Simplified Bow Model for a Striking Ship in Collision

SIMPLIFIED BOW MODEL FOR A STRIKING SHIP IN COLLISION by Suryanarayana Vakkalanka The serious consequences of ship collisions necessitate the development of regulations and requirements for the subdivision and structural design of ships to reduce damage and environmental pollution, and improve safety. Differences in striking ship bow stiffness, draft, bow height and shape have an important influence on the allocation of absorbed energy between striking and struck ships. The energy absorbed by the striking ship may be significant. The assumption of a “rigid” striking bow may no longer hold good and typical simplifying assumptions may not be sufficient. The bow collision process is simulated by developing a striking ship bow model that uses Pedersen's super-element approach and the explicit non-linear FE code LSDYNA. This model is applied to a series of collision scenarios. Results are compared with conventional FE model results, closed-form calculations, DAMAGE, DTU, ALPS/SCOL and SIMCOL. The results demonstrate that the universal assumption of a rigid striking ship bow is not valid. Bow deformation should be included in future versions of SIMCOL. A simplified bow model is proposed which approximates the results predicted by the three collision models (closed-form, conventional and intersection elements) to a reasonable degree of accuracy. This simplified bow model can be used in further calculations and damage predictions. A single stiffness can be defined for all striking ships in collision, irrespective of size.

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