The Influence Of Track Constraints On The Fragility Of Continuouss Beam Bridge In High-Speed Railways

So far, researches on seismic vulnerability analysis and Highway Bridges, failure risk in our country has mainly focused on building structures and highway bridges, while there is few relevant research on railway bridge, especially on long-span prestressed concrete continuous beam bridge, which is applied in high-speed railway. In view of the development trend of performance-based seismic design and probabilistic assessment, it’s a reasonable way to do seismic vulnerability analysis for the purose of security evaluation. And it also has great significance for evaluation of seismic safety, seismic risk management and the formulation of disaster prevention.In this paper, a longitudinal interaction mechanics model is established by analyzing the characteristics of railway bridge and track system, considering the integration of rail, track plate, rail fastener and bridge structure.The reasonable track length and the sensitivity of system parameters have been investigated, and the influence of the rail system constraints on long-span prestressed concrete continuous beam bridge has also been researched systematically. The main research contents include:1) To understand the research status and research significance, summarize the basic theory and method of vulnerability analysis.2) Define the damage index and state, and establish the probabilistic seismic demand model based on incremental dynamic analysis (IDA) and the seismic capacity model of single-dimensional and multi-dimensional earthquakes. As well as get fragility curves through the reliability theory function, explore the necessity of multiple earthquake excitations.3) Establish the model of bridges with rail system, study the effects of different rail extension length on bridge structural response through the typical numerical calculation of seismic waves,then put forward the reasonable value of the track length.4)Analysis the sensitivity of relevant parameters of track plate system, and the influence degree of the parameters by the sensitivity curves, based on the finite difference method (FDM).5) Evaluate the service state of track structure, and establish the full stiffness and stiffness reduction track structure of probabilistic seismic demand model respectively, getting the fragility curves through multidimensional seismic numerical calculation at the same time. Also, combined with the research results of the non track system under the action of multi dimension earthquake, analyzing the difference between them. At last, the influence of rail restraints on the fragility of long-span prestressed concrete continuous beam bridge is discussed.