To explore the influence of spatially varying ground motion on the dynamic behavior of a train passing through a three-tower cable-stayed bridge, a 3D traintrack-bridge coupled model is established for accurately simulating the train-bridge interaction under earthquake excitation, which is made up of a vehicle model built by multi-body dynamics, a track-bridge finite element model, and a 3D rolling wheel-rail contact model. A conditional simulation method, which takes into consideration the wave passage effect, incoherence effect, and site-response effect, is adopted to simulate the spatially varying ground motion under different soil conditions. The multi-time-step method previously proposed by the authors is also adopted to improve computational efficiency. The dynamic responses of the train running on a three-tower cablestayed bridge are calculated with differing earthquake excitations and train speeds. The results indicate that (1) the earthquake excitation significantly increases the responses of the train-bridge system, but at a design speed, all the running safety indices meet the code requirements; (2) the incoherence and site-response effects should also be considered in the seismic analysis for long-span bridges though there is no fixed pattern for determining their influences; (3) different train speeds that vary the vibration characteristics of the train-bridge system affect the vibration frequencies of the car body and bridge. Keywords Earthquake Á Spatially varying ground motion Á Long-span bridges Á Nonlinear wheel-rail contact Á Running safety

To explore the effect of canyon topography on the seismic response of railway irregular bridge–track system that crosses a V-shaped canyon, seismic ground motions of the horizontal site and V-shaped canyon site were simulated through theoretical analysis with 12 earthquake records selected from the Pacific Earthquake Engineering Research Center (PEER) Strong Ground Motion Database matching the site condition of the bridge. Nonlinear seismic response analyses of an existing 11-span irregular simply supported railway bridge–track system were performed under the simulated spatially varying ground motions. The effects of the V-shaped canyon topography on the peak ground acceleration at bridge foundations and seismic responses of the bridge–track system were analyzed. Comparisons between the results of horizontal and V-shaped canyon sites show that the top relative displacement between adjacent piers at the junction of the incident side and the back side of the V-shaped site is almost two times that of the horizontal site, which also determines the seismic response of the fastener. The maximum displacement of the fastener occurs in the V-shaped canyon site and is 1.4 times larger than that in the horizontal site. Neglecting the effect of V-shaped canyon leads to the inappropriate assessment of the maximum seismic response of the irregular high-speed railway bridge–track system. Moreover, engineers should focus on the girder end to the left or right of the two fasteners within the distance of track seismic damage.

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<p>This study mainly explores the influence of different seismic incident angles on the damage of irregular bridge track systems in complex topography regions. The seismic ground motions of the V-shaped canyon site were simulated through SH wave theoretical analysis. Nonlinear seismic response analyses of irregular simply supported railway bridge–track systems were performed under the different incident angles of seismic (0°~ 60°). The effects of different seismic incident angles on the seismic response of the bridge-track system are analyzed. The results show that the seismic displacement responses of piers top, transverse movable bearings, and fasteners are significantly different under different seismic incident angles, and the unfavorable seismic incident angle is 60°. Underestimate the maximum 37 % seismic displacement response of pier top, transverse movable bearings, and fastener without considering the influence of incident angle.</p>

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