A Simple Hysteresis model for R C Structural Elements to account for Bidirectional Interaction and its Application to Evaluation of Seismic Response of Asymmetric Systems

Abstract

The coupled lateral-torsional vibration in Reinforced Concrete (R/C) asymmetric structures under seismic excitation leads to greater lateral deformation in the load-resisting elements located at one edge than others, resulting in earlier yielding in localized form. Additionally, strength and stiffness degradation due to successive inelastic excursions create progressive shifting of stiffness and strength centers away, leading to a consequent increase of effective eccentricity. This, in turn, causes a progressive increase in torsional damaging effects. In this context, an effort has been made with a newly developed yet simpler hysteresis model by incorporating the effect of post-yielding and pinching stiffness over a previously proposed hysteresis model which can primarily capture progressive damaging effect. Recognizing the practical and significant effect of bi-directional damaging, generated as a consequence of simultaneous action of ground motion along two orthogonal principal directions, the developed model has been further extended incorporating bi-axial interaction which is governed by the principle of yield surface model. A detailed computational scheme of the developed model and its extension incorporating bi-axial interaction with its performance in the prediction of experimental test results has been presented in the present study. The efficacy of the current hysteresis models has been examined by its application on an idealized bi-directionally asymmetric R/C structural system under a considerable amount of near-fault ground motions. A higher level of realistic seismic behavior for both cases has been observed. Afterward, it is also observed that consideration of bi-directional interaction grossly amplifies seismic responses. Critical investigation has been carried out by varying different influential parameters of the structural system which may be useful for improvising design practice and torsional provisions of seismic codes.