Virtual mass of berthing ship, Which is important to calculate the ship's berthing energy, was examined experimentary in port and Harbour Research Institute. The ratio of water depth to draft of ship, H/d. has a significant meaning to virtual mass compared to the other factors such as the structural type of quay wall and load-deflection characteristics of fenders and quay walls.
　Virtual mass is defined as the linear function of displaced mass of the ship. The virtual mass coefficient obtained in experiment became nearly 2.3 at H/d=1.10. As the virtual mass coefficient calculated based on the current design standard is about 1.5 or 1.6, it is suggested to designers to give much care to the berthing energy in design works.