A FUNDAMENTAL RESEARCH ON THE EFFECTS OF A FLOATING BERTH ON REDUCTION OF TSUNAMI DAMAGES IN A HARBOR: REDUCTION EFFECTS OF THE BREAKING OF MOORING LINES AND RUNNING ON A QUAY

摘要

Tsunami consecutively brings about several types of disasters, which is described as "disaster chain." In the case that vessels are moored to the quay, the breaking of the mooring line possibly causes drift or collision with other vessels. There is also a case that a mooring tether of the vessel moored to the floating pier is not broken in the damage of tsunami, which was confirmed at Shiogama port in Miyagi when the East Japan Great Earthquake occurred on March 11, 2011. The objectives of this paper are to clarify the reduction effect of mooring line force when a vessel is moored to a floating berth. The three-dimensional MPS method is used with advantages of floating berth considered. We simulated a vessel with the cargo carrier of 3,000t. Especially, by changing the wave elevation and the incident angle, the responses of the mooring tension which acts on the vessel moored to a floating berth and to the quay respectively are compared, and its reducing efficiency is examined. A conclusion is reached that, when tsunami incident wave angle is 90 degrees, mooring vessels to a floating berth can be expected as a solution to reduce the problems of vessel's running onto a quay, in comparison with mooring them at a quay wall. Also, we propose suitable anchoring methods according to the size of the vessels.