So far, the protection of a nuclear powered ship has been evaluated by its own capacity absorbing the collision energy in its destruction. On the other hand, it is recently reported that instead of the energy absorbing type barrier, a resisting type barrier has been developed which absorbs the collision energy mainly in the destruction of the striking bow. To design such a type of barrier, it is necessary to estimate the load acting on the side structure of the nuclear powered ship. This load is obtained by the following procedure : (1) Calculate the ultimate strength of a bow construction of the striking ship to get a load-deformation curve. (2) Carry out a collision simulation analysis to obtain the bow deformation in collision. (3) Estimate the load corresponding to the bow deformation using the load-deformation curve. It seems that there is not any established method of calculating the ultimate strength of a bow construction. So we have studied the ultimate strength of a bow construction of the striking ship. First, we have made a theoretical calculation by the F. E. M. on a ideal mathematical frame model of bow construction. Then, in order to clarify the behavior of the bow collapse and verify the calculation method, we have carried out collapse experiments using 1/10-scale bow models of tanker and container ship and compared the results of the experiments with those of the theoretical calculation, by which a reasonable agreement of both has been confirmed. Further, we have estimated the collapse loads of bow construction of actual ships and obtained the load-deformation curves. By these studies, it has become possible to determine the load acting on the side structure of the nuclear powered ship and the bow deformation of the striking ship in collisions.