Wavelet analysis of strong response records of building with bilinear restoring force

摘要

It is very important to estimate the residual life of structures by analyzing a strong response quantitatively, because it is necessary to judge whether they can be used or not in the future, after they are damaged by earthquakes. During a strong earthquake, the jerk response of a structure with bilinear restoring force has discontinuity, just when the restoring force changes rapidly from the elastic region to the plastic region. Authors have tried to detect the discontinuity in the jerk by using wavelet analysis and reported a successful paper (Sone, et al., 1994). The final goal of study is to estimate the low cycle fatigue of structure by analyzing the observed records in a structure. For this object, the relationship between ductility factor; that is the ratio of peak relative displacement and yield relative displacement, and the number of discontinuity detection is needed. In this paper, the method is proposed to estimate the ductility factor of structure by the wavelet analysis of absolute acceleration response. Wavelet has the ability to detect discontinuity in acceleration response record; furthermore, it is found in this study that the wavelet coefficient is proportional to the velocity at the yield point. Besides, the ductility factor is estimated from the velocity at yield point by using the energy balance between kinetic energy at the yield point and strain energy from the yield point to the maximum relative displacement. Thus, using these relationships, the ductility factor is estimated from wavelet coefficient obtained by wavelet analysis of acceleration response. The applicability of this method is verified through some simulations.