An analytical method of predicting the response of FPSO side structures to head-on collision

Abstract

The possibility of collision between FPSO and ships exist, and consequences of such collisions can be severe. The crashworthiness of FPSO side structures must be considered in preliminary stage of structure design. In this paper, an analytical method is proposed for rapidly predicting responses of FPSO side structures in case of being struck by a ship with rigid bulbous bow. This method is particularly suitable for use in preliminary structure design phase because it is built based on a series of close-formed formulae derived using the simplified analytical method and only a few parameters are needed for calculation. The proposed analytical method is developed by combining several primary failure models of major double shell members, including the plate punching model, the plate perforating model, the plate denting model, the plate tearing model, and the X-shaped structure crushing model. Using the proposed method, curves of impact load versus indentation for three typical collision scenarios are obtained. These curves provide a detailed description of the collision process until rupture occurs in inner shell and help to evaluate crashworthiness of FPSO side structures. Accuracy of the analytical method is verified by numerical simulations using code LS_DYNA. The results of numerical simulations and those by the proposed analytical method match well.