The purpose of the study is to estimate the strength of frames against impulsive load in relation to the strength of ships subjected to wave impact. Especially authors are interested in the dynamic lateral buckling behavior of frames. In the previous report, the T-shaped beams were tested in a pendulum type impact testing machine. According to the results of experiments and elastic-analysis based on the finite element method, the dynamic lateral buckling behavior of beams were discussed. In the present report, the dynamic load is calculated by using simple model of collision between the beam and the swing weight, and elastic-plastic analysis of the beam is carried out.