Numerical simulation of dropped container impacts with an offshore platform deck in the North Sea

Abstract

This paper presents a numeric study for an offshore platform deck that encounters potential dropped container impacts in the North Sea. The commercial Abaqus Explicit code was used. Significant plastic deformation was observed due to the high impact energy. A correct tensile fracture model that simulates the steel ductile failure under complicated stress states becomes crucial in such analysis. The material test data are normally very limited in design, which makes it difficult to calibrate the failure criterion. The critical failure strain provided by rules/codes (NORSOK and DNV GL) is not explicitly based on the stress states. This paper presents two simple approaches to extend the failure strain to a wider triaxiality range. Validation has been performed for the two failure criteria that depend on stress states (based on the RTCL and first principal plastic strain). The criterion based on the first principal plastic strain is shown to give the most conservative results. The RTCL-based interpretation shows good agreement under different mesh sizes. Several practical issues during the analysis are also addressed. Both criteria have been applied in the case study. Minor differences are observed from the obtained results of the dissipated energy and impact force. However, the local failure patterns are quite different, to which further attention shall be paid.