Research on Inelastic Response Spectra for Asymmetric Plan Systems Subjected to Bi-Directional Earthquake Motions

The limitations of traditional inelastic response spectra are discussed. Considering a one-storey asymmetric plan system subjected to perpendicular bi-directional earthquake motions, the inelastic multi-dimensional strength reduction factor spectra is presented. The yield rule of the asymmetric plan system is determined by two-dimensional yield-surface plasticity function. The spectral equation is simplified by the relationship of strength reduction factors between x-direction and y-direction.The multi-dimensional spectra are analyzed based on 30 pair strong earthquake motion records for hard soil site, intermediate soil site and soft soil site. Analytic results shows that the strength reduction factor mean spectra for each soil site has its own characteristics, and the strength reduction factor spectra is affected strongly by ductility, normalized stiffness eccentricity, period and rotation frequency ratio.