IACS Common Structural Rules Knowledge Centre

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

205

206

207

208

209

210

Ref.

3/1.2.3.11

3/3.1.2.1

3/6.2.3.1

3/6.2.3.1

3/6.6.1.6

3/6.6.4.2

Type

Question

Question

Question

Question

Topic

Date
completed

Question/CI

thickness

In case of bulk carriers, thicker plates greater than 20 mm are normally used
for main structural members. Since this requirement is vague, we would like to
2006/11/30 ask you to clearly explain your intention of the regulation 2.3.11 and to makeclear the application of this requirement or criteria. If there is no criteria, it isbetter to delete the requirement to avoid confusion in design approval stage.

Corrosion
addition

According to our understanding on CSR, rules relating to corrosion addition
have been harmonized with JTP.
However, there is a difference in definition of tank top between JTP and JBP.
Note (3) in Table 1 should be revised as follows:"Note (3) Only applicable to ballast tanks with weather deck as the tank top"from CSR for Tankers

2006/11/8

Answer
The reason of this requirement is the same as the one requiring D/DH for the
SPECIAL elements i.e. Class III) with notes (4), (5) and (6), which are highly
stressed elements. In this requirement, the notion of thickness greater than 20
mm is added to the notion of highly stressed element. This corresponds in fact
D/DH for Class III elements according to Table 3.However, since theapplication of this requirement is already covered by Table 1 and otherrequirements such as 2.3.2, we propose that this requirement should bedeleted according to your suggestion.

Note (3) to be kept as it is. Example is Hopper Side Tk. not connected to
TSWB Tk. Air-/Water-Mixture will be below top of tank.
"This question and answer are superseded by KC ID 638. Please refer to
KC ID 638."

hatch
coaming

As for hatch coamings, ClassNK approves hatch coamings having lower steel
grade than that of upper deck plating, in case of the hatch coaming length
2006/11/30
being less than 0.15L. We therefore propose to delete hatch coamings fromthe last sentence.

First, it is to be noticed that this requirement is not dealing with steel grade, butwith yield strength of the steel. Secondly, the stress in shorter hatch coamings(length much more less than 0,15L) is generally equivalent to the one in the
deck. It becomes negligible only for very short hatch coaming. Some criteria
could be developed, including parameters such as length and height of hatchcoaming and their position along the ship. It seems quite complicated to solve
this easy problem. Finally we have to keep in mind a stress check is to be
carried out for the hatch coaming. Consequently, we prefer to keep the text as
it is, or we may suggest to open a door by adding the word "generally" between"The same requirement" and "is applicable".

high strength
steel

The last sentence of 2.3.1 is excess and differs from the present application
accepted by many classification societies. Higher strength steels are normallyapplied taking account of not only hull girder bending stresses but also local
stresses. For instance, higher strength steel is used to double bottom girders
taking into account local shearing stresses caused by cargo and external sea
loads acting on double bottom.And some sniped longitudinal stiffeners not
2006/11/29
contributing hull girder longitudinal strength, which are mild steel, are weldedon the girders to prevent panel buckling. Such design has been alreadyapproved by many classification societies. We consider that the steel grade ofstiffeners not contributing hull girder longitudinal strength can be selected on acase by case basis. We would like to ask you to revise the rule taking into
account the above.

The last sentence in Ch 3, Sec 6, [2.3.1] is not a matter of steel grade, butconcerns the yield strength of the steel. The matter of steel grade is relevant to
Ch 3, Sec 1. Having said that, it is understood that the original question is notabout steel grade. Ch 3, Sec 6, [2.3.1] could be considered as therequirements in general. If the stress level due to hull girder bending, inlongitudinal member not contributing to hull girder longitudinal strength, shouldbe verified as to satisfy the requirement in Ch 5, Sec 1, [3.1.1], application of
the requirements in Ch 3, Sec 6, [2.3.1] might be mitigated. As a matter of
opening the door, the word "generally" should be added between "The samerequirement" and "is applicable...".

Question

scantling
determination

Question

GRAB
notation

Attachment

2006/11/1

As shown in the caption, main intention of this requirement is continuity ofstrength, not scantling.
In the scantling determination of sloped bulkhead plating, yielding, buckling,grab handling and fatigue strength are taken into account. Continuity ofstrength can be realized by the consideration.
Therefore we would like to ask you to delete the requirement.

In applying the last sentence of 6.1.6, where the scantling of lower strake of thesloped bulkhead of hopper tanks and inner bottom plate adjacent thereto aredetermined by the requirements on FEA and fatigue strength assessment,such structures are regarded as the satisfaction of the requirement on
continuity of strength.

2006/11/1

At least, please exclude the required material properties and net thickness ofstool side plating by GRAB from this requirement.
It is not necessary to apply the required material properties and net thicknessof stool side plating by GRAB to the supporting floors.

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.

Page 1 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

2006/11/1

2006/11/22

Corrosion addition determinationFor ships equal to and larger than 150m in
length, corrosion addition for lower stool of 5.2m is very large compared withthat for sloped plating of hopper tank of 3.7m. Corrosion addition for lower
stool should be the same as that for sloped plating of hopper tank.

The corrosion additions are set according to the results estimated byprobabilistic carrion model which are calibrated by huge amount of thickness
measurement data. Therefore, the value specified in Table 1 of Chapter 3 isconsidered appropriate.

Framing system; For ships larger than 120m in length, longitudinal framing
system is required for bottom, double bottom and sloped bulkheads of hopper
2006/11/22 tanks in cargo hold. For fore and aft parts of cargo hold, however, it may bedifficult to apply this system because of abrupt change of hull form there. So
please add 'in general' to allow transverse system for these parts.

The word “in general” has been deleted from the text as far as practicable inorder to eliminate the vague expression. Furthermore, from structuralcontinuity point of view, the same framing system is desirable to adopt inwhole length of cargo hold region. However, as you pointed out, we canunderstand that it may be difficult to apply the longitudinal framing system tofore part and aft parts of cargo hold because of abrupt change of hullform.Where it is difficult for the longitudinal system to apply to fore and aftparts of cargo hold region due to its hull form, the Society may accept on acase by case basis the changing the framing system. for such parts subject toprovide an appropriate bracket or other arrangements to provide structuralcontinuity in way of changes in the framing system.

3/6.9.6.3

Question243

3/3.1.2

QuestionCorrosion
additiondeterminatio
n245

3/6.9.5.2

Answer

The extent of insert plate is larger than that of present designs. Since the
The following sentence should be added at the end of requirement 9.6.3: "Forstress concentration occurs in way of corner radius, we consider that theships having length L of 150m and above, the extent of insert plate may berequirement should be reconsidered taking account of your experience. Please
determined by the results of a direct strength assessment, including buckling
permit us to determine the extent of insert plate taking into account FEA
check and of a fatigue assessment of hatch corners."
results.

211

3/6.6.1.2

Question/CI

Topic

extent ofinsert plate

244

Date
completedTypelongi framing
Question
systemEditiorial

hatch end
beams

Attachment

SOLAS XII Regulation 6.5.2 says, “effective continuity between the side shellstructure and the rest of the hull structure shall be assured,” Although theapplication of this regulation is limited to bulk carriers of 150m in length andupwards carrying solid bulk cargoes having density of 1,000 kg/m3 and above,it is considered that the intention of this regulation is applicable to all ships.
From the structural continuity point of view, the second paragraph of Ch 3 Sec
6 [9.2.4] (topside tank structure) of CSR for Bulk Carriers says “Where adouble side primary supporting member is fitted outside of plane of the topsidetank web frame, a large bracket is to be fitted in line with.”
Hatch supporting structureHatch end beams are required to be aligned with
In addition to the side structure, to alter the large bracket in order to ensure thetransverse web frames in topside tanks. Partial transverse web or large
2006/11/30
bracket that is sufficient to transfer load should be considered as an alternative structural continuity between the hatch end beams and topside tank web frame
to transverse web. They are normal structural arrangement of existing vessels. seems to overdo.

However, in oder to clarify whether the partial transverse web or large bracket
provided in the top side tank in line with hatch end beam is acceptable insteadof providing the ordinary transverse web, for clarification, we will consider arule correction with addition of the following text:"Alternatively, the appropriate supporting structures shall be provided in top
side tanks in line with the hatch end beam."

246

3/6.9.5.3

Editiorial

hatch
supporting
structure

2006/11/28

Hatch supporting structureThe face plate of hatch coamings and longitudinaldeck girders are required to be effectively connected. On the other hand, theface plate of hatch end beam is normally tapered at end. Please explain
concrete requirements of 9.5.3.

In order to clarify this requirement, we will consider a rule correction as follows:
At hatchway corners, the face plate of hatch deck girders or their extension
parts and the face plates of hatch end beams on both ends are to beeffectively connected so as to maintain the continuity in strength.

Page 2 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

247

Ref.

3/6.10.4.1

Type

Question

Topic

Date
completed

UR S18Lower and upper stools of corrugated bulkheadsLower and upper stools are
required for corrugated watertight bulkheads of ships equal to and larger than
150m in length. According to UR s18, stools are not required for ships less
2006/11/10 than 190m in length. In view of the fact that many existing ships having
corrugated watertight bulkheads without stools less than 190m in length havebeen operated with successful results, we request this requirement be
modified so as to be the same as UR S18.

Question/CI

Answer

The issue is under consideration by IACS.

273

3/6.10.4.1

Question

corrugated
BHD

Lower stool with bottom width not less than 2.5 times mean depth ofcorrugation is required for L>=150m bulkers instead of L>=190m as defined in
IACS UR S18.We think this contradiction to be corrected as editorial error in
the corrigendum. If it is difficult to add new item in the corrigendum, IACS
should take it in the next earliest chance. As you know, most of Handy class
The corrected text in the next Corrigenda should be: "For ships of 190 m ofbulkers and also significant number of Handy max. bulkers with length between
length and above, the transverse vertically corrugated watertight bulkheads are
150m < L 190m have corrugated bulkheads without lower stool and/or withto be fitted with a lower stool, and generally with an upper stool is fittedbelow
2006/11/23
rectangular lower stool which bottom width is same as corrugation depth. If thethe deck.For ships less than 190 m in length, corrugations may extend fromdefined lower stools are installed for those vessels, necessary hold clear length
inner bottom to deck."about 27m for these class bulkers to load 2 rows of 40 feet length product suchas pipes, etc. can not obtained. The economical loss to the shipping industry
by the lower stool requirement is seemed tremendously big. Huge number ofsafely operating bulkers without required lower stools prove the safeness andpropriety of this proposal.

274

3/6.10.4.8

Question

Upper stool

2006/11/22

Question

Corrugated
BHD

Lower and upper stools are required for corrugated watertight bulkheads ofships equal to and larger than 150m in length. According to UR S18, stools are The corrected text in the next Corrigenda should be: "For ships of 190 m of
not required for ships less that 190m in length. Since there are many existing length and above, the transverse vertically corrugated watertight bulkheads are
2006/11/23 ships having corrugated watertight bulkheads without stools less thabn 190m to be fitted with a lower stool, and generally with an upper stool is fittedbelow
the deck.For ships less than 190 m in length, corrugations may extend fromin length and they have successful experiences, please amend as shown
inner bottom to deck."
below:"In ships less than 190m in length, corrugations may extend from theinner botton to the deck."

CI

Application of
CSR vs IMO
PSCS(SOLAS II-1/3-2)

2006/12/7

Interpreation: This is the date of adoption by IMO MSC 82(Maritime Safety
Committee 82nd session) of the resolution amending the SOLAS regulation IIFor ships contracted for construction on or after the date of IMO adoption of
1/3-2.
the amended SOLAS regulation II-1/3-2, by which an IMO “Performancestandard for protective coatings for ballast tanks and void spaces” will be made (Note:(1)The date of adoption is 8 December 2006;
mandatory, the coatings of internal spaces subject to the amended SOLAS(2)IMO PSPC = IMO Resolution MSC.215(82);regulation are to satisfy the requirements of the IMO performance standard.
(3) SOLAS II-1, Part A-1, Reg.3-2 = IMO Resolution MSC.216(82))

2007/1/4

The text reads: "Unless otherwise specified, the height of double bottom is not
to be less than B/20 or 2m whichever is the lesser." Does this require that theYes, this requirement is mandatory. The double bottom height in way of cargo
double bottom height in way of cargo holds is not to be less than B/20 or 2mholds is not to be less than B/20 or 2m whichever is the lesser in any case.
whichever is the lesser IN ANY CASE? For instance, even if the strength of
double bottom structures is verified by FEA, is this requirement to be
maintained?

275

316

322

3/6.10.4.1

3/5.1.2.2

3/6.6.1.3

Question

FEA

We think that "The stool top" is correct(This comment is not for your summary
but for original rule).

Attachment

The right wording should be “stool top of non-rectangular stools”. Thisrequirement comes from UR S18 (18.4.1.(b)).

Page 3 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

328

329

330

Ref.

3/6.5.2.1

Ch 3/ 3

3/6.6.4.2

Type

Question

Question

Question

Topicbrackets

cargo holdUR S18Datecompleted

Question/CI

Answer

2007/3/23

The net thickness of web stiffeners and brackets are not to be less than theminimum net thickness of primary members on which they are fitted.
The situation is the following one: for capesize with usual length of 275m, tmin
net is 10mm. Thus tgross is ranging from 13 to 14mm due to tc of about 3 to
4mm.
For primary members of wider height such as Top side frames and hoppertank frames, web stiffening are made of angles instead of flat bars. Usual
angles or T shape sections have web thickness not exceeding 12mm and thecurrent requirement can't be complied with.
Additionally, there are two requirements which are applicable at C6.S2. 4.1.1
and 4.1.2.
Our request:
Alter the formula in C3.S6 5.2.1 to limit the tgross thickness to 12mm or
restreint its field of application to only flat bars or disregard C3S6 5.2.1 should
C6.S2. 4.1.1 and/ or 4.1.2. been satisfied.?

We agree with you that the requirement asking that "the net thickness of web
stiffeners and brackets are not to be less than the minimum net thickness ofprimary members on which they are fitted" seems quite severe.
Our interpretation is that "the net thickness of web stiffeners and brackets are
not to be less than the minimum net thickness defined in Ch 6, Sec 2, [2.2.1]",
i.e. the minimum thickness of ordinary stiffeners (3 + 0.015 L2).
We will consider the Rule Change according to our interpretation

2007/1/12

Corrosion deduction on cross deck beams between hatches:
As per corrosion deduction table – Dry bulk cargo hold area with othermembers in upper part - the corrosion margin is 1.8mm on each side, i.e. 4.5mm in total. Such corrosion margin for deck beams seems too severe.
Is use of this corrosion margin mandatory or may an alternative be used?

CSR doesn't allow to use an alternative for corrosion addition table. The
corrosion additions are to be considered as being mandatory.

2007/1/12

The net thickness and material properties of the supporting floors and pipetunnel beams are to be not less than those required for the bulkhead plating or,when a stool is fitted, of the stool side plating.
In general CSR doesn't allow alternative analysis. Alternative analysis such as
This requirement is similar to that of UR18 in case where there is no lower
direct calculation could be allowed in some cases for ships greater than 150 mstool. CSR extends it to the case where a lower stool is arranged. Thisin length. However, it is a general question for the totality of CSR (oil or bulk)
extension could lead to up to +4mm for floors underneath deep tank stools on
and it should be discussed as a general matter.
capesize bulkers whereas all assessments show that it is not necessary.
Is this requirement possible to excuse when FEM calculation is satisfied? Itshould be cancelled, at least for L>150m for which FE is mandatory.

Attachment

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IACS Common Structural Rules Knowledge Centre

KCID
No.

333
attc

337

362

363

Ref.

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

Type

Question3/6.10.4.7&
Question11/2.2.4.3

3/4.2.4.1

3/4.2.4.3

Question

Question

Topic

Date
completedWeb
Stiffener(1) Primary supporting member are defined as: members of the beam, girderof stringer type which ensure the overall structural integrity of the hull envelope
and tank boundaries, e.g double bottom floors and girders, transverse side
Web stiffeners of primary supporting members:
structures, web frames/diaphragms in hopper side tanks, topside tanks, lower(1) Because there is no definition for “primary supporting member”, themeaning of “web stiffener of primary supporting member” itself is unidentified. 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
supporting members.
the both requirements for primary supporting members of Chapter6/Section4(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.

S18

hull girder

cargo hold

Question/CI

Answer

2007/2/22

For the weld of corrugations and stool side plating to the stool top plate, only
full penetration is accepted in the requirement of Ch 3, Sec 6, 10.4.7. On theother hand, not only full penetration but deep penetration is accepted in therequirement of Ch 11, Sec 2, 2.4.3. It is considered that this requirement is
We will consider the editorial correction according to UR S18.
based on IACS UR 18.4.1(a), as follows:
Also Included in Corrigenda 5
The stool side plating is to be connected to the stool top plate and the inner
bottom plating by either full penetration or deep penetration welds. Therefore,
the requirement of Ch 3, Sec 6, 10.4.7 should be changed to be consistent
with Ch 13, Sec 2, 2.4.3 and IACS UR. Please confirm.

2007/3/20“Longitudinal strength of hull girder in cargo hold flooded condition is to beassessed in accordance with Ch 5 Sec 2.” Reference to Sec 1 should also begiven for longitudinal strength in hold flooding, which is however limited to BC- Yes, your understanding is correct.
A and BC-B. Sec.2 is about ultimate strength of hull girder for ships with length
equal to 150 m in length L and above, i.e., including BC-C. Please confirm.

