Sequential Analysis of Steel Frame Building Subjected to Seismic Excitation, Tsunami, and Debris Collision

Abstract

The Great East Japan Earthquake and the following tsunami which occurred on the 11th of March, 2011, caused a big disaster along the ocean-side of Tohoku area. The big tsunami carried different kinds of debris such as ships and cars up the stream, which caused additional damages to the buildings in the area.In this study, a structural collapse analysis of a steel frame building is performed using a finite element code based upon the ASI-Gauss technique. A seismic excitation recorded in Kesennuma-shi is first applied to the steel building model, followed by an input of the drag force and buoyant force due to tsunami wave. At the last phase of the analysis, a debris model with a velocity is collided and the collapse behavior of the building is analyzed. The story drift angle and the drag force applied to the building during the sequence are both investigated, and are compared between models with and without a wall placed under water level. The latter model tends to withstand both the tsunami and the debris collision while the one with a wall is totally washed up by tsunami after a direct hit from the debris. However, the impact force of debris and continuous application of the drag force on the collided debris leads to a severe damage of the building with a story drift angle of about 0.036 rad, even if the building of the latter case has survived the tsunami itself. This indicates that the anti-collision as well as anti-tsunami considerations are both similarly important in the structural design of a tsunami refuge building.