Earthquake response prediction of seismically isolated buildings based on response spectrum method considering changes in characteristics of lead rubber bearings due to repeated deformations, part 2: Improvement of prediction accuracy by equivalent damping factor calculation method using effective ductility factor

Abstract

The response spectrum method (RSM), specified by the Ministry of Construction notification Vol. 2009, is not part of the countermeasure to address the Nankai trough long-period and long-duration ground motions (LPGMs) announced in 2016. Consequently, in this study, an approach was proposed to assess the effect of changes in characteristics due to repeated deformations using the RSM for LPGMs and seismically isolated buildings using lead rubber bearings (LRBs). However, this study identified potential areas for improvement in the calculation of effective damping using the RSM. An effective damping calculation method of the RSM using an effective ductility factor is introduced to enhance the accuracy of the proposed method. The proposed RSM-based method was verified against the methods based on nonlinear time history analysis. The earthquake response prediction results using the proposed method were compared with those of not only the simplified method but also the precise and the quasi-precise methods. The accuracy of earthquake response prediction using the proposed approach is increased by 30%–50% when the effective ductility factor is used to compute the effective damping. Therefore, earthquake response can be predicted using the proposed method, and the accuracy achieved is similar to the nonlinear time history analysis.