools. Please confirm.

Question

Yes, your interpretation is correct.

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Flooding
6/1.3.2.2 &370
Question Requirement
2.3.2.5
s

372

6/3.6

Question

corrugated
BHD

Date
completed

Question/CI

Answer

2009/9/4

The MSW,F is defined in Ch 4 Sec 3 [2.4] by flooding individual cargo holds. If
the same design moment is applied to any dry compartment such as ductkeel, the flooding requirements may, according to our calculation, give heavier
scantlings than the intact requirements. This means that the flooding
requirements may have to be applied to all structural boundaries as minimum.
Please explain.

When flooding of the compartment other than a hold is considered, sigma_x isto be calculated by the same formula as that in Ch.6 Sec.1 [3.1.5] or Ch.6
Sec.2 [3.1.5], i.e, only intact conditions should be used to determine Sigma_x,
as applicable.

2007/3/9

Shear buckling of vertical corrugated bulkhead is required for BC-A and BC-B
only. The same limitation is stated in [1.1.2 b)]. This is inconsistent to otherrequirements for corrugated bulkheads which apply to all ships. Does thisrequirement apply to all ships as well, same as Sec 1 [3.2.3] and Sec 2[3.2.6]? Please explain.

It is typo. The wordings "for BC-A and BC-B ships" are delted from the text in
Ch. 6 Sec 3 [1.1.2] and the title of [6]should be deleted. This editorial
corrrection is included in "Corrigenda 2".

Attachment

Yes, it is a typo error. The text of this requirement should be read as:373

6/4.1.3.1

374

6/4.

380

6/1.2.7.3

For primary supporting members for ships having a length of 150 m or more,
the direct strength analysis is to be carried out according to the provisions
specified in Ch 7, and the requirements in [4] are also to be complied with. In
addition, the primary supporting members for BC-A and BC-B ships are tocomply with the requirements in [3].
Also Included in Corrigenda 5

2007/3/5

In addition the primary supporting members for BC-A and BC-B ships are tocomply with the requirements in (3) and (4)" The Sub-Section (4) is aboutbuckling strength of pillars is this typo error?.

Flooding
Question Requirements

2009/9/4

This section applies to primary supporting members in intact condition only.
Do we not check primary supporting members on the boundaries of drycompartments against flooding load, such as those on a plane bulkhead at
forward of foremost hold or aft bulkhead of aftermost hold? This isinconsistent to flooding requirements for local plates and stiffeners in Ch 6
Sec 1 and Sec 2 covering all ships. Please explain.

Your comments have been noted and further studies have been made toconsider extending the requirements for flooding conditions, the outcome ofwhich will be included in a future revision of the Rules.

Holds loadedwith steel
coils

2009/10/6

The results currently obtained show an important increase of the grossthickness for plating of hopper and inner hull when applying the formulas of
Ch.6 Sec.1 [2.7.3] under steel coils loads. Should this calculation of hopper
sloping plate and inner hull plating for steel coils loads be performed?

Your comment has been noted and this issue has been addressed in RCN
No.1-3 to the July 2008 Rules.

Question

Question

directcalculation

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6/3.4.2.1

Table
6.3.2

Type

Topic

Date
completed

Question/CI
Could you please confirm how to determine the reference point of Z
cordinates of stiffeners when calculating the normal stress sigma_x ofstiffeners which contribute to the hull girder longitudinal strength? Is it thesame as JTP?

Attachment

Answer

The reference point for stresses and loads calculations is at the bottom andmiddle of its web, ie. where the stiffener joins the attached plating. This isdifferent to the CSR Oil choice which base the reference point at the top.

Question

stiffeners

2007/3/9

Question

The NormalStressSigma_n

Could you please confirm how to determine the normal stress sigma_n which
2007/10/24 is based on the axial stress calculated at the attachment point of the stiffenerto the plate? Is it the same as JTP?

We confirm that:
1)the normal stress sigma_n is the axial stress of longitudinal stiffener which is
calculated at the attachment point of the stiffener to the plate,2)it is the same way as JTP.

Case 6 of Table 2 for shear buckling is applicable only for da/a<=0.7 anddb/b<=0.7. Then, how to calculate shear buckling where da/a>0.7 ordb/b>0.7? Please advise particularly on the following points:
1) Presume that the formua of "r" yields conservative results. If so, is it
acceptable to use the formula of “r” also for the case of da/a>0.7 or db/b>0.7?
2) In case of the panel with large aspect ratio with opening of da/a>0.7 ordb/b>0.7, please advise any guidance/criteria of shear buckling calculation forthe panel with one edge free (similar to Case 3 and Case 4 for axial
compression).

If a cut out has a size beyond the limits of d_a/a<=0.7 or d_b/b<=0.7 only
small stripes are left beside the opening. The whole shear is transformed in a
S-shape deformation of the stripes. This behavior is not comparable to theassumption, that the elementary plate field acts as one buckling field. An
extrapolation of the formulae of BLC 6 is not designated. Up to now we are notable to provide user of the CSR for BC with such an additional buckling load
case.

Question

Shear
Buckling

2007/5/14

402
attc

6/1.3.1.3,
6/1.3.2.2,
6/2.3.1.3,
6/2.3.2.5

CI

Flooding
Requirements

2007/7/12

3 Questions related to flooding requirements in Ch.6, Sec.1 1 and 2

Question Q1: Your understanding is correct: Ch 6, Sec 1, [3.1.3] and Sec 2,[3.1.3] will be revised, as editorial correction to “The lateral pressure in flooded
conditions pF is defined in Ch. 4 Sec. 6 [3.2.1]”.
Question Q2: Ch 6, Sec 1, [3.2.2] and Sec 2, [3.2.6] are requirements comingfrom UR S18. The reference to the design resultant pressure in Ch 4, Sec 6,[3.3.7] only is fully in line with UR S18. Consequently, there is no need to add
any reference to [3.3.6].
Question Q3: Your understanding of the summary of flooding requirements
should take into account the answer to question Q2 above.
Also Included
in Corrigenda 5408

6/1.2.2.1

Question

scantling
determination

2007/3/12

In the determination of the minimum net thickness of side shell plating inparagraph [2.2.1] of Chapter 6, Section 1, which draught is to be used in theformula ? The moulded draught or the scantling draught ?

Since the moulded draught can change during the ship's life, the draught to be
used in the formula is the scantling draught.

409

6/1.2.2.1

Question

formula2007/3/2

In the determination of the minimum net thickness of side shell plating inparagraph (2.2.1) of chapter 6, section 1, can you recdefine more clearly theextent of side shell where the formula is to be applied.

The formula is to be applied from the minimum design lowest ballast waterline
amidships to 0.25 Ts (minimum 2.2m) above Ts.

Page 8 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

418

6/2.4.1.2

CI

Net Sectional
Modulus ofweb
Stiffeners

419

Ch.6
Sec.2

Question

Ordinary
Stiffiners

Datecompleted

Question/CI

Attachment

Answer

2007/1/14

Ch.6 Sec.2 [4.1.2] Net sectional modulus of web stiffeners of primary
supporting members.
Should the net sectional modulus be calculated with or without attachedplating? If the answer is "with the attached plate", then what is the effective
width to be considered?
Please consider clarifying the section.

The net section modulus of web stiffener of non-watertight primary supporting
member should be calculated without the attached plating.

2007/4/25

What is the definition of “ordinary stiffener”?
Are web stiffeners of primary supporting members to be considered “ordinary
stiffener”?

Web stiffeners of primary supporting members are not to be considered as"ordinary stiffeners".

Please see enclosed document "Ch6. Sec. 1 [2.7.3] Steel coil loading on
hopper plate.doc" regarding steel coil loading on inner side/hopper plate.

425 6/1.2.7.3 &2.2.5.3
attc

CI

Steel coilloading

2009/10/6

Q1: Please comment on enclosed document regarding acceleration
formulation for steel coil on hopper sloping/inner side. Please note that thehopper normal acceleration calculated directly based on the fundamental
accelerations is smaller than the rule accelerations. Dependent on the termsin(alpha-theta2) , the roll acceleration will work towards the gravity
acceleration. Please note that the acceleration is sensitive to the definition of
COG. The procedure to define COG should be clearly defined in the rules.
With reference to IACS KC #380 please consider above acceleration
calculations.

Your comment has been noted and this issue has been addressed in RCN
No.1-3 to the July 2008 Rules.

Q2: DNV have noted that the results of eq. [2.7.3] give very strict results forthe hopper sloping plate. The thickness of the hopper sloping plate is in manycases in excess of the requirement of the inner bottom. The force on thehopper is larger than the force for the inner bottom. This is caused by the Ck
factor which is 4 for 2 tiers stowage. Could you please give details regarding
the background of this term. According to our steel coil experts the stowage is,even though it is shored, quite flexible. Have there been attempted any test to
account for the amount of force taken by the hopper plating?

Page 9 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

457

Ref.

6/2.3.2.3

Type

CI

Topic

Formula460

6/3, 5/2

CI

Ordinary
Stiffeners &Stiffened
Panels470
attc

6/3.3.2.4

QuestionCompression
Stress475

6/1.2.3.3

483
attc

Table
6.3.3

CI

Net
Thickness of
the Bilge
plating

RCP

Buckling andreduction
factors forcurved plate
panelsDatecompleted

Question/CI

Attachment

Answer

2007/7/16

According #356 the span "l" in the formula of CH6, Sec3, 3.2.3 has to be
calculated taking the brackets into consideration according CH3, Sec6, 4.2.
In case of a ballast cargo hold frame of a SSS-BC the side frame brackets are For the application of Ch6, Sec2, 3.2.3 in case of a ballast cargo hold frame of
not comparable to the ones shown in Fig. 3 of CH3, Sec6, 4.2.1. The brackets a SSS-BC, the way to consider the brackets is clearly defined in the fourthof a side frame elongate the side frame more than that they shorten it.
sketch of Fig 2 of Ch3, Sec6, 4.2.1.
How should we take the brackets of a side frame in a ballast cargo hold into
consideration?

2007/7/13

Ch. 6 Sec. 3 Bucking & ultimate strength of ordinary stiffeners and stiffened
panels.
According to [1.1.2] buckling assessment of longitudinal material is not
required for flooding conditions.
According to URS 17 buckling check is required for flooding condition.
Quote: S17.5 - Strength criteria
The damaged structure is assumed to remain fully effective in resisting the1)Yes. Your assumption is correct.
applied loading.
2)Yes. Your assumption is correct.
Permissible stress and axial stress buckling strength are to be in accordancewith UR S11.Unqoute.
The Ch. 5 Sec. 2 HULS is calculating axial stress buckling of hull girder due toflooding bending moment.
Q1. We assume that CSR fulfils URS17.5 by HULS check of Ch. 5 Sec.2.
Please confirm
Q2. We assume that buckling according to Ch. 6 Sec. 3 need not becalculated in flooding condition as outlined in [1.1.2]. Please confirm.

2008/7/2

What kind of compression stresses have to be used in the buckling check
formulae for the individual compression stresses in 3.2.4 of CH6, Sec3?

2007/7/27

Ch. 6 Sec. 1 [2.3.3]:
This section requires that the “net thickness of the bilge plating is to be notless than the actual net thicknesses of the adjacent 2 m width bottom or side
plating(..)”
Is this requirement referring to:
1. As built thickness;
2. Thickness required by Ch. 6;
3. All thickness requirements in CSR. (Ch. 7 FEM requiremtns, 9 sec. 1
Strengtheing of bottom forward etc).
Please advise.

2007/8/28

Regarding the buckling and reduction factors for curved plate panels in Ch 6,
Yes. This is typo.
Sec 3, Table 3, there is a partition line in the first column between bucklingload cases 1a and 1b. However, in the original GL rules, there is no such line,
We will issue the "corrigenda" soon.
see attached. This partition line is likely to cause incorrect values of Sigma x,
Also Included in Corrigenda 5
hence should be deleted.

We will consider the rule change proposal.

Y

This requirement is referring to the net thickness offered of the adjacentbottom and side plating.

Y

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No.

493
attc

497
attc

Ref.

6/2.4.1.1

6/1.1.5

Type

CI

Question

Topic

Correct
application of
the formulawith respect
to pressure
on ordinary
stiffeners.

Pressure
point forscantlingcheck ofcorrugation
web

Date
completed2008/1/9

2007/10/9

Question/CI

Ref. Ch. 6 Sec. 2 [4.1.1]
Q1: Please advice what is the correct application of the formula with respect
to pressure on ordinary stiffeners:
a.External and internal pressures are to be considered separately.
b.Combined effect of pressures to be considered.
In case of b.) please advice how to combine pressures(see attached drawing)
Q2: We assume correct interpretation of “Web stiffener mid height” is “Webstiffener mid length” . Please advise.

Where is the pressure point in the attachment to be used for scantling checkof corrugation web ?
Please note that option 1 is inside the gusset/shedder. Therefore, eventually
there is no pressure.

Attachment

Answer
A1. The requirement of Ch 6 Sec 4 [4.1.1] is provided for checking thescantling web stiffener and web connection with ordinary stiffener.
Therefore, the checking formula is provided as a function of the pressure
acting on the ordinary stiffener with coefficient depending on the web
connection with ordinary stiffener.
In case of web stiffener attached to floor in double bottom which is used forwater ballast, the pressure p is to be calculated as follows:
A: Web stiffener and the web connection with the bottom longitudinal:
The considered pressure is the greater of:(1) Pressure acting on bottom longitudinal due to external sea water in fullload condition, or(2) Pressures acting on bottom longitudinal due to internal pressure due toballast water in double bottom tank and external sea water in ballast condition,in line with Ch 6 Sec 2, 1.3.1

Y
B: Web stiffener and web connection with the inner bottom longitudinal:
The considered pressure is the greatest of:(1) Pressures acting on inner bottom longitudinal due to bulk cargo in full loadcondition, or(2) Pressures acting on inner bottom longitudinal due to ballast water in ballast
condition, or(3) Pressure acting on inner bottom longitudinal due to ballast water in ballast
hold, if applicable, in heavy ballast condition.
The required net sectional areas of web stiffener are to be calculated
independently for the foregoing connections A & B.
The final required net sectional area of the web stiffener is the greater the
calculated areas for A & B.
A2: “Web stiffener mid height” means “Web stiffener mid length”.

For the determination of the net thickness of the web plate according to Ch 6,
Sec 1, [3.2.1], the load point for the pressure is taken at the bottom ofcorrugation (e.g., Option 1 in the attached sketch).
The reason is that the effect of shedder and gusset plates is not considered toinsure that the calculation is conservative.

Page 11 of 31

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KCID
No.

516

518

522

525

Ref.

6/3.1.1.3

6/1.2.5.3

6/2.1.4.2

6/4.1.1.1

Type

Topic

Question

elementary
plate panels

CI

Definition of
the length of"longsuperstructur
es"

CI

RCP

Pressurecalculation
positionsPrimary
SupportMembers

Datecompleted

Question/CI

Attachment

Answer

2007/7/26

BLC3 and BLC 4: These BLCs can be applied for a typical plate field, where
the plate is not continuous at one side. This side may be stiffened with aprofile without flange (e.g. Flat bar) or not stiffened. Structural examples are
Regarding to Ch 6 Sec 3/1.1.3, "The boundary condition for elementary plate
plate fields located at manholes or plate fields of the hopper transverse web
panels". We normally consider that cases 3, 4 and 7 to 10 of Table 2 areframe.
applicable where one or two plate edges are supported by solid floors, bottom
BLC7: The edge of an elementary plate panel can only be treated as agirders, non-tight/tight bulkhead plates (bottom/inner bottom plate), side web
clamped edge, when the rotation about its axis is prohibited. Therefore, thisframes, side stringers, deck plates, non-tight/tight bulkhead plates (side shell)
BLC can be applied for in a web buckling check of stiffeners without flanges
and Transv. webs, deck girders, non-tight/tight bulkhead plates (deck plate).
which are attached to a very thick plate, e.g. a Flat Bar 400*20 mm attached
Please advise an example of structures for the application of case 3.4., and 7
to a 50mm thick plate.
to 10 of tables 2 for clarity of the requirement in 1.1.3
BLC8 to BLC 10: These BLCs are mostly theoretical cases included for thesake of completeness of the Table. There is no case to be applicable for an
actual structure.

2007/8/30

Long superstructures are effective superstructures as defined in Ch.9 Sec.4
Please advise the definition of the length of "long superstructures" specified in [1.1.5], i.e. located within 0.4L amidships and having a length greater or equal
than 0.15L or 12 m.
Ch6 Sec1, 2.5.3 .
Also Included in Corrigenda 5

2007/8/28

The pressure calculation positions would be clearly defined for vertical
stiffeners where spans are corrected according to Ch3 Sec6 4.2.1. Positions
for pU and pL need not to be considered the corrected upper and lower pointsof the span. Or positions for pU and pL should be also corrected 4.2.1.
According to Sec3 5.2.2.3 of Tanker CSR, corrected span need not to beconsidered.

2007/10/2

Regarding Ch.6, Sec.4-1.1.1 (Primary supporting members - Application), theconjunction 'and' in the passage quoted below is equivocal hence it isrequested to change it to 'and/or' to be such that transverse members to bealso applied are cleary referred to.
Quote;'subjected to lateral pressure and hull girder normal stresses’
Unquote;Without the proposed change, there would be a risk of being read that therequirement can be applied only to longitudinal primary supporting members(PSM) such as bottom girders. The requirement, in particular minimum net
thickness of webs of primary supporting members (Ch.6, Sec.4-1.5.1), should
be applied to transverse PSM as well such as transverse web in hopper tank.

