Crushing resistance of web girders in ship collision and grounding

A new theoretical model for the crushing of web girders under localized in-plane loads is proposed on the basis of a comparative study of existing simplified methods and analyses of the progressive deformation process of web girders. The model captures several features of the local crushing process of the girder which have not been accounted for by any of the existing models. The behavior of web girders under in-plane loads is a relevant subject in both ship collision and grounding process as well as in the area of civil engineering. A variety of simplified methods have been proposed and developed by various authors around the latest decade. The different formulations in terms of instantaneous and mean crushing force are investigated and reproduced under some common rules for a comparative study. The predictions are compared to three series of experimental results found in literature. The applicability and correlations of these simplified methods are discussed in some detail. It is observed from the analysis of the deformation process that the existing theories cannot capture the main characteristics of the progressive crushing process. Therefore, a new simplified deformation model is proposed comprising two folding elements with the second folding element compressed partly, and a new set of simplified analytical method is developed by using plastic methods of analysis. The proposed method is verified by the three experiments, which have been used for the comparative study, and it agrees satisfactorily with the experimental results. For the purpose of practical application of the present simplified formulae, the effect of web stiffeners on the crushing resistance is studied as well as the influence of dynamic loading and the effective crushing distance.