Inelastic Response Spectrum for Simplified Deformation-Based Seismic Vulnerability Assessment

Recent studies on simplified vulnerability assessment used displacement response spectra for describing earthquake ground motions, driven by the premise that a good correlation exists between displacement and damage. The use of response spectra represents a better description for the ground motion as compared to the use of single instrumental parameters or macroscopic intensity scales. In such studies, relationships between period and displacement capacity for a particular class of buildings for different limit states are compared with a displacement response spectrum representing the demand. However, the focus of such studies has been on the derivation of the capacity relationships. A new and rational method for constructing constant ductility response spectra based on constant yield displacement load-deformation model is presented. The conceptual difference between conventional and proposed spectra is emphasized. The merit of the proposed spectra is demonstrated through its use in describing the seismic demand within a simplified vulnerability assessment procedure. Refinement is made to the derivation of the capacity curves for different limit states to match the concept adopted in developing the demand. Furthermore, the final softening damage index is incorporated in the definition of various limit states.