SHAKE-TABLE TESTS ON THE INFLUENCE OF THE POUNDING ON TRANSVERSE SEISMIC RESPONSES OF HIGH-SPEED RAILWAY SIMPLY-SUPPORTED BRIDGES

Earthquake-induced pounding is a critical factor affecting seismic responses of bridges. A high-speed railway simply-supported girder bridge with a standard span of 32 m was studied. A single-span bridge model was designed and manufactured at a scale of 1/6. A new surface-surface contact device for measuring the pounding force was proposed to overcome the shortcoming of previous point-surface devices that cannot model the actual contact form of the structures. A series of shake-table tests were conducted to investigate the transverse pounding effect of the bridge model, and the influence of the pounding on transverse seismic responses of the bridge was analyzed in the frequency domain by the fast Fourier transform (FFT). The results showed that:1) the new force measuring device could accurately measure the time history of the pounding force; 2) the pounding between the shear keys and the bearing bases restricted the development of the relative transverse displacement between the superstructure and the substructure, but it amplified the girder acceleration and the bending moment near the base of the pier; 3) when the shear keys were not installed, the power spectra of the seismic responses had higher amplitudes in the low-frequency region (near the fundamental frequency of the bridge model), i.e. the seismic responses were dominated by the fundamental frequency of the structure when the pounding was not considered. However, after the shear keys were installed, the pounding altered the frequency content of the seismic responses, and the amplitudes of power spectra were increased significantly in the high-frequency region.