IACS Common Structural Rules Knowledge Centre

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

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer224

9/2.3.1.2

Question

stiffeners

This requirement is excessive than our experience. In structural design,
2006/11/22 stiffeners are suitably arranged on floors to prevent excessive vibration ofthem. And scantlings are determined taking account of vibration.

The CSR doesn't take into account the vibration effects for the scantlings, as itis outside the scope of classification.The floor webs are to be stiffened enoughto withstand the forces induced by rudder post, propeller post and rudder
horn.As a direct calculation of floors and their stiffening arrangement isgenerally never carried out in this area, it is preferable to indicate a value forthe maximum spacing of web stiffeners.

225

9/3.3.1.3

Question

frame
spacing

This requirement is excessive than our experience. This requirement should
2006/11/29 be reconsidered taking account of present designs.Please revise the rule asfollows, or delete the rule:"not greater than 5 frame spacing

According to the last sentence of [3.1.3], wider spaces may be accepted
based on the discretion of the Society. This sentence has been added torespond the comments from Industry. Therefore, the text is kept as it is.

227

9/4.5.3.1

Questionshear area

2006/11/22 It seems that the equation of Ash is missing. Please confirm.

The formula is not missing, but the words "and the shear area Ash, in cm2,"
should be deleted.

9/2.5.1.3

Connectionof aft peak
Question
structure withrudder horn

249
attc

269

270

Table
9.1.2

Table
9.2.2

Question

Question

2006/12/1

The vertical extension of the hull structure is required not to be less than thehorn height. This requirement is considered primitive without detailed strength
basis. Normally, the vertical extension is between outer shell and steering
The feedback is noted and we will consider a rule change proposal.
gear flat and there may be many designs that could not comply with thisrequirement. Please delete this requirement or amend it considering strength
basis.

Y

Min plate
thickness

We can not see the reason for IACS to change the coefficient from 0.7 to 0.9
on the denominator of the second term in the equation. The proposal will
reduce the required plate thickness at intact condition and bow flare area. We
2006/11/23
would like to stress that plating cannot be treated in the same way as a IACS
stiffener where the corresponding coefficient is 90% (i.e. 0.9) of the yielding.
Propose to remain as it is.

The reason of changing the coefficient from 0,7 to 0,9 is a matter of editorial
correction, which was forgotten at the time of publication.This coefficient if
normally equal to 0,9 as defined in Table 6 in Chapter 6, Section 1 for platings
not contributing to the hull girder longitudinal strength.

Min plate
thickness

We can not see the reason for IACS to change the coefficient from 0.7 to 0.9
on the denominator of the second term in the equation. The proposal will
reduce the required plate thickness at intact condition and bow flare area. We
2006/11/23
would like to stress that plating cannot be treated in the same way as a IACS
stiffener where the corresponding coefficient is 90% (i.e. 0.9) of the yielding.
Propose to remain as it is.

The reason of changing the coefficient from 0,7 to 0,9 is a matter of editorial
correction, which was forgotten at the time of publication.This coefficient if
normally equal to 0,9 as defined in Table 6 in Chapter 6, Section 1 for platings
not contributing to the hull girder longitudinal strength.

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IACS Common Structural Rules Knowledge Centre

KCID
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271

9/5.2.4.3

301

9/5.1.5.1& Table
9.5.2

Type

Topic

Date
completed

Question/CI

Answer

Attachment

Questionwatertight2006/11/23

IACS's proposal to change the word "watertight" into "weathertight" is not
acceptable unless there is a Load line coaming. Propose to retain watertight.

The change from watertight to weathertight is correct. LL Regulation requests
a coaming heigth of 600mm for Pos.1 and 450mm for Pos.2. Subject to thisthe access hatches need to be weathertght only. In the CSR text in para. 2.4.1
we refer to the required coaming height. Consequently the access hatches asmentionend under para. 2.4.3 have to fulfill the requirement 'weathertight'. We
assume the questioner has mixed this with flushdeck hatches. They have to
be watertight.

Question

Allowable
stresses ofexternal
Pressure

The external Pressure of 0.8 / 0.46 ReH allowable stresses in table 2 of Ch 9,
Sec 5, 1.5.1, it is subjected to Ch 4, sec 5, [2], we think that the correct one
2006/12/21 should be subject to Ch 4, sec 5, [2.2]; the other loads are water ballast load,cargo load and container load etc. If not, please inform us what other loads
are with the detail load.|

The Table 2 of Ch 9 Sec 5 is correct. The other loads specified in Table 2 areinterpreted as internal loads such as inertia pressure due to water ballast inballast hold.

hatchcoaming

Regarding to the load point, some classes require to use the hatch cover top,
but others are still on the top of hatch coaming yet. Which is correct one, on
top of hatch cover or top of coaming? If the load point is based on top of
coaming, the sea load can be reduced a hatch cover depth height (900-1200mm) from coaming to hatch cover top. We propose that load point on top ofcover is for the sea load, on top of coaming is for water ballast load.

The proposal is agreed, but should be more specific on the location of the load
point. Regarding the second and last points in Ch 9, Sec 5, [4.2.1], we willconsider the rule correction as follows: "- transversely, at hatchway side, vertically, at the top of the hatch cover for sea pressures, and at the top of thehatch coaming for internal pressures due to ballast water."

304

9/5.4.2.1

Question305

9/5.7.5

Cleat forQuestion water ballast
load

Because the internal WB loads of CSR are very large on hatch cover bottom
2006/12/26 side, we advice that an allowable stress of cleat is needed, and propose it is0.9-1.0 ReH. As some class have an allowable and some have not it.

309
attc

Ch 9/ 5

Question

2006/12/21

Regarding to the triangular load like water ballast, both way of triangular load The load cases are “H1” and “H2”, the internal pressure due to water ballast in
and average uniformed load may be used based on class by class or local
ballast hold is treated as uniform load. The load cases are “P1”, “P2”, “R1” andoffice by office, but both calculation results is very different. What’s CSR“R2”, the internal pressure due to water ballast in ballast hold is treated as
standard for folding and side rolling hatch cover from 1 to 5 (see attachment)? triangular load.

2007/1/31

For ships greater than 150 m in length, Ch 6, Sec 4 requires normally FEA
analysis. However, in the fore and aft parts, it seems that prescriptive
formulae may be used instead of FEA. In such a case, the requirements in Ch
6, Sec 4, [2.6] may also be considered as being applicable to primary
supporting members in fore and aft parts for ships greater than 150m. We
will consider the further rule development about the application of FEA tocargo areas outside midship region and determination of the scantling ofprimary supporting members outside midship cargo regions for ships of 150m
in length and above.

312

9/1.4.4.4
Question& 9/2.4.3.4

hatch cover

FEA

2007/1/31

Which sub-section should be adopted to determine the scantlings of deckprimary supporting members of the fore part and the aft part in accordancewith Ch 6/Sec.4? For example, if the ship length L is 150m or above, thedirect strength analysis would be applied according to the provision specified
in Ch 7(see Ch 6/Sec 4/[1.3.1]), but the procedure in Ch 7 is applied on the
cargo hold structures in midship area.

As [7.3] and [7.5] are coming from UR S21, the dimensioning of cleats iscovered under [7.3.5], whatever the loads are.

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KCID
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Type

Topic

Date
completed

Question/CI

Answer

Attachment

2007/2/8

We would like to confirm a way to apply the requirement of this sub-paragraphto a structural member shown in the attachment.
(1) Which position, A, B or C, shown in Figure, is to be selected to calculate
w0 and I0? We consider that position B is suitable for this requirement. Pleaseconfirm.
(2) Which position, A, B, C or else, is to be considered when the requirementof net section modulus of ordinary stiffeners, w, is applied? We consider that
position A is appropriate for this requirement. Please confirm.

According Fig. 1 a symmetrical beam with l_1 < 0.5 l_0 is the basis for thissimplification. The example in the attachment is not covered by theassumptions of the requirement, i.e., a symmetrical beam. For an
unsymmetrical beam as shown the attached document, the calculation should
be carried out by direct calculations or beam analysis as stated in [5.4.1].

Y

336
attc

9/5.5.5

Question

376

Table
9/3.7.2 &Table 2

Question net thickness

2007/1/24

Ch.9 Sec.3 [7.2] Table 2. We assume the bedplate net thickness is in mm, not
We agree with the comment and will consider a rule amemdment proposal.
m.

377

9/5.2.2

Question

2007/1/24

Ch.9 Sec.5 [5.2.2] The first formula is incorrect? Should read t=10s, not
t=0.01s

We agree with the comment and will consider a rule amemdment proposal.

With respect to the names given in 9/5.5.5.1, considering wCS=w0 gives asection modulus of wCS=w0 only if w1>=0.8*w0, i.e only if the stiffener/PSM's
cross section is not really varying. For 0=<w1=,0.8*w0, the section modulus tobe considered is given by the second formula and is greater than the midspansection modulus w0. In addition, we can consider that the midspan section
modulus w0 is not to be equal to the section modulus of an constant crosssection stiffener/PSM for this calculation; it has to be used for the 9/5.5.5.1. A
similar approach can be applied to inertias. Furthermore, these calculations
can be replaced by a direct approach as it is usually made.

Sectionmodulusformula378

9/5.5.5.1

Question

formula2007/3/12

Our understanding of this item is that the section modulus for a stiffener/PSM
with variable cross section always is to be at least equal to the section
modulus of a stiffener/PSM with constant cross section ( w = wCS ). Thismeans there is nothing to gain by varying the cross section. Example: For asimply supported PSM with constant CS the section modulus at midspan, w0,
will be governing. Our understanding is that for a PSM with varying CS, theminimum section modulus is w0, independent of the position along the axis (w = wCS = w0 ). We have the same problem for moment of inertia. Pleaseclarify.