2007/2/22“Bulkhead structure in cargo hold flooded condition is to be assessed inaccordance with Ch 6 Sec 4.” Sec 4 does not give any requirement forbulkhead structure in flooding scenario. Is this a typo error of Sec 1 and Sec
2?

Attachment

Y

Yes, it is typo and the correct wordings are “Sec 1 and Sec 2” instead of“Sec.4”.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

388

398
attc

400

403

Ref.

3/5.1.2.2

3/6.2.3.1

3/5.1

3/6.10.4.2

Type

Question

Question

Topic

PSPC

Structural
DesignCI

Ballast HoldCI

Bending
RadiusDatecompleted

Question/CI

Answer

2007/2/5

On 8 December 2006, IMO adopted amendments to SOLAS by resolution
MSC. 216(82) which mandate compliance with the new IMO "PerformanceStandard for Protective Coatings for dedicated seawater ballast tanks in all
types of ships and double-side skin spaces of bulk carriers", (IMO PSPC,
Resolution MSC. 215(82)). Compliance with the IMO PSPC is required by the
IACS Common Structural Rules for Bulk Carriers and for Oil Tankers for ships
Since PSPC has been adopted by IACS as of Dec. 8, 2006, not by IMO, if the subject to those Rules which are contracted for construction between ship
Builder and Ship owner agreed not to apply PSPC, is it acceptable to the Class builder and ship owner on or after 8 December 2006. The relevant Rulereferences are the following:or not?
- IACS CSR for Bulk Carriers Chapter 3, Section 5, 1.2.2;- IACS CSR for double hull oil tankers, Section 6, 2.1.1.2. Therefore, for suchships (i.e. ships subject to CSR) the answer is "PSPC is to be applied if they
are contracted for construction between ship builder and ship owner on or after
8 December 2006". For other ships, the answer is that PSPC is to be appliedin accordance with IMO Resolution MSC 215(82) and IMO MSC 216(82).

2007/6/15

Ch 3, Sec 6, [2.3.1] could be considered as the requirements in general. If theAccording to this requirement, structural members welded to the strength deckstress level due to hull girder bending, in longitudinal member not contributing
or bottom plating is to be made of the same higher tensile steel of strength
to hull girder longitudinal strength, should be verified as to satisfy thedeck or bottom plating. The same requirement is applicable for non continuous
requirement in Ch 5, Sec 1, [3.1.1], application of the requirements in Ch 3,
longitudinal stiffeners welded on the web of a primary member contributing to
Sec 6, [2.3.1] might be mitigated.
the hull girder longitudinal strength. However, it is not clear which member
As a matter of opening the door, the word "generally" should be added
should be applied to this requirement. Please confirm if our understanding of
between "The same requirement" and "is applicable...".
this requirement is correct as summarized in the attached Table.

2007/3/16

1) In CSR for BC, Ch 3, Sec 5, [1.2], there are already mentioned areas which
are to comply with IMO PSPC. This means that IMO PSPC shall be applied to
all dedicated seawater ballast tanks and void double skin spaces in bulk
(1) Ballast hold used in heavy weather condition and partially floodable holds
carriers. Therefore, we believe that the cating for the ballast hold spaces
used in harbour condition for loading/unloading operations are not considereddescribed in [1.4.1] is not related to PSPC, we would like to request theas dedicated sea water ballast tanks and need not comply with IMO PSPC.
background for the interpretation.
(2) Regarding [1.4.1], an effective protective coating is not required to inner(2) Additionally, the ballast hold spaces are keeping in dry condition as otherbottom in ballast hold by the CSR/Bulker.
holds in sea-going condition. also, after cargo unloading, the tank bottom will
be damaged due to unloading action. Therefore, we would like to recommend (3) The partially floodable holds used in harbour condition for loading/unloadingthat the coating for tank bottom of all cargo hold spaces sahll not be painted as operations are not to be considered as ballast hold spaces in respect of
coating issues.
described in [1.3](3) Furthermore,please clarify whether the partially floodable hold spaces are
the ballast hold spaces or mornal cargo hold spaces in respect of coating
issues.

2007/4/10

According to CSR-Bulker Ch.3 Sec.6 [10.4.2], the bending radius R is not lessthan 3.0 t but using net plate thickness. If the intention is to control cold
forming, is it reasonable to use as-built thickness? For sake of clarity, thebending radius R should be defined as the "radius of inner plate surface" asillustrated in Figure 3.6.28.

Attachment

Y

The intention of this requirement is to control the cold forming. As described in
IACS Rec. No.47, the minimum bending radius is 3 x t, where t is the grossthickness. The definition of "R" is defined as he "radius of inner plate surface".
Threrefore, we will consider the editorial correction according to yoursuggestion.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Answer

414

3/6.1

CI

Cargo holdareas

2007/7/11

The requirements in Ch.3 Sec.6 are applicable to not only cargo hold area but
also other areas, where the application is appropriate, including the areas
Ch.3Sec.6 [1]The requirements in section [6] are only applicable for the cargo hold area. Our related to Ch.9 in general, as defined in Ch.1 Sec.1 Table.1. Actually somesubsections in Ch.3 Sec.6 specify the requirements to the structures outside ofopinion is that the subsections dealing with general principles, plating,cargo hold area.
stiffeners and primary supporting members should also apply to otherstructures, as we can not find any corresponding requirements in Ch.9. Please
However where the requirements in Ch.9 should contradict those in Ch.3
advise.
Sec.6 the former should govern.

415

3/6.2.2.5

CI

Plating
Thickness

2007/4/2

A change in plating thickness is not to exceed 50% of thicker plate thickness
for load carrying direction.” Please specify whether the requirement is basedon gross or net thickness.

416
3/6.10.5.1
attc& 3/6.5.2.1

CIDepth ofStiffener

2007/5/14

Ch.3Sec.6 [10.5.1] and Ch.3Sec.6 [5.2.1]. The requirement "Depth of stiffeneris to be more than 1/12 of stiffener length”. Case 1: Typical web spacing is(3x800mm) = 2.4meter. A flat bar on longitudinal girder is then required to be
200mm. With a ship length of 200meters, utilizing the interpretation KC#328 ina typical pipe duct (tc=2), the required thickness is (3+0.015x200+2=) 8mm.
That is minimum FB 200x8. Current comparable design is FB150x12. Case 2:
Wash bulkhead in way of ER with a height of 4.5 m. Minimum height ofsupporting stiffeners is 375mm. Current comparable design is HP200x9.
Q1: Please explain background of these requirements.
Q2: With reference to Case1. The minimum required scantling is high andslender. Compared to current design the cross sectional area is smaller,(200x8 = )16cm2 vs. (150x12=) 18cm2. The slender profile will be more prone
to tripping . It is also outside the slenderness requirement for ordinary
stiffeners listed in Ch. 6 Sec. 2 [2.3.1]. We consider the original scantling to bea better choice. Please advise.
Q3: With reference to Case 2. The dimensions required for the wash bulkhead
stiffeners will be larger than for a comparable water tight bulkhead. This does
not seem reasonable.

Attachment

In this case, Plating thickness means the as-built thickness of plating. We willconsider the Editorial Change.

A1. The requirement of 5.2.1 has been based on the modified one of thecurrent classification rules, taking into account the net scantling concept. Thisrequirement is provided to ensure the appropriate scantling and rigidity of web
stiffener for the purpose of avoiding the buckling of web plate of primary
supporting member based on the experiences.
Y
Please refer to the attached documents for the background of the requirementof 5.2.1 of Ch 3 Sec 5.
A2 and A3: Such stiffeners as described in the question are to be considered
as ordinary stiffeners, with application of the full requirements of Ch 6, Sec 2.

Page 7 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

417

422

Ref.

Ch 3 Sec
6/ 10.5.1

3/5.1.2.2

Type

CI

CI

Topic

Bulkhead
Stiffener

MeasurementsDatecompleted

Question/CI

Answer

2007/5/14

Yes, the same interpretation specified in KC 328 can be applied to [10.5.1].
This interpretation is the following one:
It is agreed that the requirement asking that "the net thickness of bulkhead
The requirement “The net thickness of bulkhead stiffener is not to be less thanstiffener is not to be less than the minimum net thickness required for thethe minimum thickness required for the considered bulkhead plate” . Withconsidered bulkhead plate" seems quite severe.
reference to KC #328 approved 22/01/07 regarding web stiffeners on primary
The interpretation is that "the net thickness of bulkhead stiffener is not to besupporting members. Can the same interpretation be applied to [10.5.1]?
less than the minimum net thickness defined in Ch 6, Sec 2, [2.2.1]", i.e. theminimum thickness of ordinary stiffeners (3 + 0.015 L2).
We will consider the Rule Change according to our interpretation.

2007/3/7

IMO PSPC is applicable for all ballast tanks of new ships of 500gt above anddouble side skin spaces of new bulk carriers of 150m above. CSR BC makes
What is the interpretation of whether under CSR the ballast tanks and the
IMO PSPC effective for CSR bulk carriers contacted for construction on anddouble side skin spaves of bulk carriers is for length of 150m and upwards.
after 8 Dec 06. Therefore, under CSR BC, IMO PSPC is applicable for all
CSR say".. For ships contracted the coating of internal spaces subject to theballast tanks of bulk carriers of 90m above and double side skin space of bulk
amended SOLAS regulations are to satisfy the requirements of the IMO
carriers of 150m above. If double side skin space is of ballast tank, PSPC is
performance standard". this would indicate that this is applicable to 150 L for
both the ballast tanks and the double side skin spaces of bulk carrier; although applicable for such space of bulk carriers of 90m above. If double side skinspace is of void space, PSPC is applicable to such space of bulk carriers of
the CSR for bulk carriers si for 90m and upwards
150m above.

Attachment

Page 8 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

424

Ref.

3/6.10.4.2,
3/6.10.4.4&
3/6.10.4.8

Type

CI

Topic

definition ofcorrugation
span “l”:

Datecompleted2007/3/9

Question/CI

Answer

Attachment[Q1] “Note” in IACS UR S18 Figure 2b indicates the following restrictions forthe definition of corrugation span “l”:
“For the definition of l, the internal end of the upper stool is not to be taken
more than a distance from the deck at the centre line equal to:- 3 times the depth of corrugation, in general- 2 times the depth of corrugation, for rectangular stool “Instead, neither CSR for BC Ch.3 Sec.6 /10.4.4 nor Figure 29 has such
restrictions. If the intent of CSR is the same as IACS UR S18, such restrictions
should be clearly indicated in the Rules.
[Q2] On the other hand, CSR for BC Ch.3 Sec.6 /10.4.4 indicates “For thedefinition of lc, the height of the upper and lower stools may not be taken
smaller than the values specified in [10.4.7] and [10.4.8]”.
This is just the opposite from IACS UR S18. Presume that this sentence
should read “For the definition of lc, the height of the upper and lower stools
may not be taken GREATER than the values specified in [10.4.7] and[10.4.8]”. Please confirm.
The intent of these requirement is the same as IACS UR S18. Namely,for thedefinition of lc, the lower end of the upper stool is not to be taken more than a[Q3] If the restrictions in [Q1] are applicable to CSR, please further advise on distance from the deck at the center line equal to:- 3 times the depth of corrugation, for non-rectangular stool
the relation 'between the upper stool width at top and maximum 'effective- 2 times the depth of corrugation, for rectangular stool.
depth for the calculation of corrugation span “lc”.
CSR Ch.3 Sec.6/10.4.8 indicates “The stool top of non-rectangular stools is to [A2]Same reply as in [A1].
have a width not less than twice the depth of corrugations”. In this connection, [A3] Option 1 should be used for calculation "lc".
in case of a non-rectangular upper stool has a width at top of 1.5d and height [A4] "0.3lc" should be measured from the upper end of corrugation span "lc".
Also Included in Corrigenda 5of 3d, where d is the depth of corrugation, how to measure the corrugation
span? There may be two options as follows. Which option (or any other else) is
to be applied?
Option 1: Treat this as a rectangular stool since the width at top is less than2d, and take into account 2d for the calculation of “lc”.
Option 2: Calculate “lc” by linear interpolation between rectangular stool andnon-rectangular stool having a width at top of 2d. In case of this example, 2.5d
is used for the calculation of “lc”.
[Q4] CSR Ch.3 Sec.6 /10.4.2 indicates that the thickness of the middle part ofcorrugations is to be maintained for a distance from the deck (if no upper stool
is fitted) or the bottom of the upper stool not greater than 0.3lc. In case “lc” isadjusted by [Q1], is “0.3lc” to be measured from the upper end of corrugation
span “lc” or may be measured from the actual upper stool bottom? Pleaseadvise.

Page 9 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

426

429

Ref.

3/5.1.2.1

3

Type

CI

Question

Topic

Double side
Skin SpacePort
ballasting

Datecompleted

Question/CI

Answer

2007/5/14

Ref. Ch. 3 Sec. 5 [1.2.1]
A1. Chapter 1 Section 1 [1.1.1] of CSR for Bulk Carrier describe “With bulk
"All dedicated seawater ballast tanks and void double side skin spaces are tocarrier ……..and with single or double side skin construction cargo length area
have an efficient corrosion prevention system (..)" Please advice on below…..”. Accordingly, the double side skin spaces specified in Ch 3 Sec 5 [1.2.1]
related questions. Q1:Could you please clarify "double side skin spaces". Is
are covering the cargo hold length spaces.
this only covering cargo hold area or entire ship?
A2. The double side spaces in machinery space is not necessary to apply to
Q2: If a ship is arranged with double side in machinery space enclosing void
the requirement of [1.2]
spaces, should such spaces have corrosion prevention according to [1.2]? Q3:
If you have a top wing tank that is a fuel oil tank the new Marpol require that
A3. Yes, such spaces arranged in cargo length area are considered as a
you add a cofferdam toward the side skin, will this then be considered as a
double side skin spaces but such spaces arranged in spaces other than cargo
double side skin space in bulk carriers? Or when you have fuel oil tanks in thelength area are not considered as a double side skin spaces.
engine room that is, for the same reason fitted with a coffrdam towards theside, is this a double side space in bulk carriers?

2009/10/6

Currently CSR Bulk has no requirement/mention of port use ballasting of
ordinary dry cargo holds which is a common practice of large bulk carriers
typically Capesize. In our opinion, the following items (may not be exhaustive)
should be clarified urgently:
1. In the past, acceptable filling height was determined for the given scantlings
and based on design formula and criteria for ballast tanks. The same approach
We note your comments and requirements for the treatment of port use ballast
may be used in CSR for local plates and stiffeners, hold frames and all internal
hold will be included in the rules at a future revision.
members, i.e., boundaries of topside and hopper tanks, inner bottom andbulkhead stools.
2. In an extreme case, the hold in question may have to be filled up to thehatchtop, then we definitely should check the strength of various membersbounding the hold in question unless it is a dedicated heavy ballast hold.
3. How much dynamic load to be considered?

Attachment

4. For corrugations and primary support members, scantlings have to beverified by a hold FEA with a separate “intact-harbour” load case because
there is no formula for corrugation in intact condition vaide for ships above 150
meters. (Ref. Ch. 6 Sec. 2 [3.2.4])
5. Any requirements against over filling, alarms, etc. if partial filling?
6. Should tank test be required?
7. What should be stated in the Loading Manual?
8. According to Chapter 3, Section 5 [1.4.1], all internal and external surace ofhatch coamings and hatch covers, and all internal surfaces of ballast holds areto have an effictive protective coating.
Is Chapter 3, Section 5 [1.4.1] applicable to port filled ballast holds?

444

3/6.7.2.1

CI

Structural
Design2007/6/11

In Chapter 3, Section 6, [7.2.1] it is stated that "Where the double side spaceis void, the structural members bounding this space are to be structurally
designed as a water ballast tank according to Ch.6. In such case thecorresponding airpipe is considered as extending 0.76m above the freeboard
deck at side"
Does this requirement apply to both scontling and welding design?.

Yes, this requirement applies both to the scantling and welding designs.

Page 10 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

445

Ref.

3/6.10.4.4

Type

RCP

Topic

Span ofcorrugations

Datecompleted

Question/CI

2007/7/11

In Chapter 3, Section 6, [10.4.4]- Span of corrugations", it is stated that "The
span lc of the corrugations is to be taken as the distance shown in Fig 29. For
the definition of lc, the height of the upper and lower stools may not be taken
smaller that the values specified in [10.4.7] and [10.4.8]".
On the basis of UR S18-fig 2b and its note, it seems that the word "smaller"
could be replaced by "greater".

Answer

Attachment

The intent of these requirement is the same as IACS UR S18. Namely,for thedefinition of lc, the lower end of the upper stool is not to be taken more than adistance from the deck at the center line equal to:- 3 times the depth of corrugation, for non-rectangular stool- 2 times the depth of corrugation, for rectangular stool.
The draft Corrigenda for clarification of this requirement will be issued.
Also Included in Corrigenda 5446

3/6.2.3.1

Question

Hull Girder
Bending2007/6/11

According to the answer of question #208 of IACS CSR KC,is the material of
mild steel for the flat bar on the double bottom girders accepted?

It is accepted, provided that the stress level due to hull girder bending in suchflat bar complies with the requirements in Chapter 5, section 1, [3.1.1]

447

3/6.5.2.1

CI

Depth ofStiffener

2007/7/11

The last sentence "Depth of stiffener is to be more than 1/12 of stiffenerlength".
What is the definition of "depth of stiffener"?
Does it mean the web height + flange thickness if any?

