Seismic Performance Of Piles In High-Speed Railway Bridges

With the development of high-speed railway, bridge structure has been widely used. Compared with the general railway bridge, transverse shear span ratios of high-speed railway bridge are small, which may lead to high-speed railway shear failure. The design of high speed Railway Bridge is controlled by stiffness, so the designers increase the cross section size of the pier to increase its yield, which improve the pier’s rigidity. Under the action of the severe earthquake, plastic hinges would not only appear in the bottom of the pier, and pile foundation may enter the plastic state early, when the designers increase the cross section size of the pier to improve its rigidity. The current specification does not consider the effect of the pile yield damage under the action of the severe earthquake, therefore this paper studies on the failure mechanism of piers under the action of lateral seismic,the failure modes of a single pile and seismic stability evaluation method of pile groups.This paper was based on the piers of simply supported bridge along the Beijing-Shanghai high-speed rail, and two1:5scale models of the pier were designed. The failure mechanism of the two piers was studied, and the displacement ductility of the two piers was calculated with a low-cycle repeated load test of transverse bridge working on two scale models of the pier. The skeleton curves and the numerical simulation results of SAP2000were compared to verify the feasibility of finite element analysis. The failure mode of two scale models of the pier was analyzed, and the shear capacity of two scale models of the pier was checked. The further study about seismic performance of the pile was based on all work above.The failure mechanism and influence factors of single piles are were studied in by Pushover analysis method. The pile foundation was simulated by uniform plastic hinges, and the pile-soil interaction was simulated by p-y curve method. Two diameters (1.25m and1.5m) single pile which are often used in high-speed railway bridges were analyzed, and the diameter of1.5m single pile was selected to study the influence of different soil parameters on the structure by changing its soil parameters.The seismic capacity of the upper part, pile group foundation and overall structure of group piles in the transverse direction and longitudinal direction was compared. The overall failure modes in different directions were obtained and the level of its stability based on reduction factor of spectrum was evaluated. The damage model was obtained by applying horizontal load of Pushover on the group piles foundation of five groups, and connections of the pile and the cap was the key part in Seismic design.The danger zone and the damage modes of bridge pile under the action of earthquake in different direction were obtained in this paper by studying the failure mechanisms of high-speed railway under the seismic effects which would play a directive role in improving domestic seismic design.