379

9/5.6.3.1

Question

formula2007/2/22

This formula comes from IACS UR S21, S21.4.2. The constant value 15.98
Ch.9 Sec.5 [6.3.1] What is the background for the factor 15.98 in this formula?
is obtaind from muttiplying 14.9 by squareroot of 1.15 (=Scoam specified in
Is it a misprint for 15.8?
UR S21.4.2). Therefore, the formula is correct.

2007/10/8

Ch.9 Sec. 3 [7.2] Table 2
The requirement for net sectional area of bedplates is significantly exceeding
current designs, in some cases by more than 50%.
The requirement for a typical Handymax vessel with current design has
P=9500kW, nr = 130, LE=8.5m
The required bedplate net area is 640cm2. Current design is about 430cm2,
which is a nearly 50% increase.

413

Table
9.3.2 &
9/3.7.2

CI

Net Sectional
area ofbedplates

It was not intended to increase the scantlings compared to current design.
We noted your comment. The following interpretation are prepared and will be
submit it to the Hull Panel for review.
"The net scantlings of the structural elements in way of seatings are to be
determined by the engine manufactures. They are to be checked on the basisof calculation result supplied by the engine manufacturers. If thesecalculations are not supplied, the net scantlings of the structural elements in
way of the internal combustion engine seatings are to be obtained from theformulae in Table 2."

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KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer

According to Ch 3 Sec 2 [2.1.1], the scantling of superstructure anddeckhouses specified in Ch 9 Sec 4 is based on the gross scantling concept.
Also, according to Ch 9 Sec 4, [1.2.1], all scantling and dimensions refered toin [4] and [5] are gross. In the requirement of [4.1.1], [4.2.1], [4.5.1] and[5.3.2], the thickness formulae are given as follows.

468

9/4.4.1.1,
4.2.1,
4.5.1 &
5.3.2

CI

Scantlings ofs/structures&
deckhouses

2009/10/6[4.1.1] t=1.21s*(k*pSI)^0.5+tc,[4.2.1] t=1.21s*(k*PD)^0.5+tc,[4.5.1] t=8s*(k)^0.5+tc,[5.3.2] t=0.9s*(kpA)^0.5+tc
Where, tc is defined as corrosion addition defined in Ch 3, Sec 3, specified in"Symbols". To refference to the corrosion addition defiend in Ch 3 Sec 3means that the scantling is based on the net scantling concept. This isinconsistet with the requirement in Ch 3 Sec 2 [2.1.1] and Ch 9 Sec 4 [1.2.1].
According to Technical Background, these formulae are based on the current
GL Rules. In the original formula, tk instead of tc is used and tk is taken equal
to 1.5mm. Please consider revising the text.

476
attc

477

9/5.1.5.1

9/5.5.2.3

CI

Question

Allowable
stress on
hatch covers

Criticalbuckling
stressAs you pointed out, the reference to the corrosion addition, tc, defined in Ch 3
Sec 3 in the formulae is inconsistent with the requirements in Ch 3 Sec 2[2.1.1] and Ch 9 Sec 4 [1.2.1]. These requirements have come from thecurrent GL Rules and there are no intention to modify the scantling approachconcept specified in Ch 9 Sec 4 [1.2.1]. Therefore, the value of tc used inthese formulae is taken equal to 1.5mm as an interpretation, according to thecurrent GL Rules. This has been reflected in RCN 1-7 to the July 2008 Rules.

2007/8/23

Ch. 9 Sec. 5 1.5.1. Allowable stress on hatch covers:
Reference in the rule text is made to ILLC Reg.15(6) and 16(5).
Regulation 15(6) is relevant for “Hatchways closed by portable covers andsecured weathertight by tarpaulins and battening devices”. The allowablestress for pontoon hatch covers given as Sigma_A = 0.68ReH is originatingfrom Reg. 15(6).
Regulation 16(5) is relevant for “Hatchways closed by weathertight covers ofsteel or other equivalent materials. The allowable stress for “weathertighthatch cover” Sigma_A = 0.8 ReH is originating from Reg. 16(5).
It is our interpretation that 15(6) is not relevant for modern bulk carriers. UR
S21 and UI LL70 are both covering Reg. 16 and relevant for pontoon hatch
covers. We assume that Pontoon hatch covers in modern bulk carriers shouldbe treated as “weathertight hatch covers” with allowable stress Sigma_A =0.8ReH. This is not clear as Table 2 is written in the current rules.

The Common Interpretation is as follows:- If hatch covers are considered weathertight by construction, and without
the need of tarpaulins and battening devices, the allowable stresses to be
used are those corresponding to the line "Weathertight hatch cover" in the
Tab 2, i.e. 0.8ReH for sigma. This is in line with ILLC Reg.16(5).
- If hatch covers are considered weathertight by using tarpaulins and battening
devices, the allowable stresses to be used are those corresponding to the line
"Pontoon hatch cover" in the Tab 2, i.e. 0.68ReH for sigma. This is in line withILLC Reg.15(6).

2007/10/4

Ch. 9 Sec. 5 5.2.3 Critical buckling stress check. Last sentence of therequirement states: “In addition, the bi-axial compression stress in the hatch
cover plating, when calculated by means of finite element analysis, is tocomply with the requirements in Ch.6 Sec.3” We assume the sentence
originates from UR S21 3.6. In case of FEM analysis, please advise if biaxial
buckling in accordance with requirement of Ch. 6 Sec. 3 is additional orinstead of the uniaxial buckling requirement in 5.2.3.

The Common Interpretation is as follows:- If no finite element analysis is performed for the buckling of the hatch coverplating, only the criteria for buckling for uniaxial compression is to be checked.
- If a finite element analysis is performed for the buckling of the hatch coverplating, criteria for buckling for bi-axial compression are to be checked.

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KCID
No.

494

495

500

524

Ref.

Table
9.1.1 &
Table
9.2.1

9/1.3 &
9/2.2

9/1.5.4.1 &9/1.5.4.2

Ch.9,
Sec.1 & 2

Type

CI

CI

CI

RCP

Topic

Fore part &Aft part

Fore part &Aft part load
model

Loaded area
between the
supports ofthe structure
considered

Scantlings ofFore Part
and Aft Part
structures

Datecompleted2007/9/13

2007/9/28

Question/CI

Attachment

Answer

Ref. Ch. 9 Sec. 1 ”Fore Part” Table 9.1.1 and Ch. 9 Sec. 2 “ Aft Part” Table
9.2.1.
Q1: Tables 9.1.1 and 9.2.1 are referring to “Platform”. It is assumed that this is
A1:Platform referred in tables 9.1.1 and 9.2.1 are effectively non-watertighta non-watertight horizontal member. Please confirm.
horizontal member.
A2:Tables 9.1.1 and 9.2.1 are incomplete with respect to horizontal andQ2: Tables 9.1.1 and 9.2.1 are extracts of Table 6.1.2. Tables 9.1.1 and 9.2.1
vertical watertight boundaries, and relevant items of Table 6.1.2 may be used
are incomplete with respect to horizontal and vertical watertight boundaries.
for watertight items in fore/aft part.
Please advise if relevant items of Table 6.1.2 may be used for watertightitems in fore/aft part. Please consider completing the Tables 9.1.1 and 9.2.1
with watertight divisions.

Ref. Ch. 9 Sec. 1 ”Fore Part – load model” [3] and Ch. 9 Sec. 2 [3] “Aft Part load model”
Following pressures are explicitly given for calculation:
1.External pressure according to Ch. 4 Sec.5
it is quite clear that internal pressures defined in Ch 4, Sec 6, [2] need also to
2.Internal lateral pressure in testing condition according to Ch.4 Sec. 6 [4]be considered for fore and aft regions in addition of testing pressures.
Internal pressures due to liquid ps+pw according to Ch. 4 Sec. 6 [2] is not
Also Included in Corrigenda 5
specified for Fore/Aft regions.
Please advise if Ch. 4 Sec. 6 [2] pressures need to be considered for fore andaft regions or if only testing pressures should be applied.

In 5.4.1,Girders
A is given by the following formula.
A=S*l
Where,
S: Spacing of center or side girders under consideration, in m.
l: Span of floors under consideration, in m.

2007/9/28

2007/9/28

In Ch 9, Sec 1, (5.4.1] and [5.4.2], a parameter A defined as "Loaded area
between the supports of the structure considered" is used in the determinationof the net thickness of girders and floors in flat bottom forward area. The
In 5.4.2, Floors
definition of this parameter is not clear enough and needs interpretation, orA is given by the following formula.
formula to calculate it.
A=S*l
Where,
S: Spacing of floors under consideration, in m.
l: Span of center or side girders under consideration, in m.
Also Included in Corrigenda 5

1) The question relates to scantlings of Fore Part and Aft Part structures inflooding condition(Ch.9, S.2, 1.1.2).
It being noted that there is no specific paragraph in Fore Part referring to needof scantling assessments in case the fore part is arranged with floodable
spaces other than the fore peak tank, it is requested that the requirement in
Ch.9, S.2,1.1.2 be incorporated in Fore Part, as well.
2) In Ch.9, S.1 and S.2, there is no requirement of net minimum thickness ofplating for watertight bulkhead, while CSR Tanker Rules specify. It isrequested that net minimum thickness of plating for watertight bulkhead in
Fore Part and Aft Part be specified.

1) We noticed your advice and will prepare a rule change accordingly.
2) Tables 9.1.1 and 9.2.1 are incomplete with respect to horizontal and verticalwatertight boundaries, and relevant items of Table 6.1.2 may be used forwatertight items in fore/aft part.

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IACS Common Structural Rules Knowledge Centre

KCID
No.

535

Ref.

