Investigating the elastic and plastic behaviour of a steel caisson subjected to ship impact

Abstract

A four-fold increase in global sea traffic over the past twenty years has led to an increased risk of ship impact on dock infrastructure. Ship impact is a highly non-linear process and it is important that the elastic and plastic behaviour of caissons subjected to ship impact is well understood so that they can be sufficiently designed against it. This project used LUSAS finite element analysis software to perform a time history analysis of a proposed steel caisson subjected to five different ship impact loads and from the results compares the behaviour of each impact case to gain a better understanding of impact behaviour. The main conclusion is that increased ship mass means an increase in kinetic energy which leads to increased plastic behaviour within the caisson. The maximum plastic strain within the caisson was 0.15% and the permanent deformation was 2.70mm. Another conclusion was that the proposed steel caisson is sufficiently designed to safely withstand ship impact from a 1500 tonne vessel traveling at 0.5m/s with only local plastic deformation occurring.