Impact Of Seismic Effects On Stress And Distortion Of Welded Turnout On Bridge

Welded turnout on bridge is a significant technical issue when laying CWR in high-speed railway or dangerous mountain railway area. When laid through earthquake region, the turnout structure itself becomes a double weak link. Research of the longitudinal stress and distortion in welded turnout on bridge under earthquake action makes great sense, especially in understanding the transfer process of earthquake load from the bridge structure to the welded turnout, analysing and evaluating the welded turnout deterioration after earthquake and finding out sensitive parameters as well as weak links of the welded turnout under earthquake. This paper provides reliable suggestions for both bridge and track engineering in aseismic design. Therefore, it is significant to study the longitudinal mechanical response of the welded turnout on bridge under earthquake action. On the basis of summarizing the domestic and foreign research, this paper focuses on the seismic response of the welded turnout on continuous beam bridge. The specific research contents are as follows:(1) Dynamic nonlinear finite element model of turnout-bridge-pier is built according to the beam-turnout interaction principle in ballasted track on bridge. Factors including longitudinal resistance elastoplasticity, turnout connector nolinearlity and bridge piers ductility are considered. Taking three span simple-supported railway beam bridge as an example, the longitudinal force in CWR on ballasted track bridge under earthquake is calculated. After comparing the results with those in related literatures, the feasibility of the turnout-bridge-pier finite element model that built in this paper is verified.(2) Taking the welded turnout on ballasted track continuous beam bridge as an example, the restraint effects under three working cases of none rail constraints, CWR constraints and welded turnout constraints are studied. The dynamic characteristics of continuous beam bridge under three cases are analysed respectively. The natural vibration frequencies and mode shapes in the first fifteen orders are obtained. The calculation results show that the low order mode frequency of the bridge structure is greatly increased under CWR and welded turnout constraints. As the longitudinal resistance improved, the bridge natural vibration frequency is increased too, this trend is more obvious in low order mode. It is suggested that the influence of the upper rail structure is considered in the design of high-speed railway bridges.(3) Nonlinear time integration method is applied in the dynamic nonlinear finite element model of turnout-bridge-pier to analyse the seismic response law. The studied working cases considers seismic wave spectrum characteristics, seismic acceleration peak, turnout area resistance, continuous beam span, pier stiffness, turnouts of vairous numbers, beam temperature and other factors.(4) Based on the influence laws of various factors on welded turnout seismic response on ballasted track bridge, suggestions in design and check of rail strength, track stability, turnout connector, relative displacement at key positions under different seismic design intensities are proposed. This paper provides certain guidance for design, laying and maintenance of welded turnout in earthquake region.