Answer:In order to be in line woth the Chapter 6,section 2, [2.3] the depth of stiffener
should be considered as only the height of its web.

Would you give me a clear interpretation for CSR BC Rule Ch.3 Sec. 6, 10.4.7.

450
3/6.10.4.7
attc

498
attc

3/6.5.7.4

CI

QuestionNet
Thickness &Corrugation
FlangePrimary
SupportMembers

2007/5/14

First, all the requirement (coming from UR S18.4.1) should be given in net
thickness. Secondly, the word "flange" in the text means "flange of the
The quoted para. is as below. "The net thickness and material of the stool top
corrugation of the transverse bulkhead".
plate are to be not less than those required for the bulkhead plating above.
Consequently, the text should be modified as:
The thickness and material properties of the upper portion of vertical or sloping"The net thickness and material of the stool top plate are to be not less thanstool side plating within the depth equal to the corrugation flange width fromthose required for the bulkhead plating above. The net thickness and material
the stool top are to be not less than the required flange plate thickness andproperties of the upper portion of vertical or sloping stool side plating within thematerial to meet the bulkhead stiffness requirement at the lower end of thedepth equal to the corrugation flange width from the stool top are to be not lesscorrugation." My interpretation is (t_S_TOP)net >= (t_BHD)net andthan the required corrugation flange net plate thickness and material to meet
(t_S_SIDE)gross >= (t_BHD)gross. (refer to the attached picture) It is because
the bulkhead stiffness requirement at the lower end of the corrugation."lower stool side plate has lower corrosion addition that transverse BHD plate.
Do I interpret correctly?

Y

2007/8/2

A] Where opening is provided, as per the attachment, in primary supporting
members such as double bottom girders, etc., should Ch.3, Sec.6, [5.7.4] beA): Your understanding is correct. You may see Fig.15 of Ch 3 Sec 6 that theinterpreted as follows regarding distances between the opening and slot
example without collar plate in cut-outs is shown.
openings for longitudinals ?
B] According to the 1st sentence of 5.7.5, the reinforcement of such openings
1) at the mid-part within 0.5 times of the span of the primary supportingis required.
members: l <= d1, d2, d3 and d4,2) at the ends of the span, l<=0.25x(d1, d2, d3 and d4).
[B] If Ch.3, Sec.6, [5.7.4] should not be applicable to the distances between the
opening in primary supporting members and the slot openings, isn't there any
restrictions to the distances ?

YPage 11 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

502

510
attc

534
attc

Ref.

Topic

Table
3.1.4

Steel gradeof lowerbracket, of
Question hold frames,of single side
BCA/BCBbulk carriers

3/6.7.2.1

Upper andDouble side
Void Space

3/6.6.1.3

540 3/6.6.5.2

560

Type

3/6.5.7.2

QuestionCI

Question

RCP

Position of
the mainpropulsion
machinery

The bilge
keel length

Lightenign
holes inprimary
supporting
members

Datecompleted

Question/CI

2007/8/2

Steel grade of lower bracket of hold frames of single side BCA/BCB bulk
carriers. Reference is made to Chapter 3 Section 1 Table 4. The requirement
is originating from SOLAS XII/6.5.3. Please advice if the requirement should
be applied to lower bracket web and flange or web plate only.

2007/8/3

In the attached document is a cross section of a DSS-BC shown, which has avoid space in the area of the top wing tank to separate a FOT from the side
shell. Is this upper part of the void spaces a double side void space according
CH3, Sec6, 7.2.1, which has to be treated like a water ballast tank?

Answer

AttachmentThis requirement is applied to web plate of lower bracket only.

The position where the main propulsion machinery is seated is normallyrecessed from the main double bottom structure in engine room. And thebaseline of this seating can be located at which the height from the baseline isless than required. Please refer to the sketch as an example (Moulded of thisship is 45m).
In this circumstance, we would like to have your confirmation whether the
2007/10/23
above arrangement is acceptable or not for the SOLAS and CSR points ofview.
In addition, we would like to have your general interpretation on the above
regulations such as the extent of exemption, necessity of bottom damage
calculation, etc.

It is considered that this answer is an interpretation but there is no change oftechnical background and no scantling impact.
Therefore, in order to clarify this matter, the corrigenda will be issued.
Also Included in Corrigenda 5

the area dashed in red in the attached document should be designed as awater ballast tank, as specified in the text of Ch 3 Sec 6 7.2.1.

Y

The minimum height for the double bottom is defined in CH9, Sec3, 2.1.2.
The proposed arrangement with a reduced double bottom height in way of themain engine is acceptable provided the lateral extent is limited to the M/E
breadth and by lateral tight girders for the CSR for bulk carriers view point andprovided the Administration agrees for SOLAS view point.
Y
The rigidity of the engine seating and the surrounding bottom structure must
be adequate to keep the deformations of the system due to the loads
within the permissible limits, given by the engine manufactures. In special
cases, proof of deformations and stresses may be required.

The last sentence in the 1st paragraph of Ch.3 Sec.6 [6.5.2] reads:" The bilge
keel with a length greater than 0.15L is to be made with the same grade of
The intermediate flat is also to be of the same steel grade as the bilge strake
2007/10/19 steel as the one of bilge strake." In this connection please confirm that theand the bilge keel in case of a bilge keel length > 0.15L.
intermediate flat is not required to be made with the same grade of steel as theone of bilge strake regardless of the length of the intermediate flat.

2008/4/11

The first sentence of Ch 3, Sec 6, 5.7.2 states:"Where openings such as lightening holes are cut in primary supporting
members, they are to be equidistant from the face plate and corners of cutouts."
Even though the above, the distance from the opening to the face plate of the
primary supporting member is larger than the ones to the corners of the cutsout as "a" indicated in Fig 15.
At the same time, the location of the opening is restricted by the note,"h<=d/2", as indicated in Fig 15.
We consider that this requirement is obviously impractical.
Therefore, the word "the face plate and" should be deleted from the 1st
sentence of 5.7.2.
Furthermore, we would like to confirm the following:(a) this requirement is not applicable to the access hole;(b) "phi" in the figure means the width of the lightening hole, not the height of
the hole;(c) even if the arrangement of holes in primary supporting member does notmeet Ch 3, Sec 6, 5.7.2, it can be accepted based on the results of DSA.

We will consider a rule change with considering your comment.
The answers to the items (a) to (c) in the question are as follows.
(a) This requirement is not applicable to the access hole.
(b) “phi” is the diameter of lightening hole, neither height nor width of openings.
(c) As there are too many locations to be assessed, it is considered
impracticable to determine the arrangement by FEA. Therefore, thearrangement of holes in primary supporting member meets this requirement asa principle. However, since it might be possible to determine the arrangementof hole in primary supporting member based on the results of FEA, it could be
accepted based on the FEA at the discretion of the Classification Society.

Page 12 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

564 3/6.8.3.1

590
3/6.5.4.1
attc

598 3/6.6.3.3

Type

Topic

Question

Side Frames- General

Question

Question

Definition of
Attached
platins ofprimary
members

Ordinary
stiffener
spacingDatecompleted

Question/CI

Answer

2007/11/2

Reference is made to Ch. 3 Sec. 6 [8.3.1] Side frames – general
This requirement is originating from UR S12.5.
In CSR the formula states r= 0.3 x (..) wihile in UR S12.5 r = 0.4 x (..).
Is this a typo? If not, what is the reason for the formula change.

2008/5/28

The main concern is on the definition of ATTACHED PLATINGS of primary
members (girders/ webs etc). I have been using a LOGICAL spreadsheet to
calculate the Effective width of attached plating for Primary members (as forsecondary members the effective width is the normal frame spacing and is welldefined).The spreadsheet I have been using for the same is attached for yourThe definition of the effective breadth in CH3, Sec6, 5.4.1 is an antagonism toreference.
the definition, given in CH6, Sec4 Symbols. In this paragraph it is clearly stated
Based on the Latest ABS CSR 2006 requirement the definition says…”
that the effective breadth b_p is defined according CH3, Sec6, 4.3, which iseffective breadth of attached plating of primary supporting member to beb_p = min(s, 0.2l).
considered in the actual net section modulus for the yielding check is to be
The definition given in CH3, Sec6, 5.4.1 will be corrected accordingly.
taken as the mean spacing between adjacent primary members.”
This would mean that the primary would be stronger if the spacing of the
primary is higher (in some cases). I have attached a case study on the
Effective Width of plating considered based on IACS requirement and earlier
Ship Rules. The summary is also attached in the same.
I would request if you could arrange to clarify my little query on the same.

2008/1/10

According to CH3, Sec6, 6.3.3 a spacing of MIN (4.5m; 5x ordinary stiffenerspacing) is required DB side girders in case of longitudinal framed double
bottom.
According to the GL rules and our experience, a spacing of maximum 2x
ordinary stiffener spacing is appropriate in the strengthening forward area of avessel.
According CH9, Sec1, 5.4.1. the spacing "S" is not limited. is this limitation
missing for the strengthening forward part?

Attachment

We will consider the rule change in order to be in line with IACS UR S12.
Also Included In Corrigenda 5

Y

In CSR of BC, the scantlings of girders and floors in the strengthened bottom
forward are determined by the scantling formulae which in turn define thespans and spacing of the floors and girders. Therefore, by using the scantling
formulae, there is no need to separately define the spacing of the girders andfloors in the strengthened bottom forward.

Page 13 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI[Q1] C3S6[9.6.3] reads in its 3rd last paragraph: "For the extreme corners ofend hatchways,…"
Please clarify the location of "the extreme corners of end hatchways".

3/6.9.6.3 &612 Figure
Question
3.6.25Extremecorners ofendhatchways

2008/5/30

Answer

Attachment[A1] The extreme corners of end hatchways are:a) the fore end hatch corners of foremost hatch, andb) the aft end hatch corners of aftmost hatch.

[A2] Please refer to 4th paragraph in Ch.3 Sec.6 [9.6.3] which reads:"Forhatchways...insert plates are, in general, not required .....where the plating cutout has an elliptical or parabolic profile and the half ....● twice the transverse
dimension, in the fore and aft direction."
According to this paragraph "60% greater" requirement needs not be applied
if the afore-quoted condition of 4th paragraph is satisfied.
[Q3] For the dimension requirements of hatch corner inserts as specified in
Fig.25 of C3S6[9.6.3], is this requirement also applicable to the corner inserts In case the condition is not satisfied a strake or an insert plate containing thewith the elliptical or parabolic profile? If yes, how to determine the value of "R" hatch corner needs to comply with the requirements of thickness in [9.6.3]
including "60% greater" requirement.
as indicated in Fig.25 for the elliptical or parabolic profile?
[Q2] According to C3S6[9.6.3], for the extreme corners of end hatchways, thethickness of insert plates is to be 60% greater than the actual thickness of theadjacent deck plating. Is this requirement also applicable to hatch corners withthe elliptical or parabolic profile?

[Q4] With regard to the question [Q3], since the required material class ofhatch corner plating is Class III and that for adjacent deck plating is Class II,
the insert plate may be required in some cases even if the corner profile is anelliptical or parabolic profile. In this case, are there any dimension
requirements for such inserts? Are the requirements in Fig.25 of C3S6[9.6.3]
applicable and if yes, how is the value of "R" shown in fig. 25 determined?

[A3] Dimension requirements of Fig.25 needs not be applied to the elliptical orparabolic profile which complies with the half axes and half lengths
requirements of 4th paragraph of C3S6[9.6.3]. In case the foregoing 4th
paragraph requirements are not satisfied a strake or an insert plate containing
the hatch corner needs to comply with the dimension requirements of Fig.25.
In such a case the starting points of d2 and d3 are to be taken from the radii's
ends of the elliptical or parabolic profile.

[A4] Please consider separately the steel grade from insert plate. In case astrake or an insert plate within 0.4L amidship includes the hatch corner, grade
III or grade E/EH is to be applied. In case a strake or an insert plate does notcontain the hatch corner and is not the stringer plate, grade II is to be applied.
Dimension requirements for insert plate need not be applied to an elliptical orparabolic profile which complies with half axes and half length requirements of
4th paragraph of C3S6[9.6.3]. Fig.25 needs to be applied only when insert
plate is required by [9.6.3].If elliptical or parabolic profile does not satisfy therequirements of half axes and half length requirements, a strake or an insert
plate containing the hatch corner needs to comply with the dimension
requirement of Fig.25. Then the steel grade of the strake or the insert plate
within 0.4L amidship to be III or grade E/EH.

Page 14 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

614
attc

Ref.

3/5.1.2.1

Type

Topic

Coatingrequirementsof doubleQuestionside skinspaces ofbulk carriers

Datecompleted2008/5/6

Question/CI

AnswerComment to the answer, A3 of KC#426
Since coating requirements of double-side skin spaces of bulk carriers in
regulation 3/5.1.2.1 of CSR for Bulk Carriers are developed based on theformer SOLAS regulation XII/6.3, definition of “double-side skin” should be inaccordance with SOLAS regulation XII/1.4.
***quote***Former SOLAS Regulation XII/6.3 (Resolution MSC.170(79))
Double-side skin spaces and dedicated seawater ballast tanks arranged in bulk
carriers of 150 m in length and upwards constructed on or after 1 July 2006
shall be coated in accordance with the requirements of regulation II-1/3-2 andalso based on the Performance standards for coatings* to be adopted by theOrganization.
SOLAS Regulation XII/1.4 (Resolution MSC.170(79))
Double-side skin means a configuration where each ship side is constructedby the side shell and a longitudinal bulkhead connecting the double bottom and We agree to your interpretation.
the deck. Hopper side tanks and top-side tanks may, where fitted, be integral
parts of the double-side skin configuration.

Attachment

Y***unquote***Accordingly, the said regulation 3/5.1.2.1 is only applicable to void spaces
when located within cargo length area in bulk carriers of double-side skinconstruction.
Therefore, the asked void spaces arranged as a part of top-side tank, whenprovided in bulk carriers of single-side skin construction, need not to beconsidered as a double-side skin space.
The attached interpretation would be effective to the amended SOLAS
regulation II-1/3-2 (resolution MSC.216(82)).
Please clarify the above again.

617 3/1.2.3.9

CI

Weldedattachments
on hullplating

2008/5/30

Ch3, Sec1, 2.3.9 states as below;"Rolled products used for welded attachments on hull plating, such as gutter
bars, are to be of the same grade asthat used for the hull plating in way."
Is it applicable to small members, such as coaming plates fitted aroundmooring winch on upper deck?
Please clarify the applicability of this requirement.

This requirement applies to the longitudinal members attached to hull plating
except internal members and which are considered in the longitudinal strength
calculation such as gutter bars.

Regarding Ch.3, Sec.6-9.2.3, the following question and suggestion are
offered for reply.

630 3/6.9.2.3

CI

Cross deckbeams

2008/6/19

A1: The continuity of structures and integration is the purpose of this section.
Base on the original intention, it is considered that the beams means not only
1. The passage says, ‘…, beams are to be adequately supported by girders
hatch end beams but also cross deck beams.
and extended up to the second longitudinal from the hatch side girders
We agree to editorial correction that bulwark is changed to deck side.
towards the bulwark’. Clarification of the beams is requested as to whether itmeans hatch end beam only or ordinary cross deck beams inclusive. A bulwark
A2: As mentioned by the questioner, this requirement does not seem to matchis not always arranged hence rewording such as 'deck side' is suggested.
the recent practice of design.
We will consider the rule change proposal in order to match the practical
2. In case that ordinary cross deck beams are inclusive, the paragraph does
design.
not seem to reflect practical design. It is therefore proposed that the extensionof beams up to the second longitudinals…can be waived provided a direct
strength analysis in compliance with the requirements in Ch.7 be foundsatisfactory.

Page 15 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

3/3.1.2.1 &
638
Table
attc
3.3.1

Type

CI

Topic

Corrosion
addition forballast water
tanks

Date
completed2008/4/22

Question/CI

AnswerRegarding corrosion addition for ballast water tank within 3 m below the top oftank in Table 1 in Ch.3, Sec.3 of CSR BC Rule, our interpretation is that itshould be applicable only to ballast tanks with weather deck as the tank top.
This interpretation is in line with Table 3 of Technical Background on Corrosion
addition and Note 1. of Table 6.3.1 of CSR for Double Hull Oil Tanker Rule.
We examined the thickness measurement data regarding the position ofPlease confirm if our interpretation is correct.
structural members in bilge hopper within 3m below from the tank top. As the
According to Table 3 of the attached Technical Background, the corrosion
result, the corrosion diminution of structural members within 3m below from thevalue of 1.7 is shown for topside tank in WBT when the tank is subject to hightank top was not different from other than those.
temperature. The high temperature is expected for the members in ballast
Therefore, we will consider the rule change proposal based on the results ofwater tank with weather deck as the tank top.
the examination.
Therefore, a tank top of WBT which is not weather deck, e.g. the tank top of
Accordingly, we will modify the answer in KC ID 206
WBT(APT) below steering gear room, should be treated not as ‘within 3 m
below the top of tank’ but as ‘elsewhere’ in Table 1 in Ch.3, Sec.3 of CSR BC
Rule.
In addition, if this interpretation is acceptable, an answer of KC ID 206(corrosion addition of hopper side tank not connected to top side WBT) should
be re-considered.

