中川 肇

This paper presents the optimum parameter analysis of a base-isolated building under the Tokachioki type (2003) and Kii peninsula southeast offshore type (2004) random earthquake excitations. From the viewpoint of seismic reliability, the optimum parameter on the base isolation interface is determined in such a way that the responses of base isolated structural systems agree with the response demanded by the structural designer. The optimality of the parameter is discussed for the performance demanded coefficient and two random earthquake excitation models.

This paper presents the shaking table test results of five types of wooden house models and the rocking base-isolated model based on the earthquake accelerogram recorded during the Niigata-ken Chuuetsu (2004) earthquake. The wooden house model is a two-story frame model with braces and seismic walls. The rocking base isolation is composed of bearings arcked in the lower part, steel balls and a stainless steel sheet. The experiments are carried out for sweep and two-direction vibration tests. In a sweep test, the first natural frequency of a base wooden model was 5.74Hz. In the two-direction vibration test, the safety model did not collapse, but the case-4 model collapsed due to the torsion vibration.

This paper is presented the response analysis results of the mid-story isolated and lower-story passively controlled structures based on the time-history response analysis. These passive dampers which applied to mitigate a seismic response on the lower stories of structural systems are elasto-plastic, non-linear viscous, and visco-elasto-plastic dampers. As a result, the lower story response of the systems can be mitigated by installed the various passive dampers and response of the upper structure more than the mid-story isolation can be also mitigated.