Effects of the three-dimensional configuration of the soil-structure system on building responses to wave propagation

The objective of this study is to investigate the effects of the three-dimensional (3-D) configuration of the soil-structure system from the viewpoint of dynamic building response to wave propagation. The authors have been motivated to make a study on this subject by the fact that strong ground motion records of the aftershocks of the 2011 off the Pacific coast of Tohoku earthquake were obtained at Iwaki City Hall located in Fukushima Prefecture, Japan. At the North station of the observation site, the shorter predominant periods ranging from 0.2 to 0.3 sec. were observed, while at the South station, the periods were longer ranging from around 0.8 to 1.2 sec. at a distance of about 150 meters from the North station. Therefore, it is interesting to investigate how the underground irregularities affect the ground motions and the seismic responses of the soil-structure. The analysis method is a combination of the 3-D finite element and the 2.5-D thin layered and 2.5-D finite element methods in conjunction with a substructure technique. It was verified that the wave field shows very complex patterns when there exist inclined boundary layers and an embedded structure, causing a big difference in the result between 2- and 3-D methods at a station close to the structure.