Performance-based earthquake engineering relies on the availability of analysis models that can be used to predict structural performance, including collapse. In this report, a lumped-plasticity element model developed by Ibarra et al. (2005) is used to model the behavior of reinforced concrete (RC) beam-columns. The backbone and its associated hysteretic rules provide for versatile modeling of cyclic behavior and, importantly, the model captures the negative stiffness of post-peak response, enabling modeling of the strain-softening behavior that is critical for simulating the collapse of RC frame structures.
The Ibarra element model has been calibrated to data from 255 reinforced concrete column tests. For each column test, the element model parameters (e.g., plastic-rotation capacity, cyclic deterioration parameters, etc.) were systematically calibrated such that the analysis results closely matched the experimental results. Column design parameters (e.g., axial load ratio, spacing of transverse reinforcement, etc.) are then related to the column element model parameters through regression analysis.
The outcome of this work is a set of predictive equations that can be used to predict a column’s element model parameters for input in to analysis models, given the various design parameters of a reinforced concrete column. Moreover, demonstrating which column design factors are most important predictors of key aspects of structural collapse behavior can provide an important tool for improving design and design provisions.
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