Attachment

YPage 16 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Figure
646
3.6.2

Type

RCP

Topic

Span length
definition forordinary
stiffeners

Datecompleted2008/5/28

Question/CI

Answer

Attachment

Reference is made to Chapter 3 Section 6 Figure 2 “Span length definition forordinary stiffeners.”
The span l of ordinary stiffeners is to be measured as shown in Figure 2, Ch.3
Sec.3 4.2.1. The fourth sketch of Figure 2 indicates that the span length on
one side is to be related to the end bracket fitted on that side and on the otherside related to the depth of the web stiffener fitted on the other side. There is
We will review your question and proposal in the course of harmonizationno indication in the figure that the span reduction should be symmetrical, which
process with CSR for Tanker.
implies that an unbalance moment will be set up at the support. There is,however, not found any requirement in the rules that may ascertain that theunbalance moment can be supported by the web stiffener or the girder. Thereis also not found any requirement formulation that ensures that the rotational
stiffness of such a support is such that the unbalance moment will be
generated.
Proposal:
Sketch 4 of Figure 2 in Ch.3 Sec.6 4.2.1 is amended to show that the span
reduction on either side is not to be taken larger than the smaller of the span
reduction by the bracket and the depth of the web stiffener. Refer also to CSR
Tank Figure 4.2.2 b)

647
attc

3/6.5.2.1

661 3/6.6.5.2

RCP

Web
Stiffeners on
primary
supporting
members

RCP

Net
Thickness oftheintermediateflat

2008/5/13

Applicable requirements to Web stiffeners on primary supporting members.
Reference is made to KC 204/328/333/416/419 which all considers therequirements to web stiffeners on primary supporting members.
The answers given to all KC items relevant to this subject (scantlings of web
We have looked into the above 5 KC items in order to gain a complete
stiffeners - KC 204/328/333/416/419) are considered are being selfoverview. To us it seem like the some of the KC is out of date and some are
explanatory.
contradictory. Summary of our findings is enclosed in Excel spreadsheet.
However, the following is reminded:
Based on the summary findings, we would like KC to clarify and update the1 - It is clearly mentioned in Ch 3, Sec 6, [5.2.1] that this requirement applies
rules on the following items:
1.Update if Ch.3Sec.6 with clear definition of web stiffeners with clear sketches to stiffening arrangement of primary supporting members. No additional sketch
showing the arrangement and table referring to applicable requirements. (KC or definition is needed.
2 - In addition, the answer to KC#419 states clearly that web stiffeners of
also refer to buckling stiffeners.)
2.Update of Ch.3Sec.6 with clear definition of ordinary stiffeners with sketches primary supporting members are not to be considered as “ordinary stiffeners”.
3 - Then both the answers (b) in KC#204 and (2) in KC#333 states that only
and table referring to applicable requirements.
the following requirements are applicable to web stiffeners:
3.Ref. KC id416 where PT advice that Ch3Sec.6 5.2.1 is ..”to ensure theappropriate scantling and rigidity of web stiffeners for the purpose of avoiding - Ch 3, Sec 6, [5.2.1] for the net thickness of such stiffeners, which refers to
the minimum net thickness of the primary members on which they are fitted,
the buckling of web plate(..)”.
i.e. to Ch 6, Sec 4, [1.5.1],and- Ch 6, Sec 2, [4] for the net scantlings of web stiffeners of primary supporting
members.
If the buckling stiffeners are calculated for buckling according to Ch.6 Sec.3
and minimum scantlings according to Ch.6 Sec.2, can the requirement of Ch.3 In conclusion, we agree that all the KC items on this matter should be
consolidated in a future corrigenda
Sec. 6 5.2.1 be waived? If so, this should be clearly written in the rules.
4.Please delete/consolidate above 5 KC items in order to avoid future
confusion.

2008/5/9

Ch3, Sect6,6.5.2 of the subject rules states "The net thickness of theintermediate flat is to be equal to that of the bilge strake. However, thickness
may generally not be greater that 15mm."
It is understood that the 15mm maximum should be the 'as-built' thickness, in
keeping with previous rule sets.
We propose the following corrigenda to clarify this:"The net thickness of the intermediate flat is to be equal to that of the bilge
strake. However, the gross thickness need not be greater than 15mm."Y

Yes, the 15mm maxumum should be the "as-built' thickness.
We will consider the editorial correction in order to clarify this.

Page 17 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

674 3/6.7.2.1

689 3/6.7.2.1

701

Table
3.3.1

702
3/6.4.5.2
attc

Type

CI

Topic

DSS BC

CI

Where thedouble side
space is void

QuestionCorrosion
addition on
one side ofstructuralmembers

Question

Ordinary
stiffeners

Datecompleted

Question/CI

Answer

2008/4/24

In case of a DSS BC which hopper and double side space forming a single sea
Answer or Interpretation:water ballast tank, whereas the topside tank is a dry compartment, we haveA1- The topside tank in this case (dry compartment from the water ballast tankthe following question:in double side space) should be considered as a dry compartment since it is
1 - In relation to KC#510, should this topside tank be considered as a waterballast compartment for the purpose of net scantling and fatigue assessment? physicaly separated from the double side space.
A2- Not relevant
In case of yes:
2 - Should this topside tank be considered as a separated water ballast tank or A3- It is considered as a dry compartment for corrosion addition tc as similar tothe design principle specified in Ch 3 Sec 6 7.2.1.
continuous with the double side tank?
3 - Since it is for the purpose of NET scantling, does that mean that corrosion
thickness tc should be considered as that of the actual dry compartment
instead of the virtual water ballast compartment?

2008/5/28

Chapter 3 Section 6 Par 7.2.1 states as follows:"Where the double side space is void, the structural members bounding thisspace are to be structurally designed
as a water ballast tank according to Ch 6. In such case the corresponding air
pipe is considered as extending 0.76
m above the freeboard deck at side."
Is therefore to be interpreted that in fatigue calculations, performed according
to Chapter 8, these spaces are to be considered void? This is reasonablebecause such spaces are actually void in operating conditions. If confirmed, it
could be useful to give explicit mention of this in Ch 3 Sec 6 Par 7.2.1.

2008/5/28

2008/5/30

Ch3 Sec3, Table 1 regulates the corrosion addition on one side of structuralmembers.
Please advise which corrosiion addition in Table 1 should be applied to theinner side of hollow pillar.

Attachment

Where the double side space is void, the requirement in Ch 3, Sec 6, [7.2.1] isclear enough as it requires only the application of Ch 6 as water ballast tankand doesn't require anything for fatigue. It is confirmed that these spaces areto be considered as void for the fatigue assessment.

A hollow pillar or the space behind a shedder or gusset plate is airtight closed.
This means that oxygen will be dissipated in the first corrosion process and will
be not replaced by new one. This is different from void spaces, where irregularinspections are carried out through man holes.
Therefore, the corrosion addition for the inside of a hollow pillar and gusset or
shedder plate is to be taken equal to 0.5mm as a void space.

Ch3 Sec6, 4.5.2 regulates as follows;
Where ordinary stiffeners are cut at primary supporting members, brackets areto be fitted to ensure structural continuity. In this case, the net section modulus
and net sectional area of the brackets are to be not less than those of theordinary stiffener.
Please confirm the definition of “the net section modulus and net sectional
area of the brackets” as follows.
1. The section of the bracket and the stiffener;
When web and/or flange of stiffener is welded to primary supporting member
1-a. at the end of the stiffener.
(1-a) may be taken. For other cases (2-b) should be taken.
1-b. at the mid-point of the free edge of the bracket.
In case 1, is the snipped flange of the stiffener included in the calculations?
2. The section of the bracket;
2-a. normal to the free edge of the bracket.
2-b. at the end of the stiffener.
2-c. attached to the stiffener.
2-d. smaller of 2-b and 2-c.
(Refer to the attached sketch)

Y

Page 18 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Answer

The requirement in CSR is correct. Referring to Class I (Tab3),it means that
A/AH is required for thicknesses up to 30 mm, then B/AH up to 40 mm andD/DH up to 50 mm.
In BV Rules it was required A/AH up to 40 mm and requirement "on a case bycase basis" above 40 mm.
We think that the requirement in CSR-BC is more clear and more easily
applicable.

This requirement applies to the longitudinal members attached to the outside
plating of the hull and which have lengths greater than 0.15L such as gutter
bars. For example, an isolated oil spill coaming at mooring winches is not in
the range of the application.

711 3/1.2.3.3

CI

Steel gradeof bedplates

2008/5/28

Technical Background document says that Ch.3, Sec.1-2.3.3 is derived from
BV Rule Part B, Ch.4, Sec.1, Note 2 of Table 3. The requirement of Ch.3,
Sec.1-2.3.3 is, however, different from the latest BV Rule, saying:‘The steel grade of bedplates of seats for propulsion and auxiliary engines
inserted in the inner bottom is not to be less than A/AH for plate thickness
lower than 40 mm. For plate thickness greater than 40 mm, different grades
may be required by the Society on a case by case basis’.
Hence the requirement of CSR BC Rule should be interpreted as same as thelatest BV Rule. Please confirm...

720 3/1.2.3.9

Question

Grades ofsteel

2009/6/2

What kind of plate member shall be considered here ? Is it also applied tosmall plate members such as oil spill coaming at mooring winches?

756 3/6.5.2.4

RCP

Symbolmissing inthe 2nd
Formula2008/5/30

A symbol, b, is missing in the 2nd formula in Ch3 Sec6, 5.2.4.
Ch3 Sec6, 5.2.4. requires the arm length of tripping brackets, where originates
This is a typo. we will consider the editorial correction.
in 4.7.6, Section 3, Chapter, 4, Part B of the BV Rules.
Please correct it.

2008/7/16

1st sentence of Ch 3 Sec 6 [6.1.3] requires the minimum height of double
bottom.
There are attached designs where the double bottom height varies according
to the transverse locations. This is due to that bottom shell is not kept flat overThe double bottom height h, measured vertically from the plane parallel withthe extent of inner bottom width.
keel line to inner bottom, is not to be less than B/20 or 2 m whichever is thelesser. However, in no case is the value of h to be less than 760 mm.
Please advise whether the foregoing requirement means:a) only double bottom height at centerline (h_CL) is to be kept to be not lessthan B/20 or 2m whichever is lesser, orb) B/20 or 2m whichever is the lesser is to be kept over the extent of inner
bottom width including h_s.

758
3/6.6.1.3
attc

CI

Minimumheight of
doublebottomAttachment

YApplicability of minimum thickness requirement to web stiffeners: Regarding
applicability of minimum thickness requirement to web stiffeners, the type of
web stiffeners is referred at the end in the question in KC328, however, theanswers in KC328 and KC647, relevant to KC328, are not clear to web
stiffener type.

760 3/6.5.2.1

CI

web stiffners

2009/3/3

The requirements of minimum thickness of web stiffener are as follows;-Ch3 Sec6, 5.2.1 : minimum net thickness of primary support members,
referred to Ch6 Sec4, 1.5.1.
-Ch6 Sec2, 2.2.1 : minimum net thickness of web of ordinary stiffeners
The types of web stiffeners are as follows;- Flat bar type- Angle or T type

Ch 3 Sec 6 [5.2.1] is only applicable to web stiffener with flat bar type.
The minimum net web thickness for web stiffener with angle or T type is to be
not less that that for ordinary stiffener specified in Ch 6 Sec 2 [2.2.1].

Please clarify the applicability of the above two requirements to the two types
of web stiffeners.

Page 19 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

761 3/6.5.6.2

762 3/6.6.3.1

765 Text 3/6

Type

CI

CI

Question

Topic

end bracket
hight ofprimary
supportmembers

centre girder

continuity ofstrengthDatecompleted

Question/CI

Answer

2009/6/26

Ch3 Sec6,5.6.2 requires that the end bracket height of primary support
members should be not less than that of the primary supporting member. Withreference to the interpretation of KC414, the requirements in Ch3 Sec6 areapplicable not only cargo hold area but aｌso other areas, where the application
is appropriate. Please confirm whether the above requirement in Ch3
Sec6,5.6.2 is applicable to side transverse web in steering gear room. If
applicable, providing large bracket according to the above requirement
interrupts the arrangement of fittings in steering gear room.

The mandatory requirements for the scantlings of the end connection is given
with the sentence "The scantlings of end brackets are to be such that thesection modulus of the PSM with end brackets is not less than that of the PSM
at mid-span". An editorial change will be made by introducing the word
"generally" in the sentence in Ch3 Sec6,5.6.2, stating that "the height of end
bracket is generally to be not less than that of the primary supporting member".

2009/3/3

Ch3 Sec6, 6.3.1 requires tightness of center girders as follows: Where double
bottom compartments are used for the carriage of fuel oil, fresh water orballast water, the centre girder is to be watertight, except for the case such as
The word "etc." means the case of small watertight compartments that freenarrow tanks at the end parts or when other watertight girders are provided
surface effects thereof are considered very small, compared with thewithin 0.25B from the centreline, etc.
arrangement specified in this requirement.
With reference to “etc” at the end, it seems that the CSR permit non-tightcenter girders under specific conditions. Please indicate the conditions inwhich non-tight center girders are permitted.

2009/3/3

Please confirm that the requirements in Ch3 Sec6 are not required to be
applied to areas other than cargo hold area, provided there is no crossreference to Ch3 Sec6 in the requirements to those areas specified in therelevant chapters, such as Ch9, etc

Attachment

According to Ch 3 Sec 6 [1], the requirements of this section apply to the cargohold area. For other areas, the requirements of Ch 9 Sec 1 to Ch 9 Sec 4 areto be applied.
In fact some requirements are applicable in the whole ship, e.g. CH3, Sec6,
5.1.1 "Continuity of strength". We will make a rule change proposal in order toclarify the applicability of this chapter.

Page 20 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

769

Ref.

Table
3.1.4

Type

RCP

Topic

Date
completed

Question/CI

Answer

AttachmentWith respect to CSR-BC, Ch.3, Sec.1, Table 4: Application of material classes
and grades, it is proposed that the following parts in Special structural member
1. We agree to your proposal.
category be editorially corrected.
2. Our understanding is that the bottom column of table 4 is applicable to bulk
Application ofcarrier having the longitudinal hatch coamings of length greater than 0.15L.
1. The terms, 'ore carriers' and 'combination carriers' are inapproriate in viewmaterial
2008/10/15
This is in line with the third column from the bottom of the table. In order toof the application set out in Ch.1, Sec.1, 1.1.2 where these ships are clearyclasses andclarify these items and to cover the revision of IACS UR S6 Rev. 5, we willruled out. The text being a transcription from C5 in Table 1 as available ingradesconsider the RCP.
IACS URS6, Rev.5, this column should be more appropriated to CSR bulk
carriers hence can only be changed to 'Strength deck plating at corners ofcargo hatch openings (2)'.
2. The bottom of the category specifying 'End brackets and deck housetransition of longitudinal cargo hatch coamings (5)' is most likely to be proper
to container ships and not to bulk carriers. Should this be the case, pleasedelete this column. If this should not be the case and applicable to CSR bulk
carriers, clarification is requested as to whether the column refers to end
brackets of discontinuous hatch side coamings having the length less than
0.15L. Otherwise, grade D/DH would be irrationally mandatory even for smallbulk carriers.

772

773

777

3/6.8.6.1

Table
3.3.1

Tanker
12/1.1.3 &Bulker3/2.3.3

780 3/6.8.2.1

Question

RCP

CI

Question

brackets
supporting
longitudinal
stiffeners

According to Ch3 Sec6, 8.6.1 of Bulker CSR, brackets above the side frames Span,"l", is the spacing of bracket or the distance between the transverse web
in every frame space are fitted to ensure structural continuity. Consequently at in bilge hopper tank or topside tank, as applicable, and the adjacent bracket,
when applying the formulas in Ch.6, Sec.2,[3.2.3], [3.2.5] or [3.2.7]. Please
least one side of the lowest longitudinal stiffeners on topside slant plates are
2008/10/15
normally supported by the brackets in every frame space. Please clarify how to note that spacing, s, is to be a half longitudinal spacing between the adjacenttake into account the effect of such brackets supporting longitudinal stiffeners longitudinal plus the half distance between the longitudinal and the connectionof topside tank/bilge hopper tank sloping plate and side shell.
with a view to determining the longiudinal stiffener span.

Corrosion
addition in
way of a
WBTThis issue relates to the application of Table.1 in Ch3 Sec3 with respect to the
corrosion addition in way of a WBT (particulary, Top Side Tank) within 3m of
the tank top. If only the part of face plate of an ordinary stiffener is locatedwithin 3m of the tank top while the web plate of the ordinary stiffener is located2008/10/10 outside 3m from the tank top, which corrosion addition applies to such a
stiffener?
(1) Corrosion addition in way of a WBT within 3m of the tank top, or(2) Corrosion addition in way of a WBT oustside 3m from the tank top. Pleaseclarify it.

According to the 2nd sentence from the bottom of Ch 3 Sec 3 [1.2.1], where a
streuctural member are affected by more than one value of the corrosion
addition, the scantling criteria are generally to be applied considering theseverest value of corrosion addition applicable to the member. This is a
general principle. Normally, the location of stiffener is judged from thecoordinate at the conection of the attached plate. Therefore, for the case inquestion, corrosion addition in way of a WBT oustside 3m below the tank top.
In order to clarify this, we will consider the RCP.

2009/5/19

The plans to be supplied onboard the ship are to include both the as-built andthe renewal thickness. Does this mean all thicknesses on all drawings shall
include as-built and renewal thickess ? Is it sufficient that renewal thickness
are shown on main drawing or in a separate document?

