Estimation of Horizontal Stiffness of Isolation Layer Based on Observed Earthquake Ground Motion and Maximum Displacement of Isolation Layer

The purpose of this study is to establish a new method for quantitatively and easily evaluating the performance of seismic isolation layers in seismic isolation structures before and after a large earthquake, thereby contributing to disaster mitigation and early recovery. This study proposes a method for estimating the horizontal stiffness of an isolation layer using records of seismic motions and the maximum displacement of the isolation layer for small and moderate earthquakes observed by an accelerometer and a displacement transducer. A seismic isolation building was modeled and the maximum displacement of the isolation layer due to small and moderate earthquakes was simulated by varying the upper and lower limits of the variation in the horizontal stiffness of the isolation layer with the necessary accuracy. The horizontal stiffness that matches these calculated results for the maximum displacement of the isolation layer using a displacement transducer is used as the estimated result. This study shows that the horizontal stiffness of seismic isolation devices can be estimated in some cases by using seismic records of one or multiple small-to-moderate earthquakes and observation of the maximum displacement of the isolation layer. However, some cases cannot be estimated.