An Analytic Method of Underwater Observation Tower Due to Wave Breaking Forces

Wave breaking forces acting on the nearshore structures, such as the underwater observation tower, are subject to breaking wave forces which leads to response behavior that is characteristically nonlinear. Most of the existing underwater observation towers in Japan were constructed in the wave breaking zone as this zone is abundant with underwater life and presents a fantastic under water scene. Convenient access to the observation tower is typically connected by a bridge connecting the tower to an onshore site. This study reported here presents the develop a structural analysis procedure for an underwater observation tower subject to the breaking wave forces using finite element analysis. The tower structure consists of vertical circular cylindrical form that may be tapered in some cases. A procedure for estimating the breaking wave forces and transferring the appropriate hydrodynamic pressure distribution to each nodal point in the finite element model is presented and discussed. The ratio between the total diffraction wave forces and total breaking wave forces was investigated, and then the breaking wave pressure distribution acting on the structural surface was studied. Using that ratio obtained through the comparative studies, the dynamic analysis was conducted in the various wave periods for a constant water depth. After summarizing these calculation results, an analytic method on underwater observation tower due to wave breaking forces was presented.