4.3.1 For passenger craft, superimposed vertical
accelerations above 1g at longitudinal centre of gravity
shall be avoided unless special precautions are taken with respect
to passenger safety.
4.3.2 Passenger craft shall be designed for the
collision design acceleration g
coll with respect
to the safety in, and escape from, the public spaces, crew accommodation
and escape routes, including in way of life-saving appliances and
emergency source of power. The size and type of craft together with
speed, displacement and building material shall be taken into consideration
when the collision load is determined. The collision design condition
shall be based on head-on impact at a defined collision speed.
4.3.3 Mounting of large masses such as main engines,
auxiliary engines, lift fans, transmissions and electrical equipment
shall be proved by calculation to withstand, without fracturing, the
design acceleration given in table 4.3.3.
Table 2.4.3 Design acceleration as
multiples of g
| Types
of craft \ Direction
|
All HSC
except amphibious ACVs
|
Amphibious ACVs
|
| Forward direction
|
g
coll
|
6
|
| After direction
|
2 or
g
coll if less
|
3
|
| Transverse direction
|
2 or
g
coll if less
|
3
|
| Vertical direction
|
2 or
g
coll if less
|
3
|
where:
|
g
coll
|
= |
the collision design acceleration expressed as a
multiple of the acceleration due to gravity (9.806 m/s2) |
|
4.3.4 Collision design acceleration g
coll (for craft other than amphibious ACVs where g
coll = 6) shall be calculated as follows:
where the load P shall be taken as the
lesser of P
1 and P
2,
where:
|
P
1
|
= |
460 (M.c
L)2/3 (E.c
H)1/3
|
|
P
2
|
= |
9000.M.c
L (c
H
D) 1/2
|
where the hull material factor M shall
be taken as:
|
M
|
= |
1.3
for high tensile steel |
|
M
|
= |
1.0
for aluminium alloy |
|
M
|
= |
0.8
for fibre-reinforced plastics, |
where the length factor c
L of
the craft is:
where the height factor c
H =
(80 - L)/45 but not greater than 0.75 or less than 0.3,
where the kinetic energy of the craft at speed V
imp is:
where the main particulars of the craft are:
|
D
|
= |
depth
of the craft from the underside of keel to the top of the effective
hull girder (m) |
|
Δ |
= |
craft displacement,
being the mean of the lightweight and maximum operational weight (t) |
|
V
imp
|
= |
estimated impact speed (m/s) = 60% of maximum speed |
|
g
|
= |
acceleration
due to gravity = 9.806 m/s2.
|
For hydrofoils, the collision design acceleration, g
coll shall be taken as the greater of either the g
coll as calculated above or:
where:
|
F
|
= |
failure
load of bow foil assembly applied at the operational waterline (kN). |
4.3.5 As an alternative to the requirements of
4.3.4, the collision design acceleration g
coll may
be determined by carrying out a collision load analysis of the craft
on a vertical rock having a maximum height of 2 m above the waterline
and using the same assumption for displacement Δ and impact
speed V
imp as described in 4.3.4. This evaluation
may be carried out as part of the safety analysis. If the collision
design accelerations are determined by both 4.3.4 and the collision
load analysis, the lower resulting value may be used as the collision
design acceleration.
4.3.6 Compliance with the provisions of 4.1.5 and 4.3.1 shall be shown for the
actual type of craft, as described in annex
9.
4.3.7 Limiting sea states for operation of the
craft shall be given in normal operation condition and in the worst
intended conditions, at 90% of maximum speed and at reduced speed
as necessary.