Evaluation of Tsunami Loads on a Seismically Isolated Building Using 3D Fluid Analysis

A seismically isolated building subject to tsunami loading was simulated using 3D flow model to evaluate the tsunami load. The building is reinforced concrete building whose size is 70 m in width, 35 m in depth and 20 m in height. A pit for isolation layer, whose height is 1.5 m, is modeled beneath the building. The gap between the building and surrounding retaining walls is 0.6 m. Analyses using a model without pit were also conducted to investigate the effect of the presence of isolation layer space. The tsunami flow was provided from the angle of 0, 45, 90 degrees to the face of the building. Inundation depth and Froude number of the flow at the front of the building is about 5 m and 1.2, respectively. Both a dynamic building model that simulates seismic isolation characteristics and a fixed-based building model were used. The results show the following: An isolation layer space provided tsunami load alleviation if the building does not displace to close the gap. When the gap was closed, water alternately escapes from the side gap, which may excite large vibrations in the orthogonal direction. For the seismically isolated building, the buoyancy force reached about half of the total weight of the building. In the case of the diagonal 45-degree input, the shock wave force at the tsunami arrival was not seen, which was observed in the results of X- and Y-directional inputs. The sustained wave force was proportional to the width of building face to the tsunami flow.