9/5.5.3.2 &9/5.5.4.2

Type

RCP

Topic

Minimum
thickness of
web ofprimary
supporting
member andordinary
stiffeners

Datecompleted

Question/CI

1. Ch 9 Sec 5 [5.3.2] and [5.4.2]
We think it is wrong in Ch 9 Sec 5 [5.3.2] and [5.4.2] to link both minimum
thickness of web of primary supporting member and ordinary stiffeners withtnet = 6 mm & tnet = 10s of hatch cover top plate on Ch 9 Sec 5 [5.2.2] in thefollowing reasons.
(1) The minimum net thickness specified in Ch 9 Sec 5 [5.2.2] is required forsteel plating forming the tops of hatch covers by ILLC Reg.16 (5) (c) which isonly applied to the top plate, not to the web of primary supporting members
and ordinary stiffeners.
(2) If the current ordinary stiffener size L 125*75*7 or stiffener with a U-profile
are satisfied with the strength requirement specified in IACS UR S21, the2007/10/26
stiffener spacing is required to be reduced to 450 to 500 from 600 or 700 mm
so that it complies with the minimum net thickness [tnet = 10s] specified in
Ch9 Sec5 [5.2.2]. In addition, the web thickness of such stiffeners is increasedby 1 to 2mm due to the minimum net thickness of 6mm.

Attachment

AnswerIn Ch 9, Sec 5, [5.3.2],the web minimum net thickness of the ordinary
stiffener, in mm, is to be not less than 4 mm.
In Ch 9, Sec 5, [5.4.2],the web minimum net thickness of the primary
supporting member, in mm, is to be not less than 6 mm.

The stiffener weight of the hatch cover will be increased about 40% comparedto the current one which satisfies the requirements of IACS UR S21.
Therefore, we propose to revise the requirement for minimum net thickness
requirement for webs of primary supporting members and ordinary stiffeners
specified in Ch 9 Sec 5 [5.3.2] and [5.4.2], respectively.

536

9/5.1.4.1

Question

Stiffeners
with a Uprofile

Ch 9 Sec 5 1.4.1 Corrosion additions(1) Box type stiffeners such as stiffeners with a U-profile are used in many
hatch covers. The internal environment in a stiffener with a U-profile is similar
to the one for internal structures of double skin hatch covers.
Therefore, we consider that the total corrosion addition for such stiffeners
should be 1.5mm for single skin hatch covers.
2007/10/26 Please clarify the requirement on the corrosion addition of such stiffeners.
(2) In applying a finite element analysis in order to evaluate the stresses in the
primary supporting members of hatch covers, are FE models considered a full
corrosion addition or a half corrosion addition?
(3) In calculating the net moment of inertia of a primary supporting member,does a full corrosion addition subtract from the gross offered thickness of a
primary supporting member?

1) As pointed out by the questioner, the corrosion environment inside of a boxtype stiffener may be the same of the inside of double skin hatch cover, but
the corrosion environment outside of a box type stiffener is the same of the
cargo side of a hatch cover. Therefore a corrosion addition of 2mm has to be
applied.
2) We think that full corrosion addition has to be considered, because incomparison of the hatch cover to the bulk carrier hull it can be assumed, thatthe whole hatch cover structure may corrode simultaneously, because theenvironmental conditions are not so different.
3) When calculating the net moment of inertia of a primary supporting
member, full corrosion addition has to be considered to be in line with S21.3.5
and the design approach in Ch6.

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537

538

Ref.

Table
9.5.2

9/5.5.2.3

Ch.9
Sec.1,
543
Sec.2 and
Sec.3

Type

Topic

Weathertighthatch covers
Questionand pontoon
hatch covers

Datecompleted

Question/CI

Attachment

Answer

3．Ch 9 Sec 5 Table 2(1) The allowable stress for weathertight hatch covers and pontoon hatch
covers subjected to external pressure are 0.80 ReH and 0.68 ReH,
respectively, in accordance with Reg.15 and Reg.16 of ILLC, but the allowablestress for both weathertight hatch covers and pontoon hatch covers subjected
to other loads is the same.
Why does the same allowable stress apply to the different types of hatch
A1: For loads which are different from ILLC sea loads, the practice of somecover?
classification Societies, since many years, is to consider an allowable stress
Please clarify.
different from the one indicated by ILLC and applicable for all types of hatch(2) According to ILLC, external pressure is only external wave pressure acting
covers.
2007/10/19 on the hatch cover. As CSR considers 4 load cases, i.e., H, F, R and P, theA2: This is related to question 527 and your interpretation is correct:
external pressure for R1, R2, P1 and P2 at any point of an exposed deck is- external pressures are sea pressuresconsidered, in addition to the external pressure for load cases H1, H2, F1 and- other loads are those defined in Ch9 Sec5 [4.1.3] to [4.1.6].
F2, that is the same as IACS UR S21. Therefore, we understand that
“External pressure, as defined in Ch 5 Sec 5, 2” means the external pressure
specified in Ch 4 Sec 5 [2.2] and [2.3] and does not include “Load carried on
exposed deck” specified in Ch 4 Sec 5 [2.4].
We also understand that other loads in Table 2 mean “load carried on
exposed deck” and internal pressure due to liquid in ballast hold specified in
Ch 4 Sec 6 [2]Please confirm.

4.Ch 9 Sec 5 [5.2.3](1) Where the stresses in the primary supporting member are evaluated by
FEA, the uni-axial buckling check can be omitted since the buckling strength
check using the bi-axial compression stress in the hatch cover plating iscarried out in accordance with the requirements of Ch 6 Sec 3.
Please confirm.
(2) As there is no stiffener buckling factor "c" or F1 in Table 1 of Ch 6 Sec 3
for special shape stiffeners such as a stiffener with a U-profile, please makean interpretation for the buckling factor of a stiffener with a U-profile.

A1 The Common Interpretation is as follows:- If no finite element analysis is performed for the buckling of the hatch coverplating, only the criteria for buckling for uniaxial compression is to be checked.
- If a finite element analysis is performed for the buckling of the hatch coverplating, criteria for buckling for bi-axial compression are to be checked.

CI

Stresses in
the primary
supporting
memberCI

Although scantling of PSMs in Fore part, Aft part and E/R are regulated in Ch9Sec1 through Sec3 in CSR, scantling requirement for not all the PSMs are
regulated in Ch9.
According to the agreed answer of question #312, PSM in the fore and aft part
Scantlings ofScantling requirements of some of the PSMs, such on decks or deep tankof the vessel may be designed according Ch6, Sec4, 2.6.
PSMs inbulkheads, refer to Ch6 Sec4. In Ch6 Sec4, scantling formulas are regulated We will consider the further rule development about the determination of the
2007/10/23
Fore Part, Aft
for ships having ship’s length L less than 150m, and direct strength analysis is scantling of primary supporting members outside midship cargo regions forPart & E/R
required for ships having L=150m or more according to provisions in Ch7.
ships of 150m in length and above.
However, Ch7 regulates direct strength analysis of cargo hold structures only.
Please advise how to determine scantling of PSMs in Fore part, Aft part andE/R for ships having L=150m or more.

2008/4/11

A2
According to the stuffiness of the stiffener with U-profile, we think thecoefficient factor F1 is acceptable to the same value for girders specified inTable 1 of Ch 6 Sec 3, i.e., F1 = 1.30.
However a higher F1 value than 1.30 may be accepted provided the bucklingstrength of panel stiffened by U-beams is verified by non-linear buckling
analysis using FEA.

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559

583

Ref.

9/3.2.1.9

Text 9/3

Ch.9
Sec.3/4 &
5

Type

CI

CI

RCP

Topic

ManholeDimensions

Longitudinalstrength andlocal strengthof plates andstiffeners inmachineryspacescantlings
for platform
structuresand pillars

Datecompleted

Question/CI

2008/2/7

Chapter 9, Section 3. [2.1.9]:
1) The 2nd paragraph has the general requirements for the manhole size infloors. We note that many ships are designed with two separate tanks
vertically in way of main engine bed. The access manholes exceeding theabove size limit due to lower floor height in way are designed in each upperand lower tanks as shown in the attachment. We understand that sucharrangement may be acceptable provided the shear area of the floor is notless than that with the hole of 40% of floor local depth based on minimum
required thickness in way and the local strength is satisfied. Please confirm orotherwise advise.
2) We understand that the requirements in paragraph 2 of 9-3/2.1.9 is notapplicable to girders. Please confirm.

2008/4/10

2007/3/23

Regarding the requirements of longitudinal strength and local strength ofplates and stiffeners in machinery space, our interpretations are as follows;
1. Longitudinal strength
1-a. Longitudinal bending and shear strength are checked according to Ch5,Sec1.
1-b. Hull girder ultimate strength is checked according to Ch5, Sec2.
2. Local strength of plate and stiffener
2-a. Flooding requirements in Ch6, Sec1, 3.2.2 and Ch6, Sec2, 3.2.5 areapplied with considering longitudinal stress sigma_x as similar to cargo area
2-b. Buckling requirements in Ch6, Sec3 3.1.2 and 4 are applied withconsidering longitudinal stress sigma_x and tau as similar to cargo area
Please clarify above interpretations.

9-3/4 and 9-3/5: The platforms and pillars will support the loads of machinery,
independent tanks etc.. However there is no loads specified in CSR for
determining the scantlings for platform structures and pillars. It is also
impracticable to obtain the dynamic loads for each machinery weight due tolack of information. Therefore, based on current CSR , it is impracticable todetermine the scantlings of platforms and pillars in engine room except theminimum plate thickness specified in CSR. As an alternative, we think thateach Class Society Rules may be used for determining the scantlings ofplatforms and pillars in addition to the minimum plate thickness requirements
specified in CSR. Please confirm. Also suggest CSR to specify the loads forplatforms in engine room and pillars.

