Yield Point Spectra: A Simple Alternative to the Capacity Spectrum Method

Abstract

A new format for representing inelastic response spectra is described. The format is similar to that used in the Capacity Spectrum method, but is simpler to use in practice. Like the Capacity Spectrum method, this format allows peak displacement response to be estimated. However, instead of relying on assumed relations between hysteretic response and equivalent viscous damping, Yield Point Spectra (YPS) directly apply strength reduction (R) factors associated with constant ductility (μ) responses. The R-factors are exact when computed for specific records or are approximate when existing R-μ-T relations are applied. Like any of the Nonlinear Static Procedures (NSPs) of FEMA-273, Yield Point Spectra can be used to estimate peak displacement response. Unlike the other NSPs, Yield Point Spectra may be used to determine admissible combinations of strength and stiffness to satisfy performance-based design objectives.