Seismic isolation of railway bridges using a self-centering pier

Abstract

Earthquakes cause severe damages to bridge structures, and rocking isolation of piers has become a superior option for the seismic protection of bridges during earthquakes. A seismic isolation method with free rocking mode is proposed for railway bridge piers with medium height. Experimental and numerical analysis are conducted to evaluate the seismic performance of the rocking-isolated bridge pier. Shaking table test is carried out with a scaled model by using three strong input earthquake records. The measured data includes displacement, acceleration and time history response of the pier-top and the bending moment of the pier-bottom. Test results show that the expected uplift and rocking of the isolated pier occur under strong earthquakes and the rocking-isolated pier has self-centering capacity. Slight damage appears at the collision surface between pier and base due to pier uplift, while there is no damage in the pier body. The bending moment of pier-bottom is less affected by the spectrum of input ground motions. The two-spring model is provided to simulate the isolated pier with free rocking mode under earthquakes. A seismic response analysis model for the rocking-ioslated pier is established with the assistance of OpenSees platform. The simulated results agree well with the measured results by shaking table test. Therefore, the seismic isolation method with a self-centering pier is worthy of promotion for railway bridges in high seismic risk regions.