Attachment

Answer

A1 - Where access manholes dimensions exceed the size limit in Ch 9, Sec 3,[2.1.9] due to lower floor height in way, such arrangement may be acceptableprovided that the shear area of the floor is not less than that with the hole of
40% of floor local depth based on minimum required thickness in way and thatthe local strength is satisfied.
A2 - The requirements in paragraph 2 of 9-3/2.1.9 are also applicable togirders.

1. Longitudinal strength in machinery space
1-a. Longitudinal bending and shear strength are checked according to Ch5,
Sec1, provided flooding in machinery space needs not be considered .
1-b. Hull girder ultimate strength is checked according to Ch5, Sec2, provided
flooding in machinery space needs not be considered .
2. Local strength of plate and stiffener in machinery space
2-a. Requirements in Ch6, Sec1, 3.2.2 and Ch6, Sec2, 3.2.5 are applied withconsidering longitudinal stress sigma_x in intact condition.
2-b. Buckling requirements in Ch6, Sec3 3.1.2 and 4 are applied withconsidering longitudinal stress sigma_x and tau as similar to cargo area.

1) There are no specific loads in CSR BC for determining the scantlings ofplatforms in machinery spaces. There is only a minimum plate thickness
requirement.
2) For determining the scantlings of platforms and pillars in addition to theminimum plate thickness requirements specified in CSR for BC, a Rule
Change will be considered in future.

Page 8 of 22

YIACS Common Structural Rules Knowledge Centre

KCID
No.

613

620

654

Ref.

Symbol
9.5 & 9Sec.5

9/5.5.4.6

9/1.4

Type

Topic

CI

Hatch Coverof ballast
hold

QuestionError in theformulagiving kt

Question

collision
bulkheadDatecompleted

Question/CI

Attachment

Answer

2008/4/24

Reference is made to Ch.9 Sec. 5
Q1 Requirement for hatch cover of ballast hold
In Chapter 9 Sec.5 Symbols, it is stated that "FS = 0 and FW = 0.9 for hatch
covers of the cargo ballast hold". It is our understanding, these coefficients areapplicable to ballast pressure only and not sea pressure or cargo pressure. If
so, please consider rephrasing the paragraph to"FS = 0 and FW = 0.9 for ballast pressure of hatch covers on the cargo ballast
hold".
A1. Your understanding that the coefficient FS = 0 and FW = 0.9 are
Q2 Ballast pressure calculation
applicable to ballast pressure only is right.
When calculating ballast pressure according to Ch.4 Sec.6 [2.2] we assume
that the fixed value of (x-xB) may be utilized. (0.75lh or -0.75lh)
A2: This fixed value has to be used in prescriptive assessment of structure.
Please confirm and if relevant, update rules accordingly.
Q3 Structural calculation
A3:Formulae as per Chapter 9, Sec.5 should be used.
a. When ballast pressure or dry cargo pressure is considered for the hatch
cover, please advise the formula to use in order to calculate the required plate
thickness, section modulus and shear area of stiffeners? Can the formula inCh.6 Sec.1 [3.2.1] and Ch.6 Sec.2 [3.2.3] or the formula in Ch.9 Sec.5 5.3.3
be used?
b. In Ch.9 Sec. 5 bending stresses of primary supporting members areaccounted for when calculating scantlings of local structures such as plate andstiffeners. If we use the formulas of Ch. 6 Sec. [3.2.1] and Ch. 6 Sec.2 [3.2.3],
shall primary bending stress be accounted for? (Ref. lambdaP and lambdaS
factors)
Please clarify the rules.

2008/5/12

In Ch 9, Sec 5, [5.4.6], it seems that there is an error in the formula giving kt,
which is not in accordance with UR S21. Please confirm?

2008/9/10

How is the additional safety taken into account for the collision bulkhead,
when not subjected to lateral loads from tanks, hence fore peak is void
space?

It is right. The formula of kt should be modified from kt=5.35+4*(a/d)^2 to
kt=5.35+4/(a/d)^2, to be in accordance with UR S21.3.6.3.
This editorial correction will be issued as a Corrigenda.

The scantling of collision bulkhead is enhanced to the other bulkheads,
according to Ch 6 Sec 1, [3.2.2] for bulkhead plating and Ch 6 Sec 2, [3.2.5]
for ordinary stiffeners. Where the collision bulkhead is a boundary of void
space, the scantling may be derived by considering the void space as flooded,using the requirements mentioned above. We will consider a rule change forprimary supporting members under flooded condition.

Page 9 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

663

Ref.

9/3.7.2.1

Type

RCP

Topic

minimum
Scantlings ofthe structuralelements

Datecompleted2008/5/13

Question/CI
1.In the course of applying CSR for Bulkers, CCS has found some problems
existing with the CSR requirements relating to minimum scantlings of thestructural elements in way of machinery seatings, as specified in CSR BC,
Chapter 9 - Other Structures, Section 3, 7.2 Minimum scantlings, which isquoted below for easy reference:"7.2.1 The net scantlings of the structural elements in way of the internal
combustion engine seatings are to be obtained from the formulae in Tab 2."
2. This requirement is found to be irrational since the calculation results
proved to be unnecessarily large.
2.1 CCS is of the opinion that the internal combustion engine manufacturers
are the ones who should be responsible for the design of the engine seatings
since they have the richest experience of application and the authority, andaccordingly the design of the seatings should follow thesuggestions/instructions provided by the manufactures.

Attachment

AnswerAs the same question is uploaded on KC ID 413, please refer to the answer in
KC ID 413.

3. Therefore, CCS proposes to substitute the above mentioned paragraph andtab.2 by the new "7.2.1 The net scantlings of the structural elements in way of
the internal combustion engine seatings are to be in accordance with thescantlings provided by the manufactures."

665

666

9/3.4.1.2

RCP

9/1.4.4.4 &Question
9/2.4.3.4

Transverse
spacing

deck primary
supporting
members

2008/4/24

Transverse spacing in machinery space
In Ch9, Sec3, 3.1.3, the side transverse spacing is restricted upto 4/5 frame
spacings.
On the other hand, greater spacing is also permitted at the last sentence
The primary support i.w.o. the platform is to be integrated with the primarystated below;
members in the side. Hence where larger spacings are allowed in the side it"Side transverse spacing greater than that above may be accepted provided
will result in an equally larger spacing in the platform.
that the scantlings of ordinary frames
are increased, according to the Society’s requirements to be defined on acase by case basis."
In Ch9, Sec3, 4.1.2, the platform transverse spacing is restricted upto 4 frame
spacings.
Can greater spacing be permitted as similar to the above?

2008/9/10

According to the answer in KC 312, the requirement of Ch6 Sec4, 2.6 isapplicable to deck primary supporting members in Fore and Aft. In calculating
the scantling of the members in Fore and Aft according to the formulaspecified in Ch 6 Sec 4, 2.6.3, we understand that the applicable allowable
shear stress and lamda_s are R_y/square root (3) and 0.9 instead of 0.4 R_y
and 0.8, respectively, because the lamda_p is 0.9 in the formula for plating of
aft part specified in Ch 9 Sec 2. Please confirm the above.

Your interpretation is not right. If the scantling formulae for primary supporting
members are used in the fore and aft part, lambda-s and the allowable shear
stress, given in CH6, Sec4, are to be used (i.e. lambda-s equal to 0.8 andallowable shear stress tau-a equal to 0.4Ry). However we will consider arule change in Ch.9 Sec.1 [4.4.4] and Ch.9 Sec.2 [4.3.4] so that therequirements to primary supporting members are coherent within Ch.9 Sec.1
and Ch.9 Sec.2 respectively.

Page 10 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Symbol9.5,
684 9/5.5.3.2,
9/5.5.4.2 &9/5.5.4.6

Type

RCP

Topic

minimum net
thickness of
web plate ofordinary
stiffeners
and primary
supportmembers

Datecompleted

Question/CI

Attachment

Answer

According to Ch.9, Sec.5, Symbols:s is defined as length, in m, of the shorter side of the elementary plate panel.
My understanding to the minimum net thickness of web plate of ordinary
stiffeners and primary supporting members is as follows:
According to Ch.9, Sec.5, [5.3.2], The minimum net thickness of web plate ofordinary stiffeners should be (tnet)min=min(10s,6), while in the calculation, theparameter s should be of web plate panel of ordinary stiffeners (normally web
height) and should have no relation to the top plate panels of hatch cover.
This understanding can also apply to determine the minimum net thickness ofRegarding the minimum net thickness of web of ordinary stiffeners andweb plate of primary supporting members.
primary supporting members, please refer to the answer in KC ID 535.
In addition, the correct formula for kt is kt=5.35+4.0/(a/d)^2 as specified in
IACS UR S21.3.6.3.

2008/5/13

According to Ch.9 Sec.5, [5.4.2],The minimum net thickness of web plate ofprimary supporting members should be (tnet)min=min(10s,6) the parameter s We will consider the Rule Change proposal or edditorial correction on thisshould be of web plate panel of primary supporting members (normally web
matter.
height) and also have no relation to the top plate panels of hatch cover.
If the above understanding is correct, then there will be no limit to use thecurrent widely used ordinary stiffenr L125x75x7 in hatch covers of vessels with
CSR BC notation.

We propose to revise the text for minimum net thickness of web plate ofordinary stiffeners and primary supporting members in Ch.9 Sec.5 [5.3.2] and[5.4.2], respectively.
The formula kt in Ch.9, Sec.5 [5.4.6] should be corrected as
kt=5.35+4.0/(a/d)^2 or kt=5.35+4.0(d/a)^2.

