Abstract
Flap-gate seawall is a coastal structure which lies down on the ground usually, and it rises up by buoyancy and closes an opening of embankments when inundation occurs. A traditional flap-gate seawall has counterweights which assist the gate in moving. Although arrangement of the traditional flap-gate's counterweights is effective, it is difficult to support the gate with over 20 meters wide on sides of the gate. Therefore, a long-span type flap-gate seawall has been developed in this study. It equips counterweights behind the gate, and then the counterweight does not prevent width of the gate from extending. In this study, motions of both gates and counterweights and wave force acting on gates were examined through a series of hydraulic experiments using a model of the long-span type flap-gate. As a result, wave force acting on the gates was within ranges in which the flap-gate can be designed reasonably. The experimental works confirmed that the long-span type flap-gate seawall has good performance for protecting target areas against tsunami.
