This appendix illustrates, by means of examples, how to
divide the ship length Ls
into discrete damage
zones. The subdivision of Ls
into damage zones
should not only take account of existing transverse bulkheads but
also separate smaller local watertight compartments, the flooding
of which has significant influence on the damage stability results.
1
Figure A-1 shows
the elevation of a part of a ship containing two compartments named
A and B. Compartment A is divided by local subdivision into the spaces
A1 and A2. For the purpose of calculating the
products ps which contribute most favourably to the attained
subdivision index, three fictitious compartments or damage zones are
considered. The bases for calculations of the p and s-values
are given below:
.1 Zone 1 of length l1
:
|
p based on l1
|
|
s based on flooding of space A1
|
.2 Zone 2 of length l2
:
|
p based on l2
|
|
s based on flooding of space A1 only or of
A2 only, or of A1 and A2,
whichever results in the least s-value
|
.3 Zone 3 (or space B) of length l3
:
|
p based on l3
|
|
s based on flooding of space B
|
.4 Zones 1 + 2:
|
p based on l1
and l2
|
|
s based on flooding of A1
or of A1 and A2, whichever results in the
lesser s-value
|
.5 Zones 2 + 3:
|
p based on l2
and l3
|
|
s based on flooding of A1 and A2 and B
or of A1 and B or of A2 and B,
whichever results in the least s-value
|
.6 Zones 1 + 2 + 3:
|
p based on l1
, l2
and l3
|
|
s based on flooding of space A1 and B or of
A1 and A2 and B, whichever results in the lesser
s-value
|
2 It would also be compatible with the regulations
to ignore the local subdivision with respect to the calculations of
the p-value. In this case, the following compartments
and group of compartments would be considered:
.1 Zone a of length l3
= l1
+ l2
:
|
p based on la
|
|
s based on flooding of space A1
or of space A2
or of spaces A1 and A2, whichever results in
the least s-value
|
.2 Zone b of length lb
(= l3
):
|
p based on lb
|
|
s based on flooding of space B
|
.3 Zone a + b:
|
p based on la
and lb
|
|
s based on flooding of A1 and B or of A2
and B or of A1 and A2 and B, whichever results
in the least s-value
|
3 Obviously, the approach given in paragraph 1
above will generally lead to an attained sub-division index which
is higher than (or at least equal to) that defined by the approach
of paragraph 2. Also, the error made by neglecting the actual distribution
of damage in the vertical direction is much smaller in the first case.
4 Another example of local subdivision is shown
in Figure A-2. The following
tables illustrate how this can be handled.
Figure A-1 Transverse subdivision into zones
Figure A-2 Transverse subdivision into zones
Table A-1 p-value calculated
including the effect of local subdivision
Damage zones measuring length of space opened
|
p based on length(s)
|
S based on the flooding of space(s) resulting in the poorest
stability
|
1
|
l1
|
space A
|
2
|
l2
|
space A or space B or
spaces A and B‡
|
3
|
l3
|
space B or space C or
spaces B and C‡
|
4
|
l4
|
space C or space D or
spaces C and D‡
|
1 + 2
|
l1
, l2
|
space A or spaces A and
B‡
|
2 + 3
|
l2
, l3
|
space B or spaces A and C
or spaces A, B and C‡
|
3 + 4
|
l3
, l4
|
space C or spaces B and D
or spaces B and C and D‡
|
1 + 2 + 3
|
l1
, l2
, l3
|
spaces A and B or A and C
or A and B and C‡
|
2 + 3 + 4
|
l2
, l3
, l4
|
spaces A and C or B and D
or A and B and C and D‡
|
1 + 2 + 3 + 4
|
l1
, l2
, l3
, l4
|
spaces A and C or A and B and
D or A and B and C and D‡
|
‡ whichever results in a smaller s-value.
Table A-2 p-value calculated
ignoring local subdivision
Damage zones measuring length of space opened
|
p based on length(s)
|
S based on the flooding of space(s) resulting in the poorest
stability
|
A
|
lA
= l1 + l2
|
space A or space B or
spaces A and B‡
|
C
|
lc
= l3
+ l4
|
space C or space B or
space D or spaces C and B or spaces B and D or spaces C
and D or spaces B and C and D‡
|
A + C
|
lA
, lC
|
space B or spaces A and C
or spaces B and D or spaces A and B and C or spaces
A and B and D or spaces A and B and C and D‡
|
‡ whichever results in a smaller s-value.