It is well known that the ship moored to a single buoy shows a large yawing motion due to severe winds, and that the motion causes a large mooring force. In this report. numerical simulations of ship motions are carried out in order to estimate the tension of the mooring chain.
　The study has yielded the following conclutions.
(1) The computed maximum tension F exerted the on the ship mooring chain in variable wind is larger than that of F in steady wind with the mean speed of the variable wind. Even for the same speeds of the winds, the ratio of F/F shows the different value, depending on the type of the vessel (tanker of freighter ) and the length of the mooring chain. Therefor, the numerical computation should be made for variable winds.
(2) The maximum tension of the mooring chain is varied by the length of the chain. The tension decreases as the length of the chain becomes long for a tanker, while the tension has a peak value at the length about 50m for a freighter.