The submitted structural drawings (Section 3, 2.2.2.1, (a) & (c) in CSRTankers and Ch 3 Sec 2, 3.3 in CSR-BC) is to show renewal thickness and asbuilt thickness. Any owner's extra thickness is also to be clearly indicated. For
the plans to be supplied on board the ship, see Section 3/2.2.3 in CSRTankers. Alternatively, it is acceptable to present renewal thickness in a
separate plan ("Renewal thickness plan") in which the as-built thickness may
not be presented, and any owner's extra thickness is also to be clearly
indicated. This plan is to be approved and supplied on board the ship.

2009/3/3

The 2nd sentence in Ch.3 Sec.6 [8.2.1] reads: " If air pipes are passing
through the cargo hold, they are to be protected by appropriate measures toavoid a mechanical damage."
Please advise what the appropriate
measures are.

Appropriate measures to avoid mechanical damages to air pipes passing
through the cargo hold should be subjected to the Class Society.

as-built
thickness

air pipes

Page 21 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Answer786

3/6.4.1.1

Questionbulb profile

2008/9/10

In CSR-BC, Ch 3 Sec 6, [4.1.1], the thickness tw of the web of the built-up
section equivalent to a bulb profile is not defined. We assume that the
thickness of the web is taken equal to the thickness t'w of the web of the bulb
profile. Please confirm our interpretion.

Your interpretation is correct: in CSR-BC, Ch 3, Sec 6, [4.1.1] the thickness twof the web of the built-up section equivalent to a bulb profile is to be taken
equal to the original thickness t'w of the web of the bulb profile.

787

3/1.2.3

Question

UR S6

2008/9/10

Considering Rev.5 (Sept 2007) of IACS UR S6, it seems necessary to update
CSR-BC Ch 3, Sec 1, [2.3] to be in accordance with this revision.

We agree with your comment. The requirements in CSR-BC Ch 3, Sec 1, [2.3]will be updated to be in line with Rev.5 (sept2007) of IACS UR S6.

2009/4/1

1.Reference is made to IACS KC ID: 711 regarding the material grade of the
top plate of main engine seats inserted into inner bottom.
2.It is understood that a thicker top plate of main engine seats is required tosuit securing the engine bolts on installation of a main engine, then, it isconsidered to be a very local strength item.
3.Consequently it is also understood that Grade A/AH is acceptable for the top
plate of the engine seats located outside 0.6L amidships of any plate thickness This question will be addressed within the harmonisation process of both CSR
and the requirement of Ch. 3, Sec.1, Para. 2.3.3 of the CSR BC is applicable BC and CSR OT.
to the top plate of the engine seats located inside 0.6L amidships.
4.For information, LR Rules accept A/AH for the top plate of the engine seatsoutside 0.6L amidships and few damage has been reported for it so far. Mostof the classification societies’ Rules are understood to be in line with thisrequirement.
5.A prompt confirmation on Para. 3 as above would be very much appreciated.

2009/3/3

Ch3 Sec6, 6.4.2 requires that the net thickness and material of floors in way oflower stools should not be less than those of lower stool side plating. The
requirement originates from the requirement of UR S18.4.1 (c)-"Alignment",
which requires the net thickness and material of floors in way of corrugate
bulkheads not to be less than those of corrugation flanges, in cases without
lower stools. In cases without lower stools, the floor supports bulkhead
corrugation and the necessities of equal net thickness and material of the floor This issues are included in RCP4 (Rule Change Notice 1, 2009) which has
been reviewed according to PR32.
are understandable from a structural viewpoint.
In cases with lower stools, however, bulkhead corrugation is supported by such
lower stools and the floor supports the stool side plating. Accordingly, any
connections between lower stool side plating and floors are considered to becontinuous enough by assuring equal thickness. Therefore, we would like torequest a rule change stating that the material of floors will not be required in
Ch3 Sec6, 6.4.2 in cases with lower stools.

2009/3/10

Ch3 Sec6, 5.2.2 generally requires tripping brackets welded to the face plates.
In addition, the last sentence in Ch3 Sec6, 5.2.2 also requires that the faceCh.3 Sec.6 [5.2.2] means that the side of the flange should be supported whenplates of the primary supporting members, which exceed 180 mm on eitherside, should be supported by tripping brackets. We are of the opinion that the the size of the side exceeds 180mm.
tripping brackets shoud only support the face plate of PSM in case where such
face plates exceed either side of the web. Please confirm the above.

794

808

817

3/1.2.3.3

3/6.6.4.2

3/6.5.2.2

CI

RCP

Question

top plate ofengine seats- material
gradealignment

tripping
brackets

Attachment

Page 22 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

827
3/6.7.2.1
attc

Type

CI

Topic

void spaceDatecompleted2009/3/3

Question/CI

AnswerPlease refer to the attached sketch of a bulk carrier with double side skinconstruction. This bulk carrier has FOT and pipe trunk in the topside area. The
pipe trunk is considered as void space.
Ch3 Sec6, 7.2.1 requires as follows; Where the double side space is void,
the structural members bounding this space are to be structurally designed as
It was not the intention of the CSR to derive irrational dimensions for voida water ballast tank according to Ch 6.
bounding structures. We suggest to use the corresponding cargo hold length
In the bulk carrier, FOTs are arranged with cargo hold length and the pipe
for l_H in the formula for inertial water ballast pressure.
trunk is running through whole the cargo area length. According to our
We will make a rule change proposal to eliminate this drawback.
calculation based on the above, the dynamic pressure in the long pipe trunk isestimated about twice the large pressure in FOTs and excessive scantlings are
required by the calculation based on the pipe trunk pressure. However,taking into account the technical background of Ch3 Sec6, 7.2.1 as quoted
below, requiring the above-mentioned excessive scantling is irrational;

Attachment

Y

If the double side skin part is to be used as a void space, and cargo of highdensity is to be carried in the cargo holds, then local loads are not presumed toact on the side structure of the cargo hold on the double skin side. Even insuch cases, appropriate thickness exceeding the minimum thickness is
considered necessary. As a conclusion, even if the double skin side part is avoid space, it is treated as a ballast tank and assessment of local strength isspecified.
In this bulk carrier, the longitudinal bulkhead can be considered appropriatelyby the estimation of the pressure in FOT.
Therefore, we are of the opinion that the longitudinal bulkhead between thepipe trunk and the FOT has an appropriate construction by calculating FOTinternal pressure, therefore, the bulk carrier is in compliance with Ch3 Sec6,
7.2.1, without calculation of the pipe trunk internal pressure.

842

843

3/6.5

Text
3/6.2.2.5

Question

Questioncurved faceplatestapering

2009/7/6

Ch.3 Sec.6 [5]In CSR Tanker rules 4/2.3.4 there is a correction formula for the effective
flange area of curved primary supporting members. In CSR Bulk there is nosuch formula. Does this mean that curved flanges, e.g. in the top wing webs
and bilge webs, are to be considered 100% effective?

There is no formula to evaluate the effectiveness of the curved part in the
curved flange in CSR –BC. The formula to evaluate the effective breadth oreffective area of curved flange is necessary in order to take into account theeffect due to cross bending phenomenon.
Therefore, this matter should be submitted to the Hull Panel to make aharmonized interpretation.
Furthermore, the RCP will be considered in accordance with the harmonizedinterpretation.

2009/6/25

Ch.3 Sec.6 [2.2.5] Change in plating thickness
Main machinery seatings are typically more than double the thickness of theinner bottom. In case the seating is included in the double bottom strucure, isthe requirement Ch.3 Sec.6 [2.2.5] to be complied with? If this is the case,insert plates will often be required in the inner bottom plating.
In our opinion it is sufficient to use tapering in accordance with Ch.11 Sec.2[2.2.2]. Please advise.

The meaning of "load" in "load carrying direction" in Ch. 3 Sec. 6 [2.2.5] isconsidered to be of a global type, such as hull girder loads. Where global loads
are considered small or can be ignored, e.g. machinery seatings or reinforced
openings in bulkhead, tapering according to Ch.11 Sec. 2 [2.2.2] is consideredsufficient.

Page 23 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

844

Ref.

3/6.10.3.4

Type

Question

Topic

Stiffener
brackets onplanebulkheads

Datecompleted

Question/CI

Answer

2010/1/18

Ch.3 Sec.6 [10.3.4]
The requirement for arm length a for stiffener brackets is very large for long
stiffeners not subject to pressure.
Example: Bulkhead in engine room between platform deck and upper deck.
Length is 5.5 m. 9 mm plating is stiffened with HP140x8 stiffeners. The
requirement to the arm length a then becomes 550 mm for the lower brackets
and 440 mm for the upper brackets. The actual arm length a is 250 mm.
In our opinion the bracket size should be decided based on the required
section modulus for the stiffener, not the length. Please comment.

You are right. The bracket size should be decided based on the required
section modulus for the stiffener, not the length. We will consider a rule change
proposal in order to harmonize CSR for BC with CSR for OT.

Attachment

Page 24 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

871
3/6.10.4.7
attc

884

885

Text
3/2.3.3.1

Table
3.3.1

Type

Question

Topic

S 18

question

net scantling
approach

Question

collision
bulkhead &machinery
space front
bulkheadDatecompleted

Question/CI

Answer

Attachment

The requirement of Ch3/Sec6/[10.4.7] comes from S18, and is in line withSOLAS Ch. XII - SOLAS/CONF.4-Resolution of the Conference of Contracting
Governments to the International Convention for Safety of Life at Sea, 1974(November 1997) – Resolution3 –Recommendation on Compliance withSOLAS Regulation XII/5 – (Adopted on 27 November 1997). We should keep it
as is.

Y

2009/5/13

See the attached comment/question forwarded by ABS re BC CSR
Ch.3/6.10.4.7.

2009/6/24

From a viewpoint of net scantling approach, Ch3 Sec2, 3.3.1 requires that
renewal thicknesses of structural members be indicated on the structural
drawing. A renewal thickness is defined in Ch13 Sec2 as follows;t_renewal = t_as_built - t_C – t_voluntary_addition
On the other hand, superstructures and deck houses required in Ch9 Sec4 are Renewal of structures of superstructures and deck houses is to be left todiscretion of each classification society. The same goes to all structures listed
based on gross scantling as indicated in Ch3 Sec2, 2.1.1. Accordingly, it isconsidered that renewal thicknesses of superstructures and deck houses are in Ch.3 Sec.2 [2.1.1].
not in line with the above definition and consequently follow that specified ineach Class Rules. Therefore, we consider it unnecessary to indicate renewal
thicknesses of superstructures and deck houses on the structural drawing.
Please confirm the above.

2009/8/27

The question is on collision bulkhead and machinery space front bulkhead
The corrosion addition for lower stool plates intend to deal with the high level of
without upper stool and lower stool.
Please confirm that only "Transverse bulkhead"-"Other parts" & "Upper parts" corrosion that takes place within the lower stool space. As there is no lowerof "Structural member" category, in Ch.3 Sec.3 Table 1,are to be applied to the stool, the corrosion addition to be considered here is the "Transverse bulkhead
corrosion addition on cargo hold side of these bulkheads but that "Lower stool / other parts".
sloping plate, vertical plate and top plate" category needs not be applied.

In Ch.3 Sec.6 [10.4.5], it is stated that "In general, the first vertical corrugation
connected to the boundary structures is to have a width not smaller thantypical width of corrugation flange".

920

3/6.10.4.5

Question

corrugated
BHD

2009/7/16

Q1. We assume that "boundary structures" is side shell plate.
Please advise correct interpretation of "boundary structure".
Q2. We understand that the width of first vertical corrugation connected to side
shell plate is more than typical width of corrugation flange.
Please clarify the meaning of above paragraph whether our understading iscorrect or not.

926

Text
question
3/6.4.1.1

built-up
stiffener

2009/6/24

Ch.3 Sec.6 [4.1.1] Bulb section, equivalent built-up stiffener.
It is not clear if the text and Fig.1 are referring to net or gross dimensions of
the bulb profile and the equivalent built-up profile. Please clarify if t'w, tw, h'w,
bf and tf are net or gross dimensions

A1: Boundary structure is the ship side structure.
A2: The first corrugation is to be at least as width as a "typical" corrugation of
the bulkhead. A larger width is not mandatory.

t'w, tw, h'w, bf and tf used in Ch.3 Sec.6 [4.1.1] are net dimensions. A
corrigenda will be prepared to clarify it.

Page 25 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Answer

AttachmentThis question has to be considered within the scope of the harmonisation. The
position expressed by ABS hereafter will be submitted to the relevant
harmonisation team.

931

933
attc

944
attc

Table
3.3.1

3/5.1.3.4

Table
3.1.4

QuestionCI

Question

corrosion
additioncargo holdpainting speccategories ofstructuralmembers

ABS proposal:
Bilge and drainage store tanks would generally contain a combination of oil
and water.
However, in the extreme case they may contain salt water only. Considering
stiffeners of FOT the two sided corrosion addition (without t-reserve) is 1.4mm-> 1.5mm and in the case of a Ballast Tank the two sided corrosion addition
would be 2.4mm -> 2.5mm.
It is believed that a two sided corrosion addition of 2.0mm to 2.5mm would beappropriate.
Considering the amount of the structure to which this would be applied, and“fitting” of this category of tank into the existing categories of compartments it
is recommended that these be treated as Ballast Tanks.

2009/7/24

Please clarify the corrosion addition for bilge tank/drainage store tank.

2009/7/16

We, from HHIC-Phil had a discussion regarding the Painting Specification of
our Bulk Carrier which will be constructed in our yard by next year. The
Painting Specification was prepared in accordance with the CSR and PSPC
Rules together with the paint maker's recommendation and building
specification. Regarding this matter we encountered a problem on theinterpretation of the CSR for Bulk Carriers on the Transverse bulkhead Areas
to be coated. If we apply the CSR strictly, the painting demarcation line of thetransverse bulkhead will vary according to the position of the frame end
your interpretation is correct.
brackets.
We would like to request an interpretation of the Common Structural Rules(CSR) regarding the cargo hold painting demarcation line for Single Side Bulk
Carrier. Please see the attachment to give us some clarification on the painted
areas and no-painting areas of the cargo hold corrugated transverse bulkhead
and the likes.
Thank You very much in advance. Your kind attention and prompt reply would
be much appreciated.

Y

2009/9/1

Q1: Yes, your understanding is correct and "Deck Plate 2" is regarded as"PRIMARY" category, except that "Deck Plate 2" is to be regarded as of"SPECIAL" category when the strake contains the strength deck plating at theCh.3 Sec.1 Table 4 defines the category of structural member, regarding
which, Q1: Is the deck plate strake (Deck Plate 2 in the attachment) in way of corners of cargo hatch openings.
Q2: In the Table 4 "Deck plate at longitudinal bulkhead" is categorized ashatch side girder to be regarded as of "PRIMARY" category?
Q2: The design is provided with longitudinal watertight bulkhead separating the "SPECIAL". However UR S6 (Rev.4), which is the basis of Table 4, adds thetopside space into two compartments. Is the deck plate strake (Deck Plate 1 in Note [2] to "Deck plate at longitudinal bulkhead" as follows:"Excluding deck
the attachment) above longitudinal bulkhead to be regarded as of "PRIMARY" plating in way of inner-skin bulkhead of double hull ships". This exception may
be applied similarly to the longitudinal bulkhead in the topside space in the
category? Please advise.
attachment. Accordingly "Deck Plate 1" may be regarded as of "PRIMARY"
category.

Y

Page 26 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Answer

Attachment

We noticed that paragraph 9.5.4 of Ch3, Sec6 is not in line with IACS UISC208.
The requirement stated in the CSR-BC

945

3/6.9.5.4

RCP

protection ofhatches

2009/7/30

The correction of this paragraph to be in line with IACS UI SC208 is already
QUOTE
included in the RCP2-6". It will be changed as follows:
9.5.4" For ships with holds designed for loading / discharging by grabs and having
Wire rope grooving in way of cargo holds openings is to be prevented by fitting
the additional class notation GRAB[X], wire rope grooving in way of cargo
suitable protection such as halfround bar on the hatch side girders (i.e. upper
holds openings is to be prevented by fitting suitable protection such as halfportion of top side tank plates)/hatch end beams in cargo hold or upper portion
round bar on the hatch side girders (i.e. upper portion of top side tankof hatch coamings.
plates)/hatch end beams in cargo hold and upper portion of hatch coamings."
UNQUOTE
leads to the wrong assumption that exclusive protection of hatch girder OR
hatch coaming is sufficient.

949

3/5.1.3.4

CI

coating oftransverse
bulkheadareas

It is specified in CSR Background Document that the requirements of 1.3.3
and 1.3.4 are in accordance with UR Z 9. According to 1.3.4, some area oftransverse bulkhead (below horizontal level located at distance of 300 mm
below the frame end bracket for single side bulk carriers or below the hoppertank upper end for double side bulk carriers) may not be coated. But according
to UR Z 9, all area of tranverse bulkhead including stool are to be coated.
Please clarify the coating area.
2009/9/3

The coating of transverse bulkhead is to be considered as per Ch.3 Sec.5
Quote: UR Z 9 ~ and all internal surfaces of the cargo holds, excluding the flat [1.3.4] as the requirement of UR Z9 should be applicable to the stool plating,sloped or not.
tank top areas and the hopper tanks sloping plating approximately 300 mm
below the side shell frame and brackets, are to have an efficient protective
coating ~ Unquote
Quote: CSR Bulk Carriers Ch3 Sec 5 1.3.4 The areas of transverse bulkheads
to be coated are all the areas located above an horizontal level located at a
distance of 300 mm below the frame end bracket for single side bulk carriers
or below the hopper tank upper end for double side bulk carriers. Unquote

Page 27 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

950

Ref.

