Regulation 6 - Attained
Subdivision Index A
(a)
-
(i) In addition to complying with Regulation 5
the attained Subdivision Index A shall be determined for the ship
by formula (II):
- Where:
|
“a”
|
= |
accounts
for the probability of damage as related to the position of the compartment
in the ship's length, |
|
“p”
|
= |
evaluates
the effect of the variation in longitudinal extent of damage on the
probability that only the compartment or group of compartments under
consideration may be flooded, and |
|
“s”
|
= |
evaluates
the effect of freeboard, stability and heel in the final flooded condition
for the compartment or group of compartments under consideration. |
-
(ii) The summation indicated by formula (II) is
taken over the ship's length for each compartment taken singly. To
the extent that the related buoyancy and stability in the final condition
of flooding are such that “s” is more than
zero, the summation is also taken for all possible pairs of adjacent
compartments, and may be taken for all possible groups of a higher
number of adjacent compartments if it is found that such inclusion
contributes to the value of the attained Subdivision Index A.
-
(iii) Wherever wing compartments are fitted and
where the assumed damage used in the damage stability calculations
according to Regulation 5 forming the basis for the “s” calculation does not result in flooding of the associated
inboard spaces, “p” shall be multiplied by “r” as determined in Regulation 7(b).
(b) The factor “a” in
formula (II) shall be determined for each compartment
and for each group of compartments by formula (III):
Where:
and otherwise
and otherwise
and otherwise
and where:
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χ1
|
= |
the
distance from the aft terminal of Ls
to the
aft end of the considered compartment or group of adjacent compartments;
|
|
χ2
|
= |
the
distance from the aft terminal of Ls
to the
forward end of the considered compartment or group of adjacent compartments.
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For the purposes of this paragraph and of paragraph (c) of this
Regulation, with respect to the length any compartment or groups of
compartments under consideration, where one or both of the limiting
bulkheads have steps, the forward and after ends of the considered
compartment or group of compartments will be taken at the portions
of the bulkheads which are nearest to each other.
(c) The factor “p” in formula (II)
shall be determined for each compartment and for each group of compartments
by formulae (IV)-(VII).
-
(i) In general “p” shall
be:
- Where:
|
l
|
= |
the
length of compartment or group of compartments as defined in paragraph
(b) of this Regulation |
|
W
|
= |
1.0
and λ = Ls
for Ls
=
655 feet (200 metres) or less
|
and otherwise, 
-
(ii) To evaluate “p” for
compartments taken singly, formulae (IV) are applied
directly.
-
(iii) To evaluate the “p” values
attributable to groups of compartments, the following supplementary
nomenclature and formulae apply:
l
1, l
2, l
3, l
4, etc. are the lengths of compartments
taken singly
l
12, l
23, l
34, etc. are the lengths of pairs of adjacent compartments
l
123, l
234,
etc. are the lengths of groups of three adjacent compartments
l
1234, etc. is the length of a group
of four adjacent compartments
p
1, p
2, p
3, p
4, etc. are p calculated by formulae
(IV)
using l
1, l
2, l
3, l
4, etc. as l.
p
12, p
23, p
34, etc. are p calculated using l
12, l
23, l
34, etc. as l
p
123, p
234,
etc. are p calculated using l
123, l
234, etc. as l
p
1234, etc. is p calculated using l
1234, etc. as l
For compartments taken by pairs,
For compartments taken by groups of three,
For compartments taken by groups of four,
(d) The factor “s” in
formula (II) shall be determined for the final stage
of flooding for each compartment and for each group of compartments
by formulae (VIII) and (IX).
-
(i) In general, for any condition of flooding
from any initial draught di
, si
shall
be:
but not more than 1.0
- Where:
|
θ
|
= |
the
angle of heel due to unsymmetrical flooding in the final condition
after cross-flooding, if any; |
|
GMR
|
= |
the highest required intact metacentric height at the relative
draught, as determined in Regulation
5(e) or if a higher metacentric height is to be specified in
the instructions to the Master, that value may be used;
|
|
MMS
|
= |
the reduction in the height of the metacentre as a result of
flooding, calculated for the ship in the upright position in the final
stage of flooding. |
-
(ii) For each compartment and for each group of
compartments, “s” is taken as:
- Where:
|
s
1
|
= |
si
calculated for the ship at initial
draught d
1
|
|
s2
|
= |
si
calculated for the ship at initial
draught d
2
|
|
s
3
|
= |
si
calculated for the ship at initial
draught d
3
|
d
1, d
2 and d
3 as defined in Regulation
1(g)(iii).
Values of GMR
for the draughts d
1, d
2 and d
3 are
determined from the plot of GMR
versus draught
to be furnished to the Master of the ship in accordance with Regulation 8. Values of MMS
, θ and F
1 for
these draughts are determined from plots of damaged condition vertical
metacentre, trim, draught and heel versus undamaged draught, determined
in accordance with Regulation 5(e).
-
(iii) Provided a positive contribution to the
attained Subdivision Index A is obtained thereby, the flooding of
combinations of adjacent compartments in excess of those required
for compliance with Regulation 5(b)(i)
and (ii) may be included in the calculations. However, si
shall be taken as zero for any case of flooding which
results.
-
(1) during intermediate flooding or prior to equalization
in an angle of heel in excess of 20 degrees or which immerses any
opening through which downflooding might take place, or
-
(2) for the final stage of flooding, except in
way of the flooded compartment or compartments, in immersion of the
relevant bulkhead deck at side, or heel in excess of 12 degrees, or
(GMR
- MMS
) less than
2 inches (0.05 metre).
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