The pressures pU and pL are to be calculated at the ends of the vertical
stiffener - i.e. without considering any correction of span - as it is stated in thedefinition of pU and pL in Ch 6 Sec 2 [1.4.2] and in accordance with thepractice.

The requirements of this Section apply to the strength check of pillars
and primary supporting members,subjected to lateral pressure and/or hull
girder normal stresses for such members contributing to the hull girderlongitudinal strength.
Also Included In Corrigenda 5

Page 12 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

529 6/3.4.2.2 &attc 6/3.5.1.1

Type

RCP

Topic

Buckling
requirementforlongitudinalandtransverse
stiffeners

Datecompleted

Question/CI

2008/6/19

Regarding the buckling requirement for longitudinal and transverse stiffeners(6/3.4.2.2, 6/3.5.1.1), it is requested that the Rule sub-paragraphs below are
given editorial review in respect of the comments/questions attached thereto.
If these be found justifiable, a corrigendum would be considered necessary.
1. Nominal lateral load (Pzy) for transverse stiffeners (6/3.4.2.2):
In the equation, sigma_xl should be changed to sigma_x , since the sigma_x
in this case is not axial stress of the transverse stiffeners and hence theattached area will not be necessary.
2. Elastic support provided by the stiffener (cf) for transverse stiffeners:(6/3.4.2.2):
Cs depends upon a degree of fixity at the ends of the stiffener sustaining
lateral pressure and is independent of any elastic support due to in-planestresses working in the attached plate. The Cs should therefore be deleted in
the relevant equation.

3. Effective width of attached plating for transverse stiffeners (6/3.5.1.1): The
effective width of the attached plate is considered part of the stiffener spaceand depends upon working stress along the stiffener. In this connection,
kappa_y in the formula should read kappa_y' which is calculated in Ch. 6,
Sec. 3, Table 2 as kappa_x in Buckling Load Case 1 with a in place of b. It
should be noted that kappa_y itself in Buckling Load Case 2 depends upon
the stress working normal in the case of application to transversely stiffened
stiffeners.

546

6/1.2.7.4 &
6/2.2.5.4

CI

Weight of theSteel Coil2008/2/7

JBP rules Chapter 6,Section 1.2.7.4 and Chapter 6,Section 2.2.5.4 (steel coil).
In this requirement it is stated that where the number of load points perelement plate panel n2 is greater than 10 and/or the number of dunnages n3
is greater than 5, the inner bottom may be considered as loaded by a uniform
distributed load.
The question is how to calculate the above uniform distributed load. Is it theweight of the steel coil divided by the diameter and length of the steel coil as
the uniform load, or the weight of the steel coil divided by the length of thesteel coil only?

Attachment

Answer

A1 - It is agreed that in the equation giving the nominal lateral load (Pzy) for
transverse stiffeners (6/3.4.2.2), sigma_xl should be changed to sigma_x.
A2 The parameter c_s defines the degree of fixation for the transverse
stiffener. In case of a structure as defined in Fig. 1 the transverse stiffener will
collapse between the longitudinal girder and not between the longitudinal
stiffeners. In this case c_s reduces the buckling length of the stiffeneraccording the Euler buckling case (partially restrained).
If it can be assumed that the transverse stiffener will collapse between theordinary longitudinal stiffener c_s =1.
Therefore no modifications of the formulas are necessary.

A3 The effective breadth has to be calculated under the assumption that theneighbouring elementary plate field is buckled under loads, acting parallel tothe stiffener. Therefore the effective plate breadth has to be reduced to theeffective width. The formulae in 4.2.2 are connected to the co-ordinate
system, defined in Figure 1. In this figure a transverse ordinary stiffener (n=1)
is located on the shorter edge of the elementary plate panel. In case of an
ordinary stiffener, located normal to the ship's x-axis, but at the longer side of
the attached elementary plate field, this stiffener is a LONGITUDINAL stiffenerin terms of buckling! Therefore the formula for p_zx has to be used with theeffective with a_m and S_x= transverse stress is ship co-ordinate system. But
this translation has not to be done in the rules text.
Therefore no modifications of the formulas are necessary.

A similar question was asked under KC ID #331. The approved answer (on12/01/2007) was "A definition of uniform loads on inner bottom will be includedin CSR for bulk carriers.
Considering your specific proposals, the interpretation is that the uniform load
is the weight of the steel coil divided by the diameter and length of the steel .
We will consider the rule change proposal based on the output of the Hull
Panel.

Page 13 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer

The sequence of the buckling checks follows the arrangement of Chapter 6,
Section 3.
In case of the buckling check for a typical ship structure (e.g. longitudinal
stiffened bottom) the elementary plate panel has to be dimensioned firstaccording the plate buckling criteria.

547

6/3.1

CI

The
Sequence of
Buckling
Assessment

2008/1/9

What is the right sequence of performing the buckling assessment according
CH6, Sec3?

In the following lateral buckling check of the stiffeners the net moments ofinertia is derived including the effective width of the attached plating. Thiseffective width depends on the thickness of the plate field. If this thickness is
not sufficient for plate buckling, the effective width and also the moment ofinertia of the stiffener is too small. As a result a larger stiffener would be
required to pass the lateral buckling check. And this larger stiffener gives nobonus for the plate buckling check.
Therefore it is important to make the plate buckling check before performing
the lateral buckling check.

551

557
attc

Symbol
6.1

Question6/1.2.3.2,
6/1.3.2.1, Question& 6/1.3.2.4

Countermea
sure forpanel
buckling

As a countermeasure for panel buckling, a carling with snipped ends is fitted
on a slender panel so as to reduce the aspect ratio of the panel.
2007/10/24 Can the reduced aspect ratio of the panel which is calculated by (s/l) be usedin determining the thickness of such panel according to Ch 6 Sec 1?
Where s and l are defined in "Symbols" in Ch 6 Sec 1.

Regarding bilge plate thickness,
Q1: Is always C6/S1/[2.3.2] to be applied regardless of the spacing (sb) of
floors or transverse bilge bracket vs chord length (l)?
Q2: Is C6/S1/[3.2.1] to be applied regardless of the spacing (sb)of floors ortransverse bilge bracket vs chord length (l)?
Bilge Plate
Thickness

2008/1/28

Q3: Is C6/S1/[3.2.4] to be applied regardless of the spacing (sb)of floors ortransverse bilge bracket vs chord length (l)?
Q4: If C6/S1/[3.2.4]is to be applied,is cr to be calculated as follows;(a) when sb < l: cr=1-0.5sb/R=1.0 assuming that R=infinitive,(b) when sb>=l: cr=1-0.5l/R?

Yes, the reduced aspect ratio of the panel which is calculated by (s/l) may be
used in determining the thickness of such panel according to Ch 6 Sec 1.

A1: The requirement of Ch6 Sec 1 2.3.2 applies only to bilge plating which aretransversally framed.
A2: The requirement of Ch 6 Sec 1 3.2.1 is applied to bilge plating regardlessof the framing system.
A3: The requirement of Ch 6 Sec 1 3.2.4 is applied to bilge plating regardlessof the framing system.
A4: The additional stiffness of a panel due to curvature is given by theparameters radius and chord length. If sb>=chord_length, the elemenatry
plate panel is longitudinal stiffened, hence cr=1-0.5*s/r. If sb<chord length, theelementary plate panel is transversally stiffened, Cr is taken equal to 1.

Page 14 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

3.6.19,563
6/2.3.3.3 & Question
attc
6/2.3.3.4

Topic

Modulus of
the Lower or
upper
BracketDatecompleted

Question/CI
According to Ch.6 Sec.2 [3.3.3] and [3.3.4], section modulus of side
frame+bracket is required at the level of lower or upper bracket as shown in
Ch.3 Sec.6 Fig.19. According to the Fig.19, it is unclear how to measure theheight of the bracket for the purpose of section modulus calculation. For the
purpose of hLB/tLB ratio the height of the bracket is defined in Ch. 3 Sec. 6
figure 22, which is also unclear.

2008/2/7

We assume hLB for section modulus and hLB for hLB/tLB ratio is calculated
in the same way. Please confirm.
Attached please find two alternative approaches for calculation of hLB.
A. hLB is measured perpendicular to bracket flange.
B. hLB is measured perpendicular to the projection of the lower bracket slope.
Please confirm correct approach for measuring bracket height hLB.

Attachment

AnswerIn Ch 6, Sec 3, [3.3.3] and [3.3.4], for the purpose of calculating the actual
section modulus of the lower (respectively upper) bracket, the web height is tobe measured at section noted "lOWER BRACKET" (respectively "UPPER
BRACKET") on Fig 19 of Ch 3, Sec 6.
In Ch 6, Sec 3, [3.3.3], for the purpose of hLB/tLB ratio the height hLB of thebracket is measured according to the definition in [3.3.3] and so according to
Ch 3, Sec 6, Fig 22. It is corresponding to the Figure B of your attacheddocument.

Y

Reference is made to IACS KC#475.
Quote
This thickness requirement is referring to the net thickness offered of theadjacent bottom and side plating.
Unquote

567
attc

579

6/1.2.3.3

Within 0,4L amidship the definition of bilge plate is the same as defined inTable 4.1.1 of Section 4, CSR for DH oil tanker. That is:“The area of curved plating between the bottom shell and side shell. To beNettaken as follows:
thickness
From the start of the curvature at the lower turn of bilge on the bottom to theoffered of the
Please advise how to define the bilge plating for fwd and aft parts of the cargo lesser of, the end of curvature at the upper turn of the bilge on the side shell or
Question
2007/10/26
adjacent
hold region.
0.2 D above the baseline/local centerline elevation.”bottom andE.g.
side plating- attached sketch is showing a cross section in the fore part of a bulk carrier.
Outside of 0.4L amidships the bilge plate scantlings and arrangement are to- Bottom is strengthened for bow impact
comply with the requirements of ordinary side or bottom shell plating in the- bilge plating is to comply with KC#475.
same region. Consideration is to be given where there is increased loading in
Please advise bilge extent.
the forward region.

6/3.2.1.3

Total shear force for buckling check is to be obtained by following formulaYes, it is correct but the scantling discontinuity is not expected.
Q = Q_SW + C_QW x Q_WV.
Then the distribution of total shear force is discontinuing at midship since the We will consider the rule change proposal in order to eliminate or minimize thesign of C_QW is to be change at midship according to the foot note of Table 3 scantling discontinuity, considering the answer in KC 685.
in Ch4 Sec 4. This discontinuity will cause scantling change between midship,especially for H1, H2, F1 and F2 load cases. Is it correct and expected?

Question

Shear force
for buckling

2008/5/30

Page 15 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

580
attc

581

584

594

Ref.

6/2.3.2.4

Type

CI

Topic

Date
completed

Question/CI

The line
Supported by
In Ch 6, Sec 2, [3.2.4], it seems that in Table 4 (case with lower stool), the line
girders or“Supported by girders or welded directly to decks or inner bottoms” should notweldedbe mentioned in the table since this case is a case without any lower stool.
2007/10/26
directly toPlease confirm our interpretation.
decks orFurthermore, both Table 4 and Table 5 should not mention the column
inner“Supported by girders” since it is not applicable to bulk carriers.
bottoms

Attachment

Answer

We agree with your interpretation: in Table 4, the only case to be taken into
account is the “Welded to stool efficiently supported by ship structure” one.
Also, the “supported by girder ends” do not correspond to bulk carriers but
other type of ships.
Consequently, the column “Supported by girders” should be deleted in Table 4
and 5.
Corrected table 4 and 5 are given in attached file.

6/2.3.2.4

Span "I" tobe
In Ch 6, Sec 2, [3.2.4], what is the span "l" to be considered for the calculation The span “l” to be considered for the calculation of pressures (p_mid-span,consideredof pressures (p_mid-span, p_u , P_L)?
p_u, p_L) is the span as defined in figure 6.
Question
2007/10/25
for theIs it the span defined in figure 6 or the span between upper level of lower stool
calculation ofand lower level of upper stool?
pressures

6/4.4.1.1

We understand that the compressive stress of pillars mentioned in 6-4/4.1.1 isthe stress by the static loads and the dynamic loads. However, there is noCompressive
Yes, the stress to be checked is the one induced by the static and dynamic
clear statement in CSR how to calculate the loads on pillars. The clear
stress of
2007/10/23
loads that are acting onto the decks above the considered pillar.
interpretation on this is to be developed. As an alternative, we think that thepillars
These loads are to be calculated accordingly to chapter 4.
current Class Society Rules may be used for determine the pillar scantlings.
Please confirm.

6/1.2.3.3

CI

The
Thickness of
Questionthe Bilge
Strake2008/2/7

The thickness of the bilge strake is determined according CH6, Sec1. The
scantling check includes also a buckling check of the longitudinal ortransverse framed curved plating. Nevertheless it is required, that the
thickness of the bilge strake is not less than the greater thickness of thebottom and the side shell plating. What is the reason, that the thickness of thebilge strake has to be increased, if the bilge strake with a thickness smaller
than the bottom and the side shell passes all design checks (Yield, Buckling,
FE-Analyses).
The GL-Rules (I-Part 1, Sec6, 4.1) allows a smaller thickness, if the shear
strength is sufficient and if the bilge plate panels passes the buckling checkincluding buckling of curved panels.

In order to have no large discrepancies in thicknesses for welding, it is anormal building practice to provide a continuity of thicknesses between
bottom, bilge and side shell.
That is the reason of the requirement that the thickness of the bilge strake is
not less than the greater thickness of the bottom and the side shell.
However, provided all the design criteria have been fullfilled:- minimum thickness,- yield,- buckling,- FE analyses,a smaller thickness of the bilge strake may be accepted.

Page 16 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

609 6/1.2.7.1&
attc 6/2.2.5.4

Type

RCP

Topic

Steel Coil
LoadingDatecompleted2008/2/7

Question/CI

Attachment

Answer

Reference is made to Ch. 6 Sec. 1 [2.7.1] and Sec. 2 [2.5.4] Steel coil loading
and related KC# 331 and 546.
Ch. 6 Sec. 1 [2.7.1] and Sec. 2 [2.5.4]
Quote“Where the number of load points per elementary plate panel n2 is greaterthan 10/or the number of dunnages n3 is greater then 5, the inner bottom may
be considered as loaded by a uniform distributed load. In such a case, thescantling of the inner bottom ordinary stiffeners is to be obtained according to This question is identical to KC ID#546, and the answer is that the uniform
load of due to steel coil is the weight of the steel coil divided by the diameter[3.2.3]”and length of the steel .
UnquoteA rule change proposal will be considered based on the output of the Hull
Panel.
We understand that “distributed load” is sometimes interpreted as P =WCoil/(lcoil x dcoil) where lcoil and dcoil is the length and diameter of coilrespectively. DNV have investigated the effect of such interpretation with thestiffener scantling as example. Our conclusion is that such a interpretation isunsafe and should be changed to distributed load over one elementary plate
panel as described below.
Please find enclosed DNV report and rule change proposal enclosed for yourconsideration.

1. Lateral buckling assessment of stiffened panel including side frame istreated as longitudinally stiffened panel which has a stiffener arranged on the
direction of the longer side of the panel. Please confirm it.

Ch.6,
610
Sec.3 4.2.

RCP

Buckling
Assessmentof stiffended
panel

2008/5/30

2. In case that shear stress on side shell as attached plate of side frame is
A1) Confirmed.
large, shear stress is the dominant load of lateral buckling of side frame. It is
not understandable for us. Please show the technical background in thisComment on 2) and 3)
regard.
It is obvious, that for transverse members the axial stress component is zero
Even though the thickness of side shell plates comply with Ch5 Sec1, 2.2 &in the formula for the criteria and the equation for p_z (nominal lateral load).
Ch6 Sec3, 2.1.3, the side shell plate thickness should be increased due to the The remaining stress component is the hull girder bending stress with its zero
result of lateral buckling assessment of side frame.
crossing and shear. And so shear becomes dominant.
It is necessary to reconsider the above requirements which require increase of We support to reconsider the requirements for lateral buckling.
scantling of hull girder members due to the result of local strength check.
3. We request to reconsider the requirement of lateral buckling assessment
for side frame in connection with above 1. and 2.

621

6/3-4.2
and 5.1

CI

Ultimate
Strength inlateralbuckling
mode of side
frames2008/4/11

Regarding ultimate strength in lateral buckling mode of side frames of single
side bulk carriers in Ch.6, Sec.3-4, our interpretation is that 'transversely
arranged' side frames should be treated as ‘longitudinal stiffeners’ in Ch.6,
Sec.3-4.2 and -5.1 since the ends of side frames can be considered as fixedends taking account of the requirements of upper and lower connections ofside frames as stipulated in Ch.6, Sec.2-3.4.
Confirmation is requested as to whether the above interpretation is correct ornot.

Yes, side frames of single side bulk carriers are longitudinal frames in context
of CH6, Sec3. The definition "longitudinal" is given in CH6, Sec3, Symbols andFig. 1. This is independent from the fixation of the ends of the frames.

Page 17 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

623
6/A1.1.3.2
attc

624
attc

Symbol6.3 &
6/3.1.1.2

Type

RCP

CI

Topic

Buckling
Panel
idealization
for d)
GeneralTriangle

Applicationof buckling
requirements

Datecompleted

Question/CI

Answer

Attachment

2008/4/24

Regarding the buckling panel idealization for d) General triangle in Ch 6,
Appendix 1, 1.3.2, it is mentioned that general triangle is treated according toa) "Quadrilateral panels" above. However, in the case of a triangle with allacute angles, a rectangle with the smallest area cannot be specified as thethree rectangles that completely surround the general triangle have the same
area, see attached. Just the original paragraph cannot result into a final
rectangular panel with the smallest area represented by the dimensions, a, b
and panel angle Theta. As such, an alternative stipulation covering both
obtuse triangles and acute triangles is requested.

