Seismic design of inelastic structures using equivalent linear system parameters: Part 1 - derivation and comparison

This article, which is the first of a two-part article, presents equations for computing equivalent linear system (ELS) parameters using a two-dimensional minimisation technique for estimating inelastic seismic demand of structures from elastic response spectra. Using two hysteretic models, the effects of initial damping, post-yield stiffness and degrading behaviour on the ELS parameters are investigated. The maximum inelastic response of structures modelled as single degree-of-freedom systems computed using the proposed method are compared with five other approximate methods as well as with results obtained using inelastic time-history analysis. It is observed that the proposed approach gives good results for structures that experience ductile behaviour with natural periods in the 0.3- to 3-s range.