Abstract
This paper conducts a parametric study on the seismic response of multistorey bidirectional eccentric structures from elastic stage to inelastic stage. Based on a simplified multistorey bidirectional eccentric model composed of bidirectional lateral load-resisting members, a general law is proposed for three-stage natural frequency variation behaviour from elastic stage to inelastic stage of eccentric frame structures with different layers. Different simplification treatments are conducted on each stage and the three stable parameter analysis stages are defined. The corresponding dynamic stiffness matrices and motion equations in different loading stages are derived. On this basis, a parametric analysis of seismic response of a three-storey bidirectional regular eccentric structure from elastic stage to inelastic stage is conducted. Effects of the uncoupled torsion to lateral frequency ratios (Ω) and bidirectional eccentricities on the seismic responses are investigated. The results reveal that as Ω increases, translational displacement in the load direction first decreases and then increases; meanwhile, the displacement perpendicular to load direction and torsion displacement first rise and then decrease sharply. When Ω=1.1, the coupling effect between the translation in the load direction and the torsion is at its strongest condition. Increasing the eccentricities leads to a decrease in the displacement in the load direction as well as an increase in the displacement perpendicular to load direction and torsion displacement. Variation regularity of inelastic seismic response is remarkably different from that in elastic stage. The lateral-torsional coupling effect of the bidirectional eccentric structure is closely related to both the period ratio and the bidirectional eccentricities.
Highlights
The trends toward developing modern buildings with complex and irregular shapes have led to serious concerns with problems associated with structural irregularities
The primary aim of this paper is to present a systematic parametric study on the variation of lateral-torsional coupling behaviour of multistorey bidirectional eccentric structure, thereby providing a basis for intensive studies leading to their effective improvement on other aspects
This paper focuses on conducting a parametric analysis of the whole process from elastic to inelastic stage
Summary
The trends toward developing modern buildings with complex and irregular shapes have led to serious concerns with problems associated with structural irregularities In these irregular structures having an uneven distribution of mass or stiffness, the centers of resistance do not coincide with the centers of mass. The system parameters of a single-storey, oneway eccentric structure in an elastic earthquake response can be analytically determined These parameters include the uncoupled torsion to lateral frequency ratio, the stiffness eccentricity of the floor, and the natural period of the structure [7, 8]. Kan and Chopra [9] conducted the first parametric studies on the inelastic response of single-storey one-way eccentric structure They declared that the lateral-torsional coupling effect in inelastic stage depends significantly on uncoupled torsion to lateral frequency ratio.
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