After the 2011 Great East Japan Earthquake, it is becoming important to consider the influence by tsunami flotsam colliding with an important structure. Also, the collision analysis method is being received much attention. However, practical applications of the collision analysis have not been investigated yet. Therefore the purpose of this study is to develop and evaluate a collision analysis method capable of simulating the phenomenon to which large flotsam collides with an important structure like the long-span bridge, particularly damaged in mega earthquakes. Moreover, the marginal size of tsunami flotsam which can avoid collapse to an object bridge is computed using this method.
