Abstract: A simplified analysis method which takes into account the influence of friction is proposed to evaluate the crashworthiness behavior of stiffened side plates of ship. The progressive collapse behavior of the stiffened side plates collided by a bulbous bow are described. The curves of collision force-penetration depth and energy absorption-penetration depth are presented for the plates and compared with the existing experimental results. The results show that simplified analysis method can well predict the stiffened side plates. The method can be applied to evaluate the crashworthiness behavior of the side structure in ship design.