3/6.10.4.9

Type

CI

Topic

weldingrequirements

Datecompleted

Question/CI

Answer

2009/9/4

This requirement comes from of UR S 18 like as 10.4.7 and 10.4.8. But I thinkthat the requirement specified below quotations is different from UR S 18.
According to UR S 18, full or deep penetration welding can be used forconnection between plating of supporting floor and inner bottom. But in Ch 3
Sec.6 10.4.9, only full penetration welding can be used for it. On the other
hand, not only full penetration but deep penetration is accepted in therequirement of Ch 11, Sec 2, 2.4.4. Please clarify which type of welding isright.

You are right: both full and deep penetration welding can be used forconnection between plating of supporting floor and inner bottom. The
sentence, “The weld of corrugations and floors or girders to the inner bottom
plating are to be full penetration ones”, in Ch3 Sec6 10.4.9 will be revised as:
Corrugated bulkhead plating is to be connected to the inner bottom plating by
full penetration welds. The plating of supporting floors or girders is to beconnected to the inner bottom by either full penetration or deep penetration
welds.

Attachment

Quote: UR S 18. 4. 1 (c) Alignment At bottom, if no stool is fitted, thecorrugation flanges are to be in line with the supporting floors. Corrugatedbulkhead plating is to be connected to the inner bottom plating by full
penetration welds. The plating of supporting floors is to be connected to theinner bottom by either full penetration or deep penetration welds. Unquote
Quote: CSR Bulk Carriers Ch3 Sec 6 10.4.9 At bottom, if no lower stool isfitted, the corrugation flanges are to be in line with the supporting floors or
girders. The weld of corrugations and floors or girders to the inner bottom
plating are to be full penetration ones. Unquote952

3/1.2.3.1

RCP

Grades ofsteel

2009/7/21

Correction of wrong reference number.
The last sentence of Ch.3 Sec.1 [2.3.1] states;"For strength members not mentioned in Tab 3, grade A/AH may be used."
Please correct the reference "Tab 3" into "Tab 4".

954

3/6.4.4

CI

Ordinary
stiffeners shear section

2009/9/10

For the yielding check of shear sectional area Ash of ordinary stiffeners as
required in Ch 6, Sec 2, [3] of CSR-BC, the actual shear sectional area of theordinary stiffener needs to be calculated. However, it is not stated in CSR-BC(Ch 3, Sec 6, [4.4]) how to calculate the actual shear sectional area of such
stiffener, and in particular if the net thicknesses of attached plate and flange, ifany, are to be included in this calculation. In CSR-OT (Ref Section 4, 2.4.2.2),
thicknesses of attached plate and flange, if any, are included in thedetermination of the "effective shear depth dshr" used for the yielding check of
the shear sectional area. Our interpretation is that both CSRs should have thesame approach, i.e. the one of CSR-OT.

You are right. The strength members are considered in Table 4, not in Table 3.
We will prepare corrigenda to correct it as following:
For strength members not mentioned in Tab 4, grade A/AH may be used.

It is agreed that the way to calculate the actual shear sectional area of ordinary
stiffener should be defined in CSR-BC Ch 3, Sec 6, [4.4]. It is also agreed thatboth CSRs should have the same approach, i.e. the one of CSR-OT. It meansthat the thicknesses of attached plate and flange, if any, are to be considered
for the calculation of the actual shear sectional area of an ordinary stiffener.

Page 28 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

961

978

Ref.

Table
3.3.1

Table
3.3.1

1004 3/6.4.1.1

1030 3/5.1.4.1

Type

Topic

Question

Normalballastdraught

Corrosion
Interpretati
addition foronlower stool

Datecompleted

Question/CI

Answer

2009/9/3

Definition of “normal ballast draught” According to Ch.3, Sec.3, Table1 Note(7), “Outer side shell between normal ballast draught and scantling draught is
to be increased by 0.5mm”.
Your interpretation is correct.
We understand that the definition of “normal ballast draught” is same as that in
Ch.6, Sec.1 [2.2.1], which has been interpreted as the minimum design lowest
ballast waterline amidships in KC ID409. Please confirm the above.

2010/3/30

Ch3 Sec3 Table 1, Corrosion addition for lower stool
Reference is made to KC 243. The corrosion addition for hopper plating issmaller than for the lower stool plating. Our understanding is that the reason
for this difference is that the hopper plating is cooled down by the ballast water
inside in ballast conditions. The lower stool is normally void, so the lower stool We agree with your interpretation.
plating will not experience the same cooling effect.
Based on the above, it seems reasonable to apply tc=3.7 mm instead of tc=5.2
mm to the lower stool plating if the stool is arranged as ballast water tank.
Please confirm our interpretation.

Attachment

In CSR BC, a bulb section may be taken as equivalent to an angle section,
which is defined in Ch.3 Sec.6 [4.1.1]. From our experience, for some kinds ofbulb sections, the section properties of bulb sections are comparable to thoseof equivalent angle sections; for others, they are not.
For example: the inertial moment about the horizontal neutral axis of a bulb
Your comment is noted. Ch.3, Sec.6, [4.1.1] will be modified. The following
200x10paragraph will be included in [4.1.1]: The sections properties of bulb profiles
Question bulb sections 2009/12/16
1. Equivalent to an angle section, I=1019cm4.
should be determined by direct calculations. Otherwise... [4.1.1 as it is now].
2.Direct method. For Holland Profile, I=1017cm4.
For Russian Profile, I=1083cm4.
In CSR OT RCN2, the descriptive method, calculating the section properties ofa bulb section, is deleted, and a direct method should be adopted.
The two set of rules should be harmonized.

RCP

Protective
coating inballast holds

2010/4/14

Regarding the protective coating in ballast holds, the paragraph of 3/5.1.4
should be deleted in order to be in line with IACS UR Z9.
CSR for Bulk Carriers January 2006 Background Document Chapter 3 saysthat “This regulation (3/5.1.4.1 Protection of ballast hold spaces) is inaccordance with IACS UR Z9.” And Z9 stipulates the same requirement ofprotective coating in both ballast holds and other cargo holds, which isequivalent to 3/5.1.3 of CSR BC Rules.
However, 3/5.1.4 requires that all internal surfaces of ballast holds are to havean effective protective coating (It is noted that IACS KC 400 exempts inner
bottoms in ballast holds.), and are beyond the requirement of Z9.

This KC is same as KC400, that is, Ch.3 Sec.5 [1.3] should have be modified
to include dry cargo holds which may carry water ballast and [1.4] should bedeleted. A corrigenda will be considered.

Therefore, 3/5.1.4 should be deleted so that 3/5.1.3 can cover both ballast
holds and other cargo holds..

Page 29 of 30

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

CSR-B Ch.3, Sec.6, 6.5.2 Bilge keel
The following requirement is to prevent cracks propagated to bilge strakes
from these occurred in bilge keels due to longitudinal bending moments.
“The bilge keel and intermediate flat are to be made of steel with the sameyield stress as the one of the bilge strake.”
1046 3/6.6.52

Question

Steel grade
requirementof Bilge Keel2010/8/4

For bilge strakes, even when the use of HT steel is not required by Ch.5,
Sec.1, 4.5 for longitudinal strength consideration, HT steel may be used forconvenience of design.
However, in light of the above, we consider that this requirement may bedispensed with if bilge keels are not located in the HT zones specified Ch.5,
Sec.1, 4.5.

Refer to Chapter 3/ Section 2.
Quoted
3.3 Available information on structural drawings
Indication of
3.3.1 The structural drawings are to indicate for each structural element
gross andthe gross scantling and the renewal thickness as specified in Ch 13, Sec 2.2".
Interpretati
renewal2010/11/15
1065 3/2.3.3.1
Unquotedon
thickness in
Our understanding of this paragraph could only be interpreted that all
the structural
structural drawings submitted to the IACS class are to indicate for eachdrawings
structural member the Gross and RENEWAL THICKNESS.
We would appreciate if our understanding is correct.

1077
attc

Bulker
3/6.5.7

Question

Depth of cutouts

2010/11/10

Harmonisation request for depth of cut-outs and naming of cut-outs/slots?
(Original request: Please refer to attachment)

Answer

Attachment

Since a large number of comments from shipowners have been received aboutbilge keel and prevention of damage to its ends, it was decided that thematerial of the bilge keel should have the same strength as the bilge strake.
Similar to long hatch side coamings of 0.15L specified in the IACS UR S6, if
the length of the bilge keel is greater than 0.15L, the material of the bilge keel
is required to be the same as that of the bilge strake.
The material requirement for the bilge keel is also found in Ch3/Sec6/[2.3.1].
The intermediate flat is to be made of steel with the same yield stress as theone of the bilge strake in order to ensure continuity of material.

As you mention, Chapter 3 Section 2 3.3.1 states that for each structuralmember, gross scantling and renewal thickness should be indicated.
However, for clarification of extension and alternative methods we refer toKC777, KC948 and KC1058.
A common position will be issued by the harmonization project.

Your comment is noted. We will retain your comment for consideration during
the harmonisation of the two CSR Rules.

Y

Page 30 of 30

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#398
Ch 3, Sec 6, 2.3.1 – Connections with higher tensile steel
According to this requirement, structural members welded to the strength deck or bottom plating is to bemade of the same higher tensile steel of strength deck or bottom plating. The same requirement isapplicable for non continuous longitudinal stiffeners welded on the web of a primary member contributing
to the hull girder longitudinal strength.
However, it is not clear which member should be applied to this requirement.
Please confirm if our understanding of this requirement is correct as summarized in the table below.

<Summary of connections with higher tensile steel>
Item

Application

1. Longitudinal members not contributing to the hull girder longitudinal strength(a) Longitudinal hatch coamings (length < 0.15L)(b) End bracket(c) Gutter bar, strengthening of deck opening, bilge keel

Web plateX

Top plate??

Web plate??

Face plate, if any??

Web plateX

Face plate, if any??

2. Members contributing to the hull girder longitudinal strength
Web plateNA

Top plateNA

Web plateNA(a) Non continuous longitudinal stiffeners welded on the
web of a primary member not contributing hull girderlongitudinal strength

Web plateNA

Face plate, if any

NA(b) Non continuous longitudinal stiffeners welded on the
web of a primary member contributing hull girderlongitudinal strength

Web plateX

Face plate, if any??

(a) Longitudinal hatch coamings (length  0.15L)(b) Stringers and girders
3. Members welded on the web of a primary member

Notes:
X : applicable
NA : not applicable?? : unclear

KC#416
Technical Background of Ch 3 Sec 6 [5.2.1] of CSR for Bulker
The web stiffener of the primary supporting member (PSM) is provided to prevent thebuckling failure of the web plate of PSM.
Even if the buckling failure occurs in the web plate of PSM, the web stiffener has to withstandthe buckling loads. For that reason, the stiffness of the web stiffener is always larger than thatof the web plate of PSM.
Now, the ratio of the stiffness of the web stiffener to that of the web plate of PSM sets to C
and the web stiffener is assumed to be of flat bar with thickness “t” and depth “h”a

The stiffness of the web plate of PSM:

V

Et 3

V
t

Web plate12(1  Q 2 )The stiffness of the web stiffener:b

Eth3 / 3

Web stiffener

The critical value “C” can be obtained by the following formula;C

Eth 3 / 3
Et 3 / 12(1  Q 2 )bt §h·
3.64 ¨ ¸b© t ¹

3

The critical value C varies depending on the aspect ratio of web plate. Here, the critical value
C is taken to 20, based on the actual designs. Then, we can get the following formula.
h
b

2

§t· 3
1.77¨ ¸©h¹

The ratio of thickness and height of flat bar varies to 135 to 80 which are obtained from thecurrent design, then,hb0.067 to 0.095 #The value “1/12” is the average value of11
tocan be obtained.
15 10habove.
b

Considering the actual design, it was found that this relationship between web stiffener heightand panel length can apply to web stiffeners with flat bar fitted to all PSM.
Then, to simplify this relationship, the web stiffener length l has been used instead of b.
As a conclusion, CSR has been adopted the last sentence of the requirement of Ch 3 Sec 6
5.1.2 that the depth of web stiffener is to be more than 1/12 of stiffener length.
***

KC#450

KC#498

d1

d2
h
d3

"
d4

KC#510

FOT

Void

WBT

KC#534

KC#590
SECTION MODULUS CALCULATION (IRS, Part 3 ,Chapter 3, Section 4)
Project:-

aaaaa

w

w

t1

t1
t2

d

For Bracket Design (LR) CLICK>>t2<<PRIMARY>>For Corossion allowance to SM CLICK>>>

d

t3

t3
wf
<<Double Sided Flange,D>><<Single Sided Flange,S>>

Flange (S,D for Single,Double sided flange)
Type number of equally spaced load point on member
Input 0 for stiffener/ secondary; 1 for girder/ primary
Thickness of attached Plating (t1) mm
Depth of Web (d)mm
Thickness of Web (t2)mm
Width of flange (wf)mm
Thickness of flange (t3),mm
Span of member (mm)Spacing of member (mm)
Effective Width of attached plating (w)mm
A (sqmm)Width atached pltg (mm)Thk. Attached pltg (mm)Depth of web (mm)Thk. Of web (mm)Width of flange (mm)Thk. Of flange (mm)NOTE:Openings in primary WEB to be REINFORCED ALONG
EDGE OF OPENING if the Opening depth>d/4 (or) 300mm(AND) Opening length>web depth,d (OR) Opening length >60%
Secondary spacing

wf

838.992273
10
550
10
150
10
Area Total

INPUTS
S<<<Provide Tripping Brackets>>>
0<<<Web Stiffening Required>>>1
Web Stiff FB (Reqd.)=
56 X 1010d/t2 STATUS
560
d/t2=
56.00 Check d/t2
Max.5510
wf/t3 STATUS
150 wf/t3,D=
15.00 Wf/t3 OK
N/A
10 wf/t3,S=
15.00 Wf/t3 OK
Max. 154410 C1Value=
0.77
0.77
1830 C2Value=
0.46
0.46
838.99 C Value=
0.46

8389.92

L(mm)
565

AL
ALL
4740306

2678273082

69916.02

5500.00

285

1567500

446737500

138645833.33

1500.00

5

7500

37500

12500.00

6315306

3125048082

138728249.36

15389.92

Height Of N/A from BaseLine (mm)410.35 Ymin=

159.6467

Height Of N/A from TopLine (mm)159.65 Ymax=

410.3533

MOI about BaseLine (mm^4)
MOI about Neutral Axis (mm^4)
Zmax (mm^3)=I NA/Ymin
Zmin (mm^3)=I NA/Ymax

3263776331.76
672269221.34
4210982 mm^31638269 mm^3

Max.Shear Area (Web)
Total sectional area (Web+Fl.)

5700 mm^215390 mm^2

Iown

Note Kg/m below is EXCLUDING ATTACHED PLTG
55.74 Kg/m (Stiffener OR Primary ONLY)
67226.92 cm^4
I N/A
4210.98 cm^3
1638.27 cm^3
Z min.
57.00 cm^2
153.90 cm^2

For Clarifications Contact: G.Jayasankar (jayasankar007@yahoo.com)

A shear
A totalSUB: CSR assumption on the Effective Width of attached plating for thePrimary Members & Section Modulus values for Primary.
Please refer to ABS CSR 2006 for Bulk Carriers Part 5B, Chapter 3, Section 6, 5.4.1
Effective Breadth of Primary Supporting member quotes " effective breadth of theattached plating of a primary supporting member to be considered in the actual net
section modulus for the yielding check is to be taken as the mean spacing between
adjacent primary supporting members".
The ABS Steel Vessels 2007 (also other Ship Rules) Part 3 Chapter 1 Section 2 13.3
stipulates "…effective width of plating not exceeding one half of the sum of spacing
on each side of the member (OR) 33% of the unsupported span of the member
whichever is LESS."The Effective width of attached plating for a primary seems to be over estimated in
the ABS CSR for the bulk carriers. In some cases this assumption leads to higher
differences; especially when the span of the primary < than the primary spacing.
As an example assuming a T section primary 900x10/ 150x15 spaced at 3000mm(say 600mm x 5 Spaces) and spanning 2000mm would result in different section
modulus values. Attached plating say 12 mm thick.
A) Based on ABS CSR 2006 ;Effective width of attached plating : 3000mm (= primary spacing)
Corresponding Section Modulus: 4420 cm^3B) Based on ABS Steel Vessels 2007
Effective width of attached plating : Minimum of (0.33x2000=660mm (or)3000mm)=660mm
Corresponding Section Modulus: 3920 cm^3 (88 % of CSR Section Modulus)C) Based on IRS Steel Vessels (With Effective width correction)
Effective width of attached plating : 437mm
Corresponding Section Modulus: 3722 cm^3 (84 % of CSR Section Modulus)
D) Based on LRS Steel Vessels 2003 Part 3 Chapter 3 Section 9
Effective width of attached plating : 687mm
Corresponding Section Modulus: 4009 cm^3 (90 % of CSR Section Modulus)
The above difference in the SECTION MODULUS of PRIMARY MEMBERS
seems to be significant in some cases and would require your advice.
Please arrange to clarify on the above and advice on the EFFECTIVE WIDTHOF ATTACHED PLATING TO BE CONSIDERED FOR PRIMARYMEMBERS.
(The respective calculations A, B, C & D are attached for your reference)

(A) ABS CSR 2006 Section Modulus Calculation (Effective width of attachedplating 3000mm= Primary Spacing)(B) ABS Steel Vessels 2007 Section Modulus Calculation (Effective width of
attached plating =Minimum of 1 Primary Spacing OR 33% of
Span=.33x2000=660mm)

(C ) IRS Steel Vessels (Effective Width of attached plating of primary= 437mm
only)(D) LRS Steel Vessels 2003 Part 3 Chapter 3 Section 9 (Effective width of
attached plating = 687mm)

KC#614

KC#638
JBP – IACS Common Structural Rules for Bulk Carriers

Technical Background on Corrosion Addition
Oct 28, 2004
Rev. Apr. 8 2005
JBP

Introduction
The IACS Unified Requirements for strength criteria of structures such as double bottom and bulkheads ofsingle side skin bulk carriers have adopted the “Net Scantling Approach” in which the gross scantling is
obtained by adding the net scantling obtained from the structural strength requirement to the thickness
diminution due to corrosion. In using the net scantling approach, the following terminology is used.
Net thickness:
the thickness required solely based on the structural strength aspect which is theminimum scantling that must be kept throughout the service life of the ship
Wastage allowance: the value of thickness diminution due to corrosion expected during the service life of
the ship obtained by statistical analysis based on the thickness measurement data ofships and the steel renewal criteria which ensure that the net thickness is kept
throughout the service life of the ship.
Corrosion additions: the value is obtained from Wastage allowance by adding to the thickness diminution
predicted till the next thickness measurement.
In order to introduce this Net Scantling Approach to the hull structural rules, at first, we have to have an
accurate grasp of the real thickness diminution. For this, corrosion process from occurrence throughpropagation were investigated on extensive thickness measurement data, and a corrosion process model
was developed based on probabilistic theory thus estimating the thickness diminution of structuralmembers. Based on this, a guideline on corrosion addition for bulk carriers and tankers was developed andwas submitted to the IACS Working party on strength (WP/S). The philosophy of Net scantling approachand the corrosion addition values are adapted in the draft IACS Common structural rules for bulk carriers
and tankers. This paper describes on how to determine the corrosion addition, how to apply the corrosion
addition and how to treat the wastage allowance.

