An experimental, numerical and analytical study on deformation mechanisms of web girders in a collision or grounding incident

This paper presents an experimental, numerical, and analytical study on the crushing of web girders, to provide insights into the behaviour of a ship's structure in a collision or grounding incident. Web girders, which are plated structures subjected to in-plane loads in an accident, develop a variety of deformation mechanics to absorb impact energy. The web stiffeners on them provide additional resistance. However, studies devoted to the contributions of longitudinal and transverse stiffeners to the load-carrying capacity of web girders are scarce. It remains a technical challenge to quantify the crushing strength of stiffened web girders, particularly the extent by which longitudinal and transverse web stiffeners can increase the load-carrying capacity of web girders in a collision or grounding incident. To further research on the behaviour of web girders in a collision or grounding incident, a new series of laboratory experiments was conducted, where four scaled double hull specimens were crushed in a quasi-static manner. The specimens included one unstiffened web girder, one longitudinally stiffened web girder, and two transversely stiffened web girders. Experiments of this nature provide a good basis for comparing different designs of web girders, and they have been seldom reported in publicly available literature. The aim of our work is to provide experimental data suitable for a comparative study. To supplement the laboratory experiments, nonlinear finite element method (FEM) analyses were also conducted to provide additional information that was not possible to obtain solely from experimental measurements. Certain existing analytical models were reviewed, and their predictions were compared with the experimental results. While all these simplified analytical formulae provide reasonable estimates, their predictions deviate more from the experimental results when the web girders are stiffened. Finally, the typically applied approach of equivalent plate thickness is not optimal, particularly when the web stiffeners are in line with the striking indenter.