Neither the DIN18800 nor the GL-buckling rules, which are the basis for CH6
Sec3 of the CSR-BC, consider triangular elementary plate panels as describedabove. The appendix of CH6 describes general approaches for an engineer toevaluate non standard geometry. Remeining items are up to engineering
judgement.

Y

2008/5/12

This question relates to application of buckling requirement (Ch.6, Sec.3) and
SOLAS XII/6.5.3.
(A) According to IACS Unified Interpretation of SOLAS XII/6.5.3 (SC209, June
2006), safety factor of 1.15 for buckling requirement should be applied tolongitudinal and transverse ordinary stiffeners for the following areas: hatchway coaming, - inner bottom, - sloped panel of topside tanks and hoppertanks (if any), - inner side (if any), - top stool and bottom stool of transverse
bulkhead (if any), - stiffened trasnverse bulkhead (if any), and - side shell (ifdirectly bounding the cargo hold).
(B) According to Symbols in Ch.6, Sec.3 of CSR-BC Rule, safety factor (S) forbuckling requirement refers to the same members as stated in above (A)except stiffened transverse bulkhead, e.g. collision bulkhead and aft bulkead
Your interpreation (A) to (C) is correct.
in an aftermost cargo hold.
(C) According to Ch.6 Sec.3-1.1.2 (a) of CSR-BC Rule, the application of theWe will consider the Rule Change proposal or Edditorial correction forbuckling requriement is to 'ordinary stiffeners in a hull transverse section
clarification of the application.
analysis'. We think the interpretation of 'hull transverse section analysis' is'longitudinal members and hold frames'.

Y

If the interpretation is correct, locations to be checked are the same as statedin above (A) except stiffened transverse bulkhead and top/bottom stools.
Considering the above situation, it is considered necessary that the following
elements be inserted:in Safety factor (S) in Symbols in Ch.6, Sec.3, 'stiffened transverse bulkhead,
if any',in Ch.6, Sec.3-1.1.2(a), 'ordinary stiffeners on stiffened transverse bulkhead
and on top and bottom stools, if any'.

Page 18 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

629

Ref.

6/1.2.5.1

Type

CI

Topic

Net
thinkness ofa welded
sheerstrake

Datecompleted2008/5/9

Question/CI

Attachment

AnswerRegarding the requirement of welded sheerstrake (Ch.6, Sec.1-2.5.1, ‘The net
thickness of a welded sheerstrake is to be not less than the actual net
thickness of the adjacent 2 m width side plating, taking into account higher
strength steel corrections if needed’), it is noted that there is the relevant Q&A(KC ID No.212). However, the answer does not seem clear hence it would beappreciated if the following proposal be considered.
The answer of KC ID No.212 says, ‘Generally, when the side shell plating
adjacent to sheerstrake includes single side part and is increased due to thebuckling and hull girder shear strength, it is also the case for the sheerstrake,
which is located above. Consequently, we see no reason to modify thisrequirement’. This will be the case when the sheerstrake covers part of single We agree to the interpretation that the net thickness of a welded sheerstrakeside skin (SSS) area. However the fact is that almost all sheerstrakes do not
is to be not less than the net required thickness of the adjacent 2 m width side
cover the part of single side skin area, i.e. they are located within top side tank plating, which is calculated according to the relevant requirements in Ch.6,(TST).
Sec.1

Generally speaking, hull girder shear strength is occasionally critical to thescantling of single side skin, while it is not to the scantling of sheerstrake
within TST area since the relevant shear flow calculation shows that the shear
stress in SSS is considerably bigger than that in TST area.
Such being the case, the requirement should be interpreted as follows: ‘The
net thickness of a welded sheerstrake is to be not less than the net required
thickness of the adjacent 2 m width side plating, which is calculated according
to the relevant requirements in Ch.6, Sec.1'.

Regarding Ch.6, Sec.1-2.7 and Sec.2-2.5 about steel coils, it would beappreciated for KC to reply to the following comments.
1. The requirement for plates and ordinary stiffeners on hopper sloping andinner hull plating (Ch.6, Sec.1-2.7.3 and Sec.2-2.5.3) seems to requireconsiderably severe scantlings as compared to that in pre-CSR BC. In thisconnection, it is requested that a background document be supplied to users.
631
attc

6/1-2.7,
6/2-2.5

CI

Steel coils

2008/4/11

2. It is understood that the requirements of Ch.6, Sec.1-2.7.3 and Sec.2-2.5.3
are based on the assumption that the steel coils are in uniform contact on thehopper sloping or inner hull plating. In aft and forward cargo holds, however,there are some cases where the steel coils do not uniformly touch on them.
Attached is the example. Hence it is necessary that a procedure of how todeal with it in that case be provided.

A1: A Rule Change Proposal with associated Technical Background ispresently under preparation.
A2 and A3: Please, refer to the answer of KC ID#546 and 609.

Y

3. Regarding Ch.6, Sec.1-2.7.4, it is noted that an answer of KC ID.331 saysthat a definition of uniform load will be included in CSR BC Rules. In themeantime, it is requested beforehand to be confirmed that the 'uniform load' is
not uniform load over the inner bottom plate but uniform line loads.

Page 19 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

639

Ref.

6/4.2.2
and 4.2.4

Type

Question

Topic

Net Webthicknessrequirements

Datecompleted

Question/CI

Answer

2008/7/16

With respect to Net Web Thickness requirements for centre girders, side
girders, floors, stringer of double side structure and transverse web in doubleside structure for ships of less than 150m in length, it is requested to confirm
whether our interpretation below is correct or not.
1. Ch6/4.2.2.1,
1.1 pS,IB and pW,IB are Cargo pressures from Cargo Hold or Ballastpressures from Ballast Hold. These still water and wave internal pressures areto be reduced from the corresponding Ballast pressures from Water Ballast
Tank.
1.2 pS,BM and pW,BM are External sea pressures. These still water andwave internal pressures are to be reduced from the corresponding Ballastpressures from Water Ballast Tank.
2. Ch6/4.2.4.1,
2.1 pS,SS and pW,SS are External sea pressures. These still water and wave
internal pressures are to be reduced from the corresponding Ballast pressuresfrom Water Ballast Tank.

1.1 When the water ballast tank of the double bottom is filled up to the tank
top, the static and dynamic pressures due to dry cargoes or heavy ballast are
to be reduced from the corresponding ballast pressure of the water ballast
tank.
1.2 When the water ballast tank of the double bottom is filled up to the top, theexternal still water and hydrodynamic pressures are to be reduced from thecorresponding ballast pressure of the water ballast tank.
2.1 When the water ballast tank of the double side is filled up to the top, theexternal still water and hydrodynamic pressures are to be reduced from thecorresponding ballast pressure from water ballast tank.
2.2 When the water ballast tank of the double side is filled up to the top, thestatic and dynamic pressures due to dry cargoes or heavy ballast are to be
reduced from the corresponding ballast pressure from water ballast tank.
It should be noticed that the static and dynamic pressure combination of eachload is not to be negative (see CH4, Sec5, 1.1.1)

Attachment

2.2 pS,LB and pW,LB are Cargo pressures from Cargo Hold or Ballastpressures from Ballast Hold. These still water and wave internal pressures areto be reduced from the corresponding Ballast pressures from Water Ballast
Tank. In this requirement, Cargo pressure from Cargo Hold is to be ignored.

659

664

6/3.3.1.1

6/1.3.2.3

Question

Bilge strakeor othercurvedpanelsthickness forcorrugated
Questionbulkheadplate

Application of the requirement "t>b/100"
The formula does not seem applicable to bilge strake or other curved panels

This is right. This requirement is only applicable to planar plate panels. A rulechange will be considered.

Required thickness for corrugated bulkhead plate Ref. CSR for Bulk Carriers
Ch6 Sec.1 2.1.1, 3.2.1 and 3.2.3 When calculating the required thickness forbuild-up corrugation bulkheads in intact condition by 3.2.1 of Ch.6 Sec.1,
should s of the formula be taken greater width of flange or web according to
2008/10/10
2.1.1? We understand that the requirements of 2.1.1 are come from UR S18
and only applicable to the requirement of flooding condition. Please clarify.
According to UR S18.4.7, s of the formula for obtaining tN is taken narrower
plate width. Can we use narrower width for tN in CSR? Please clarify.

1. Ch 6 Sec 1 [3.2.1] and [3.2.4] “s” is to be taken equal to the value defined in[2.1.1]. For built up corrugation, when the different thickness of flange andweb are designed, “s” is to be taken equal to the flange and web ofcorrugation respectively.
2. Ch 6 Sec 1 [3.2.3]
1) “s” and “p” of the 1st formula should be selected respectively for web andflange in general, (e.g., applied to also for cold forming corrugated bulkhead),2) “s” and “p” of the 2nd formula should be selected for narrower plating,3) “s” and “p” of the 3rd to 5th formulas should be selected for wider plating.
In order to clarify these requirements, we will conisder the RCP. Regarding
the answer of KC 553 The answer seems to be vague but not to be incorrect
because it is obviously that the elementary plate panel for built-up corrugatedbulkhead is divided into the flange and web of corrugation.

2008/7/2

Page 20 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

681
attc

6/2.3.3.3

RCP

Gross
Thicknessand NetThickness
Scantling682

6/3.4.2 &6/3.4.3

Question

stiffeners

685

697
attc

6/3.2.1.3 &Question
5/1.2.2.1

6/2.1.4.2

Question

Shear force
for bucklingassessment

The pressureP

Datecompleted

Question/CI

Answer

Attachment

Y

2008/4/11

It is proposed that the paragraph in CSR-BC, Ch.6, Sec.2, 3.3.3 be changedin part to eliminate the equivocality as shown in the separate attachment.

IACS UR S12 Rev. 4 is based on the gross thickness.
CSR is based on the net thickness scantling.
According to Ch 3 Sec 3, the total corrosion addition for webs and flanges oflower brackets of side frame is 5.0mm, and the total corrosion addition of side
frame other than lowe brackets and upper brackets is 4.5mm.
According to the current requirement of 3.3.3, the gross thickness of lower
bracket is greater than 2.0mm of the thickenss of web of side frame.
Therefore, as the current rule of Ch 6 Sec 2 3.3.3 is in line with IACS UR S12,
the text is kept as it is2009/3/3

Are Ch.6, Sec.3, [4.2] and [4.3] applicable to stiffeners on watertighttransverse bulkheads in lower/upper wing tanks and double side and on
watertight floors ?

Ch.6, Sec.3, [4.2] and [4.3] are applicable to the stiffeners on watertighttransverse bulkheads in lower/upper wing tanks and double side and on
watertight floors. In case of hull transverse section analysis, the axial stress forstiffener and shear stress in attached plate are not to be considered.

2008/5/30

Ch.6,Sec.3,[2.1.3] defines the shear force for buckling assessment as follows:
Q=Q_SW + C_QW x Q_WV.
There seems to be no limitation to the signs of Q_SW and Q_WV for their
combinations. On the other hand Ch.5, Sec.1, [2.2.1] reads: "When they are
combined, vertical shear forces Q_SW and Q_WV in intact condition are to betaken with the same sign."
Which way should be taken when calculating Q in Ch.6, Sec.3, [2.1.3]:a) Q to be calculated only for the combinations where Q_SW and Q_WV areof same sign, orb) Q to be calculated for all combinations where Q_SW and Q_WV are ofeither same sign or opposite signs ?

Hull girder shear stress check should be performed at the maximum absoluteshear force. Such case occurs at the combination of either(1) Q_SW_pos +(C_QW_pos x Q_WV), or(2) Q_SW_neg +(C_QW_neg x Q_WV), where,
C_QW_pos , C_QW_neg : positive and negative load combination factors
according to load cases as defined in Ch.4, sec.4,Table 3.
The sentence in Ch.5, Sec.1, [2.2.1], which is quoted in the question, reflects
this interpretation.
Therefore we will consolidate the paragraphs referring to shear force
combination into CH5, Sec1 [2.2.1] and replace CH6, Sec3, [2.1.3] with a notereferring to CH5, Sec1.

2008/7/16(1)The pressure distributions shown in cases (c) to (f) may effectively occur
when differential pressures are to be considered, i.e. only for vertical stiffenersof the outer shell. However, the scantling of such stiffeners is quite always
governed by the case "still water and wave external pressures" to be applied
The attachment contains four pressure distibutions, where the pressure p can
independently of the differential pressures (see Ch 6, Sec 2, [1.3.1]).
not be derived according to the formulae in Ch.6 Sec.2 1.4.2 How to calculate(2)In addition, such distribution of presssure may be approached by one of thethe pressure p, used in Ch.6 Sec.2 3.2.3 for examples
two "standard cases" defined in [1.4.2]. This gives wrong results, but
regarding the comment in (1), it doesn't affect the scantling.
(3)Of course, some definition of "p" for these distributions may be developped,
but no effect on scantlings will occur (see comment in (1)above).

Page 21 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

708
attc

Ref.

6/2.4.1.3 &Figure
6.2.9

Type

CI

Topic

Web
stiffeners ofprimary
supporting
members717
attc

6/3.3.2.4

CIbuckling
check

722

6/4.4.1.1

Question

Pillars

748 6/A.1.1.2.2CIelementary
plate panels

Datecompleted

Question/CI

Answer

Attachment

2008/5/28

Ch.6, Sec.2, [4.1.3] says that this requirement is applicable to the web
stiffeners of primary supporting members in water ballast tanks when no
bracket is fitted.
On the other hand Fig.9 shows, at its left end, the stiffener with integrated
bracket at toe to which the subject requirement is applicable.
What is meant by "when no bracket is fitted". Please advise if theinterpretation on applicability of the requirement is as per the attached casesof stiffener.

It is obviously that Case 1 and Case 3 is applicable to this requirement
because the bracket is not fitted as shown in the attached file.
For Case 4 to Case 6, as the bracket is fitted to the web stiffener and thevalue “h’” becomes large, the stress range delta-sigma is small, then suchcases are always complied with this requirement.
Therefore, although Case 4 to Case 6 shown in the attached file is applicableto the requirement, it is not considered that the check according to thisrequirement is necessary for such cases.
For Case 2 shown in the attached file, although the bracket is fitted, thesmallest breadth of such case depends on the bracket size and shape and issimilar to that of Case 3. Therefore, this case should be applied to therequirement of Ch 6 Sec 2 [4.1.3] as mentioned in the attached file.
As a conclusion, the interpretation specified in the attached file is correct.
In order to clarify this interpretation, the editorial correction will be considered
as "Corrigenda".

Y

2008/9/10

Chapter6_Sec3_[3.2.4] Does tensile stress need to be considered for bucklingcheck? Regarding the tensile stress , there is still different view point onwhether it need to be considered for buckling check or not. There would be asolution that, 1) For check the resultant buckling utilization factor, combinedby sigma_x, sigma_y and tao, the tensile stress need to be considered as theactual values but with negative sign. 2) For check the individual buckling
utilization facor, the factor would be taken as 0. Please be kindly request to
provide clarification or confirmation.

1) Even if the estimated stress is negative (tensile stress), the buckling checkshould be carried out according to the first formula specified in Ch 6 Sec 3[3.2.4] using the actual values. 2) No individual buckling checks have to be
performed for tensile stresses. It is clearly stated, "In addition, each
COMPRESSIVE STRESS ... are comply with the following formulae."Y

2009/6/2

Please clarify the design load for pillar scantling calculation.

The design loads acting on the pillar are the static and dynamic loads that are
acting onto the decks above the pillar under consideration. These loads are to
be determined according to Chapter 4 considering the relevant loads on thedecks above.

2008/9/10

It seems that the 2nd & 3rd sentences in Ch 6, appendix 1, [1.2.2] such as"The effective width ... in accordance with Ch6, Sec 3 [5]. A constant stress...
adjacent elementary plate panels." could be interpreted as follows:
1) When a width of the attached plate is calculated a constant compressive
stress to be assumed, accordingly always psi=1.0 both for longitudinal andtransverse stiffeners.
2) Sigma_a in Ch 6, Sec 3 [4.2.1]
and sigma_x in [4.3.1] for longitudinal stiffener are to be taken as the greaterof the following hull girder bending stresses:(a) stress at
half length of the stiffener, and(b) 0.5 of the maximum compressive stress of the adjacent elementary plate
panels. Please advise if the above interpretation is correct.

1) Your interpretation is right. Regardless of the actual stress distribution of theadjecent plates, psi equal to 1 is assumed for the calculation of the effective
width according to CH6, Sec.3, 5.
2)sigma_a is theaxial stress of the stiffener. In the transverse section analysis this stress is aconstant value, which is equal to sigma_n for a stiffener in ship length
direction. sigma_x, sigma_y (in EPP co-ordinate system) and tau are stresses
in the adjacent plates, acting at the position of the stiffener, which causes
additonal vertical forces on the stiffener. In case of the transverse section
analysis normal stresses in other directions than in ships longitudinal direction
may be set to zero.
We willconsider the RCP in order to clarify these interpretation.

Page 22 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

764

767

Ref.

6/2.4.1.3

6/3.1.1.2

Type

RCP

Question

Topic

Date
completed

Question/CI

Attachment

AnswerCorrosion
FormulaWith reference to the Technical Background, Ch6 Sec2, 4.1.3 is based on NK
Rules. The coefficient, 1.1, of the stress formula in Ch6 Sec2, 4.1.3 is also
shown in NK Rules as “correction coefficient for corrosion”. However, CSR
2008/10/27 adopts a net scantling approach and the scantling considered in thecalculation formula is the net scantling, excluding corrosion additions.
Accordingly, the formula in Ch6 Sec2, 4.1.3 incorrectly counts corrosion twice.
Please reconsider the way to consider corrosion in this formula.