686

693

9/5.5.2.1

9/4.3.2.1

CI

Question

Water
BallastPressure

Lateralpressure fordeck

2008/4/10

2008/5/1

FEM’s Fs and Fw for water ballast pressure on Ch 9 Sec 5
The water ballast pressure will be calculated by using Fw (=0.9) for net
thickness (Ch9, Sec 5. 5.2.1) and isolated beam models.
We think it can be applied for FEM too, is it correct?
Ch9 Sec4, 3.2.1 regulates the lateral pressure for deck to be p_D in Ch4
Sec5, 2.1.
However p_D in Ch4 Sec5, 2 is the external pressure on the exposed deck.
No clear indications are found in CSR for the lateral pressure on theunexposed deck, such as the deck inside of accommodation.
Please clarify the above.

We think that the combination of the static load and dynamic load for hatch
cover in way of ballast hold is introduced as a special case.
Therefore, the factor FW=0.9 is also applicable for FEA.

A lateral load for unexposed decks will be defined. We will initiate a rulechange proposal.

Page 11 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer

The formula in Ch 6 Sec 2 [4.1.2) is the based on the following assumption.
(See attached file)
With regard to a requirement of web stiffener on non-watertight double bottom(a) web stiffener is flat bar type.
floor in Engine Room, it is requested to provide the detailed technical(b) thickness of web of web stiffener is equal to that of web of PSM.
background while it is understood to have been based on the protection of(c) the height of web stiffener is approximately equal to (stiffener length/12) as
web plate buckling, and it is also requested to modify it considering current
specified in Ch 3 Sec 6 [5.1.2]
designs with almost no damage record.
(d) the effect of the attached plate is considered as a function of spacing of
web stiffener

699
attc

700

709

9/3.2.1.8

9/3.3.1.2

9/6.3.3.4

Question

wef stiffener

Question

Longitudinal
Structure

Question

Required
thickness ofthoughened
glasses inside scuttles

2008/9/10

Re. the technical background, it is noted that the equation in 6/2.4.1.2 is notdimensionally balanced, i.e., left side = cm3, right side = m5. In addition,
9/3.2.1.8 requires the section modulus as 1.2 times of that required by
6/2.4.1.2. The reason of this 1.2 times should be also clarified.

This requirement is provided to ensure the minimum stiffeness of web
stiffener, hence this requirement is applicable to all types of stiffener (flat bar,angle, T-section). The meaning of 1.2 times of that required by Ch 6 Sec 2[4.1.2] seams to the safety margin based on experiences.

Re. the section modulus requirement compared with the current design of
non-CSR, it is noted that CSR BC Rule requires much severe web stiffener
scantling than that of non-CSR. Our example calculations show:(A)Capesize – 300*90*13/17 (CSR),à200*90*8/14 (as built)(B)Panamax – 150*16 FB (as 200*20 FB (CSR),àbuilt)
250*90*9/15à
(C)Handymax – 200*90*9/14 (as built) (CSR)
Hence the requirement should be modified considering current designs withalmost no damage record..

When the effect of the attached plate is considered, the mentioned example isprobably satisfied with the requirement in Ch 9 Sec 3 [2.1.8]. However, we
will consider the RCP in order to elminate the dimentional unbalance between
left side and right side in the formula of Ch 6 Sec 2 [4.1.2] together with thecarifiction of the application. Furthermore, according to this TB, the answer in
KC ID 418 should be modified as follows: The net sction modulus of web
stiffener of non-watertight primary supporting member should be calculatedwith the attached plating, according to Ch 3 Sec 6 [4.3.1].

2008/7/16

Ch9 Sec3, 3.1.2 regulates that the longitudinal structure should be maintained
for at least 0.3 times the length of the machinery space.
We have an opinion that the above requirement is not applicable to thefollowing members.
-Longitudinal bulkheads-Topside slant plates-Bilge hopper slant plates
Because the longitudinal continuity of the above members can be ensured by
the appropriate fitting of girders/large brackets on the back side of E/R
bulkhead.
Please confirm the above.

2008/5/28

Ch.9, Sec.6, [3.3.4] specifies the required thickness of toughened glasses inside scuttles.
Is the calculated thickness to be rounded up or round off or others?
For instance, in case the calculated values are 12.24mm, 12.27mm,
12.40mm, 12.52mm, 12.85mm, what are the required actual thicknesses
respectively?

We confirm your interpretation.
The extension concerns only the longitudinal structure attached to the side
shell and doesn't apply to the plantings and attached ordinary stiffeners ofstringers of DSS, topside tank and bilge hopper tank. In addition, thecontinuity of strength is to be ensured in the machinery space in way ofstringers of DSS and strake of topside tank / bilge hopper tank directly
attached to the side shell.

The glass thickness to be fitted is the thickness available from the glasses
manufacturers and above the calculated value.

Page 12 of 22

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

Attachment

Answer723

9/2.4.1.1 &Question
Table 1

Net minimum
thickness ofplating

2009/6/2

To which dose the tank top plate of steering gear flat correspond in Table 1,[Inner bottom] or [Platform and wash bulkhead] ?

Platform and wash bulkheads in Table 1 Ch 9 Sec 2 are non-watertight plating
members. As the tank top plate of steering gear flat is a watertight plating
member and not inner bottom, the net minimum thickness for the tank top
plate of steering gear flat is not specified in Table 1. As an interpretation, thenet minimum thickness for the tank top plate of steering gear flat is the sameas that for watertight bulkhead specified in Ch 6 Sec 1, Table 2, i.e.
0.6xL^(0.5) mm.

724

9/2.5.2.1

sidetransverse

2009/6/2

Is there any exceptional easing steps concerning spacing of a ship's sidetransverse spacing?

The required side transverse spacing is based on design experience andservice history. It has proven to be satisfactory and cannot be relaxed.

2009/6/2

Refer to KC ID 543 which states: PSM in the fore and aft part of the vessel
may be designed according Ch6, Sec4, 2.6. We will consider the further rule
development about the determination of the scantling of primary supporting
Please explain a specific procedure of the direct strength calculation in engine
members outside midship cargo regions for ships of 150m in length androom construction.
above. For the time being, the direct strength calculation should be submitted
to the Society for examination on a case by case basis, as specified in Ch 9
Sec 3, [1.2.3].

725

9/3.1.2.3

Question

Question

Primary
SupportMembers

2009/6/2

The width of aft peak tank is generally narrow at the double bottom level ofengine room when the engine room is located immediately forward of aft peaktank. Considering the aspect ratio (l/b) of double bottom in such an engine
Please explain the reason that the double bottom is to be transversely framed.
room becomes very large, where l is the length of engine room and b is themean breadth of engine room, it would be natural to provide main supporting
members transversely. This requirement stands on this background.

2009/6/2

We would like to have your confirmation whether the arrangement ofoverlapping tank top is acceptable as continuous structure.
Please see attachment below.

CSR-BC allows only a sloped transition, when the inner bottom of the cargoarea is on another level than that of the machinery space.

Is the extension of longitudinal structure applied to the platings of topsidetank and bilge hopper tank?

The extension described in [3.1.2] concerns only the longitudinal structureattached to the side shell and doesn't apply to the platings and attachedordinary stiffeners of side stringers, topside tank and bilge hopper tank.
However, in the light of Ch 9, Sec 3, [1.3.2], the continuity of strength is to beensured in the machinery space in way of side stringers and strake of topsidetank / bilge hopper.

726

9/3.2.1.1

Question

doublebottomgeneral727
attc

9/3.2.1.2

Question

doublebottomheight

Question

longitudinal
structure
within themachinery
space

728

9/3.3.1.2

2009/6/2

Page 13 of 22

YIACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Date
completed

Question/CI

729

9/3.4.1.2

Question

platformtransverse

2009/6/2

Is it possible to arrange platform transverses 5 frame spacings as well as
3.1.3 Side transverses? Usually , the platform transverses are connecting toside ransverses continuously.

According to the last sentence of [3.1.3], wider spaces may be accepted
based on the discretion of the Society.

Question

Ordinary
stiffener
spacing

2009/6/2

Is there any exceptional easing steps to the regulation about 750 mm
spacing? Usually, the vertical stiffeners are connecting to the deck
longitudinals continuously.

No, there is not. The required value of about 750mm for spacing, which wasdeveloped based on many years of experience, is applied and considered tobe satisfactory. However, the vertical stiffeners are to be connected to thedeck longitudinals continuously.

The requirement in Ch 9, Sec 2, [3.1.2] requiring that "Solid floors are to be
fitted at every frame spacing" seems very severe and is not in line with someactual design of ships.We would like to ask IACS to review this requirement
and to introduce a Rule Change Proposal.

It is not required to built solid floors at every frame spacing in the whole aftpeak area. Solid frames up to the tank top are only required in way and nearof rudder post, propeller post and rudder horn. The transverse extension
depends on the arrangements proposed. It might be neccessary to built solid
floors below tank top over the whole breadth, e.g. if no longitudinal walls arearranged. In case, where floors are not extended over the full breadth,paragraph [3.1.3] covers the design of the transverse primary supporting
members. We will consider a rule change to clarify this requirement

730

739

759

9/3.6.1.1

9/2.3.1.2

9/1.2.3.2

RCP

RCP

frame
spacing

2008/9/10

Spacing ofsolid floors

The requirement in Ch 9, Sec 1, [2.3.2] says that the spacing of solid floors
should be Min.[3.5m, 4 frame spaces] in case of the longitudinal stiffened
system. We understand the philosophy that the spacing must not be too big,
however, for example, when the design in fore part has a spacing of 3.75m (52008/10/27 frame spaces), the actual difference of spacing is just 0.25m from therequirement. Is it possible to allow a greater value of spacing after
confirmination that the strength or scantlings are enough, on the basis of FE
analysis, for exemple? We would like to ask IACS to review this requirement
and to introduce a Rule Change Proposal.

