Analysis on the Seismic Response of RC Bridge Piers Under Long-duration Earthquake Ground Motions

Reinforced concrete (RC) bridge piers may be affected by long duration earthquake ground motions, and the piers may be seriously damaged.Seismic analysis model for the piers considering the cumulative damages to the concrete and reinforcement was built by using the OpenSees platform.A total of 100 groups of long-duration and matched short-duration earthquake ground motions were selected according to the principle of spectrum matching method.The influence of the ground motion duration on the pier response was studied.The fragility analysis was conducted for the piers under different ground motions by cloud chart method.The results show that, for the piers with aspect ratio of 6, the maximum drift ratio, the residual drift ratio and the curvature ductility factor of the piers under long duration ground motions are 1.2-1.3 times, 1.6-1.7 times and 1.5-1.6 times of that under short duration ground motions.For the piers with aspect ratio of 4, the maximum drift ratio, the residual drift ratio and the curvature ductility factor of the piers under long duration ground motions are 1.6-1.7 times, 2.3-2.9 times and 2.1-2.6 times of that under short duration motions.Under the ground motions with the same PGA, the exceedance probability of piers with different damage states under long-duration ground motions are greater than that under short-duration ground motions.Long duration ground motions would lead to more significant damage to bridge piers.The influence of ground motion duration should be considered in the seismic behavior evaluation of bridges.