Relationship between response modification coefficient and displacement amplification factor for different seismic levels and site classes

Abstract

Modern seismic design provisions allow structural systems to be designed for reduced forces, which are typically much smaller than the corresponding elastic design loads. This reduction in seismic loads is done by using response modification coefficient. The maximum deflection or drift of structural systems is typically predicted by scaling deflections corresponding to this reduced force on elastic line by displacement amplification factor. The values of these two seismic design factors, which are independent of seismic level and site (soil) class for a given type of structure, are mostly based on accumulated experience from past earthquakes and engineering judgment. In this study, a large number of five story parking garage structures were designed with a range of response modification factors for two seismic levels and for different site classes. The seismic performance of the structures was determined by performing nonlinear time history analysis with several recorded earthquake records on corresponding site classes. The computed maximum drift values were used to develop relationship between response modification coefficient and corresponding deflection amplification factor for each site class and seismic level. The results show that these two seismic design parameters are related but seismic level and site classes does not have significant effects on the relationship.