A Comparative Study on the Plastic Formulations of Ship Shell Plating Under Patch Loading

Abstract

The purpose of the present study is to further develop the response formulation of ship shell plating under general patch loading, considering the effect of finite, permanent deformation. A comparative study is conducted between various formulations for the load-carrying capacity of laterally patch loaded plates with the aid of nonlinear finite element method. The increasing public interest of transportation and resource exploitation in Arctic area gives rise to advances in ice strengthening of ship structures. As a result, the subject of ship shell plating under ice loads has been extensively studied. Similar to ice loads, wave slamming loads, wheel loads of vehicles and accidental loads, e.g. collision and grounding, are all likely to take place over a limited area of the plate, and can be termed as ‘patch loading’. Consequently, the resistance of ship shell plating under ‘patch loading’ is of significant interest. In this study, a recently developed plastic formulation for patch loaded plates is further extended for general patch loading condition, i.e. patch load with limited extension in both length and height direction. After a brief review of the development of the response and design formulations for plates under uniform lateral load and patch load, comparative studies are made in cases of limited and finite permanent deformation with the aid of nonlinear finite element methods. By allowing a certain level of permanent deformation, significant weight savings can be achieved. Some main findings will be concluded from the comparative study. The present formulation may be used as a versatile tool for predicting the resistance of plates under various types of patch loads, notably when finite, permanent deformations are accepted, e.g. in the Accidental (Abnormal) Limit States design.