The Study On Track Fastening And Beam Pounding Of Urban Rail Transit Viaduct Under Earthquake

With the rapid development of economic,China has become one of the fastest growing countries in the field of urban rail transit all over the world.Because of its ability of making full use of urban land,low cost,fast construction and superior adaption to the line type,the elevated line has been widely adopted in urban rail construction.However,80%of the overhead lines in operation,under construction and in planning at present in China,are in the 7th or higher seismic-intensity area..Thus,threats of earthquakes to urban rail viaducts should be fully considered.Hence,given the unsolved problems of rail fasten constraints and inter-beam collision in the seismic analysis of urban rail transit viaducts,the focuses of this paper are as follows:(1)The characteristics of typical historical disasters of urban viaducts are reviewed and summarized.The research status on the rail fasten constraints and inter-beam collision in the seismic analysis of urban rail transit viaducts is investigated.(2)Given the three kinds of rail fasteners used in the urban transit,pseudo static experiment and dynamic experiment are conducted and the dynamic characteristics of the rail fasteners are analyzed.In addition,effects of several nonlinear constitutive models are compared with the test results.The Hardin-Drnevich model is found to be superior in simulating the longitudinal restraint in seismic analysis.Moreover,the traditional linear model is adopted to carry out the safety numerical simulation under earthquake action.(3)Due to the deficiency of Hardin-Drnevich model in describing the nonlinear dynamic response of rail fastener,the Davidenkov model is selected.Combined with the test results of rail fasteners,via OpenSees software secondary development function,the numerical Davidenkov constitutive model is realized.The correctness of the introduced model is verified and its advantages are presented through a numerical analysis.(4)A shaking table test for bridge beams is carried out to investigate the effect of buffer device and pull-rod device on the displacement,acceleration and collision force of bridge beams under earthquake.Furthermore,the influence of collision condition and longitudinal pull off beam protection device on the inter-beam collision and pier force are studied.Finally,according to the test results of the collision vibration table between the bridge beams,the reliability of Hertz-damp model is analyzed and verified.