Ultimate Strength and Load Response of a Single Side Shell Panel of Bulk Carrier under Longitudinal Thrust and Out-of-plane Pressure

The aim of the present study is to obtain the ultimate strength and load response of a single side shell panel of a bulk carrier under longitudinal thrust and out-of-plane pressure. Time-domain analysis using nonlinear strip method and a whole ship finite element analysis are performed to calculate the pressure and stress responses of the side shell panel. It is shown that the most critical sea condition in terms of buckling strength is an oblique sea that causes the maximum longitudinal stress due to horizontal bending moment, and the longitudinal thrust and out-of-plane pressure work on the panel almost in the same phase. The elastic buckling analysis and elastoplastic large deflection analysis of the side shell panel are carried out to investigate the collapse behavior. It is found that the collapse mode of the panel is a local buckling mode and a whole hull structure has a sufficient strength reserve even after the ultimate strength of the panel is attained. This suggests that the scantling of side shell structure under the current rule may be reduced. FORM (First Order Reliability Method) is adopted to identify the critical combined load condition using the limit state function based on the results of the ultimate strength analysis. Safety indices obtained by FORM show that the oblique sea of 120° heading angle is the worst condition similar to the result of time-domain analysis of load responses in short-term irregular waves. Integrating the findings of load and strength analyses, a rational method of ultimate strength evaluation of a side shell panel of a bulk carrier is discussed.