Hydro-elastoplastic behaviour of VLFS under extreme vertical bending moment by segmented beam approach

•Collapse behavior of VLFS under extreme loads is clarified by a series of numerical simulation and tank test.•A simulation method for the hydro-elastoplastic behavior of VLFS is developed.•A scaled model for VLFS which can reproduce the collapse behavior is developed.•It is shown that VLFS collapses only locally while its global stability is maintained in the extreme event.

This paper addresses collapse behaviour of Very Large Floating Structure (VLFS) under extreme vertical bending moment. The study is performed as part of risk analysis to evaluate the consequence of a rare collapse event. Elastic and plastic deformation of VLFS develops under the extreme vertical bending moment while the deformation interacts with the fluid around VLFS. Therefore, hydro-elastoplasticity analysis need be developed taking account of these effects. In this study, the whole VLFS structure is modeled as two elastic beams with an elasto-plastic hinge embedded at the connection. The structural deformation is formulated by using finite element method (FEM). The hydrodynamic behaviour is modeled by using Rankine source panel method in time domain based on two-dimensional potential theory. The two models are coupled. A series of scaled model tests is performed for validation. Simulation and tank test results for the basic collapse behaviour of VLFS are presented and discussed. The numerical method is applied further to a realistic VLFS design to clarify its collapse behaviour.