Simplified Collapse Analysis Model for RC Frames with Cyclic Deterioration Behaviors

Abstract

ABSTRACT Equivalent single-degree-of-freedom (ESDOF) models are widely used to evaluate the collapse capacity of multistory structures, and their rationality is very important because it greatly affects the accuracy of the evaluation results. Prior studies have indicated that obvious cyclic deterioration (CD) behaviors exist before structural collapse, and such deterioration behaviors are the primary sources of collapse for reinforced concrete (RC) frames subjected to long-duration ground motions. Although several ESDOF models have been developed to represent the global mechanical behaviors during the collapse of RC frames, such models cannot reasonably consider CD behaviors. This paper establishes an ESDOF model capable of considering CD behaviors by utilizing the Ibarra-Krawinkler (I-K) model. The ESDOF model includes a monotonic backbone curve with a negative tangent stiffness and a hysteretic rule to consider CD behaviors based on hysteretic energy dissipation. A simple method utilizing the empirical relationship between the monotonic ductility capacity and hysteretic energy dissipation capacity of RC columns to determine the hysteretic energy dissipation capacity of the ESDOF model is proposed. The CD behaviors are simulated by calculating the hysteretic energy dissipation capacity of the ESDOF model using the empirical relationship, which is obtained by the regression analysis of the existing experimental data of the RC column tests. The proposed ESDOF model is validated by pseudo-static collapse experiments and collapse fragility analyses. The results demonstrate that CD behaviors cannot be ignored when performing the collapse analyses of RC frames and that the proposed ESDOF model can adequately predict the collapse capacity of RC frames.