Calibration of model to simulate response of reinforced concrete beam-columns to collapse

Abstract

This paper describes the calibration of a phenomenological hinge model to simulate the nonlinear hysteretic response of reinforced concrete (RC) beam-columns under large deformations. The model is developed to enable simulation of the nonlinear dynamic response of RC frame buildings, from the initiation of damage to the onset of sidesway collapse, under earthquake ground motions. The model's monotonic backbone curve and hysteretic degradation rules capture post-peak in-cycle softening, combined with cyclic deterioration, which are associated with concrete crushing and reinforcing bar buckling at large cyclic deformations. The model calibration is based on experimental data for 255 rectangular RC columns with widely varying seismic design and detailing characteristics. For each of the 255 tests, the element model parameters, including initial stiffness, inelastic rotation limits, and cyclic energy dissipation capacity, are systematically calibrated to laboratory test data. Regression analyses are then used to develop semi-empirical equations to calculate the model parameters as functions of the column design parameters. The model parameters are calibrated in a statistically rigorous manner, where both median estimates and lognormal standard deviations are reported for each parameter. Important design parameters that affect the column model properties are the axial load ratio, confinement steel ratio, and spacing of confinement steel.