Attachment

AnswerSuch larger distances may be used, when the structure is verified by means of
FEA deemed appropriately by the Society, using direct, calculated, slammingloads

Page 14 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

763

Ref.

Table
9.3.2

Type

QuestionTopic

net crosssectional
area ruleDatecompleted2009/3/3

Question/CI

Attachment

AnswerWe have noted your answer concerning our complaints on requirements for
Net Cross Sectional Area on tank top bedplates (KC ID #611). Your answer
does not lead to a better understanding of the problem since we have alreadybeen informed about the answer on the approved question KC ID#413. We do
not understand the reason for the requirement and would like you to explainYour comment has been reflected to the Rule Change Proposal 4 which has
the meaning of this formulae. As an example the width of each tank top
been reviewed according to PR 32.
bedplate for our engine S70MC-C is 1365 mm. When fulfilling the IACS rules
the thickness is required to be 69 mm and the cross sectional area will be1826 cm^2. Accordingly a width of 2640 mm of each tank top bedplate isrequired. This will in some cases mean that the tank top plate penetrates thehull at the aft part of the engine.

Alternatively the thickness of the bedplate must be twice the normal size, 134
mm which is obviously a meaningless size. So we are of the opinion that the
IACS rule on net cross sectional area should refer to “bedplates in total” andnot to “each bedplate” as we proposed in our letter to IACS. Several shipyards
are asking us for calculations on this matter, referring to the question KC
ID#413, but it is not possible for us to make such calculations.

766

770

785

9/3.2.1.8

9/6.6.3.1

9/4.3.2.1

Questionweb
stiffeners

2009/3/3

Please confirm that the following our interpretation, on the web stiffeners on
the double bottom floors and side transverse web frames in machinery space,is correct.
1) In Ch 9 Sec 3 [2.1.8], Ch 3 Sec 6 is referred to in the first sentence, as "inaddition to the requirements in Ch 3 Sec 6". It means the stiffeners provided
to the double bottom floors in Machinery space shall comply with Ch.3 Sec 6
It is agreed that some requirements of Ch 3 Sec 6 are applicable to theand Ch 9 Sec 3 [2.1.8].
structural arrangement of the entire hull structure. In this regard, modifications
The depth of the stiffeners provided to the floors in Machinery space is to be
in CSR will be prepared for clarification.
more than 1/12 stiffener length and the section modulus is to be not less than
1.2 times that required in Ch 6 Sec 2 [4.1.2].
2) There is no cross reference to Ch.3 Sec 6 in the side transverse
requirements in [3.1.3] of Ch 9 Sec 3 "Machinery space". Accordingly it is not
required to apply the requirements of C3 Sec 6 to the web stiffeners on theside transverses in machinery space.

RCP

coamingheight ofenergency
generatorroom

2008/9/10

Coaming height of emergency generator room. Ch9 Sec6, 6.3.1 states thecoaming height of emergency generator room with reference to 8.1.3.
However 8.1.3. requires closing appliance and it seems that the reference is
to be corrected to 8.1.2. Please confirm it.

This is typo. We will conisider an editorial correction.

2009/3/3

The lateral pressure for decks of superstructures and deckhouses is definedin Ch9, Sec4, [3.2.1].
This requirement refers to the external pressure pD defined in Ch4, Sec5,[2.1], which is a pressure for EXPOSED deck.
In case of non-exposed decks of superstructure and deckhouses, as nointernal pressure is defined for such decks in Ch4, Sec6, we would like toknow what is the pressure to be used?

Effectively, no internal pressure is defined in CSR-BC for non-exposed decks
of superstructures and deckhouses. Such internal pressure will be added in
CSR-BC, and we suggest to use a value of 5 kN/m2 including dynamic load
effect.

CI

Lateralpressure fordeck

Page 15 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

789

799

802

816

Ref.

9/5.5.4.5

Table
9.2.5

9/5.7.3.5

Type

Topic

CI

deflection
limit

Question

castpropellerpostsecuring
Question arrangements

9/5.5.2.1 &Question
9/5.5.3.3

hatch cover
top plating

Datecompleted

Question/CI

Attachment

Answer

2008/9/10

We would like to confirm the interpretation of "Common Structural Rules for
Bulk Carriers" Part CSR-B Ch.9 Sec.5 5.4.5 : Deflection Limit of Primary
supporting members for Hatch Covers.
We interpret this Ch.9 Sec.5 5.4.5 as follows:
As clearly described as "when loaded by sea pressure" in Ch.9 Sec.5 5.4.5,
The "Sea pressure" means the pressure defined in [4.1.2] of Ch 9 Sec 5.
necessary considering load to keep deflection within the limit ( = ulmax ) is
Even when the requirement of [5.4.5] applies to the hatch cover of ballast
only the "Sea pressures" defined in Ch.9 Sec.5 4.1.2 and does not include the hold, sea pressure defined in [4.1.2] of Ch 9 Sec 5 is only considered.
"Internal pressures due to ballast water" defined in Ch,9 Sec.5 4.1.3, even incase of Ballast hold Hatch Covers.
We are looking
forward to receiving your reply with your confirmation to above ourinterpretation.

2009/3/3

In Chapter 9, Section 2, Table 5 the following change is proposed:
Column: "Cast propeller post", Row "R" the formula should be changed from:50 L^1/2 to: 50 mm.
Reason: typo found in the formula coming from RINA Rules and corrected in
RINA Rules 2008.

Your comment is noted and we will consider a rule change proposal changing
to 50 mm from 50L^1/2.

2009/3/3

In the first part of [7.3.5], the general formula for determining the gross crossarea A of each securing device is given.
Then, in the second part of [7.3.5], some special cases (packing linepressures exceeding 5 N/mm or securing arrangements which are particularly
stressed due to the unusual width of the hatchway) are specified and thecorresponding net cross area A.
Why the general formula is given for the gross cross area A when the crossarea for particular cases is the net one?

[7.3.5] is the copy of a part of UR S21.5.1 which specifies A as net sectional
area. In the light of S21.5.1 "gross cross area" is a typo which should becorrected. However the "gross cross area" of the current CSR is intended tomean the area measured at the root of threads of securing device which issame as the "net sectional area" of S21.5.1. Accordingly the foregoingcorrection of the current rule text from "gross cross area" to "net cross area"
will be considered as Corrigenda.

2009/3/3

CSR for bulker specifies the prescriptive rule requirements to the thickness ofhatch cover top plating in Ch.9 Sec. 5 [5.2.1] and the section modulus andshear area of ordinary stiffener in Ch.9 Sec. 5 [5.3.3].
1) Is it acceptable to apply FEA for the to evaluation of those scantlings in lieu
of the prescriptive rule requirements in Ch.9 Sec. 5 [5.2.1] and [5.3.3]
The formula for t_net, given in CH9, Sec5, 5.2.1, is equivalent to S21.3.3.
provided:This requirement is a minimum requirement, which can not be superseded by(i) all other relevant rules (e.g. minimum thickness, buckling etc.) are to bea direct calculation.
fully complied with, and(ii) the allowable stresses, specified in Table 2 of Ch.9 Sec.5 [1.5] are to be
used in FEA for the scantling evaluation of top plating and ordinary stiffeners?
2) If FEA is acceptable please advise the criteria on the modeling.?

Page 16 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

823

825

826

834

Ref.

Type

9/5.1.4.2 &Question
Table 3/3

9/1.2.3

9/5.6.2.4

9/1.2.2.1

Question

Question

QuestionTopiccorrosion
addition

collision
bulkheadhatchcoaming

tripping
brackets

Datecompleted

Question/CI

Attachment

Answer

2009/3/3

The 2nd sentence in Ch.9, Sec.5, [1.4.1] reads: "The corrosion addition for
hatch coamings and coaming stays is defined according to Ch 3, Sec 3."
The 1st sentence in UR S21.6.2 reads: "For the structures of hatch coamings
and coaming stays, the corrosion addition t_s is to be 1.5mm."We
believe that the following corrosion additions for L>=150m are to be appliedreferring to Ch.3 Sec.3 Table 1;
Your understanding is correct.
(a) Hatch coaming web: Roundup0.5[(1.8+1.0)]+0.5=3.5mm(b) Web of horizontal stiffener on coamings: Roundup0.5[(2x1.7)]+0.5=4.0mm(c) Flange of horizontal stiffener on coamings:
Rounduo0.5[(2x1.0)]+0.5=2.5mm(d) Coaming stays: Roundup0.5[(2x1.0)]+0.5=2.5mm.
Please confirm the above corrosion additions.

2009/3/10

Ch.9 Sec.1 is applicable to the structure in the area located forward of thecollision bulkhead, the bow flare area and the flat bottom forward area,according to Ch9 Sec1, 1.1.1. Each requirement has individual applicableareas, such as the bow flare area in 4.1.1 and the bottom forward area in
5.1.1. We are of the opinion that the requirements in 2.3 are applicable to thearea located forward of the collision bulkhead only. In other words, therequirements in 2.3 are not applicable to the area located aft of the collisionbulkhead. Please confirm the above.

2009/3/10

Hatch coaming stiffeners are required to be estimated with considering thewave lateral pressure as stated in Ch9 Sec5, 6.2.1. In addition, hatch coaming
stiffeners in way of ballast hold are also required to be estimated withconsidering the ballast pressure in Ch4 Sec6 as stated in 6.2.4. In thiscontext, to consider the ballast pressure in Ch4 Sec6, the hatch coaming
stiffeners need to be applied with the applicable requirements in Ch6 Sec2.
More specifically, we are of the opinion that following applications of the
The hatch coaming is a part of the central part as defined in Ch1 Sec1 [2.1.3],
requirements in Ch6 Sec2 should be considered;hence all the relevant requirements in Ch6 shall be complied with, in addition
1) Hatch coaming stiffeners in way of ballast holds;
to the relevant requirements in Ch9 Sec5.
Applicable : Section modulus and shear area in 3.2
Applicable : Dimensions in 2.3
2) The other hatch coaming stiffeners
NA : Section modulus and shear area in 3.2
NA : Dimensions in 2.3
Please confirm the above applications

2009/1/26

Ch.9 Sec.1 [2.2.1] Tripping brackets in fore part According to the technicalbackground this requirement is based on URS 12. URS 12 deals withasymmetrical sections, while no distinction is made between symmetrical andasymmetrical sections in Ch.9 Sec.1 [2.2.1]. Please clarify if this requirement
applies to symmetrical sections.

