Construction of Response Spectra for Inelastic Asymmetric-Plan Structures

Abstract

Conventional inelastic response spectra constructed by using the single-degree-of-freedom (SDOF) systems to represent the relationship of roof translation to base shear are not sufficiently accurate for the estimation of rotational seismic demands of asymmetric-plan structures. This study introduces a method for constructing the response spectra, referred to as T-R response spectra, for inelastic asymmetric-plan structures using the two-degree-of-freedom (2DOF) modal systems. The 2DOF modal system simultaneously simulates two kinds of the modal force-deformation relationships of one-way asymmetric-plan structures. One is the roof translation vs. base shear relationship and the other is the roof rotation vs. base torque relationship. Three tasks have been accomplished in developing the T-R response spectra. First, the key independent elastic 2DOF modal parameters are identified. Second, the relationships between the inelastic 2DOF modal parameters and the strength ratio are established. Third, the ranges of 2DOF modal parameter values have been investigated. Constant-strength T-R response spectra are constructed and presented in the paper.