EARTHQUAKE RESPONSE OF STRUCTURES CONSIDERING THE EFFECT OF GROUND COMPLIANCE (4TH REPORT)

Abstract

To estimate reasonably the safety of a building structure subjected to earthquakes, it is im-portant to analyze earthquake response of the structure coupled with sub-soil ground and tomake clear the effect of ground-structure interaction on the earthquake response.In this study, the dynamical characteristics of the ground is simulated mathematically to atransfer function, expressed by a rational function, which approximates the dynamical groundcompliance of a rectangular foundation on an elastic half-space. An above-ground structure isidealyzed, for the simplicity, as a one-degree-of-freedom system, the restoring characteristics ofwhich are supposed to be a bilinear hysteretic type. As the adjacent soil-ground to the founda-tion may behave inelastically during strong earthquakes, the elasto-plastic boundary layer isplaced between the above-ground structure and the elastic ground.A set of band-limited white noise which has a finite duration-time is used as the earthquakeacceleration excitation, and making use of an analog computer the non-stationary response analy-sss ss carried out for various sets of parameter of the ground characteristics and earthquake ex-citation. An effect of ground-structure interaction on the average of the maximum relativedisplacement responses for the excitation ensemble is discussed.As a result, the following remark can be mainly pointed out. The ground-structure inter-action has a significant influence on the transmission of excitation energy to the above-groundstructure. The response of the above-ground structure is suppressed by the hysteretic energydissipation of the boundary layer as well as the energy radiation into the ground. This advan-tageous coupling effect of the ground may be much more anticipated for the relatively rigidstructure on a soft ground.