Bending response of a damaged ship hull girder predicted by the cyclic progressive collapse method

This paper applies the cyclic progressive collapse method to predict the bending response of a damaged ship hull girder. As an essential index of the structural performance, the residual load-carrying capacity of a damaged ship hull girder is particularly important for assessing the consequence of an accidental event. In this regard, considerable effort has been devoted to develop an efficient calculation methodology that can provide a reliable estimation of the residual ultimate bending strength of a damaged hull girder. However, the actual hull girder collapse can involve multiple load cycles, such as that experienced in a rough sea. The cyclic loading may lead to the onset of plasticity and local buckling, which can permanently reduce the overall strength of the ship hull. Hence a cyclic progressive collapse method is proposed. It follows the major assumptions and procedure embedded in the original Smith method with an extended capability to re-formulate the load-shortening curve of structural elements when an unloading or reloading is activated. A case study is carried out to predict the cyclic bending response of an asymmetrically damaged box girder model with various extents. The effect of the instantaneous neutral axis rotation is accounted for. Additionally, equivalent nonlinear finite element analysis is performed as a validation.