A cyclic progressive collapse method to predict the bending response of a ship hull girder

This paper describes a cyclic progressive collapse method for the prediction of ship hull girder cyclic bending response. The proposed methodology extends the established simplified progressive collapse method, which is only capable of simulating the monotonic bending moment-curvature relationship. However, the actual hull girder collapse can involve multiple load cycles, such as that caused by a series of storm waves. During these load cycles, the onset of plasticity and local buckling can reduce the overall strength and stiffness of the hull girder. Hence, a cyclic progressive collapse method is proposed to predict the ship hull girder structural response under cyclic bending. This method 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 element under cyclic loading. The proposed methodology is applied to predict the cyclic bending responses of two box girder models. Nonlinear finite element analysis is performed as a validation. The present study shows the feasibility of the proposed cyclic progressive collapse method, but also suggests the need to develop an enhanced model to predict the cyclic behaviour of structural components.