Reliability Analysis of Ro-Ro Vessel Movable Vehicle Ramps Under Vehicle Moving Load

In the design of roll-on/roll-off ship structures, movable vehicle ramps serve as a bridge connecting different decks and are typically subjected to various moving vehicles. However, the loads carried by the ramp during its operation often vary from the design loads considered in the design phase. Due to the uncertainty of vehicle loads and the structural materials, it is of significant importance to assess the reliability of the movable vehicle ramp structure. To investigate the structural reliability of the movable vehicle ramp structure under vehicle moving loads, the weight of the vehicle, the moving speed, and the thickness of the top plate of the ramp were selected as random variables. Based on numerical results, the limit state equation of the movable vehicle ramp structure was obtained by the Box-Behnken design response surface method. Then, the structural reliability index was calculated by the checking point (JC) method, and the influence of each variable on the structural reliability of the movable ramp was derived through sensitivity analysis. Finally, the structural optimization of the plate thickness was carried out according to the reliability analysis, which is significance guidance for the optimization of the movable ramp design.