Innovative Hysteresis Model and Parameter Identification Method for Reinforced Concrete Rectangular Hollow Piers

In order to precisely simulate the stiffness degradation of RC (reinforced concrete) rectangular hollow piers and provide the theoretical base for the research on post-earthquake resilient bridges, 14 RC rectangular hollow pier specimens with different design parameters were tested under semi-static loading. A modified Bouc-Wen-Baber-Noori (BWBN) hysteresis model was built, in which a peak-displacement coefficient was introduced to reflect the correlation between stiffness degradation and peak displacement. The hysteresis model parameters of each measured hysteresis curve were identified by combination of particle swarm optimization and gravitational search algorithm (PSOGSA). The relationship between the design parameters of hollow piers and hysteresis model parameters were regressed, and an empirical prediction method was summarized. The results show that the modified BWBN hysteresis curve is well matched with the measured hysteresis curve and the correlation coefficients are all above 0.98. The new hysteresis model can reflect how the lateral stiffness of piers degrades with peak displacement. PSOGSA is able to identify the hysteresis model parameters of the measured hysteresis curve precisely. The correlation coefficients between the measured hysteresis curve and modelling curve generated by empirical prediction method is 0.83. The method is applicable to the cases of bridge piers without the measured hysteresis curves.