Research On Seismic Performance And Fragility Of Isolated Railway Bridges

In recent years, with the rapid development of high-speed railway and passenger line construction in our country, some new-style cushion seats have been applied in railway high-pier simply-supported girder bridge. However most of railway bridges with new-style cushion seats have not been tested under strong earthquake, of which the seismic performance research are inadequate. Based on this background, a series of comprehensive studies on seismic design theory, seismic performance as well as seismic vulnerability of railway high-pier bridge with cushion seats are developed in this paper, combined with two32-span simply-supported beam bridges(the pier more than40m) of dedicated high-speed passenger railway lines installed with different cushion seats. The main work and the results achieved are as follows:1. A nonlinear solid FE model of E-steel damping bearing has been developed by ABAQUS. With this model:the influence of the yield strength of E-steel damping bearing on its attenuation property is discussed to get the simplified triple-line mechanical model of this kind of bearing; the railway’s lateral-oriented M-φ curve is calculated to get its simplified double-line mechanical model; Considering the seismic behavior of the railway bridge with cushion seats, a rail-bridge integration nonlinear FE model has been established to research its dynamic characteristic, based on which the influence of railway constraints on structural dynamic is observed and a more rational nonlinear FE model has been discussed in detail.2. Based on the two high-pier simply-supported girder bridges with different cushion seats on the high-speed railway passenger line, the rail-bridge integration nonlinear FE models, relatively considering or non-considering the railway constraints, are developed. These two different models are helped to analyses the influence of the constraints and the road-bed damping factor on the seismic behavior of the rail-bridge with cushion seats by the seismic time history analysis. Meanwhile, the influential mechanism of rail’s lateral bending to residual deformation is studied to develop a seismic design reference of rail-bridge with cushion seats.3. A further study of the rule of seismic behavior of railway simple-supported bridge with cushion seats of different parameters and the influence of rail-constraints on distinct kinds of bridges’s seismic behavior has been made with the example of the high-pier simply-supported girder bridges on the high-speed railway passenger line. Based on these examples, this paper establishes40calculating model with different dynamic characteristics, which varying the pier heights, and chooses20earthquake line that suits for the II venue from the PEER SE database.4. This paper systematically studies the impact of the near-field earthquake and different pulse parameters on the seismic response of the cushioning railway simply-supported girder bridge with E-steel damping bearings. In this study, the near-field seismic action, as a seismic input, is been simulated by trigonometric functions and the near-field seismic characteristic has been fully considered. The improved collision analysis model is used to simulate the collision effect of the limit device of friction pendulum bearings under near-field earthquake. The influence of the collision effect on the structural seismic behavior is discussed and meanwhile, the cushioning device is set to minimize the collision effect.5. Based on the high-pier simply-supported girder bridge with E-steel damping bearings on the passenger line,100history earthquake lines with the very venue the bridge belonging to, have been chosen from PEER to make a nonlinear time-history analysis. Defining the ultimate broken condition, the lateral and longitude pier-bearing vulnerability curves have been developed by means of the traditional reliability probability theory. Based on the study mentioned above, this paper makes a comparison analyses of the members’seismic vulnerability and evaluates the seismic behavior of rail-bridge with cushion seats from the perspective of seismic vulnerability analysis.