Your understanding is right.

The reference, given in the technical background, is wrong. This paragraph isbased on GL-Rules I-Part 1, Section 9A 5.5. The requirements are valid forsymmetrical and asymmetrical side frames, because the loads (sea and tankpressures) act not parallel to the webs of the frames and cause obliquebending. We will adjust the technical background on this paragraph.

Page 17 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

835

Ref.

9/2.5.2.1

Type

Question

Topic

side
transverse
spacingDatecompleted

Question/CI

Attachment

Answer

2009/2/11

Please explain why the required side transverse spacing is reduced to 2 frame
spacing in way of the rudder horn. This is not in line with common industry
practice. According to Chapter 9, Section 2 [3.1.2] solid floors are to be fitted
Referring to answer to question ID739 on 9/2.3.1.2, a rule change will be
at every frame spacing in way of the rudder horn and are to be extended up to
issued covering both requirements 9/2.3.1.2 and 9/2.5.2.1.
the peak tank top. In our opinion, this requirement should give proper support
for the rudder horn, and the requirement in Chapter 9, Section 2 [5.2.1] cantherefore be disregarded.

As the framing system and girder system changes at the engine room
bulkhead there is a change in hull girder stiffness and in local stiffness. The
extend of the foundation girders into the adjacent space (e.g. pipe duct ortank) reduces this abrupt change of stiffness. Structural continuity is to beensured in double bottom by bottom girders tapered and effectively connected
to hull structure forward of engine room. Specific designs are to be allowed ona case by case basis by each Society, provided the above provisions arerespected. A Rule Change proposal will be made.

836

9/3.2.1.5

Question

machinery
space

2009/3/10"Forward of the machinery space forward bulkhead, the bottom girder are to
be tapered for at least three frame spaces and are to be effectively connectedto the hull structure." This implies that the additional bottom girder in way ofthe machinery seating has to be extended into the pipe duct in the aftmost
cargo hold. In our opinion, there is no room to extend this additional girder
inside the pipe duct. The requirement is not in accordance with common
industry practice and should be disregarded.

847

Table
9.1.1

Questionfore peak

2009/2/11

Reference is made to Ch.9 Sec.1 Table 1 and to KC ID 494 What is the
A non tight floor in the fore peak is considered as a platform with regard tocorrect application of Table 1 for a non-tight floor top in the fore peak? Should
Ch.9 Sec. 1 Tab.1
this structure be regarded as platform or inner bottom?

2009/6/23

t1 is the post minimum thickness, to be measured at the connection with theshell plating (excluding a possible tapered transition to the shell plating
Ch9 Sec2, Table5 requires thicknesses t1 and t2 of cast propeller posts ofthickness) t2 is the post maximum thickness, to be measured at the edge ofsingle screw ship. The applicable area of required thicknesses t1 and t2 is not
the circular area with radius R. In addition, the word "to be taken not less thanso clear as to distinguish required thickness at any point of post. Please
19mm" and Note 1 in Table 5 should be deleted because it is impossible for
confirm it.
CSR ships >=90m. In order to clarify these, figure in the table and the wording
will be corrected in the next corrigenda.

2009/9/18

1st paragraph in Ch.9 Sec. 2 [6.5.1] reads:"The sterntube thickness is
considered by the Society on a case by case basis. In no case, however, may Answer: Your understanding is correct. The thickness of the side plating to be
it be less than the thickness of the side plating adjacent to the stern-frame."used is the required net thickness. This requirement has also to be considered
Please confirm that the thickness of the side plating to be used is the required within the harmonisation.
net thickness?

2009/9/8

Ch9 Sec2, 3.1.2 requires “Floors are to be provided with stiffeners located atintervals not exceeding 800 mm.” in its last sentence. We are of following
opinions; - This requirement is applicable only in way of and near the rudder
post, propeller post and rudder horn. - Intervals of stiffeners depend on the
thickness of floor as required in Ch3 Sec6, 5.2.1 Please confirm the above.

863

887

891

Table
/9.2.5

9/2.6.5.1

9/2.3.1.2

Question

Questionci

single screw
ship

stern tube
thickness

Aft peak

The last sentence of Ch9 Sec2, 3.1.2 “Floors are to be provided with stiffeners
located at intervals not exceeding 800 mm.” is applicable only in way of andnear the rudder post, propeller post and rudder horn. This requirement should
be applied in addition to Ch3 Sec6, 5.2.1.

Page 18 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Text
9/2.4.2.3(tanker) &930
Text
9/1.4.3.3(bulker)

questionmax netthickness

9/1.2.3.3

Questionbottom girder
spacing932

970

9/2.4.2.3

QuestionNet
thickness of
web ofordinary
stiffeners

Datecompleted

Question/CI

Answer

2009/6/23

Incorrect reference number in 2008RCN1-4
The last sentences of Ch9 Sec1, 4.3.3 and Ch9 Sec2, 4.2.3 indicate thereference to the requirement of maximum net thickness of web of ordinary
stiffener in Ch6 Sec2.
However the reference number is incorrect, because the maximum web
thickness requirement has been moved from 2.2.2 to 2.2.3 in Ch6 Sec2
during finalization of the RCP.
Please correct the reference number of the last sentences of Ch9 Sec1, 4.3.3
and Ch9 Sec2, 4.2.3 as follows; “The net dimensions of ordinary stiffeners areto comply with the requirement in Ch 6 Sec 2, [2.2.3] and [2.3].”

Your comment is correct. The reference number of the last sentences of Ch9
Sec1, 4.3.3 and Ch9 Sec2, 4.2.3 should be as follows: “The net dimensions ofordinary stiffeners are to comply with the requirement in Ch 6 Sec 2, [2.2.3]
and [2.3].” This will be corrected in the next corrigenda.

2009/7/16

Chapter 9 Section 1 [2.3.3] requires in the fore part that ”In case of transverse The spacing of bottom girders of 2.7m may be used when the structure isframing, the spacing of bottom girders is not to exceed 2.5m”. Is a spacing of verified by means of FEA deemed appropriately by the Society, using directly
bottom girders of 2.7m acceptable considering the similar Q & A in KC759?
calculated slamming loads.

2010/3/30

CSR BC Ch.9 Sec.2 [4.2.3][QUOTE]The net thickness of the web of ordinary stiffeners, in mm, is to be not lessthan the greater of:• t = 3.0 + 0.015L2• 40% of the net required thickness of the attached plating, to be determinedaccording to [4.1].
Your understanding is correct.
[UNQUOTE]
40% of the net required thickness of the attached plating, to be determined
The requirements of the net thickness of plating according to [4.1] only include according to [1.1.2] and [4.1].
the requirements of net minimum thickness, net thickness under intact
conditions and net thickness under testing conditions. We think the net
thickness requirement under flooded conditions, to be determined accordingto [1.1.2], should be considered for the net required thickness of the attachedplating.
Please consider.

Attachment

Page 19 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

9/1.4.3.3 &Question971
9/2.4.2.3

Topic

Date
completed

stiffeners

CSR BC Ch.9 Sec.1 [4.3.3] and Sec.2 [4.2.3].
[QUOTE]The net dimensions of ordinary stiffeners are to comply with the requirement
2009/10/27 in Ch 6, Sec 2, [2.2.2] and [2.3].
[UNQUOTE]
We think the reference to [2.2.2] should be corrected to [2.2.3]. Pleaseconsider.

Question/CI

1001

9/1.7

Q&A

Forecastle
requirements

2010/5/12

CSR BC Ch.1 Sec.4 [3.13.1][QUOTE]
Ref. ILLC, as amended (Resolution MSC.143(77) Reg. 3(10,g))
A forecastle is a superstructure which extends from the forward perpendicular
aft to a point which is forward of the after perpendicular. The forecastle may
originate from a point forward of the forward perpendicular.
[UNQUOTE]
From the above definition, a forecastle is defined as a superstructure, but therequirements of forecastle are given in Ch.9 Sec.1 Fore Part.
We propose that
1.The requirements of forecastle given in Ch.9 Sec.1 Fore Part should betransferred to Ch.9 Sec.4 Superstructures and Deckhouses.
2.The requirements of forecastle structure, such as forecastle deck,
supporting member, ordinary stiffener and etc., should be added.
Please consider.

1003

9/1.5.2.1

Questionintermediate
longitudinal

2009/12/16

For clarity, please give the definition of intermediate longitudinal, referred in
Ch.9 Sec.1 [5.2.1].

Attachment

Answer

The reference number of the last sentences of Ch9 Sec1, 4.3.3 and Ch9Sec2, 4.2.3 should be as follows: “The net dimensions of ordinary stiffeners
are to comply with the requirement in Ch 6 Sec 2, [2.2.3] and [2.3].” This will
be corrected in the next corrigenda.

1.The requirements of forecastle given in Ch.9 Sec.1 Fore Part should betransferred to Ch.9 Sec.4 Superstructures and Deckhouses.
This will be considered in the next Corrigenda.
2. The requirements of forecastle structure, such as forecastle deck,
supporting member, ordinary stiffener and etc., should not be included. A
reference of the forecastle to bow flare reinforcement in Ch.9 Sec.1 should be
made.
This will be considered in the next Corrigenda.

