RESISTANCE CHARACTERISTICS OF RETAINING WALL WITH BACK SOIL IN THE COLLISION OF BASE-ISOLATION BUILDING

Abstract

 When extreme large earthquake occurs, a base-isolated building may collide with its surrounding retaining wall. To evaluate precisely the acceleration response of superstructure and the deformation of base isolator, resistance characteristics of a retaining wall with back soil should be made clear. In this study, shaking table tests of model base-isolated building are carried out to investigate the collision with building and retaining wall. We analyze the collisions in detail compared with experiment results and its simulation analysis by 3D-FEM. Furthermore collision responses of an existing base-isolation building are analyzed by 3D-FEM focusing on height and width of retaining wall, rigidity of back soil and nonlinear of retaining wall.
 The obtained results are summarized as follows.
 1) By the shaking table tests of base-isolated model building and its simulation analyses, it is cleared that the height of retaining wall effects to acceleration response of building and its restoring force. The lower height of retaining wall reduces acceleration response of building because of the progression of plasticity of retaining wall and back soil.
 2) Collision analyses of an existing base-isolated building show that stress concentrations occur at the bottom of retaining wall and contact area at the corner of building. In the collision with building, the center part of retaining wall contacts at the bottom of building, however the corner part of that contacts along the building foundation. This is because that flange parts of retaining wall inhibit the deformation of that. Therefore flange parts of retaining wall influence greatly to the deformation mode and the maximum strength of retaining wall.
 3) Parametric analyses considering collision speed, height and width of retaining wall and rigidity of back soil show the following results. The collision speed effects to the increase of yield stress of retaining wall because of the difference of its deformation mode. In comparison with the height of retaining wall, the width of that effects larger to the strength of its restoring force. Rigidity of back soil increases slightly the maximum strength of restoring force of retaining wall.