Damage Accumulation in Vertical Breakwaters due to Combined Impact Loading and Pulsating Wave Loads

Vertical wall breakwaters used to protect for example an harbour from large waves usually consist of large concrete caissons placed on the seabed. The wave loads can be divided in two types, pulsating and impact loads. For some types of breakwaters especially the impact wave loads can be very large. Permanent displacements of breakwaters can be observed as a result of especially the impact loads. In this paper a stochastic model is formulated for the accumulation of permanent rotations of a breakwater subjected to both pulsating and impact wave loads. The permanent deformations are modelled by an ideal elasto-plastic oscillator. The pulsating part of the wave loading is modelled as a filtered white noise process, and the impact load is modelled by a filtered Poisson process. It is shown how a distribution function for the accumulated permanent deformations can be obtained. Finally, an illustrative example is shown.