Interaction Between Continuously Welded Rail And Medium/Small Bridges Of High-speed Railway

In China’s high-speed railway, the embankment was often replaced by the bridge as the support of track to save farmland and reduce embankment settlement. The interaction between the continuously welded rail (CWR) and bridge was one of the important topics in high-speed railway bridge.After the CWR was laid on the bridge, the relative displacement took place between beam and track under the action of the temperature, creep, braking force and earthquake. Due to the nonlinear constraint between beam and track, the longitudinal force was generated in the track, beam and pier. The longitudinal force was both a controlling indicator of the track strength and stability. It was an important factor to affect the bridge design as well. In the high-speed railway, the bridge forms of the widest applied range and largest quantity were simply-supported beam and continuous beam with standard span length. The cable-stayed bridge was also often used across the existing line. It was necessary to study the force characteristics of the beam-track system on medium and small simply-supported beam, continuous beam and cable-stayed bridge.In this dissertation, on the basis of existing researches, the beam-track mechanics model for the temperature, live load and seismic response analysis was established. The related utility program was compiled. The beam-track interaction was analyzed for standard span length simply-supported beam and continuous beam widely used in high-speed railway as well as cable-stayed bridge of the increasingly widespread application. The impact of the design parameters on the beam-track system was explored. The beam-track system force characteristics on simply-supported beam, continuous beam and single-tower cable-stayed bridge were summarized, and the design proposals were put forward. The main contents in this dissertation included:1. The iterative formula of track longitudinal resistance was derived. The nonlinear bar elements were used to simulate the track resistance and the beam element with rigid arms was used to simulate the bridge. The beam-track finite element model was established considering the loading history and adjacent structures. Analyzing the temperature and live load, the impact of the movable bearing friction and vertical stiffness of the fastener was considered. Analyzing the seismic response, the pile-soil interaction, pier nonlinearity, traveling wave effect and pounding effect between beams were also taken into account. Compared with the examples in the relevant literatures, the correctness of the model was proved.2. Based on the ANSYS, the practical finite element programs, SBCWR and CBCWR, for simply-supported beam and continuous beam with the standard span length were developed by the Visual Basic.net graphical interface and Access database, which could be used to analyze beam-track system response under the temperature, live load, earthquake and three coupling. Based on the client/server, the beam-track analysis program was developed.3. It was explored that the span number of double unballasted track simply-supported box beams with standard span length, cross-sectional form, track resistance, roadbed track length, movable bearing friction, substructure stiffness and other factors made the impact on the beam-track interaction. Under the different seismic excitation directions and traveling wave effects, the dynamic response to the beam-track system was analyzed, and it was also analyzed that the track made the impact on the dynamic characteristics and pounding effect of simply-supported beams.4. It was explored that the span number of adjacent simply-supported beams, pier stiffness and other factors made the impact on the continuous beams with a main span of40-100m carrying double unballasted track. For the large continuous beam, the small resistance fastener and track expansion device arrangements were set to do the comparison. Based on the related standards, the maximum expansion length and minimum stiffness of continuous beam pier were put forward. It was discussed that the pounding effect made the impact on the CWR and continuous beam.5. The longitudinal force distribution for the beam-track system of an U-shape section and single-tower cable-stayed bridge was analyzed, and the impact of adjacent simply-supported beams, cable-stayed bridge structure system, cross-sectional form, tower and cable temperature variation as well as wind load was explored. Under the action of uniform excitation and traveling wave effect, the dynamic response to the beam-track system of cable-stayed bridge was analyzed.