Inelastic Seismic Behavior of Kinematically Irregular Single-Story Buildings

Abstract eng:
Various damage to structures due to the torsional response in past earthquakes highlights the importance to understand the coupled lateral-torsional response of irregular structures. From a literature review, it is found that despite a number of previous studies devoted to this topic, there is still a lack of understanding of the inelastic seismic response of irregular structures. Also, the design eccentricities adopted by current torsional provisions in various seismic codes have been called into question because the provisions are driven by results of elastic models or overly-simplified inelastic models. Thus, by using sophisticated inelastic models with an advanced analysis tool, this study conducts intensive analyses of the seismic torsional response of kinematically irregular buildings. Since eccentricity between centers of mass and stiffness in plan correlates directly to torsional effects, the variation of eccentricity is selected as a focal point in this study. In order to obtain the instantaneous eccentricity, a method for evaluating inelastic stiffness of lateral load resisting members is proposed and utilized. The observed maximum variations of eccentricities are shown to potentially be higher than the design accidental eccentricities proposed in current seismic codes. This observation supports the notion that the current torsional provisions can considerably underestimate the seismic torsional response of irregular buildings. The maximum instantaneous eccentricities of irregular buildings during earthquake events can be analytically estimated with the proposed method. It is found that the maximum eccentricities occur when one or a few of the lateral load resisting members yield. Because such eccentricities play a significant role in the transient inelastic torsional response of irregular structures, it is recommended to utilize these eccentricities with the stiffness and strength eccentricities to evaluate the seismic torsional response of irregular structures.

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