Section 2 Analysis Procedure

2.1.1 The prescriptive requirement of B/5 was developed based on collision damage statistics collected mainly by IMO many years ago. This means the ships were old designs and constructed in single hulls. Clearly, better design or strengthened designs have higher capability to absorb collision energy, and thus reduce damage penetration. The methodologies adopted in this procedure for equivalent collision protection are described in this Section.

2.2.1 Two ships are involved in a ship-ship collision analysis: a striking ship and a struck ship. It is assumed that, as illustrated in Figure 1.2.1 Illustration of ship-ship collisions, the struck ship is to be collided by a same sized striking ship.

2.2.2 The collision scenario is that the striking ship impacts the struck ship at the location where the fuel tank is located. The struck ship is assumed to be stationary before collision and the striking angle between striking and struck ship is assumed to be 90 degrees in the horizontal plane.

Figure 1.2.1 Illustration of ship-ship collisions

2.2.4 It is assumed that the striking bow is rigid and all collision energy is absorbed by the struck ship and in this case the worst damage to the struck ship can be determined.

2.2.5 Two struck ships are to be assessed: one is called the Reference Ship and the other the Target Ship. Both struck ships are assumed to be collided by the same striking ship with the same collision scenarios.

2.2.6 The Target Ship refers to the new design where the fuel tank location does not meet the Rule requirement and the tank boundaries are too close to the ship side.

2.2.7 The Reference Ship is a ship which meets the current minimum Class Rule requirements. It is a similarly sized ship as the Target Ship, and constructed in single hull and without any specific strengthening (e.g. ice strengthening).

2.2.8 The Reference Ship is subjected to a collision directly into the side shell at the location where the fuel tank is located. The rigid striking bow penetrates to B/5 from the struck ship side. The collision energy absorbed (E_ref) by the Reference Ship is calculated.

2.2.9 The Target Ship is subjected to the same collisions. The extent of penetration into the ship and the absorbed energy (E_crit) at the critical penetration (B_crit), e.g. just before reaching the boundary of the fuel tank (as illustrated in Figure 1.2.3 Illustration of absorbed energy of reference ship and target ship), is calculated.

Figure 1.2.3 Illustration of absorbed energy of reference ship and target ship

2.2.10 Collision energies for the three cases of loading conditions, as illustrated in Figure 1.2.2 Three collision cases of loading conditions, are calculated based on the above routines. The absorbed energy weighted from the three collision cases is to be used for comparison and determined from the following:

2.2.11 If the Target Ship absorbs the same amount of energy or more at the critical penetration (B_crit), then the equivalence of strength to resist collision damage is demonstrated. That is:

2.2.12 Simplified analytical methods as described in the following Section, or alternative methods subject to Lloyd’s Register’s agreement, may be considered in use for the collision damage assessments.