1. Corrosion addition
1.1 Determination of corrosion addition
The corrosion addition was determined by the following procedure (details can be found in the technicalpaper published in ClassNK Technical Bulletin, Vol.21, 2003, pp 55-71).
(1) Gather about 600,000 thickness measurement data sampled from single hull tankers and single sideskin bulk carriers of age 5 to 27 years.
(2) Select the thickness measurement data of single hull tankers complying with MARPOL 73/78
Convention and with no coating of structural members in cargo oil tanks and of bulk carriers withcoated structural members in cargo holds required by the existing IACS UR.
(3) Develop a corrosion propagation model to simulate the realistic corrosion phenomenon based on
probabilistic theory and identify the necessary parameters for each structural member using the
thickness measurement data.
(4) Estimate the corrosion diminution at the cumulative probability of 95% for 20 years using thecorrosion propagation model.
(5) Sort out the corrosive environment to which each structural member is exposed and calculate theamount of corrosion of each corrosive environment using the estimated corrosion diminution of eachstructural member.
(6) Corrosion addition is determined based on the environment to which each structural member is
exposed.
However, the average scrapping age of ships is about 25 years, and the design life of ships is proposed as
25 years by the submission paper on “Goal Based Standard” MSC/78/6/2 of IMO. Therefore the estimation
period of corrosion diminution is changed to 25 years from 20 years. Moreover, in the real corrosion
phenomena, scatter of thickness diminution depends on the maintenance condition of the individual shiprather than the thickness measurement of each structural member as shown in Figure 1.

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JBP – IACS Common Structural Rules for Bulk Carriers
Upper Deck ( COT )Upper Deck ( COT )

8.0

8.0
Gauged Data

7.0

7.0

mean
mean+stdv.
mean+2*stdv.

6.0

Diminution ( mm )Diminution ( mm )

6.0
5.0

98%
4.0
3.0

90%

2.0

70%
50%

1.0

5.0

98%
4.0
3.0

90%

2.0

70%
50%

1.0

0.0

0.0
0

5

10

15

20

25

0

5

10

Ship's Age ( year )Side Shell ( WBT )25

4.0
Gauged Data

3.5

3.5

mean
mean+stdv.
mean+2*stdv.

3.0

Diminution ( mm )3.0

Diminution ( mm )20

Side Shell ( WBT )

4.0

2.5

98%
2.0
1.5

90%

1.0

70%
50%

0.5

2.5

98%
2.0
1.5

90%

1.0

70%
50%

0.5

0.0

0.0
0

5

10

15

20

25

0

5

10

Ship's Age ( year )

15

20

25

Ship's Age ( year )Side Longl. / Web ( WBT )Side Longl. / Web ( WBT )

3.0

3.0
Gauged Data

2.5

mean
mean+stdv.
mean+2*stdv.

2.5

98%

Diminution ( mm )Diminution ( mm )15

Ship's Age ( year )

2.0

1.5

90%

1.0

70%

98%

2.0

1.5

90%

1.0

70%

50%

50%

0.5

0.5

0.0

0.0
0

5

10

15

20

25

0

Ship's Age ( year )

5

10

15

20

25

Ship's Age ( year )Figure 1 Statistical analysis of thickness measurement data of structural members of tankers
The conclusions drawn from the figure are:
The mean value of thickness diminution of upper deck plating that is exposed to severe corrosive
environment exceeds the estimated value at the cumulative probability of 70% in seven ships among75 ships. And the “mean + 2 times standard deviation” value exceeds the estimated value at the
cumulative probability of 98% in only 5 ships.
(2) The ”mean + 2 times standard deviations” value of side shell plating and structural members in ballast
water tanks the environment of which is less corrosive than upper deck exceeds the estimated value atthe cumulative probability of 98% in none and 1 ship, respectively.
(3) The individual mean value of thickness measurement for most of the ships is lower than the estimatedvalue at the cumulative probability of 50%.
(4) The thickness measurement data of structural members other than upper deck plating, side shell
plating and internals of ballast water tank also have similar tendencies as in item (2).
These conclusions show that, except for a small number of ships with poor maintenance, steel renewal is
not required if structural members have sufficient corrosion additions according to the estimated corrosion
value at the cumulative probability of 90% for 25 years. Therefore the corrosion additions are determinedbased on the estimated corrosion at the cumulative probability of 90% for 25 years.
Tables 1 and 2 show the estimated corrosion at the cumulative probability of 90% for 25 years for structuralmembers of tankers and bulk carriers respectively.
(1)

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JBP – IACS Common Structural Rules for Bulk Carriers

Table 1 The estimated corrosion for structural members of tankers Unit mm
Structural Member
Upper Deck Plate
Side Shell Plate
Bottom Plate
Longl. Bhd. Plate
Trans. Bhd. Plate
Deck Longl.
Deck Trans. Web / Face
Horizontal Girder Web / Face
Cross Tie Web / FaceL. Bhd. Longl. Web / FaceL. Bhd. Trans. Web / Face
Side Longl. Web / Face
Side Trans. Web / Face
Bottom Trans. Web / Face
Bottom Longl. Web / Face

COT
2.93
1.90
4.05
1.92
2.35
1.94
2.07 / 2.36
2.03 / 2.89
1.84 / 1.90
1.85 / 1.87
2.50 / 1.93
1.85 / 1.87
1.99 / 2.01
2.41 / 1.94
1.88 / 1.90

WBT
2.19
1.79
3.15
2.00
2.34
1.81
1.90 / 2.73
1.90 / 2.77
1.69 / 1.81
1.68 / 1.71
1.48 / 1.94
1.68 / 1.71
2.36 / 2.00
1.38 / 1.74
1.73 / 1.74

Table 2 The estimated corrosion for structural members of bulk carriers Unit mm
Structural
Member
Bhd. Plate

Hold Frame

Position
Lower
MiddleUpper
Lower
MiddleUpper

Lower Stool
Upper Deck Plate
Hatch Coaming
Bottom Plate
Side Shell Plate
Inner Bottom Plate
Sloped Plate in TST
Sloped Plate in BHT
Floor
GirderLongl. in DBT & BHT
Longl. in TSTTrans. Ring in BHT
Trans. Ring in TST

Cargo Hold
DW<50,000
50,000 d DW
1.98
4.35
1.98
4.17
1.82
4.40
2.42
3.99
2.42
3.80
1.92
3.49
2.09
5.50
DW<50000
3.82
1.71
*
*
3.29
1.78
2.06
*
*
*
*
*
*

Ballast Hold
DW<50,000
50,000 d DW
2.06*
3.28
2.06*
4.62
1.92*
3.14
2.42*
2.93
2.42*
2.85
3.62*
3.45
3.68*
5.53
50000 d DW
3.66
2.79
1.92
2.91
4.86
2.95
3.83
2.27
2.34
2.17
3.12
2.39
3.40

*: indicates that the estimated value is unreliable or estimation is not possible due to the lack of thickness measurement dataor the data is taken from ships of similar age.

Further to the above considerations, corrosion addition of structural members in fuel oil tanks, fresh watertanks and their boundaries are also evaluated so that corrosion addition can be specified for all structuralmembers of the ship. The results are summarized below:
1.1.1 Keel plate and bottom shell plating
In the current class rules, the keel plate is required to have a thickness 1.0 or 2.0 mm above the adjacentbottom plating thickness. This was provided based on the assumption that the keel plate corrodes faster as it
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JBP – IACS Common Structural Rules for Bulk Carriers

is difficult to paint the keel block due to docking blocks in the dry dock. However, this effect could not be
observed from the corrosion analysis mentioned above, though the thickness measurement data of keel
plate is also included in the bottom plating. Gathering 684 thickness measurement data for bottom platingand 103 data for keel plate of general cargo ships and bulk carriers of age of 14 to 24 years, statisticalvalues like the maximum diminution value, average diminution value, etc are investigated. Figure 2 shows
the result of the investigation which clearly indicates that thickness diminution of keel plate is not different
from that of bottom plating.
Average thickness dim inution(Keelplate V.S.O therbottom shell)

M axim um thickness dim inution(Keelplate V.S.O ther bottom shell)

1.400

5.000

Keelplating
O therbottom shell
Estim ation

Dim inution (m m )1.000

Keelplating
Otherbottom shell
Estim ation(90%)
Estim ation(98%)

4.500

0.800
0.600
0.400

4.000
3.500
3.000
2.500
2.000
1.500
1.000

0.200

0.500

0.000

0.000
10

12

14

16

18

20

22

24

26

10

12

14

Ship's age (year)

16

18

20

22

24

Ship's age (year)

Figure 2 Thickness diminution of keel plate and bottom plating
1.1.2 Thickness diminution of structural members in fuel oil tanks (FOTs) and their boundaries
Structural members in FOTs are generally examined visually for corrosion at periodical surveys, andthickness measurement is dispensed with if the condition is found satisfactory. Therefore, thickness
measurement data of structural members in FOTs or lubricated oil tanks are very limited. About 320
thickness measurement data of three general cargo ships of age 12 to 20 years were collected from among
the massive thickness measurement data. The maximum diminution was 0.6mm at about 20 years and theaverage diminution was 0.3mm. A simple extrapolation to 25 years gives the maximum diminution of
1.0mm. From this result, the value for corrosive environment in such oil tanks is considered to be 0.5mm
for one side which is the same for void space as given in Table 3.
On the other hand, the boundaries of FOTs, especially the boundary plate between FOT with heated fuel oil
and water ballast tank (WBT), have heavier corrosion than those within the tanks. In order to confirm thisinference from the thickness measurement data, about 360 thickness measurement data from ten ships ofage 12 to 20 years are sampled. A maximum value of 2.7mm, an average value of 1.0mm and a 90percentile value of 2.4mm at about 20 years are obtained from the statistical analysis of the data. The
sampled data are of the boundaries between FOT and WBT within double bottom. This result is shown in
Figure 3.
3

Max.

Ave.

2.5

Diminution (mm)Dim inution (m m )

1.200

2

90% probability value
for girder in WBT
1.5

1

0.5

0
0

5

10

15

20

25

Ship's age (years)

Figure 3 The thickness diminution of boundaries of FOT loaded with heated oil

Page 4 of 10

26

JBP – IACS Common Structural Rules for Bulk Carriers

An extrapolation to 25 years using this result gives the 90-percentile value of 2.9mm. The value of
corrosion addition on one side in WBT is given as 1.2mm from Table 3 and 0.5mm in FOT from the result
mentioned above. Therefore, the corrosion value of 1.2mm due to heated fuel oil effect is obtained by
reducing 1.2mm for WBT and 0.5mm for FOT from 2.9. This effect is limited to the boundaries between
FOTs and WBTs and does not appear in other boundaries such as bottom plate that is always cooled down
by seawater.
1.1.3 Fresh water tanks (FWTs)
Similar to FOTs, thickness measurement of structural members in fresh water tanks is also seldom carriedout, and therefore the thickness measurement data of structural members in FWT is very limited. From thesampling of 22 thickness measurement data of three ships of age 12 to 18 years, the maximum diminution
was found to be 0.4mm, and the average was 0.1mm at about 18 years. Therefore, the value of corrosive
environment in FWTs is considered to be 0.5mm.
1.1.4 Lower bracket of hold frame
Thickness measurement data of hold frames is classed into 3 categories; upper part, middle part and lower
part. Thickness measurement data of the lower part and upper part of hold frame include the data of both
webplate and faceplate of frames and their bracket. However, lower brackets of ships of deadweight
50,000 tons and above are considered to be more corroded than lower part of hold frame because stress on
the lower bracket is higher than that on the webplate and faceplate of lower part of hold frame. This effectis considered as the additional corrosion effect for lower brackets.
1.1.5 Classification of bulk carriers
Corrosion phenomenon of structural members in cargo holds of bulk carriers strongly depends on the kindof loaded cargo. The kind of cargo is closely related to the deadweight of the ship; ships of deadweight
50,000 tons and above mainly load iron ore and/or coal, and ships of deadweight under 50,000 tons mainly
load cargo other than iron ore and coal. However, since the kind of loaded cargo is more related to theship’s length than ship’s deadweight, the bulk carriers are classed into 2 categories corresponding to theirlength; ships of length 200 m and above, and ships under 200m in length.
On the other hand, IACS Unified Requirements S25 (UR/S25) regarding harmonized notations and design
loading condition has been adopted in 2002. In this UR, bulk carriers having length of 150m or above areclassed into 3 categories with notation BC-A, BC-B and BC-C. Corresponding to this classification of bulk
carriers, the draft guideline for corrosion addition of bulk carriers and tankers submitted to IACS WP/S
specifies that bulk carriers classed into BC-A and BC-B ships mainly carry iron ore and/or coal, and BC-C
ships and ships of length under 150m mainly carry cargo other than iron ore and coal.
Further, ballast hold for all bulk carriers is used both as ballast hold and cargo hold. Since thickness
diminution of structural members in ballast hold is smaller than that of cargo hold, corrosion addition of
structural members in cargo hold is applied to that in the ballast hold.
Based on these results, the corrosion value of each corrosion environment for double hull tankers and bulk
carriers is given in Table 3. The corrosion addition is obtained by summing up the values given in Table 3
corresponding to the environment on the two sides of the structural member plus reserved corrosion margin(0.5mm). This corrosion addition value is corresponding to the value obtained by mean + 2 times standard
deviations at 25 years.
In this case, rounding operation to the nearest 0.5mm could not be accepted. This is because the corrosion
value is derived based on the corrosive environment corresponding to actual corrosion phenomenon, androunding off of this figure may result in too large or small value. Therefore, the corrosion addition should
be expressed in 0.1 mm increments without rounding off.