Considering the original rules and the background, it is not considered that theconstant value 1.1 used in the formula of CSR based on the net scantling
approach is necessary. We will consider the RCP because the correction of
the formula will give the scantling impact.

Buckling
Assessment

1. It has come to our notice that there is an inconsistency between the CSR
BC and IACS UR S17 about assessment of the buckling capability of the hull
structure in flooded condition.
2. S17.5 requires buckling assessment for elementary plate panels andordinary stiffeners in a hull transverse section stating that “Permissible stressand axial stress buckling strength are to be in accordance with UR S11”.
3. However, Paragraph 1.1.2 of Chapter 6, Section 3 of the CSR BC requires
buckling assessment only for transverse vertically corrugated watertightbulkheads in flooded condition.
4. Both are IACS documents and are to be consistent for bucklingassessment for the elementary plate panels and ordinary stiffeners.

With the additional ultimate strength check according to CH5, Sec2 for flooded
condition, the requirements of UR S17 and UR S11 for the bucklingassessment in flooded conditions are fulfilled.

2009/3/3

768
attc

6/3.4.2.2

RCP

stiffeners

2009/11/3

Please see the Rule Change Proposal in the attached file.

For continuous stiffeners, the bending moment due to the deformation of
stiffener (M0) always takes the same sign as the bending moment due to thelateral load (M1), i.e. since Mo can act in any direction. However, for a sniped
stiffener, the eccentricity of the compressive load and the neutral axis of theplate-stiffener combination means that M0 can only act in one direction (i.e.
plate in compression). Accordingly, Mo and M1 should have the same signwhen the lateral pressure is acting on the plate side, but different signs when
the lateral pressure is acting on the stiffener side.

771

Ch. 6,
Sec. 1CI

carlings

2009/5/27

It seems that the answer in KC551 is applicable when fitted with carling
effective enough to prevent buckling. Please show the conditions such as
minimum scantlings of the carling which are effective enough to prevent
buckling.

We will make a rule change proposal to establish minimum scantling
requirements for such carlings.

Page 23 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

800

Ref.

6.3.4.2

Type

RCP

Topic

lateralbuckling of
longitudinal
stiffeners

Datecompleted2009/3/3

Question/CI

We have checked both criteria given in Ch 6, Sec 3 for lateral buckling of
longitudinal stiffeners not subjected to lateral pressure: criteria in [4.2.1] and[4.2.2] on one side and criteria in [4.2.3] on the other side.
These criteria were checked in case of longitudinal stiffeners (flat bars) of nonwatertight girders.
The conclusions are:(1) - When considering ends of stiffener not sniped: both criteria areequivalent.
(2) - When considering ends of stiffener sniped: both criteria seems
equivalent, but it is noticed that there is no convergence when increasing thescantling of the flat bar. The same problem occurs if bulb or T-bar are
considered. instead of a flat bar. Consequently, there are some doubts on theapplication of the formulae for sniped stiffeners and in particular on the default
value taken for the assumed imperfection w0.

Attachment

AnswerIn case of longitudinal stiffeners sniped at ends and located on non watertightgirders, when applying the criteria for lateral buckling given in Ch 6, Sec 3[4.2.1] and [4.2.2] on one side and [4.2.3] on the other side, it is right that
there is no convergence when increasing the scantling of the stiffener.
The requirement Ch 6, Sec 3, [4.2.3] is only applicable for non-sniped
ordinary stiffeners.
We will make a rule change proposal to clarify this matter.

Requirement should be re-considered in case of sniped stiffeners and atechnical background should be provided.

820

831

833

6/2.2.3.2

6/1.2.4.1

6/4.3

Question

Gross
Thicknessand NetThickness
ScantlingCI

FE and local
requirements

Question

Primary
SupportMembers

2009/3/3

Regarding the application of Ch6 Sec2 2.3, should hw and bf of the formulae
be measured as gross scantling or net scantling?
In Tanker CSR Table 10.2.1, it is clearly defined that the breadth and depth of It is clearly mentioned in the text of [2.3] that all scantling is the net
stiffeners are based on gross scantling.
dimensions.
But, in Bulker CSR, there is no clear definition for the calculation of the net
dimensions of ordinary stiffeners given in Ch6 Sec2 2.3. Please clarify.

2009/3/3

Please explain the technical background of this requirement.
Does this requirement refer toa) only the thickness required by local requirements?
b) both the thickness required by FE and local requirements?
Typically, we have pipe duct in way of the keel plating, and the length of theelementary plate panels are smaller than outside the pipe duct. The required
thickness obtained from the bi-axial FE buckling in way of the pipe duct may
then be smaller than outside the pipe duct. Can we accept this smaller
thickness?

This requirement refers to both the thickness required by FE and local
requirements, as it refers to "actual" thickness, for a matter of continuity ofstrength, and enough strength for docking.

2009/3/10

Reference is made to Ch. 6 Sec. 4 [3] “Additional requirements for primary
supporting members of BC-A and BC-B ships.”
The section is referring to net dimensions. Please advice how to obtain the
net dimensions: a) deduct 0.5tc from gross scantling (In line PSM scantling
applied in FEM) b) deduct tc from gross scantling. (In line with scantling
applied in local checks) Please consider specifying this in Ch.3 Sec.2

The full corrosion addition is to be considered when applying Ch.6 Sec.4 [3].
Ch.3 Sec.2 [2.1.1] and [3.2] define the cases where other corrosion values areto be used for determining the net dimensions.

Page 24 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

849

Text
6/A1.1.3.4

852
attc

6/2.4.1.1& 6/2.2.5

856

866
attc

Text
6/1.2.3

Figure6.2.10

Type

Topic

Question

corrugated
BHD

Question

Steel Coil
Loading

QuestionRCP

6/1.2.6.3 &878
Question6/1.2.6.2

bilge plating

web stiffenerendconnections

effective
structureDatecompleted

Question/CI

Attachment

Answer

2009/6/16

Regarding the buckling assessment of corrugated bulkhead plates, the edge
stress ratio for their web plates is defined as 1.0 according to Ch.6 App.1[1.3.4(b)]. This means that the stress distribution of such web plates isassumed to be uniform. However, due to bending, the actual stress
The correct value of psi is -1.0. We will consider a Rule Change Proposal.
distributions of these web plates are not uniform. Therefore, the edge stressratio,ψ, should be -1.0 in case where applying buckling case1. Please confirm
that ψ=1.0 is correct or not.

2009/9/4

Ch.6 Sec.2 [4.1.1] defines the required net sectional area of web stiffeners.
1) Please confirm the requirement is not applicable in case of steel coil
1. The requirement of Ch 6 Sec 2 [4.1.1] is applicable in case of steel coilloading as specified in Ch.6 Sec.2 [2.5].
loading becasue the load due to steel coil is acting on the ordinary stiffener.
2) If 1) is not the case please advise how to calculate the pressure "p" in case 2. Please find the attached document. We will conisder the RCP.
of steel coil loading.

2009/6/16

Clarification of the criteria of the application of any increased thickness
required for the bilge plating to the adjacent bottom and side shell plating.
In case the straight plate of bottom or side shell shares a transversely framed
and curved EPP with the bilge plating, should the required thickness of thebilge plating be applied to the adjacent bottom or side shell plating?
Regarding this, in Tanker CSR Corrigenda 3 Section 8/ 2.2.3.2, the criteria
have been defined clearly for the application of the required thickness of thebilge plating. However, in Bulker CSR Ch 6, Section 1 [2.3], there is no clear
guideline.
Please clarify.

The text of Ch 6 Sec 1 [2.3.3] says: The net thickness of the bilge plating is tobe not less than the actual net thicknesses of the adjacent 2 m width bottom
or side plating, whichever is the greater. Therefore, the required thickness ofthe bilge plating should not be applied to the adjacent bottom or side shell
plating

2009/8/3

In the estimation of web stiffener connection ends, the definition of theparameters is to be clarified.
When fitting with large collar plate supporting stiffener flange as attachedfigure, the parameters, l_1 and l_2 as defined in the left figure of Fig. 10, arenot clear.
Please clarify the above.

In case that Ch.6 Sec.2 [4.1.3] is applied to the design in question, "scallop
width" and "slot width" in the attached figure may be treated as theparameters l1 and l2.

2009/3/10

In corrigenda 5, the “long superstructure” and “short superstructure” aremodified into “effective structure” and “non-effective structure” in Ch 6, Sec 1,[2.5.3] and [2.5.4]. We think Ch 6, Sec 1, [2.6.2] and [2.6.3] should also be
modified.

To be in accordance with Ch.6 Sec.1 [2.5], terms "long superstructure" has tobe change to "effective superstructure" in Ch.6 Sec.1 [2.6.2], and "shortsuperstructure" to "non-effective superstructure" in Ch.6 Sec.1 [2.6.3]

Page 25 of 31

YYIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer

Ch 6, Sec 2, [2.5.3] ordinary stiffeners located on hopper sloping plate or innerhull plating

879

Text
6/2.2.5.3

question

hoppersloping tanks

2009/6/16[quote]l' : Distance, in m, between load points per elementary plate panel of inner
bottom plate in ship length, sloping plate or inner hull plating, as defined in
Ch6, Sec 1, [2.7.2].
[unquote]

Your observation is correct. The definition of l' is related to the factor K3 andhence valid for both [2.5.2] and [2.5.3]. We will consider to move the definition
to Symbols or Table 1 for K3 in a corrigenda.

The title of Subsection [2.5.3] concerns hopper sloping panel and inner hullplate, excluding inner bottom plate, so the definition of l' should be modified.

Scantlings ofprimary
6/4.2.2.1,
supporting
6/4.2.3.1,
members for
Question880
6/4.2.4.1 &ships of less6/4.2.5.1
than 150m in
length definitions

832 6/2.4.1.3

Question

Connection
ends of web
stiffeners differences
between NK
rules & CSR

2010/3/30

With respect to Ch 6, Sec 4, we have the following questions:
1.Subsection [2.2.1] and [2.3.1] define BDB as distance between the toes ofhopper tanks at the midship part, and define Ps, IB, Pw, IB, Ps, BM, Pw, BM
as pressures at the center of the double bottom structure. We think theposition to calculate BDB should also be the center of the double bottom
structure as that of Ps, IB, Pw, IB, Ps, BM, Pw, BM. Please consider.
2.Subsection [2.4.1] and [2.5.1] define hDS as height of the double sidestructure between upper end of hopper tank and lower end of topside tank,and define Ps, SS, Pw, SS, Ps, LB, Pw, LB as pressures at the center of lDS
which is length of the double side structure between the transverse bulkheads
under consideration. We think that the position of hDS should also be at thecenter of lDS as that of Ps, SS, Pw, SS, Ps, LB, Pw, LB. Please consider.

2010/8/6

According to TB, the requirement originates from NK Rules. However, therequirement in CSR seems conservative on the following items:
1.The factor Cship in NK is depending on ship length. In CSR thisdependence is deleted. This means that we obtain stricter results for L<200m.
2.In NK, Klongi is 1.0 for bulbs. In CSR Klongi is 1.3. This seems
conservative, because skew bending moment for bulbs is much less than forangle bars.
3.In NK, the pressure is clearly only considering vertical acceleration. Thismeans that the stress induced by the dynamic load is under the assumptionthat the vessel is under maximum vertical hull girder bending moment. In
CSR, there is no specification about which wave the dynamic pressure isbased on. R and P waves will give high dynamic pressure in top wing tank.
However, R and P wave will not give highest vertical hull girder bending
moment. CSR should clearly state the dynamic pressure is under H or F
wave.
Are the above differences between NK and CSR Rules intended? If they are
not intended, please advise how they should be handled.

We agree to your opinion that B_DB and h_DS should be calculated at thecenter of double bottom and double side of the considered hold respectively.
On the other hand, it is necessary to note that B'_DB is separately defined as
the breadth at the position of the floor in Ch6 Sec4, 2.3.1.
In addition, it is necessary to define h'_DS separately as the height at theposition of the side transverse web in 2.5.1.
Accordingly, the second h_DS in the formula of t1 is changed to h'_DS in
2.5.1.
We will consider a Corrigendum.

1. Design philosopy underlying CSR is based on the "North Atlantic
Navigation" and service life of 25 years. This is different from NK rules.
The factor "Cship" is intentionally deleted.
2. We agree with you. This is not intended. We will consider a corrigenda toclarify this.
3. We have noted your comment and we will send it to the Harmonization
Team.

Page 26 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

845 6/3.3.1.1

Type

Topic

MinimumInterpretati thickness ofonelementary
plate panels

Datecompleted2010/9/7

Question/CI

Please specify where the requirement Ch.6 Sec.3 [3.1.1] applies. Does it only
apply to the cargo area, or also to other areas, such as the aft and fore partsand machinery spaces? If it applies also to the latter areas, we will get
significant increases in plating thickness for some structures, such as wash
bulkheads, platform decks, etc..

Attachment

Answer

Ch6, Sec3 applies to the central part as defined in Ch1, Sec1, [2.1.3]. It also
apply to machinery space as stated in Ch9, Sec3, [1.2.2] with respect torequirements of Ch9, Sec3.
However, the minimum thickness requirement based on space in the first
sentence of Ch6, Sec3, [3.1.1] was made as the first approach at the initialdesign stage so that initial scantling has certain stiffness. Less scantling may
be accepted on members under little load.
We will consider a rule change to delete this requirement

883
Text
attc 6/A1.1.3.3

questionbuckling
assessment

2009/6/16

Ch6 App1, 1.3.3 requires treatments on buckling assessment of side shellplates which are stiffened vertically in the following two cases;
Case 1: with approximately constant stresses
Case 2: with distributed stresses
According to the Rules, Case 2 is applicable to side shell panel under
distributed stress over the panel height. In general, the panels in way of sideYour understanding is correct.
frames are such stress and Case 2, therefore, is applied to them. On thecontrary, regarding side shell panels in way of brackets above/below side
frames as shown in the attached sketch, it is considered that the stress
distribution in the panels is approximately constant. So the treatment of above
Case 1 is applied to the buckling assessment of the panels.
Please confirm the above.

Y

Page 27 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

896

911

914
attc

Ref.

Text
6/4.1.5.1

6/1.2.3.2

Text
6/2.3.3.1

Typequestion

RCP

RCP

Topic

primary
supporting
membersbilge plating
thickness

Datecompleted2009/6/26

2009/8/3

Question/CI

Ch.9 Sec.2 [4.3] specifies scantling requirements of primary supporting
members in aft part. The minimum thickness of floors is defined in [4.3.1].
However for other PSMs such requirement is not so clear. Please advise on
the following questions:[A] [4.3.4] refers to Ch.6 Sec.4 requirements for deck PSMs. Do theserequirements include Ch.6 Sec.4 [1.5.1]?
[B] Please confirm that:(1) there is no requirement to minimum thickness for PSMs other than for
floors, i.e., there is no minimum thickness requirment for deck PSMs, sidetransverses, side girders, etc.; or(2) there is no requirement to minimum thickness for PSMs other than for
floors and deck PSMs, i.e., there is no minimum thickness requirements forside transverses, side girders, etc.

Attachment

AnswerA1) Yes, deck PSM have to fulfill the requirements of Ch.6 Sec.4 considering
the loads defined in Ch.9 sec.2 [2.2], and in particular the minimum web
thickness defined in Ch.6 Sec.4 [1.5.1].
A2) No, the requirement for a minimum web thickness defined in Ch.9 Sec.2[4.3.1] applies to all the PSM except those of the deck (see answer A1 herein).
A rule change will be issued for clarifying this.

Ch6 Sec1 [2.3.2]
Our understanding is that the for formula net thickness of bilge plating isYour understanding is correct, and we will make an editorial correction to
based on buckling of thin cylindrical shells subjected to external pressure.
clarify this.
Hence, please specify that only the external pressures are to be considered in
the formula.

Requirement
Ch6 Sec2 [3.3.1] Side frames in ballast holds
s for side
2010/10/20 Please consider the attached Rule Change Proposal regarding requirements
frames in
to side frames in ballast holds.
ballast holds

As notified in the Technical Background, the requirement Ch.6 Sec.2 [3.3.1] isbased on requirement S12.4.1 of the draft text of IACS UR S12 Rev.4 agreed
at the WP/S meeting of 8-10 April 2003.
In order to agree with URS12, the m-factors must be adjusted.
The new m-factors will be presented to the Hull Panel and to theHarmonization Team in a CI.
Once the new m-factors approved, they will be modified in CSR BC.

Page 28 of 31

YIACS Common Structural Rules Knowledge Centre

KCID
No.

918

962

Ref.

