Improved simpler R/C hysteresis model considering biaxial interaction

Abstract

From practical point of view, it is evident that the seismic wave acted on structures through two mutually orthogonal components which have significant combined effect on inelastic demands of the structure. Usually a smaller amount of ground motion generally applied in only one direction than the other and in most of the cases the studies considered only limited inelasticity. Therefore, further research is needed that considers ground motion in both horizontal directions with corresponding bi-directional intensities. Study shows, the combined effects cause significant amount of degradation of strength and stiffness which in turn cause early yielding of R/C(Reinforced Concrete) structural member. Conventional uni-axial model does not consider this type of bi-directional interaction. Some existing simpler bi-axial hysteresis model which can capture biaxial interaction shows satisfactory results, but still the deviation from experimental results are very prominent. On the other hand, some existing sophisticated bi-axial hysteresis model shows better accuracy in predicting response of R/C structural elements but these types of models require large number of calibrated test results which makes them case-specific. In this backdrop, by using principle of yield surface, this study aims to incorporate bi-directional interaction over a simpler hysteresis model which primarily able to capture uni-directional loading effects. Detailed computational scheme of the enhanced simpler uni-axial hysteresis model and extension of the model to capture bi-directional interaction with its performance in prediction of inelastic cyclic behaviour of R/C structural members are presented in this paper. From the performance point of view, it is clearly visible that the proposed simple bi-axial hysteresis model can predict experimental load–displacement curves of R/C structural members under bi-directional reversible loading with acceptable accuracy. The requirement of limited number of input parameters for the present proposed bi-axial hysteresis model make it more convenient to assess the progressive seismic damage under bi-directional ground motion.