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JBP – IACS Common Structural Rules for Bulk Carriers

Table 3 The corrosion value for different corrosive environments (the values are given for one sideof the structural member)Corrosive environment
Main environment

Additional factor

Corrosion value
(mm)
1.1

In COT

TopsidetankHigh temperature

1.1 + 0.5

High stress

1.1 + 0.3

Pitting effect

1.1 + 1.6

High temperature

1.7High stress

1.7 + 0.3

In WBT
Other
than
above
Upper
part

In cargo holdof BC-A and
BC-B ships

Middleand lower
parts

Upper
part
In cargo holdof BC-C
ships or shipsof length
below 150m

Middlepart andlower part

1.2
High stress

1.2 + 0.3

Members not between
cargo holds
Boundary between
cargo holds
Members not between
cargo holds
Lower bracket
Boundary between
cargo holds
Horizontal member
Slant plate of lower
stool
Members not between
cargo holds
Boundary between
cargo holds
Members not between
cargo holds
Boundary between
cargo holds
Horizontal member
Slant plate of lower
stool
Horizontal

Atmosphere

Vertical

1.8
2.0

2.0 + 0.2

Transverse bulkhead

1.8 + 0.2 + 1.7

Inner bottom plate, sloping
plate of bilge hopper tank

2.0 + 0.2 + 2.2

Slant plate of lower stool

1.0

Hold frame and inner sideskin plating

1.0

Transverse bulkhead

1.0 + 0.2

Hold frame and inner sideskin plating

1.0 + 0.2

Transverse bulkhead

1.0 + 0.2 + 1.2

Inner bottom plate, sloping
plate of bilge hopper tank

1.0 + 0.2 + 1.0

Slant plate of lower stool

1.7

Exposed upper deck plating
Side shell plating and hatchcoaming
Side shell and bottom shell
plating
Internal members in FOT
Tight girders and floors
between FOT and WBTInternals in such spaces

1.0

Void spaces, FWT

Boundary between
FOT and WBTTransverse bulkhead

1.8 + 0.2 + 0.3

0.5
FOT

Structural member other thanthose mentioned below
Deck plating
Faceplates of girders andtransverses
Inner bottom plating
Structural member other thanthose mentioned below
Faceplates of girders andtransverses
Structural member other thanthat mentioned below
Faceplates of girders andtransverses
Hold frame and inner sideskin plating

Hold frame and inner sideskin plating
Lower bracket

1.8 + 0.2

1.0

Sea water

Applicable structural member

1.7
0.5

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JBP – IACS Common Structural Rules for Bulk Carriers

1.2 Application of corrosion addition
1.2.1 Corrosion addition for local strength members
Corrosion addition is applied to the local strength member according to the definition of net scantling
approach. That is, the necessary minimum scantling of a structural member t gross _ required is given by adding
the necessary scantling from the strength point of view t Net and corrosion addition t CA . This is obvious fromthe basic assumption of local strength assessment.
Generally, the necessary scantling from the strength point of view t Net given by the scantling formula isexpressed in increments of 0.1mm by rounding off the two decimal places to the nearest single digit. Also
the corrosion addition t CA is expressed in increments of 0.1mm as mentioned above. Therefore, thenecessary minimum scantling of a structural member t gross _ required is also expressed in increments of 0.1mm.
Though current classification rules for hull structure do not allow the actual scantling to be less than thatobtained from the rule formula, conventionally classification societies may accept a smaller scantling
expressed in increments of 0.5mm obtained by rounding off to the nearest 0.5 mm that may correspond to
the nominal thickness of rolled steels which comes in increments of 0.5mm. This is possible becauset gross _ required is considered to have sufficient safety margin including corrosion, and hence the safety margincompensates for the reduction in scantling due to rounding down in the current rules. However, in the net
scantling approach, such a rounding down will result in the reduction in values of t Net or t CA which is not
appropriate. As the solution, the following 3 approaches may be adapted in the new structural rules.
(1) t gross _ required is expressed in intervals of 0.1mm and rounding down is not accepted.
(2) t gross _ required is rounded up to the nearest higher 0.5mm unit
(3) Both t Net and t CA are rounded up to the nearest 0.5mm unit
Since the approach specified in above (1) is in terms of 0.1mm unit, it will require a great deal to order,
produce, and control rolled steels and it will be likely that the problem of minus tolerance of thickness ofrolled steels is brought to the scantling requirements. On the other hand, the approach (2) or (3) is not
likely to have the above problem. Furthermore, the approach (3) results in scantlings 0.25mm greater thanthat specified in (2). The designers and some owners may not welcome the approach (3) because of theweight increase due to the addition of 0.25mm on an average, but some owners may welcome this due tothe merit of increased wastage allowance. Since the proposed corrosion addition is sufficient to minimize
the steel renewal of structural members for a ship which is properly maintained, approach (2) is considered
to be an optimal one.
1.2.2 Corrosion addition for global strength members
The strength assessment of major load carrying structural members such as transverse girders is carried out
considering the mutual interaction of such members covering a wide extent of the structure rather thanusing simplified scantling formula such as for a local strength member. Generally, finite element analysis(FEA) is widely used for the strength assessment of such structures. In FEA, a wide extent of the structure
is modeled in order to consider the mutual interaction of primary supporting members and the structural
response of the whole structure when the loads act on them is obtained. In this case, when the thickness
diminution of one structural component is uniformly reached its corrosion addition value, it is mostunlikely that the rest of the structure also has reached its corrosion addition value from the viewpoint ofprobabilistic theory. Normally, corroded areas and less corroded areas are scattered in the structure at
random. The structural response in the corroded condition mentioned above is considered equivalent tothat in uniformly corroded condition with average diminution. In this case, it is necessary to consider the
average corrosion value of all the structural members, but it is a complicated task to prepare the average
corrosion value of each structural member that has a different corrosion addition value. The average
corrosion value is nearly equal to half the corrosion addition of each structural member. Therefore, half thecorrosion addition value is applied to the structural strength analysis of primary supporting members inusing the FEA. Hence the actual structural model for FEA is prepared by reducing half the corrosion
addition value from the original scantling in the drawings, and strength assessment is carried out. Hullgirder strength assessment and ultimate strength assessment for hull girder when a ship is regarded as asimple girder are also carried out in the same manner.
When assessing the buckling strength of panel elements of shell plating and web plate of primary
supporting members, the stress acting on the panel element estimated from the result of the FEA is used.
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JBP – IACS Common Structural Rules for Bulk Carriers

However, critical buckling stress of the panel element is calculated using the scantling obtained by reducing
the full corrosion addition from the original scantling because the panel element is regarded as a local
strength member.
1.2.3 Corrosion addition for fatigue strength assessment
Fatigue strength of structural members can be assessed by the cumulative damage estimated against thecyclic loads encountered by the ship during her design life. The scantling of the structural member varies
from no thickness diminution at the initial stage to thickness diminution equal to the corrosion addition at
the end of the design life. However, it is not practical and is very difficult to consider the diminution of thescantling which varies over time in fatigue strength assessment. Therefore fatigue assessment considering
the corrosion effect is generally used instead of considering the actual scantling diminution. In this case, itis necessary to consider many coefficients of corrosion effect for every corrosive environment because thecorrosion effect depends on the environment to which structural members are exposed. Thus this method is
also seemed to be impractical. Assuming that the thickness diminution is zero prior to service andthickness diminution reaches full corrosion addition at the ship’s design life, the average diminution can behalf the corrosion addition through the ship’s design life. Therefore, half the corrosion addition can beapplied for fatigue strength assessment.
2 Wastage allowance in the current rules and the net scantling approach
2.1 Wastage allowance for the local strength member
The current classification rules give scantlings that are necessary to prevent structural damage mainly basedon extensive experience, but it is not clear what is the actual scantling that is sufficient enough. Further the
lower acceptable level of structural strength due to corrosion is also not clear. Surveys of the ships inservice have been carried out by experienced surveyors using specified wastage allowance set as apercentage of original thickness based on experience. For that reason, the chances of causing serious
problems due to corrosion are very limited.
For example, in the case where the thickness diminution limit of the upper deck plate is 20% of the original
thickness at the midship region and the thickness of the whole upper plate is worn out about 20% of theoriginal thickness, the section modulus of the transverse section also reaches 80% of the original. And thiscase is never accepted from the viewpoint on longitudinal strength of hull girder in the current rules.
Therefore wastage allowance criteria for the transverse section modulus are defined in the current
classification rules to ensure sufficient hull girder strength. The more critical criteria among the twowastage allowance criteria mentioned above are applied in actual survey of ships in service. For theexample case mentioned above, wastage allowance is 10% diminution of the original thickness. The
wastage allowance criteria from a similar point of view are also applied to the bottom plates which
contribute to the longitudinal strength of hull girder. In case of inner bottom plating, since it is close to theneutral axis of transverse section, the wastage allowance is set as about 20% of the original thickness.
Considering the example of a Cape size bulk carrier with deck plating 38mm, inner bottom plating 25mm,
and bottom plating 20mm, the wastage allowance and proposed corrosion addition mentioned above is
given in Table 4.
Table 4 Current Wastage allowance and proposed corrosion addition
Original
thicknesst
Upper deck plating

38mm

Inner
plating

25mm

bottom

Bottom plating

20mm

Wastage allowancefrom the viewpoint oflocal strength
8.6mm (20% *t +1mm)
6.0mm (20% *t +1mm)
5.0mm (20% *t +1mm)

Wastage allowancefrom the viewpointof longitudinalstrength

Proposed Proposed
wastagecorrosion
allowance addition

3.8mm

3.5mm

3.9mm

5.0mm

5.0mm

5.4mm

2.0mm

2.5mm

2.7mm

In can be concluded that the proposed wastage allowance is approximately equal to the current actualwastage allowance criteria applied in actual survey. Therefore, the proposed wastage allowance andcorrosion addition provide a sufficient value considering the actual wastage allowance in the new structural
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JBP – IACS Common Structural Rules for Bulk Carriers

rule based on the net scantling approach

2.2 Wastage allowance for the global strength member
As mentioned before, the global strength of structural members is assessed using scantlings obtained by
reducing half the corrosion addition from the original scantling. The result of hull girder strength
assessment considering this approach is given in Figure 4 which shows that the transverse section modulus
considering half the corrosion addition is nearly equal to 90% of the original value, which can be thewastage limit from the viewpoint of longitudinal strength. Thus the strength assessment of global structuralmembers considering half the corrosion addition implies the strength assessment of structural members
whose scantlings reach their wastage limit. In this case, since some structural members are assumed toreach the wastage limit from the viewpoint of local strength, the wastage limit of structural members is
dealt with in the same manner as the local strength member. However, the actual wastage limit from theviewpoint of longitudinal strength is judged based on the actual thickness measurement data. Therefore, thetreatment of the wastage allowance of global structural members mentioned above depends on accurate
thickness measurement.
1.000
0.915

0.907

0.899

0.906

0.904

0.896

0.889

0.900

0.904

0.888

0.901

0.800
0.700
0.600
0.500
0.400
0.300
0.200
0.100

(B
ot
to
m

)

(D
ec
k)

BC

BC

Ca
pe

Ca
pe

S
SS

SS

S

ax
Pm
SS
S

Pm

ax

BC

BC

(B
ot
to
m

)

(D
ec
k)

)
(B
ot
to
m
SS
S

S
SS

SS

S

Ha
nd
y

Ha
nd
y

BC

BC

(D
ec
k)

)
Ta
nk
er
(B
ot
to
m

Af
ra
DH

)

Ta
nk
er
(D
ec
k)

DH

Af
ra

(B
ot
to
m
VL
CC

DH

DH

VL
CC

(D
ec
k)

0.000

Figure 4 Transverse section modulus considering half the corrosion addition
In using FEA for the strength assessment of global structures such as structures within the cargo holdregion, half the corrosion addition is taken as the average thickness diminution. Full corrosion addition isconsidered for buckling strength assessment. Therefore, the wastage allowance of structural members
whose scantling is determined by FEA is also the same as the wastage allowance for local strength member.
3 Conclusions
The conventional method based on the corrosion rate obtained by dividing the thickness diminution by theelapsed years cannot explain the actual corrosion phenomenon of structural members. However the
corrosion progress process model newly developed based on the probabilistic theory can explain the actual
corrosion phenomenon. This is because the probabilistic parameters of the corrosion process model are
identified by using more than half a million thickness measurement data sampled considering coated ballast
tanks and cargo holds, uncoated cargo oil tanks, and maintenance condition of individual ships.
The conclusions of this study can be summarized as follows:(1) The estimation period of corrosion diminution is 25 years which is the average age of scrapped ships.
(2) The estimated corrosion at the cumulative probability of 90% gives a sufficient level because thePage 9 of 10

JBP – IACS Common Structural Rules for Bulk Carriers

thickness diminution of most of the structural members of ships that are properly maintained does notexceed the estimated corrosion values during their life.
(3) Based on the estimated corrosion, the wastage allowance is defined which minimizes the steel renewalof structural members during the ship’s design life as given the following formula.
t wastage _ allowanceroundup 0.5 (t CA  t c 2 )This wastage allowance is close to the actual current criteria on wastage allowance applied in thesurvey of ships in service.
(4) The wastage allowance is defined for each side of the structural member as the corrosive environment
to which each side is exposed may be different. The total corrosion addition t CA is obtained by adding
the corrosion addition value of one side t C1 and that of the other side t C 2 plus 0.5mm taken as t reserve ,which are expressed in increments of 0.1mm. Where t reserve (=0.5mm) is the thickness in reserve toaccount for anticipated maximum thickness diminution t hat may occur during the assumed inspection
intervals of 2.5 years after the thickness measurement. Then corrosion addition value is nearly equal tothe estimated corrosion diminution taking into account the 2 standard deviation at 25 years.
(5) The scantling of a structural member consists of two necessary minimum components as follows:
One is t Net which is the net scantling required from the structural strength viewpoint that should be kept
throughout the design life of the ship. The other is the corrosion addition t CA which corresponds to theestimated thickness diminution during the design life of the ship plus t reserve . The estimation ofrational corrosion addition makes the introduction of the net scantling approach to the new structural
rules.
(6) The required scantling of local structural members t gross _ offered is obtained by the following formula.
t gross _ required

roundup 0.5 (t Net  t CA )It is preferable that t gross _ required is rounded up to the nearest higher 0.5mm.
(7) Transverse section modulus considering half the corrosion addition is about 90% of the original value
which corresponds to the wastage allowance from the viewpoint of hull girder longitudinal strength.
Wastage allowance for global structural members can be obtained using the same formulation as for
local structural members.
(8) Global strength members such as those contributing to the hull girder strength can be assessed by FEA
considering half the corrosion addition.
(9) Fatigue strength of structural details can be assessed considering half the corrosion addition as a mean
thickness diminution during the design life of ships.

Page 10 of 10

KC#647㪪㫌㫄㫄㪸㫉㫐㩷㫆㪽㩷㪢㪚㩷㫀㫋㪼㫄㫊㩷㫆㫅㩷㫎㪼㪹㩷㫊㫋㫀㪽㪽㪼㫅㪼㫉㫊㩷㪽㫆㫉㩷㫇㫉㫀㫄㪸㫉㫐㩷㫊㫌㫇㫇㫆㫉㫋㫀㫅㪾㩷㫄㪼㫄㪹㪼㫉㫊㪅㪚㪿㪸㫇㫋㪼㫉㩷㪍㪚㪿㪸㫇㫋㪼㫉㩷㪊㪪㪼㪺㫋㫀㫆㫅㩷㪉㪪㪼㪺㫋㫀㫆㫅㩷㪍
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KC#702(Primary supporting member)(2-b)(Bracket)
(2-a)

(2-c)
(Ordinary stiffener)

(1-b)

(1-a)

1. The section of the bracket and the stiffener;
1-a. at the end of the stiffener.
1-b. at the mid-point of the free edge of the bracket.
In case 1, is the snipped flange of the stiffener included in the calculations?
2. The section of the bracket;
2-a. normal to the free edge of the bracket.
2-b. at the end of the stiffener.
2-c. attached to the stiffener.
2-d. smaller of 2-b and 2-c.

KC#758

C.L.

hS

hCL

Inner Bottom

KC#827

PIPE TRUNK, running through whole
the cargo area length

FOT
SWBT

DBWBT

KC#871
Comment/question, 31st July 2008

Chapter 3 Section 6 “Structural Arrangement
Principles”
Re: 10.4.7 – Lower Stool – Rule includes, the inadequately discussed changes
proposed in “Corrigenda 5” as quoted below by ignoring our previous comments:
Quote:
Where corrugations are cut at the lower stool, corrugated bulkhead plating is to beconnected to the stool top plate by full penetration welds. The stool side plating is tobe connected to the stool top late and the inner bottom by either full penetration or
deep penetration welds. The supporting floors are to be connected to inner bottom
by either full penetration or deep penetration weld.
UnquoteVersus the following text as submitted by IACS UR S18 (1998) to IMO for the
inception of SOLAS Ch. XII.
Quote:
Where corrugations are cut at the lower stool, corrugations and stool side plating
are generally to be connected to the stool top plate by full penetration welds. The
plating of lower stool and supporting floors is generally to be connected to theinner bottom by full penetration welds.
IACS should really consider very closely their submittals to IMO for the development
of SOLAS Ch. XII and assure their similarities and consistency. Unless IACS wishes
to resubmit the bulkhead welding requirements to IMO with proposed changes forapproval by all IMO Administrations, such changes should be avoided.
Until such time we hereby request IACS to replace the text as per the original CSR
wording that is in agreement with IACS UR S18 originally submitted to IMO.

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KC#944

Deck Plate 1

Deck Plate 2

KC#1077
Dear sir,
Chapter 3, Section 6

Common Structural Rules for Bulk Carriers

5.7 Cut-outs and holes
5.7.1
Cut-outs for the passage of ordinary stiffeners are to be as small as possible and well roundedwith smooth edges.
The depth of cut-outs is to be not greater than 50% of the depth of the primary supporting
member.

Section 8 Common Structural Rules For Oil Tankers

SECTION 8.2/PAGE 24
2.6.1.7 Webs of the primary support members are to have a depth of not less than given by
the requirements of 2.6.4.1, 2.6.6.1 and 2.6.7.1, as applicable. Lesser depths may be
accepted where equivalent stiffness is demonstrated. See 3/5.3.3.4. Primary support
members that have open slots for stiffeners are to have a depth not less than 2.5
times the depth of the slots.
SECTION 8.3/PAGE 53.3.3.5 The web depth of primary support members is not to be less than 14% of thebending span and is to be at least 2.5 times as deep as the slots for stiffeners if theslots are not closed.
SECTION 8.4/PAGE 54.3.4.4 The web depth is to be not less than 2.5 times the web depth of the adjacent frames
if the slots are not closed.
SECTION 8.5/PAGE 7
5.3.3.5 The web depth of primary support members is not to be less than 14% of thebending span and is to be at least 2.5 times as deep as the slots for stiffeners if theslots are not closed.
For tankers, D>=2.5d, then d<=40%D. It could be described as " The depth of cut-outs is to be
not greater than 40% of the depth of the primary supporting member."I suggested the requirement in two rules to be harmonized as well as the names 'cut-out' and 'slot'.