6/1.3.2.3bi
s2

6/3.6.1.1

Type

CI

Question

Topic

Thickness of
supporting
floor ofcorrugatedbulkhead

Buckling
check ofcorrugatedbulkheads

Datecompleted

Question/CI

Attachment

Answer

2010/5/12

With regard to required net thickness of supporting floor of corrugatedbulkhead (Corr.BHD.) with lower stool, please reply to the following questions.
1.In 6/1.3.2.3 bis2 of RCN No.1-8, the wording of “by the first sentence” in thesecond sentence should be deleted because there is no relevant sentence in 1:
6/1.3.2.2.
Your observation is right: The wording of “by the first sentence” in the second
sentence should be deleted because there is no relevant sentence in
2.It is noted that the requirement of 6/1.3.2.2 (required plate thickness in
6/1.3.2.2.
flooding) is not applicable to lower stool side plating in ballast hold because it
is only applicable to the plating which constitutes the boundary of
2:compartments not intended to carry liquids. According to 6/1.3.2.3 bis2 ofYes, you are correct. Required thickness of supporting floor in way of ballast
RCN No.1-8, on the other hand, required thickness of supporting floor in way hold is to be based on the required thickness of 6/1.3.2.2. Imaginary requiredof ballast hold is to be based on the required thickness of 6/1.3.2.2. Our
thickness of lower stool side plating in ballast hold needs to be calculated inunderstanding is that imaginary required thickness of lower stool side plating accordance with 6/1.3.2.2 in order to obtain required thickness of thein ballast hold needs to be calculated in accordance with 6/1.3.2.2 in order to supporting floor in way of ballast hold.
obtain required thickness of the supporting floor in way of ballast holdbecause the concept of 6/1.3.2.3 bis2 comes from UR S18 (Flooding
requirement of Corr.T.BHD). But please confirm.

2009/9/4

Shear buckling check of bulkhead corrugation webs
When Ch.6, Sec.2, [3.2.6] was moved to Ch.6, Sec.2, [3.6.1] by RCN1 (1 July
2008 Consolidated edition), shear force Q which was used for the shear
buckling check of bulkhead corrugation webs was clarified as “Shear force atYour interpretation is correct. We will consider a Corrigendum to clarify it.
the lower end of a corrugation” as defined in original requirement, UR S18,
[3.2]. We understand that shear buckling check of bulkhead corrugation webs
in Ch 6, Sec.3, [6.1.1] is also applicable only to the lower ends of corrugation.
Please confirm the above.

Please advise the answer to the question on the design with the following
Table
non-homogeneous loading conditions in the loading manual:
4.6.1, Text
Design with- cargo density is 3.0 and cargo hold is not loaded up to upper deck,
4/6.3.3.2,
non- cargo density is lighter than 1.78 (for instance 1.7) and cargo hold is loaded
963 6/1.3.2.1, Question homogeneou 2009/12/16
This question is considered together with KC 851, 859 and 972
up to upper deck.
6/1.3.2.3,
s loading
For this design is local strength check required for intact condition and flooded
6/2.3.2.3 &condition
condition for the above loading conditions according to Ch.6 Sec.1 [3.2.1] &6/2.3.2.6[3.2.3] and Ch.6 Sec.2 [3.2.3] & [3.2.6] (or [3.6] by RCN1-8)?

Page 29 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

968

972

974

975

Ref.

6/3.1.1.2

6/4.4.1.1

6/1.3.2.3
bis1

6/1.3.2.3
bis2

Type

Topic

Flooding
requirements
Questionof CSRbulker

Question

Loads onpillars

QuestionNet
thickness ofstool side
plating

Thickness &material
requirements
Questionforcorrugatedbulkheads

Datecompleted

Question/CI

Attachment

Answer

According to KC 460, the buckling check is covered by HULS.

2010/9/2

Buckling check is required for longitudinal members in intact condition only.
Please explain how the buckling requirement of URS17 (axial bucklingaccording to URS11) is satisfied for at lease BC-A and BC-B ships.

2010/3/8

There is only the formula about critical column buckling stress of pillars but noclear interpretation on how to calculate the loads on pillars in CSR BC 6/4.4.1.
We will consider a Rule Change to include a design load for pillar scantling
According to our experiences, the loads on pillars are similar between BC andcalculation similar to CSR OT
OT, so we think a similar design load for pillar scantling calculation as 8/3.9.5
in CSR OT should be provided.

2010/3/8

Our understanding is that the following sentence in 6/1.3.2.3 bis1 of CSR BC
is only applicable to upper stool, please confirm.
[QUOTE]The net thickness of the lower portion of stool side plating is to not be lessthan 80% of the upper part of the bulkhead plating required by [3.2.3], asapplicable, whichever is the greater, where the same material isused.[UNQUOTE]

2010/3/8

Rule Ref.: CSR BC 6/1.3.2.3 bis2
[QUOTE]The net thickness and material of the supporting floors and pipe tunnel beams
of corrugated bulkhead, when no stool is fitted, are to be not less than thoseof the corrugation flanges required by [3.2.3].
When a lower stool is fitted, the net thickness of supporting floors are to be
not less than that of the stool side plating required by the first sentence of[3.2.2].”[UNQUOTE][3.2.2] and [3.2.3] are requirements of flooding condition, which areinconsistent with KC ID210 as followers:
QUOTE: KC ID210
In applying this requirement 6.4.2, the net thickness and. material properties
required for the bulkhead plating, or when a stool is fitted, of the stool side
plating mean that they are required by the scantling requirement except for
the grab loading and under flooded condition.
UNQUOTE
Please clarify above.

Further consideration including the necessity of additional buckling check inflooded condition will be requested to the Harmonization Team.

Yes, your understanding is correct. We will consider a corrigenda to clarify
this.

We agree that the reply to KC 210 is inconsistent to the original requirementsof IACS UR S18 which reads; “the thickness and material properties of the
supporting floors are to be at least equal to those provided for the corrugation
flanges.” Only requirement for GRAB notation should be excluded. It was also
the original intention of KC210.
Reference is made to KC 918 for additional information

Page 30 of 31

IACS Common Structural Rules Knowledge Centre

KCID
No.

1005

1040

Ref.

6/1

6/4.3.1.2

Type

Topic

QuestionYieldstrength ofnonrectangular
EPP

RCP

Allowable
stress factors
for floors
adjacent tostools ortransverse
bulkheads

Datecompleted

Question/CI

When assess the yield strength of non-rectangle EPP, such as EPP of
2010/10/20 watertight transverse webs of wing tanks, how to measure the longer or
shorter side of EPP?

2010/5/5

According to UR S20.3.1, allowable shear stress for floors adjacent to thestools or transverse bulkheads may be taken sigma_F/3^0.5. On the other
hand, in CSR-B of Ch.6, Sec.4, [3.1.2], there is no description about thistreatment. It seems that to apply this treatment to CSR-B is rational because
this requirement has come from UR20.
Please consider a RCP to add this treatment into CSR-B.

Attachment

AnswerSince this issue involves both CSR BC and OT, it will be submitted to theharmonization team.

In CSR-B of Ch.6, Sec.4, [3.1.2], the following treatement will be added:
allowable shear stress for floors adjacent to the stools or transverse bulkheads
may be taken sigma_F/3^0.5 as notified in UR S20.3.1.
A corrigenda will be issued.

Keel Plating
The following requirements for keel plating can be found:
Ch3, Sec6, 6.2.1. Minimum breadth of the keel "b".
Ch6, Sec1, Table 2 Minimum thickness of keel
Ch6, Sec1, 2.4.1 The net thickness of the keel plating is to be not less than
the actual net thickness of the adjacent 2 m width bottom plating.

1055 Text
attc 6/1.2.4.1

Firstly, we do not agree with your interpretation: as for bilge plating, theadjacent 2m are to be considered from the edge of the keel strake, this is in
Measuremen
Interpretati
It is not mentioned, if the adjacent 2 m width bottom plating has to beorder to avoid large discrepancies in thicknesses for welding.
t of adjacent 2010/10/20
onmeasured from the edge of the actual keel strake or from b/2. Some current
In addition, considering the adjacent 2m starting from b/2 will in most caseplate width
ship designs have an actual keel plating width of more than 3 times the size of include the keel strake which may lead to misinterpretations.
b (see attachment). If Ch6, Sec1, 2.4.1 is interpeted in a way that the adjacent Consequently the rules are kept as they are and no interpretation is emitted.
plate width has to be measured from the edge of the actual keel strake, thewidth of affected bottom plating and the potential increase of the thickness
depends on this arbitrary strake width. We propose to initiate a Common
Interpretation (CI) or to include the outcome of this question in next RCP toclarify that the adjacent plate width has to be measured from b/2 of CL.

Page 31 of 31

YKC#204
Sniped stiffeners, requirement to buckling capacity.
The CSR Ch. 6 Sec. 3.4 gives requirement to the buckling capacity of “longitudinal and transverse
ordinary stiffeners of partial and total plate panels”. According to Ch. 3 Sec. 6 we understand that“ordinary stiffeners” does not address sniped buckling stiffeners of primary supporting members.
a) Please explain whether Ch. 6 Sec. 3.4 is applicable to e.g. the sniped flat bars of a longitudinal
double bottom girder as shown below.

b) Ch. 6 Sec. 2 is giving minimum requirements to ordinary stiffeners. Please advice if this requirement
is applicable to sniped buckling stiffeners as shown above.
If above items a) and b) are not applicable for buckling stiffeners, please comment on the followinginterpretation.
Buckling stiffeners are subject to the following requirements in CSR Bulk:
1. Ch. 3 Sec. 6 Sec. 5.2.1. hstiffener > lstiffener/12 and tnetStiffener>tminimumGirderWeb.
2. Ch. 6 Sec. 2 4.1.2 “Net section modulus of web stiffeners of non-watertight primary supporting
members”
Please advise if the above item 1 is referring to the minimum thickness of the girder web or the load
thickness of the girder web.
Please also explain what is meant by the unclear expression; “web stiffener mid-height” as stated in
Ch.6 Sec.2 4.1.1 which reads; “their net sectional area at the web stiffener mid-height is to be not lessthan ---”.

KC#311
Side Shell






Supporting areapillar










KC#319
Computation of upper and lower connection of side frames of single sidebulk carriers
The following note is extracted from the WP/S background document for UR S12 revision 4.
This version of the UR was neither officially released, but is the basis for the requirements of
the IACS Common Structural Rules for bulk carriers.
This note is related to the calculation of the longitudinals that support the lower and upper
connecting brackets of the side shell frames in hopper and topside tanks.
The relevant requirements are provided in Ch 6, Sec 2, [3.4] of IACS CSR for bulk carriers.
The technical background document has been modified to adopt the symbols and notations of
the Common structural rules for bulk carriers Chapter 6, Section 2, in order to facilitate thereading. For the meaning of the symbols not defined hereunder, please refer to the text of theCommon Structural Rules.

Checking of section modulus of the longitudinals in Ch 6, Sec 2 [3.4.1]
The section modulus of the longitudinals is required to have sufficient bending strength tosupport the end fixing moment of the side frame about the intersection point of the sloping
bulkhead and the side shell.
The end fixing moment of the side frame is that induced by the external sea pressure acting on
the side frame (end brackets excluded) and the deflection and rotation of the end support due
to the loading on the hopper and the double bottom.
The sea pressure loading on the end brackets is not included because the sea pressure loadingon this and on the connecting structure of the hopper and topside tank are assumed to cancel.
The end fixing moment, Mef, of the side frame about the intersection point of the sloping
bulkhead and the side shell in Nm is given as:
M ef DT (pS  pW )sl 2(1)
The end fixing moment, Mef, gives rise to line loads on the connected side and sloping
bulkhead stiffeners, qefi, in N/m such that:
M ef(2)¦i qefi dis
The line load, qefi, gives rise to plastic bending moments in the connected side and sloping
bulkhead stiffeners, Mci, in Nm given as:
qefi "2l(3)16Hence, assuming an allowable stress equal to yield, the section modulus requirement for aconnected side or sloping bulkhead longitudinal in cm3 becomes:
M ci
(4)
wi
RY
Injecting the expression of Mci from (4) into (3) and putting qefi in (2), we obtain:(pS  pW )l 2 ll2
M ef ll2
(5)
w

d

D
¦i i i 16sRY T 16RY
The above expression allows the required section modulus of the connected longitudinals tobe determined and is given under [3.4.1] of Common Structural Rules for bulk carriers,
Chapter 6, Section 2.
M ci

Checking of connection area in Ch 6, Sec 2 [3.4.2]
The connecting force Qefi in N is transferred through shear between the brackets and thelongitudinals, with:
Qefi sqefi(6)2
Assuming an allowable shear stress equal to 0.5 RY, we have, with Ai in cm the connection
area between bracket and longitudinal:
RYbkt 102 Qefi 102 sqefi
(7)
2
Ai
Ai
Injecting qefi from (3) and (4) inside (7), we obtain:wi sR
Ai [0.32] 2 Y lg
(8)ll RYbkt
The above expression provides the required connection area and is given with the coefficient
0.32 rounded up to 0.4 and introducing the material factors for bracket and stiffener to replace
the yield strengths ratio, under [3.4.2] of Common Structural rules for bulk carriers, Chapter 6,
Section 2.

KC#333
Requirements for web stiffeners attached primary supporting members
Chapter 6

Capter 3

Capter 6

Section 2

Section 6

Section 4
1.5

Type

2.2

2.3

5.2

Water tight

Apply

Apply

Apply or N. A. ?

Non tight

N. A

N. A

Apply

Rule
Chapter 6

Scetion 2

Title
2.2

Minimum net thickness of webs of ordinary stiffeners

2.3

Net Dimensions of ordinary stiffeners

Chapter 3

Section 6

5.2

Stiffening arrangement

Chapter 6

Section 4

1.5

Minimum net thickness of webs of primary supporting members

KC#356
Ch. 6 Sec. 2 [3.3] - Sectional modulus of main frames of single side bulk carriers in way
of ballast hold.
The requirement for mid-span sectional modulus is given in [3.3.1]
Quote:The net section modulus w, in cm3, and the net shear sectional area Ash , in cm2, of side frames subjected to lateralpressure are to be not less, in the mid-span area, than the values obtained from the following formulae:
w 1.125D m

Ash

1.1D Sp S  p W s" 2 3
10mO S RY(Eq1)

5 p S  pW s" § "  2" B ·¨¸W a sin I © " ¹(..)
In addition to the above provision, the net section modulus w, in cm3, and the net shear sectional area Ash , incm2, of side frames subjected to lateral pressure in holds intended to carry ballast water are to be in accordancewith [3.2.3].

Unquote.
We assume (ps + pw) is all intact pressures as specified in Ch. 6 Sec. 2 [1.3]. Please confirm.
The requirement of [3.2.3] is
Quote

The net section modulus w, in cm3, and the net shear sectional area Ash , in cm2, of single span ordinary stiffeners
subjected to lateral pressure are to be not less than the values obtained from the following formulae:w

pS  pW s" 2 3
10mOS RYAsh

5 p S  pW s"
W a sin I(Eq2)

UnqouteWe assume this is applicable for (ps + pw) from ballast inside the cargo hold only.
Our experience is that the ballast pressure is normally decisive for these main frames.
For a BCA vessel, the sectional modulus requirement of [3.3.1] can be written as:p  pW s" 2 3p  pW s" 2 3 wEq 2100.47 S10 |wEq1 1.125D m S
2
mO S RYmO S RY
That is, the requirement from Eq2 is 2 x Eq1.
The requirement at ends are defined in [3.3.3] for Lower End and [3.3.4] for Upper End.
Requirement for ends are required as 2 x [3.3.1] equation.
Q1: In the text above Eq1 it is quoted “in the mid span area”. Is the sectional modulus of Eq2
also intended to be satisfied in the mid span area?
Q2: The requirement of [3.3.3] and [3.3.4] specifies wEND to be two times the section modulus
required for midspan area according to [3.3.1]. We assume this is 2 x Eq 1 only and not 2 xmax(Eq1, Eq2). Please confirm.

KC#360

Correction:

Reference stress, to be the following for LC 1 and 2:b': shorter side of elementary plate panel

Reference stress, to be the following for LC 3 through 10:

KC#402

Question / Interpretation Request / Rule Change Proposal Form
Please complete this form and submit it to the IACS Senior Technical Officer, Mr. Gil Yong Han,at gilyonghan@iacs.org.uk and zoewright@iacs.org.uk or fax it to +44 (0)20 7808 1100

Page 1 of 2

Question, Request for Interpretation or Rule Change Proposal (RCP):
Questions related to requirements in Ch. 6 Sec.1 and 2 for flooding:
Q1:
Ref. Ch. 6 Sec. 1 [3.1.3]/ [3.2.2] and Sec. 2 [3.1.3]/[3.2.5]
The item Ch. 6 Sec. 1 [3.2.2] is giving “ Net thickness under flooded condition excluding corrugation of transverse
vertically corrugated bulkheads separating cargo holds” and Sec.2 [3.2.5] “Net section modulus and net shear
sectional area of single span ordinary stiffeners under flooded conditions(..)”. The flooding pressure to pF to be
used in the formulas is according to Ch.6 Sec. 1 [3.1.3] and Sec. 2[3.1.3] the flooding pressure pF of Ch. 4 Sec. 6[3].
Ch. 4 Sec. 6 [3] have two definitions of pF:•[3.2.1] flooding water pressure - static water head including 60% vertical acceleration.
•[3.3.6] flooding water pressure – static water head only
As Ch. 4 Sec. 6 [3.3.6] is referring to “pressure on corrugation in empty hold” we assume [3.2.1] should be used inthis context.
Please consider revising Ch. 6 Sec. 1 [3.1.3] and Sec. 2 [3.1.3] to “The lateral pressure in flooded conditions pF is
defined in Ch. 4 Sec. 6 [3.2.1]”
Q2:
Ref. Ch. 6 Sec. 1 [3.2.3] and Sec. 2 [3.2.6]
The item Ch. 6 Sec. 1 [3.2.2] is giving “Net thickness of corrugations (..) for flooded conditions” and Sec. 2 [3.2.6]
is giving “Bending capacity and shear capacity (..) for flooded conditions.” Both items refer to the design resultant
pressure and resultant force as defined in Ch. 4 Sec. 6 [3.3.7].
Ch. 4 Sec. 6 [3.3.7] is defining the resultant pressure in combined bulk cargo water flooding. [3.3.6] is defining thepure water flooding pressures on corrugations. This pressure seem to be overlooked in Ch.6. We assume that thereference to [3.3.6] is missing in Ch. 6.
Please consider revising the definition of p in Ch. 6 Sec. 1 [3.2.3] and Sec. 2 [3.2.6] to "(..)either [3.3.6] or [3.3.7]
whichever greater".
Q3:
Reference is made to above Q1 and Q2.
A summary of the flooding requirements in Ch. 6 is enclosed below. Please confirm/comment our understanding.
The following is noted with respect to flooding pressures:
Plane boundaries – covering plane bulkheads/stools of corrugated bulkheads etc.
– flooding pressure to be water head + 60% dynamic vertical acceleration
Corrugations of transverse bulkhead – covering corrugations in between stools only
•flooding of cargo and water combined•flooding of water, static head only.

Flooding in Ch.6Sec1 and Sec2

Use of requirements for flooding and corresponding pressure:
Ch 6
Ch 6
Ch 6
Ch 6
Sec 1
|
Sec 1
|
Sec2
|
Sec2
Type
3.2.2
|
3.2.3
|
3.2.5
|
3.2.6
..................................................... .............|...................................|.............................|.....................
Corrugations of|
Ch.4 Sec.6||
Ch.4 Sec.6
corrugated bhd
N. A|[3.3.6]/[3.3.7] |N. A|[3.3.6]/[3.3.7]|||
Stool plating of|||corrugate bulkheads
Ch.4 Sec.6||
Ch.4 Sec.6 |[3.2.1] |N. A|[3.2.1]
|
N. A
|
|
|
|
|
|
Plane bulkheads
Ch.4 Sec.6||
Ch.4 Sec.6 |[3.2.1] |N. A|[3.2.1] |N. A
Rules:

Tanker

Bulker

Both

Type:

Interpretation

Question

RCP

Rule Reference
EITHER:
Type

Section Name

Text

FigureTable

Symbol (BC only)

Ch 6

Sub Section 1
1
1
2
2

Sub Section 233
33

Sub Section 322
22

Sub Section 4
2
3
5
6

OR:
General Rule Reference (e.g. 2/, or General):Received (e.g. 12/02/06):

Day:

Month:

Respondent:

Client:IACS Member (AB, LR, etc.): DNV

Confidential:

Year:

Y

N

Answer or Interpretation:

Answer has already been provided to client.

Attachments included.

Number of attachments:

Flooding in Ch.6Sec1 and Sec2

KC#425
Steel coil loading on hopper plate
According to Ch. 6 Sec. 1 [2.7.3] Hopper sloping plate and inner hull plating thickness
The net thickness of plating of longitudinally framed hopper sloping plate and inner hull is to be not less than thevalue obtained, in mm, from the following formula:t>g cos T1  T 2  aY sin T1 @F c

K1

OP RY

where:

aY:

Transverse acceleration, in m/s2, defined in Ch 4, Sec2, [3.2]

According to Ch. 4 Sec2 [3.2]aY

CYG g sin T  CYS asway  CYR aroll y

A typical steel coil loading pattern is shown in the figure below. The T2 is denoting the roll angle and COG isindicating the centre of gravity of the coils towards the hopper tank. Please see below calculation of theacceleraton term in the eq. [2.7.3], aA

g cos T1  T 2  aY sin T1

T2

COG

T1

CL

The rule formulation for acceleration according to Ch.4 Sec2 [3.2]:
The component originating from the roll motion CYR aroll y is shown in the figure below.

T2aroll,y
az

aR

T1

CL

The component CYG g 0 sin T 2 is given in the following figure:T2

gy=g0sin(T)
g0 gz
T1

CL

The total component aY

CYG g sin T  CYR aroll y , when neglecting the asway component, is illustrated in the

figure below. The component normal to the hopper, aA

a y sin T1 , is also indicated in the drawing.

T2

aŏ

gy=g0sin(T)aroll,yaŒ

T1The second term, g ACL

g 0 cos T1  T 2 , is shown in the figure below:

T2

g0

gŒ

gŏ
T1

CL

Total rule acceleration aAg cos T1  T 2  aY sin T1 is shown below:

T2gŏ
Total hopper
acceleration

T1

aŏ
CL

Please note following:
1. Gravity component in the equation is accounted for twice.
2. The roll component is decomposed twice. That is, the component normal to ( ŏ) the hopper tank isdecomposed from the transverse acceleration ay.
3. The rule formulation is in some cases summing the vectors without sign. This depend on the ratio
between the hopper angle and the angle of the vector R. Please see below sketches.
Please consider below alternative calculation. The calculation is based on the two fundamental acceleration
components gravity,g0, and roll acceleration aroll.
The coil closest to the hopper is resting on the hopper only. That is, the force on the inner bottom is neglected.

The acceleration component normal to ( ŏ) the hopper from roll acceleration may be described as shown in
the figure below:

T2
D
R

R

T1

aR
aŒ
aŏ
T1

CL

The angle D is expressed as:

yCOG
&
R

sin D

&

Further more the vector R is the vector from the ship roll centre to the coil COG:&
R

>yCOG , R@

Consequently the angle D may be expressed as:

yCOG

sin D

yCOG  R 2
2

The normal acceleration can be expressed as:aAaRa R sin D  T1

T2

2
S § 2S · &¨¸ R
180 ¨© TR ¸¹

T2

S § 2S ·¨¸
180 ¨© TR ¸¹

2

yCOG  R 2
2

The gravity component is expressed in the same way as the rule formulation- g A

g cos T 1  T 2.

Ref. below figure.

T2

g0

gŒ

gŏ
T1

CL

The total acceleration is the sum of the contribution from the roll and the gravity component.

aAaR sin D  T1  g cos T1  T 2

T2

gŏ
T1

aŏ

Total hopper
acceleration

CL

If we include the sway component and introduce the load combination factors, the acceleration can be written as:

aA

CYR a R sin D  T1  g cos T1  CYGT 2  CYS aSway Sin (T1 )Example for straight inner side (no hopper) configuration T1 = 90. The EDW R1 is choosen as the condition isnormally decisive for inner side/hopper structure.
Acceleration term according to the rules (EDW R1):aA

g cos T1  T 2  aY sin T1

g cos 90  T 2  aY sin 90 g sin T 2  aYaY

CYG g sin T 2  CYS asway  CYR aroll yaAg sin T 2  g sin T 2  aroll yg sin T 2  aroll y

2 g sin T 2  aroll y

Acceleration term according to DNV above assumption (EDW R1)aAaA

CYR a R sin D  T1  g cos T1  CYGT 2  CYS a Sway Sin(T1 ) a R cos D  g sin T 2

aA

 a R cos D  g sin T 2aA aroll y  g sin T 2

T 2

T 2

S § 2S ·2yCOG  R 2 cos D  g sin T 2 , cos D

R

2

¨
¸
180 ¨© TR ¸¹

S § 2S ·a R sin D  90  g cos 90  T 22¨¸
180 ¨© TR ¸¹yCOG  R 2 R

yCOG  R 2
2

2

yCOG  R 2
2

 g sin T 2

Please note that the aroll,y term is negative in the CSR. Except the 2 x factor the two terms are identical.
For a small handy the trem aroll,y is about 0.5 m/s2 and gsinT2 = 4.1m/s2 (typical T2=25 deg)
CSR acceleration aŏ=7.8m/s2
DNV interpretation aŏ = 3.6m/s2
Q1: Please note that the hopper normal acceleration calculated directly based on the fundamental accelerations issmaller than the rule accelerations. Dependent on the term sin D  T1 , the roll acceleration will work towards
the gravity acceleration. Please note that the acceleration is sensitive to the definition of COG. The procedure todefine COG should be clearly defined in the rules. With reference to IACS KC #380 please consider above
acceleration calculations.

Q2: DNV have noted that the results of eq. [2.7.3] give very strict results for the hopper sloping plate. The
thickness of the hopper sloping plate is in many cases in excess of the requirement of the inner bottom.
The force on the hopper is larger than the force for the inner bottom. This is caused by the Ck factor which is 4
for 2 tiers stowage. Could you please give details regarding the background of this term. According to our steel
coil experts the stowage is, even though it is shored, quite flexible. Have there been attempted any test to accountfor the amount of force taken by the hopper plating?

KC#470
CH6, Sec3, 3.2.4 – Checking criteria
Rule Change:
In addition each compressive stress ıX and ıY and the shear stress Ĳ are to comply with the following formulae:

GL-Answer: In General we consider only the rule defined load cases and loading conditions
for the dimensioning of the structure, which are called design-load cases. In case of bucklingchecks we have to accept, that in reality also load cases exist, they give other load andtherefore stress combinations as defined in the design-load-cases. Of course it is guaranteed,that the design-load cases cover the cases with respect of the calculation of the most criticalstress-components. In case of buckling we have to consider all possible stress combinations.
This is somewhat different and because of that we require, that the buckling strength of theplate has to be high enough to withstand each compressive stress acting alone. This means,that possible stabilizing effects of pressure stresses are neglected.
This can be illustrated with the following figures.
In Figure 1 the interaction curve is shown including the Poisson effect. As can be seen there
are stress combinations allowable for which the Sy-component can be greater, than in the casefor Sy is acting alone on the plate. Because of the problem mentioned above, the interaction
curve as the base for the rule requirements is limited to stress combinations as shown in figure
2. Please note that this figure is given in Appendix 1 of the Buckling-TB-document. Pleaserefer to ̌Buckling Strength Assessment of Plates in the IACS Common Structural rules for
Bulk Carriers – Sample Applications̍, Figure 2.
200

Stresses including Poisson
effect (from finite element
analyses)

150

225,1; 145,7

Vx < 0,3 * Vy

Stresses excluding Poisson effect(for buckling strength assessment)

2

Vy [N/mm ]100

199,4; 85,9
Vy < 0,3 * Vx

50

0
-50

0

50

100

150

200

250

300

350

-50
2

V x [N/mm ]Figure 1: interaction without the requirement that the plate has to be stiff enough to withstandeach compressive stress alone

200
Including Poisson EffectExcluding Poisson Effect150

0,0; 145,4

43,6; 145,4

223,0; 145,4

2

Vx < 0,3 * Vy

2Vy [N/mm ]

1

3

100

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

Vy < 0,3 * Vx

50

4308,3; 0,0

0
0

50

100

150

200

250

300

350

2

Vx [N/mm ]Figure 2: interaction with the requirement that the plate has to be stiff enough to withstandeach compressive stress alone

Input Values
FE-Stresses

Calculated Values

Buck. red. factor

Material

Corrected Stresses

Results of Interaction Formula (IF)Factors

Single Terms with converted stresses

Proper usage of IF

σ x*

σy*

τ

κx

κy

κt

ReH

σx

σy

B

e1

e2

e3

1st Term IF

2nd Term IF

IF

1st Term IF

2nd Term IF

IF

200

200

0

1.00

1.00

1.00

235

154

154

1.00

2.00

2.00

2.00

0.43

0.43

0.72

0.72

0.72

0.72

200

150

0

1.00

1.00

1.00

235

170

99

1.00

2.00

2.00

2.00

0.53

0.18

0.59

0.72

0.41

0.59

200

100

0

1.00

1.00

1.00

235

187

44

1.00

2.00

2.00

2.00

0.63

0.03

0.54

0.72

0.18

0.54

200

50

0

1.00

1.00

1.00

235

200

0

1.00

2.00

2.00

2.00

0.72

0.00

0.59

0.72

0.05

0.59

200

0

0

1.00

1.00

1.00

235

200

0

1.00

2.00

2.00

2.00

0.72

0.00

0.72

0.72

0.00

0.72

200

-50

0

1.00

1.00

1.00

235

200

-50

1.00

2.00

2.00

2.00

0.72

0.05

0.95

0.72

0.05

0.95

200

-100

0

1.00

1.00

1.00

235

200

-100

1.00

2.00

2.00

2.00

0.72

0.18

1.27

0.72

0.18

1.27

200

-150

0

1.00

1.00

1.00

235

200

-150

1.00

2.00

2.00

2.00

0.72

0.41

1.67

0.72

0.41

1.67

200

-200

0

1.00

1.00

1.00

235

200

-200

1.00

2.00

2.00

2.00

0.72

0.72

2.17

0.72

0.72

2.17

200

200

0

0.70

1.00

1.00

235

154

154

0.17

1.24

2.00

1.70

0.92

0.43

1.88

1.27

0.72

1.88

200

150

0

0.70

1.00

1.00

235

170

99

0.17

1.24

2.00

1.70

1.04

0.18

1.59

1.27

0.41

1.59

200

100

0

0.70

1.00

1.00

235

187

44

0.17

1.24

2.00

1.70

1.17

0.03

1.39

1.27

0.18

1.39

200

50

0

0.70

1.00

1.00

235

200

0

1.00

1.24

2.00

1.70

1.27

0.00

1.14

1.27

0.05

1.14

200

0

0

0.70

1.00

1.00

235

200

0

1.00

1.24

2.00

1.70

1.27

0.00

1.27

1.27

0.00

1.27

200

-50

0

0.70

1.00

1.00

235

200

-50

1.00

1.24

2.00

1.70

1.27

0.05

1.50

1.27

0.05

1.50

200

-100

0

0.70

1.00

1.00

235

200

-100

1.00

1.24

2.00

1.70

1.27

0.18

1.82

1.27

0.18

1.82

200

-150

0

0.70

1.00

1.00

235

200

-150

1.00

1.24

2.00

1.70

1.27

0.41

2.22

1.27

0.41

2.22

200

-200

0

0.70

1.00

1.00

235

200

-200

1.00

1.24

2.00

1.70

1.27

0.72

2.72

1.27

0.72

2.72

200

200

0

0.40

1.00

1.00

235

154

154

0.01

1.03

2.00

1.40

1.66

0.43

2.89

2.17

0.72

2.89

200

150

0

0.40

1.00

1.00

235

170

99

0.01

1.03

2.00

1.40

1.84

0.18

2.57

2.17

0.41

2.57

200

100

0

0.40

1.00

1.00

235

187

44

0.01

1.03

2.00

1.40

2.02

0.03

2.35

2.17

0.18

2.35

200

50

0

0.40

1.00

1.00

235

200

0

1.00

1.03

2.00

1.40

2.17

0.00

2.03

2.17

0.05

2.03

200

0

0

0.40

1.00

1.00

235

200

0

1.00

1.03

2.00

1.40

2.17

0.00

2.17

2.17

0.00

2.17

200

-50

0

0.40

1.00

1.00

235

200

-50

1.00

1.03

2.00

1.40

2.17

0.05

2.40

2.17

0.05

2.40

200

-100

0

0.40

1.00

1.00

235

200

-100

1.00

1.03

2.00

1.40

2.17

0.18

2.71

2.17

0.18

2.71

200

-150

0

0.40

1.00

1.00

235

200

-150

1.00

1.03

2.00

1.40

2.17

0.41

3.12

2.17

0.41

3.12

200

-200

0

0.40

1.00

1.00

235

200

-200

1.00

1.03

2.00

1.40

2.17

0.72

3.62

2.17

0.72

3.62

200

200

0

0.10

1.00

1.00

235

154

154

0.00

1.00

2.00

1.10

6.55

0.43

9.24

8.51

0.72

9.24

200

150

0

0.10

1.00

1.00

235

170

99

0.00

1.00

2.00

1.10

7.25

0.18

8.92

8.51

0.41

8.92

200

100

0

0.10

1.00

1.00

235

187

44

0.00

1.00

2.00

1.10

7.95

0.03

8.69

8.51

0.18

8.69

200

50

0

0.10

1.00

1.00

235

200

0

1.00

1.00

2.00

1.10

8.51

0.00

8.38

8.51

0.05

8.38

200

0

0

0.10

1.00

1.00

235

200

0

1.00

1.00

2.00

1.10

8.51

0.00

8.51

8.51

0.00

8.51

200

-50

0

0.10

1.00

1.00

235

200

-50

1.00

1.00

2.00

1.10

8.51

0.05

8.74

8.51

0.05

8.74

200

-100

0

0.10

1.00

1.00

235

200

-100

1.00

1.00

2.00

1.10

8.51

0.18

9.06

8.51

0.18

9.06

200

-150

0

0.10

1.00

1.00

235

200

-150

1.00

1.00

2.00

1.10

8.51

0.41

9.46

8.51

0.41

9.46

200

-200

0

0.10

1.00

1.00

235

200

-200

1.00

1.00

2.00

1.10

8.51

0.72

9.96

8.51

0.72

9.96

200

200

0

1.00

0.70

1.00

235

154

154

0.17

2.00

1.24

1.70

0.43

1.88

0.72

0.72

1.27

1.88

200

150

0

1.00

0.70

1.00

235

170

99

0.17

2.00

1.24

1.70

0.53

1.52

0.59

0.72

0.89

1.52

200

100

0

1.00

0.70

1.00

235

187

44

0.17

2.00

1.24

1.70

0.63

1.20

0.54

0.72

0.54

1.20

200

50

0

1.00

0.70

1.00

235

200

0

1.00

2.00

1.24

1.70

0.72

0.77

0.59

0.72

0.23

0.77

200

0

0

1.00

0.70

1.00

235

200

0

1.00

2.00

1.24

1.70

0.72

0.72

0.72

0.72

0.00

0.72

200

-50

0

1.00

0.70

1.00

235

200

-50

1.00

2.00

1.24

1.70

0.72

1.13

0.95

0.72

0.23

1.13

200

-100

0

1.00

0.70

1.00

235

200

-100

1.00

2.00

1.24

1.70

0.72

1.63

1.27

0.72

0.54

1.63

200

-150

0

1.00

0.70

1.00

235

200

-150

1.00

2.00

1.24

1.70

0.72

2.16

1.67

0.72

0.89

2.16

200

-200

0

1.00

0.70

1.00

235

200

-200

1.00

2.00

1.24

1.70

0.72

2.72

2.17

0.72

1.27

2.72

200

200

0

1.00

0.40

1.00

235

154

154

0.01

2.00

1.03

1.40

0.43

1.66

2.89

0.72

2.17

2.89

200

150

0

1.00

0.40

1.00

235

170

99

0.01

2.00

1.03

1.40

0.53

1.05

2.33

0.72

1.61

2.33

200

100

0

1.00

0.40

1.00

235

187

44

0.01

2.00

1.03

1.40

0.63

0.46

1.79

0.72

1.07

1.79

200

50

0

1.00

0.40

1.00

235

200

0

1.00

2.00

1.03

1.40

0.72

0.00

1.07

0.72

0.52

1.07

200

0

0

1.00

0.40

1.00

235

200

0

1.00

2.00

1.03

1.40

0.72

0.00

0.72

0.72

0.00

0.72

200

-50

0

1.00

0.40

1.00

235

200

-50

1.00

2.00

1.03

1.40

0.72

0.52

1.43

0.72

0.52

1.43

200

-100

0

1.00

0.40

1.00

235

200

-100

1.00

2.00

1.03

1.40

0.72

1.07

2.15

0.72

1.07

2.15

200

-150

0

1.00

0.40

1.00

235

200

-150

1.00

2.00

1.03

1.40

0.72

1.61

2.88

0.72

1.61

2.88

200

-200

0

1.00

0.40

1.00

235

200

-200

1.00

2.00

1.03

1.40

0.72

2.17

3.62

0.72

2.17

3.62

200

200

0

1.00

0.10

1.00

235

154

154

0.00

2.00

1.00

1.10

0.43

6.55

9.24

0.72

8.51

9.24

200

150

0

1.00

0.10

1.00

235

170

99

0.00

2.00

1.00

1.10

0.53

4.21

7.11

0.72

6.38

7.11

200

100

0

1.00

0.10

1.00

235

187

44

0.00

2.00

1.00

1.10

0.63

1.87

4.98

0.72

4.26

4.98

200

50

0

1.00

0.10

1.00

235

200

0

1.00

2.00

1.00

1.10

0.72

0.00

2.67

0.72

2.13

2.67

200

0

0

1.00

0.10

1.00

235

200

0

1.00

2.00

1.00

1.10

0.72

0.00

0.72

0.72

0.00

0.72

200

-50

0

1.00

0.10

1.00

235

200

-50

1.00

2.00

1.00

1.10

0.72

2.13

3.03

0.72

2.13

3.03

200

-100

0

1.00

0.10

1.00

235

200

-100

1.00

2.00

1.00

1.10

0.72

4.26

5.34

0.72

4.26

5.34

200

-150

0

1.00

0.10

1.00

235

200

-150

1.00

2.00

1.00

1.10

0.72

6.38

7.65

0.72

6.38

7.65

200

-200

0

1.00

0.10

1.00

235

200

-200

1.00

2.00

1.00

1.10

0.72

8.51

9.96

0.72

8.51

9.96

99

99

0

0.50

1.00

1.00

235

76

76

0.03

1.06

2.00

1.50

0.63

0.11

1.01

0.83

0.18

1.01

KC#483

KC#493-1

Internal pressures

Loc. of web
stiff area

External pressures

KC#493-2

KC#493 Technical backgroundThe combined effect of external and internal pressures applied on ordinary stiffeners depends
on the position of the stiffener as specified in CSR BC Chapter 6 – Section 1 – [1.3].

Elements of the outer shell
Two cases are to be considered:
1. the stiffener is located below the waterline
a. the compartment is empty: only the external still water and wave pressures are
considered.
b. the compartment is intended to carry liquids: the internal still water and wave
pressures are to be reduced by the external still water and wave pressures
The external pressures are to be set in accordance with the draught that matches theloading condition to be assessed.
2. the stiffener is located above the waterline
only the still water and wave internal pressures are to be considered.

Other elements
If the stiffener is attached to an element that separates two adjacent compartments, then thepressures to be considered are the still water and wave lateral pressures of each compartment
individually loaded.

KC#497

Where is the pressure point to be used for scantling check of corrugation web?
Please note that option 1 is inside the gusset/shedder. Therefore, eventually there is nopressure.

Option 3: at the top of shedder

Option 2: at the middle of shedder

Option 1: at the bottom of corrugation

KC#529
Derivation of the normal stress terms in the formulae for pzi CH6, Sec3, 4.2.2(Dr.-Ing. Arne Schulz-Heimbeck)

The formulae for the nominal pressures pzx and pzy contain the influence of normal stresses.
2·ta §¨ § S  b ·V xl ¨¸  2  c y  V y  2W 1 ¸¨¸b© © a ¹
¹
2
§
·
Ay ·
ta ¨
§ S  a · §¨¸  2W 1 ¸p zy
2  c x  V xl  V y ¨¸ ¨1 ¸a ¨©
© n  b ¹ © a  ta ¸¹
¹
§
Ax ·
¸
with V xl V x ¨¨1 ¸© b  ta ¹

p zx

The axial acting stresses can be calculated according the TB document New Req. of GL for
Proof of Buckling Strength (inkl DIN18800).pdf

The following derivation shows the equivalence of the formula for pzx and the first term of theformula for pzx.
2
§ t S 2b 2 t S 2b 2 Ax ·ta §¨ § S  b · ·¸¸V xl ¨V x ¨¨ a 2  a 2¸b ¨© © a ¹ ¸¹a b  bta ¸¹
© ab

Vx

S2
a

tab  Ax
2

Vx

S2
a2

A

This derivation shows in addition, that the stress V x in the formulae for pzx and pzy is the axial
stress, acting in the stiffener.

Vx

V a with V a

V x*  0.3  V *y where V x* and V *y are FE-stresses.

In case of a transverse stiffener, the stress of the second term with V y can be derived
accordingly.

In the two formulae for pzx and pzy are different assumptions.
x Longitudinal stiffeners
o are not supported by intermediate transverse stiffeners.
o act always as secondary members
x Transverse stiffeners
o are classified in two kind of stiffenersa) small transverse stiffener (secondary member), located between two
longitudinalsb) transverse stiffener with higher rigidity than the longitudinal stiffener,
which is supported by intermediate longitudinal stiffeners and partiallyconstrained at the ends (primary member)
The factor cs characterises the support condition at the ends of the transverse
stiffener in line with the categorisation. A secondary (transverse stiffener) is
simply supported, a primary stiffener is partially constrained.
In case a) the stress acting normal to the stiffener is V x* . No intermediate longitudinals have tobe taken into account, so Ax is zero and the term V xl

V x* . In this case is n z 1 .

In case b) the intermediate longitudinal stifferners provide an additional support for thetransverse stiffener and shift the acting normal stress out of the plate plane. It is obvious thatthe normal stress has to be reduced.
ta
2cxV xla§ 2ta cx 2ta cx Ax ·¸abta ¸¹© a

V x ¨¨A ·§t
2cxV x ¨ a  x ¸© a ab ¹§t ·§A ·Both terms ¨ a ¸ and ¨ x ¸ are much more smaller than 1 and represent the reduction factors©a¹© ab ¹for the normal acting stress V x with V x V a .

KC#557
Bilge Shell Plate

Chord length "KC#563baFig. A

Fig. BKC#567

KC#580
Table 4: Values of K, in case d H t 2.5d 0Upper end support
Welded directly
to deck

Welded to stool efficiently
supported by ship structure

1.00

0.83

Table 5: Values of K, in case d H  2.5d 0

Section modulus ofUpper end support
Connected to deck

Connected to stool

Corrugated bulkhead

0.71

0.65

Stool at bottom

1.25

1.13

KC#609-1

RCP on evenly distributed load according to Ch. 6 Sec. 1 [2.7.1] andSec. 2 [2.5.4] Steel coil loading
Load to be distributed over 1 elementary plate panel at per sketch
below.

Uniform distributed load, when distributed to one elementary plate
panel becomes:
P = ( ntier x Wcoil x lstiff/lcoil ) / (lstiff x Sstiff) = ( ntier x Wcoil ) / (lcoil x Sstiff)
Load on one
EPP

Area of
EPP

According to our understanding of Ch.6 Sec.1 Table 3 and Table 4, a
20% gap between steel coils is included in the calculations. The same
gap could be included in the formulation for uniform load giving:P = ( ntier x Wcoil ) / (1.2 x lcoil x Sstiff)KC#609-2

Steel coil loading according to Ch. 6 Sec. 1 [2.7.1] and Sec. 2[2.5.4]
Abstract
In the 3rd JBP October 2005 draft Ch. 6 Sec. 1 [2.7.4] and Sec. 2 [2.5.4] for steel coil loading,
it is proposed to calculate the double bottom as uniformly loaded if steel coils are supported
by a large number of dunnages. This pre assumes that the dunnages are very stiff and able totransfer the load efficiently to the nearest longitudinals. There are no requirements in the rules
as to the scantlings or stiffness of dunnages. If dunnage stiffness are disregarded the load on
stiffeners should be changed to a line load. Comparative calculations enclosed herein show
the requirement in the Rules to be non conservative for this case. Increase of up to 78% isrequired depending on the longitudinal spacing. Even when calculating the full plastic
utilisation of the panel, disregarding longitudinal stresses, the required sectional modulus oflongitudinals was 3-10% higher than the Rule formulation.
The calculations show that significant permanent deflection should be expected for both theplating and the longitudinals of the inner bottom when the design load condition is applied to
the net scantled structure. Significant permanent deflection governed by the membrane
response is therefore anticipated.
Based on this assessment, we are of the opinion that the rule formulation for inner bottom
plating and longitudinals should be changed to a line load formulation. It is our considerationthat the introduction of explicit requirements to the scantling and stiffness of the dunnages isimpractical.

Table of contents
Abstract ...................................................................................................................................... 1
Table of contents ........................................................................................................................ 2
Introduction ................................................................................................................................ 3
Rule calculation.......................................................................................................................... 4
DNV alternative calculation....................................................................................................... 4
Plastic coil calculation................................................................................................................ 5
Calculation procedure outline ................................................................................................ 5
Plastic calculation................................................................................................................... 7
Summary .................................................................................................................................... 8

Introduction
JBP 3rd draft, Ch.6 Sec.2 [2.5.4]:“Where the number of load points per elementary plate panel n2 is greater than 10/or thenumber of dunnages n3 is greater then 5, the inner bottom may be considered as loaded by auniform distributed load. In such a case, the scantling of the inner bottom ordinary stiffeners
is to be obtained according to [3.2.3]”
DNV interpretation of the text is: If the bottom coil is supported by 6 or more dunnages goingtransversally, the load from the coil on the inner bottom can be simplified to a uniform
pressure. See below figure.

The load is then transferred between the longitudinals by the wooden dunnages. This requires
the dunnages to be extremely stiff. It is our opinion that this assumption is wrong and that thepressure load should be changed to a line load on the stiffener. We have performed a small
comparison case below in order to elaborate our understanding of the problem.
The following is pre-assumed. Coil, (or bottom coil), weight is 40t § 400kN. Coil length is,including spacing, lc = 1.2 meters and diameter D =1.5 meters. The allowable stress is
assumed to be OsRY=0.9x235/0.78=271N/mm2, which is maximum allowable stress for AH32
steel if longitudinal stresses are disregarded. Two stiffener spacings are calculated s1=500mm
and s2=850mm. The length of stiffeners between floors is assumed to be ls=2.4m. The
dynamic acceleration av is assumed to be g/2.

W=40t

Rule calculation
The rule calculation assumes that the double bottom is uniformly loaded.

s=500/850mm
ls=2.4m

Pressure from coil is:
P W ( g  av ) /( Dlc ) 40(9.81u1.5) /(1.5 u1.2)

327kN / m 2

Required plate thickness according to Sec. 1[2.7.4](Ca=Cr=1)
P
t req , s1 500 15.8Ca Cr s
8.68mm  t k

V all

t req , s2 850 15.8Ca Cr s

P

V all

14.75mm  t k

Typical tk for inner bottom adjacent to ballast tank is 5.4 mm.
Required section modulus on stiffener is:2
Psl s
wreq , s1 500 10 3
290cm 312V
2
Psl swreq , s2 850 103
492cm 312V

DNV alternative calculation
We assume that the load from the coils are transferred as a line load to the nearest
longitudinal(s). As the coils diameter does not match the stiffener spacing exactly, there will
always be one or more coils within the double bottom that will meet one longitudinal. As thisis the worse case, it should be the dimensioning case for the longitudinals.

F=327kN/m

Line load on the most severe loaded longitudinal is:
ql W ( g  av ) / lc 40(9.81u1.5) / 1.2 491kN / m

Corresponding end moment on stiffener is:
2
ql ls
M
235kNm12
The required section modulus is:
M 160
wreq
u103 869cm3
V 271
The section modulus is independent of the stiffener spacing.

The required section modulus for the DNV calculation is three times the section modulus
required by the Rules when the stiffener spacing is s1=500mm. In order to calculate thelongitudinals according to the Rules, the dunnages have to be extremely stiff in order totransfer the load efficiently between longitudinals.

Plastic coil response calculation
For reference, we have calculated the ultimate capacity of the inner bottom subjected to steel
coil loading (plastic capacity). The calculation procedure used is originally derived forevaluation of ice loads on longitudinally stiffened panels.

Calculation procedure outline
Load model
It is assumed that the diameter of the coils is larger than two primary frame spaces, D>2s.The
steel coil is loaded on a wooden support, which is soft compared to the steel coil. The coil will
deform in to the wood and spread the load over a small distance b of the inner bottom plating,see Figure 1.

b
Figure 1 Steel coil deforming in to the wooden support

As described earlier, the coils will be loaded randomly within the double bottom. The
diameter, D, of the coils do not match the primary longitudinal spacing. Consequently, there
will always be coils meeting a longitudinal and coils at the middle of a plate field. The firstwill be the governing condition for the stiffeners scantlings, whereas the latter will be thegoverning condition for the plate scantlings.
floor
floor
b
longitudinalbslFigure 2 Load model plates and longitudinals

When the number of dunnages is large, the pressure from the steel coils on the wooden
support will converge towards a uniform pressure within the breadth b, see Figure 2.
Longitudinals
We further assume plastic response of the plate and longitudinals.

The pressure within b is:ql W ( g  av )Pb
lc b
The required shear area is defined as:
P u 0.5 u b1l
As ,req 10

Vy3

Where b1/b is the portion of the load transferred in to the longitudinal and (b –b1)/b is the
portion transferred through plate bending in to the adjacent longitudinals. See Figure 3.
lb1

Figure 3 Relationship between b1 and b

b1 is given by:b1 max>k 0b, b / 3@bLongitudinal

½°
10 3 t 2V y
2 ­°
 ( s  b / 2)¾
k 0 1  ® ( s  b / 2) 2 
b °̄
P
°¿
The plastic sectional modulus of longitudinal is given by:
Pb l 2Dz req 103 1 Plastc
8V y

Where Dplastic is the relation between the plastic capacity of the longitudinal at the boundary to
the plastic capacity at mid span.
1
D Plastic2
2  k wl ª 1  D shear  1º«¬»¼

D shear

As ,req

As , act

without being larger than 1. As,req is the required shear area of longitudinal,

whereas As,act is the actual fitted shear area. Ds=1 will give the maximum required sectional
modulus for the longitudinal.
1
where Afl,act is the fitted flange area of the stiffener.
k wl
A fl ,act1 2
As ,act
PlatesBased on plastic response of the plate the required thickness is:

t req

b §b·
15.8s 2  ¨ ¸
s ©s¹

2

P

Vy

Plastic calculation
The plastic calculation have been done for the case with longitudinal spacing, s=850mm.
If we assume b=0.15 m, the required scantling for the above condition will be:
W ( g  av ) 40(9.81u 1.5)
3270kN / m 2
ql0.15 u 1.2
blc
The fraction of the pressure carried by the stiffener:½°
10 3 t 2V y
2 ­°2k 0, s2 850 1  ® ( s  b / 2)  ( s  b / 2)¾ 0.8326
b °̄
P
°¿
b1 max>k 0b, b / 3@ max>0.1249,0.05@ 0.1249m
That is, the fraction of the load transferred to the adjacent stiffener is 16.7%.
The required shear area:
P u 0.5 u b1l
3270 u 0.5 u 0.1249 x 2.4
As ,req 10
10
Vy
301
3
3

28.22cm 3

Required section modulus assuming Dshear =1.
k wl
1 2

1
A fl ,act

D Plastic

1
(
90
13.1)
u
1 2

As ,act
10.458119.91
10.64862
2  k wl ª 1  D shear  1º 2  0.4581 1  1  1«¬»¼
2
Pb l D3270 u 0.1249 u 2.4 2 u 0.6486
z req 103 1 Plastc 103
634cm 38V y
8 u 301
It should be noted that this is the required net plastic sectional modulus for the longitudinal.
The elastic sectional modulus is typically §15-20% smaller. Hence, the equivalent net elastic
section modulus is about 507-540cm3.
2>@

Plates

t req

b §b·
15.8s 2  ¨ ¸
s ©s¹

2

P

Vy

0.15 § 0.15 ·15.8 u 0.85 2
¨¸
0.85 © 0.85 ¹

2

3270
301

25.11mm

It should be noted that b=0.15 is assumed to be slightly conservative at the middle of the plate
span. If b=0.3m is used the requirement would decrease to 23.86mm.
It should be noted that the global, axial, stresses are disregarded in above calculation. The
design condition is plastic, with allowable stress equal to yield. Fatigue is not evaluated.
If actual section modulus is smaller than the above calculated, the longitudinal will deform
plastically. The shortage will be carried by the plate to the nearest longitudinals by membrane
response. (i.e. significant permanent deformations)

Summary
In the 3rd JBP draft October 2005 Ch. 6 Sec. 1 [2.7.4] and Sec. 2 [2.5.4] for steel coil loading,
it is proposed to calculate the double bottom as uniformly loaded if steel coils are supported
by a large number of dunnages. This is pre assuming that the dunnages are very stiff and able
to transfer the load efficiently to the nearest longitudinals.
Three calculations procedures are calculated above. All with the following coil particulars:
W=40 tonnes, length 1.2 meters, diameter 1.5 meters and number of dunnages per coil >6.
(s=850mm)
DunnageWreq,net treq,net
assumption [cm3] [mm]Rule calculation
Very stiff
490
14.75
DNV alternative
No stiffness 870(not calc)
Plastic capacity
No stiffness 540*
25.11**
disregarding
longitudinal stress*Estimated elastic sectional modulus** based on an assumed load breadth b=0.15 meters, see above calculation for details.

There is no requirement in the Rules as to the dimensions of dunnages. It is therefore
unreasonable to assume a uniform pressure according to the Rule formulation. If dunnages are
assumed to be without stiffness, the load should be applied as a line load on the longitudinals.
In our calculation this corresponds to an increase of longitudinal section modulus of up to
78%, depending on the spacing of the longitudinals.
For reference, a plastic calculation was conducted for the latter case. The calculation wasmade without global stresses, allowing full plastic utilization of the longitudinals, Vy=300.
The calculation showed a required sectional modulus, compared to the Rule formulation, of+3-10% depending on the wplastic/welastic ratio of the longitudinals.
The calculations show that significant permanent deflection should be expected for both theplating and the longitudinals of the inner bottom when the design load condition is applied to
the net scantled structure. Significant permanent deflection governed by the membrane
response is therefore anticipated.
Based on this assessment, we are of the opinion that the rule formulation for inner bottom
plating and longitudinals should be changed to a line load formulation. It is our considerationthat the introduction of explicit requirements to the scantling and stiffness of the dunnages isimpractical.

KC#623

KC#624
CSR-BC Safety factors for stiffener buckling

In the third draft of the CSR_BC, the SOLAS safety factor S=1.15 for special members has
been added. Only the stiffeners of transverse bulkheads is missing in the list.

BV gives the following explanations by E-mail:For the following, it is based on the evolution within MSC discussions.
Some extracts are listed to illustrate the process.
Iacs submission to MSC 80: Extract
Quote
XII/6.5.3 - the structure of cargo areas shall be such that single failure of one
stiffening structural member will not lead to immediate consequential failure ofother structural items potentially leading to the collapse of the entire stiffened
panel.
a. As written this regulation could be understood to apply to stiffened plate panels of
the bottom, side shell, deck, inner bottom, longitudinal bulkheads, upper wing tanks
and/or lower wing tanks which are bounded by primary structural elements such astransverse and longitudinal bulkheads, transverse webs, floors or girders (or evenmore broadly to also include each stiffened plate panel of the transverse webs, floors
and girders themselves). IACS considers that this requirement does not apply tocorrugated transverse bulkheads, which have already been reinforced according
to IACS Unified Requirement S18.
UnquoteThe IACS proposal of interpretation, document MSC 80/18/2, was not supported
during the MSC 80, and the task of proposing an interpretation was allocated to anintersessional working group of the MSC meeting on 12/13 September 2005.
A new IACS proposal has been submitted, document ISR ISWG 1/3/2. The
submission deals with SOLAS regulation XII/6.5.3 as follows:
Quote
XII/6.5.3 - the structure of cargo areas shall be such that single failure of
one stiffening structural member will not lead to immediate
consequential failure of other structural items potentially leading to thecollapse of the entire stiffened panel.
5.3 IACS understands that the objective of this regulation is to avoid
immediate collapse of the stiffened panel after a single, localizedmechanical damage (such as local permanent deformation, cracking or weld
failure that might result from accidental damage within the cargo hold from cargo
operations) of one stiffener of the structure bounding the cargo holds (such as
inner bottom, lower hopper tanks, lower half of internal longitudinal bulkhead of
double side skin bulk carriers or side shell of single hull bulk carriers and lower
stool of transverse corrugated bulkheads). Then, for the scope of application
described in 3. and 4. above, two cases are to be considered:
UnquoteExtract of JBP interpretation sent by JF Segretain on 29/12/2005
Quote
IACS JOINT BULKER PROJECT – Technical Backgrounds
A3(CCS/KR/NK) – UNITAS (BV/GL/RINA) - RS
Structural redundancy requirements of SOLAS regulation XII/6.5.1and 6.5.3 in CSR for
Bulk Carriers
1 Introduction
During the 24th assembly, MSC Committee of IMO adopted the unified interpretation of
SOLAS regulations XII/6.5.1 and 6.5.3 provided here:
Regulation XII/6.5.1 . Protection of cargo holds from loading/discharge equipment
1 The protection of the structure of the cargo holds should be achieved by structural design
features such as mandatory application of classification society grab notation.
2 The protection of hatchways and coamings from grab wire damage may be achieved byfitting protection bars (e.g. half-round bar) on the hatch side girder (e.g. upper portion of top
side tank plates), hatch-end beams and the upper portion of hatch coamings.
Regulation XII/6.5.3 . Failure of cargo hold structural members and panels
1 Stiffening structural member means a stiffener attached to a structural plating panel.
2 For the purpose of this interpretation, cargo area includes hatchway coamings, topsidetanks, side shells, longitudinal bulkheads of double-side skin construction, bilge hopper tanks
and double bottom, but excludes hatchway covers.
3 Structural members of a cargo hold are the hatchway coamings, transverse bulkheads, panel
plates of the top-side tanks and bilge hopper tanks facing the cargo hold, inner bottom, side
shell of single-side skin construction or longitudinal bulkhead of double-side skinconstruction.
UnquoteConclusions
So the factor s=1.15 applied to ordinary stiffeners which could be fitted on stools oftransverse Bhds but not in my mind to the corrugation itself.

KC#631

Example of an arrangement of steel coil in aftermost cargo hold, showing
the steel coils do not uniformly contact the hopper sloping plate.

KC#681-

Quote for immediate reference

1. CSR BC Rule, Ch.3 Sec.6/8.4.1

2. CSR BC Rule, Ch.6 Sec.2/3.3.3

3. IACS UR S12 (Rev 4)-

UnquoteComments:
1. It is considered CSR BC Rule, Ch.3, Sec.6/8.4.1 is equivalent to “The thickness ofthe frame lower brackets is not to be less than the greater of tw ……, where tw is thefitted thickness of the side frame web. …….” in IACS UR S12.
2. It is also considered “the net thickness of the side frame web plus 1.5mm” in CSR
BC Rule, Ch.6, Sec.2/3.3.3 is equivalent to “tw,min+2 mm” in IACS UR S12.
(Underlined in red)
3. As such, CSR BC Rule, Ch.6, Sec.2/3.3.3 is recommended to be changed to “……
the net minimum thickness defined in Ch.6 Sec.2/2.2.2 of the side frame web plus
1.5mm.”

KC#697
CH6, Sec2, 1.4.2
The formulae in this paragraph derive the pressure p for two cases:(a) The stiffener is loaded with pressure over the whole height(b) The stiffener is loaded with pressure only in a part of its height
Both cases are valid under the assumption, that the slope of the pressure curve is constant.
In case of structure, loaded from both sides the following additional pressure distributions are
possible.

(c)

(d)

(e)

(f)

How to calculate the pressure p, used in CH6, Sec2, 3.2.3 for examples (c) to (f)?

KC#708

Applicability of C6S2[4.1.3]
Case 1

Applicable

Case 2

Applicable

Case 3

Applicable

Case 4

Not Applicable

Case 5

Not Applicable

Case 6

Not ApplicableKC#717

Notes:
Tensile stress need to be considered as the actual values

Notes:The buckling utilization factor is taken as zero, where the normal stress is tensile.

KC#768
Rule Change Proposal
for Net Section Modulus of Stiffener Wst
in Paragraph 4.2.2 of Chapter 6, Section 3 of CSR BC
LR Yokohama Design Support Office
4 June 2008
1. In Paragraph 4.2.2 of Chapter 6, Section 3 of the CSR BC, it is noted that the net
section modulus Wst of a stiffener is calculated at its flange (or face plate) or theattached plate to it, where compressive bending stress may appear, to assess its
buckling capability, in both cases of availability of lateral pressure and no pressure onit.
2. However, it is not clear there how the net section modulus of a stiffener snipped atboth ends is calculated.
3. When the stiffener is under compression, compressive stress is induced at theattached plate by a moment due to eccentricity of a compression force off the neutral
axis of the stiffener. Consequently the net section modulus is to be calculated at theattached plate for this purpose.

M
P

M
e

P

neutral axis

4. A description in the definition of imperfection wo seems to support the above, i.e.,“For stiffeners sniped at both ends wo must not be taken less than the distance fromthe midpoint of the attached plating to the neutral axis of the stiffener”.
5. It is proposed that the net section modulus of a stiffener snipped at both ends is to
be clearly defined in the CSR in line with the above.

KC#852
Application of Ch.6 Sec. 2 , [4.1.1] for steel coil loads

In according to the current text of Ch. 6, Sec.2 [4.1.1], pressure, in kN/m2, acting on theordinary stiffener is considered.
It is obviously that the loads due to steel coil is also acting on the ordinary stiffener.
Therefore, the requirement of Ch.6 Sec.2, [4.1.1] is applicable in case of steel coil loading.
In this case, the load due to steel coil specified in Ch.6 Sec 2 [2.2.3] should be considered,instead of the pressure.
In addition, as the load due to steel coil is the concentrated load, “s” and “l” in the formula of
Ch 6 Sec 2, [4.1.1] should not use.
For your reference, the following formula should be used in case of steel coil loading.
When steel coils are loaded, the net section area at the web stiffener mid-height is to be notless than the value obtained, in cm2, from the following formula:
A 0.1k1 Fcoil

where:
Fcoil : Steel coil load, in kN, acting on the elementary panel in which the ordinary stiffener is
attached, to be taken as:>g cos(C ZPI ) cos(C ZRT )  a Z @F for double bottom structures
Fcoil
1000
Fcoil

a hopper F 'for bilge hopper structures

1000

C ZP , C ZR : Load combination factors defined in Ch.4 Sec.4 2.2

I : Single pitch amplitude, in deg, defined in Ch.4 Sec.2 2.2
T : Single roll amplitude, in deg, defined in Ch.4 Sec.2 2.1
2a Z : Acceleration, in m/s , in vertical direction defined in Ch.4 Sec.2 3.2
2

a hopper : Acceleration, in m/s , defined in Ch.6 Sec.1 2.7

F : Force due to steel coil, in kg, defined in Ch.6 Sec.1 2.7
F ' : Force due to steel coil, in kg, defined in Ch.6 Sec.1 2.7

The above formulae have been included in RCN 1 adopted by the Council in January 2009.
We will propose the RCP in order to clarify the application.

KC#866

Large collar plate

Radius of scallop

Width of slot

KC#883

Side shell panels in
way of brackets
above/below side
framesKC#914
Rule Change Proposal
Requirement to single side frame section modulus due to ballast pressure.
Reference is made to requirements for frames of single side bulk carrier subject to ballast pressure. Ch.
6 Sec. 2 [3.3.1]. IACS KC 457/215/356
Summary of DNV understanding, Ballast hold assumed.
Section modulus at mid span
1. [3.3.1] (All pressures) with length as defined in Ch. 3 Sec. 6 Figure 16
2. [3.2.3] (Ballast pressure only) with length as defined in sketch 4 of Figure 2 in Ch.
3 Sec. 6.
Sectional modulus at ends ref. [3.3.3]/[3.3.4]
1. 2xW[3.3.1] (All pressures) with length as defined in Ch. 3 Sec. 6 Figure 16
2. 2xW[3.2.3] (Ballast pressure only) with length as defined in Ch. 3 Sec. 6 Figure 2
Requirements for bracket length are given in Ch. 3 Sec. 6 Figure 20 (same as UR S12).

At the connection of top wing tank, the bracket height is 0.5d. The effective length iscalculated according to Ch. 3 Sec. 6 Figure 2.

It should be noted, that for the standard UR S12 bracket arrangement, the effective lengths are
identical to the length between topwing and hopper knuckle (leff=l). That is, no reduction byeffective span as stipulated in KC #215.
In KC#356 it is shown that for leff=l the sectional modulus for [3.2.3]= 2x [3.3.1]. In practicethis correspond to an m-factor of mmid=10 and mend=5, which is very conservative. Note alsothat m=10 is normally the end moment of a vertical stiffener.

In order to accommodate the equation [3.2.3] we see designs with long and slender brackets
for side frame as shown in the figure below.
d/2l

The brackets give large reduction to effective length. DNV is concerned about thisdevelopment as the length may be reduced to an extent so that the mid span sectional modulus
is below originally required by DNV Rules.
DNV is of the opinion that the requirement of [3.2.3] should be substituted by equations
giving a more physically representation of the moment distribution of the frame, removing thepossibility to manipulate the requirement by bracket design.
Please note following
1. The effective span evaluation according to Ch.3Sec.6Figure2 is not valid for side
frames.
The span of single side frames should be according to Ch.3Sec.6Figure2. In Fig. 2 typicalend connections for continuous stiffeners are shown. End connection cases where thestiffener is terminated at the end support have not been shown. Also, no precaution istaken. E.g. stating that the stipulations of Figure 2 only apply provided the end bracket iseffectively supported. Hence, Figure 2 should not be used for single side frames.
2. Bending moment distribution of the side frames is governed by elastic response of the
supporting structure in top wing and hopper tank.
The side frames in bulk carriers is a typical case where the effectiveness of the end support
could be questioned. The end support for side frames in Ch.6 Sec.2 [3.4.1] is formulated
as a requirement to the section modulus of the longitudinal stiffeners supporting the upperand lower connecting brackets of the side frame. The requirement ensures that the end
supports have bending moment capacities (plastic) that are related to the sea pressure loadon the side frame. The actual bending moment by the connecting brackets on a side frame
subject to the sea or the ballast pressure load will be determined by the elastic response of
the structure.
It may be noted that the required bending moment capacity of the upper end is only half ofthat required for the lower end support. Current formulation for section modulus isassuming same bending moment in both ends (m=5).

3. Increased extent of main frame bracket gives limited effect of the bending moment
distribution of the main frame.
According to the present CSR, an increase of frame bracket length allow for reduction of
span length according to Ch.3 Sec. 6 Figure 2 (sketch 4), and thus the section modulus of
the frame. Bearing in mind item 1 and 2 above, it is expected that increase of bracket
length have a marginal effect on the bending moment of the frame.
We therefore ask for background documentation for the requirement of the last sentence of
3.3.1 of Ch.6 Sec.2.
If documentation is not available, it is suggested that the requirement formulation is revised
such that the same span length is applied for the ballast load as for the sea pressure load. The
revised formulation should reflect that the bending moment distribution in the frame isdependent on the elastic response of the supports, which is the internal structure in hopper andtopwing tank. As discussed above, the elastic stiffness of the bottom support is larger than the
top support. Additionally the pressure distribution on the frame should be taken in to account.
Possible rule formulation
Following rule formula is provided as a basis for discussion. The formula is based on DNV
Pt.5 Ch.2 Sec.8 and valid for ballast pressure only:W

l 2 s ( Ps  Pw ) 3
100.9mR YmUpperEnd

12, mMidSpan

18, mLowerEnd

9Span length l is as defined in Ch. 3 Sec. 6 Figure 19, same as UR S12.
Motivation for change:
1. The proposed equation will give a more physical representation of the bending moment
distribution in the frame.
2. For bracket designs as per Ch. 3 Sec. 6 Figure 20, the sectional modulus requirements will
be more realistic.
mUpperEnd change from 5 => 12
mMidSpan change from 10 => 18
mLowerEnd change from 5 => 9
3. Section modulus can not be manipulated by large slender brackets in order to bring therequirement of [3.2.3] back to a realistic value.

1.90 mComparative calculation

CSR Cape Size Bulk BC-A
230 kN/m2
920 mm315 N/mm2

CSR[3.2.3] CSR[3.2.3],
BKT 1.9m

URS12Bkt

CSRProposal

5973
2987

8779
4390

12642
6321

5267
3512

cm3
cm3

5973

8779

12642

7023

cm3

1.90 mUpper(2xMid)MidspanLower(2xMid)CSR[3.3.1]

9.00 mSectional modulus calculation:

7.50 mPBallast,Mid Span
Fr. Sp.
SteelMain frame sectional modulus requirement
14000

12000
CSR[3.3.1]
CSR[3.2.3],1.9m Bkt

10000

CSR[3.2.3],URS12Bkt
CSRProposal

cm3

8000

6000

4000

2000

0
Upper (2xMid)

MidspanLower (2xMid)

KC#1055

Attachment to GL-KC-Request referring to Ch6, Sec1, 2.4.1

Pressure distribution on bottom plating

Scantling pressure load for adjacent plating
Applicationadj. 2m
actual keel strake

Minimum keel strake widthCLbactual keel strake
Misinterpetrationadj. 2m
Scantling pressure load for adjacent plating