Intermediate longitudinals (additional stiffeners) are stiffeners installed in thespacing between ordinary stiffeners (so the stiffener spacing is halved).

Page 20 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

1012

Ref.

9/2.4.3.1 &KC ID 896

Type

Q&A

Topic

Net
thickness of
PSMs

Date
completed

Question/CI

With reference to KC ID 896:
The answer to KC ID 896 is quoted below:[Quote]A1) Yes, deck PSM have to fulfill the requirements of Ch.6 Sec.4 considering
the loads defined in Ch.9 sec.2 [2.2], and in particular the minimum web
thickness defined in Ch.6 Sec.4 [1.5.1].
A2) No, the requirement for a minimum web thickness defined in Ch.9 Sec.2[4.3.1] applies to all the PSM except those of the deck (see answer A1herein).
A rule change will be issued for clarifying this.
[Unquote]
2010/5/12
Ch.9 Sec.2 [4.3.1] only specifically mentions floors. No mention is made of
any other PSM. However, Answer 2 (A2) goes beyond the scope of Ch.9
Sec.2 [4.3.1]. A2 implies that all PSM, except those decks, are required toapply the formula given in 4.3.1. If A2 is applied, there will be a large impact
on scantlings.
In addition, we consider that a technical background clearly explaining thedifference between the minimum net thickness of deck PSMs and other PSMs
in the same space should be provided.

Answer

Attachment

KC 896 is categorised as a Rule Change as defined in PR32, hence
implementation date will be decided by Hull Panel.

Therefore, please confirm the effective application date of KC ID 896 and if
necessary, please revise the answer to KC ID 896.

Page 21 of 22

IACS Common Structural Rules Knowledge Centre

KCID
No.

Ref.

Type

Topic

Extension of
longitudinal
9/3.3.1.2 & Interpretati structure1018
9/3.1.3.2
onwithin themachinery
space

Date
completed2010/3/30

Attachment

Question/CI

AnswerWe understand from KC Question ID 700 and 728 that the extension of
longitudinal structure for at least 0.3 times the length of the machinery spaceis only required for the upper portions of the side shell. Due to generally finer
hull form in way of the engine room, particularly for the lower part of the aftcross section, it is not always practical to extend longitudinal side shellstructure aft of the engine room forward bulkhead for the stipulated 0.3 timesof the length of the machinery space. Such extension, especially in the lower
part of the hull cross-section below the level of the topside tank, may require
deeper side shell web frame structure resulting in a reduction in usable
volume and floor area in the engine room space. In every case the hull girderstrength, ultimate strength of the cross-section aft of the engine room forward
bulkhead are checked and prescriptive buckling check of side shell panels in
the machinery space are carried out.

It would appear reasonable to limit extension of side shell longitudinal
structure for 0.3 times the length of the machinery space to side shellstructure above the lowest level of the top side tank, subject to the condition
that abrupt structural discontinuities between longitudinal and transversely
framed structure are to be avoided and that hull girder strength, ultimate
strength and prescriptive buckling checks of the cross-sections and side shell
panels in the machinery space are performed and satisfied. The extension of
longitudinal stiffeners of the upper part of the side shell is to be maintained inview of the generally higher stresses in this area, the relative ease of providing
such extension and to improve strength margin in this region of higher stress.
Due consideration is to be given to proper tapering of major longitudinal
members as required by Ch. 9/3.1.3.2. Notwithstanding the above, bottom
shell and bilge longitudinal stiffeners in the aftermost cargo hold of larger andfull form vessels are to be extended into the engine room to the extent
practicable.
We agree with your proposal and a CI will be issued to this effect.

Side shell plate panels in the lower hull cross-section are not planar but havea curvature that provides added buckling resistance. Furthermore thesatisfactory service experience of numerous bulk carriers of all sizes that havebeen built without such a specific extension of side shell longitudinal structure
could be considered. We request the urgent confirmation of the above
interpretation and/or issuance of a CI to this effect.

1039

1074
attc

9/5.2.2.1

9/3.2.2

CI

Requirementof ballast
hold andhatch coverof the ballast
holdInterpretati Definition ofonMargin Plate

2010/5/17

Regarding the requirement of Ch.9, Sec.5, 2.2.1, we would like to confirm thatYour interpretation is correct. A hatch cover of the ballast hold is required toa ballast hold is not included in ballast tanks and other tanks, and a hatch
be weathertight.
cover of the ballast hold is required to be weathertight.

There is no definition of “Margin Plate” in CSR Bulk Carrier.
1. Rule Application of CSR Bulk Carrier: Chapter 9, Section 3/2.2. Table 1:
Minimum Thickness Application of Margin Plate.
2. Since there is no definition about “Margin Plate” in CSR Bulk Carrier Rule,
we are using the “Margin Plate” definition in CSR Tanker (Ref. Sec.4/ Table
2010/11/15 4.1.1)
3. According to the definition of terms in CSR Tanker, we may think of thefollowing two cases;
Case 1 & Case 2 (see attachments)
4. Does you consider both cases are Margin Plate? or One of two cases is
Margin Plate?

The definition of Margin Plate in Ch9/Sec3/Table 1 should be given and in linewith CSR OT in which the definition comes from IACS Recommendation
82,"Surveyor’s Glossary, Hull terms and hull survey terms".
Both Case 1 and Case 2 are Margin Plate.
A corrigenda will be considered.

Page 22 of 22

YPage 1 of 1

KC#249http://207.235.44.25/iacs27rz/documents/249/rudderhorn.JPG

08/06/2007

KC#309

KC#336
Comments on CSR for Bulk Carriers

Dec 2006

Attachment
Ch 9, Sec 5, [5.5.1]
We would like to confirm a way to apply the requirement of this sub-paragraph to a
structural member shown in the attachment.
(1) Which position, A, B or C, shown in Figure, is to be selected to calculate w0 and I0?
We consider that position B is suitable for this requirement. Please confirm.
(2) Which position, A, B, C or else, is to be considered when the requirement of net
section modulus of ordinary stiffeners, w, is applied?
We consider that position A is appropriate for this requirement. Please confirm.

w1, I1

w0, I0A

B

C

Trans.
Trans.

"1/2
"0/2
"1
"0

Figure : Variable cross-section stiffenerKC#476

KC#476 Technical background
The proposed answer by BV relies onto the ILLC regulations 15(6) and 16(5) that are to be fully applied. The
excerpts of ILLC are added herein.

Pontoon covers
The proposed interpretation is:If hatch covers are considered weathertight by using tarpaulins and battening devices, the allowablestresses to be used are those corresponding to the line "Pontoon hatch cover" in the Tab 2, i.e. 0.68ReH
for sigma. This is in line with ILLC Reg.15(6)This regulation ILLC 15(6) is:(6). Where pontoon covers used in place of portable beams and covers are made of mild steel, thestrength shall be calculated in accordance with the requirement of regulation 16 (2) to (4) and the
product of the maximum stress thus calculated and the factor 1.47 shall not exceed the minimum upper
yield point strength of the material. They shall be so designed as to limit the deflection to not more than
0.0044 times the span. Mild steel plating forming the tops of covers shall be not less in thickness than
1% of the spacing of stiffeners or 6 mm if that be greater.

Hatch cover minimum design loads
The proposed interpretation is:If hatch covers are considered weathertight by construction, and without
the need of tarpaulins and battening devices, the allowable stresses to be used are those corresponding
to the line "Weathertight hatch cover" in the Tab 2, i.e. 0.8ReH for sigma. This is in line with ILLC
Reg.16(5).
The regulation ILLC 16(5) is:(5). All hatch covers shall be designed such that:(a). the product of the maximum stress determined in accordance with the above loads and the factor of
1.25 does not exceed the minimum upper yield point strength of the material in tension and the critical
buckling strength in compression;(b). the deflection is limited to not more than 0.0056 times the span;(c). steel plating forming the tops of covers is not less in thickness than 1% of the spacing of stiffeners
or 6 mm if that be greater; and(d). an appropriate corrosion margin is incorporated.

KC#582

Double bottom Floor of E/R

KC#699
The background of formula for net section modulus of web stiffener in
Ch 6 Sec 2 [4.1.2]

Model

Web stiffener is flat bar type and the web thickness of the web stiffener is equal tothat of the attached plate
z
h

t

e2

t

h1=t+he1yb
In this case, the moment of inertia of the stiffener with attached panel is given by thefollowing equations.

Iy

h1 t  (b  t )t 3
2
 t (b  h) * e1
3

(1)

e1

1 h1  (b  t )tand e2
bh
2

(2)

3

Moment of inertia

2

Z

Minimum Section modulus

h1  e1

I y / e2(3)

Normally, t  b, and t  h , then the equation (3) for the section modulus can be expressesby the following equationZ

th 2 1  4b / h
6 1  2b / h

th 2 §
1
·
¨2 
¸
6 ©
1  2b / h ¹
th 2 §0.5 ·¨1 ¸
3 © 1  2b / h ¹§©

If the term ¨1 

(4)

0.5 ·
¸ is assumed to be proportional to the square of a spacing Ss, in m,
1  2b / h ¹

of web stiffener and the height of web stiffener can be assumed to be " / 12 , where " is thelength of web stiffener, according to the requirement in Ch 3 Sec 6 5.2.1, then we can get thefollowing equation.

Zth 2 §0.5 ·¸¨1 
3 © 1  2b / h ¹

2t§ " · 2¨ ¸ Ss3 © 12 ¹

1 3 2
2t" S s | 2.5 *10 3 t" 2 S s
432

(5)

Considering the used units of symbols, we can get the rule formula in Ch 6 Sec 2 [4.1.2].

1

KC#727

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 
㪙㫆㫋㫋㫆㫄

 

KC#1074
Case 1:Case 2: