Seismic Research Of A Long-span Rail-cum-road Cable-stayed Bridge

China is located in the world between two major seismic zones,squeezed by the Pacific plate,the Indian plate and the Philippine-sea plate,where the earthquake fault line is very developed and the earthquake disaster is serious.As an important part of the traffic network,bridges play a vital role in the anti-seismic disaster prevention system of the lifeline.Compared with the common-span bridge,a long-span bridge has more investment,higher cost and more complicated construction procedure.Therefore,the seismic requirements are much higher.The Hutong long-span rail-cum-road cable-stayed bridge is under construction and used for crossing the Yangtze river channel.The upper deck is six-lane Xitong expressway with the maximum speed of 100 km/h.The lower deck carries four tracks,two for the Tongsujia Intercity railway and two for the Hutong railway,with the maximum train speed of 200 km/h.The bridge has a length of 2300 m and the main span of 1092 m.It will become the longest rail-cum-road cable-stayed bridge in the world after completion.Once the bridge collapses,not only leads to traffic blocked,but also has a negative impact on the rescue work.Therefore,it is very important to analyze the seismic response of the bridge.This paper takes the Hutong long-span rail-cum-road cable-stayed bridge as the engineering background,the seismic performance of this bridge is analyzed by means of the finite element software Midas Civil 2015,and the main research contents are as follows:(1)The spatial finite element model of the full-bridge is established.The natural vibration characteristics of the bridge are analyzed.(2)The response spectrum analysis of the bridge is calculated after determining the parameters of the response spectrum.The structural responses are analyzed under four load conditions,i.e.the longitudinal input,the lateral input,both longitudinal and vertical input,both lateral and vertical input.The influences of the long-period-revised response spectrum on the displacement and internal force are discussed emphatically.(3)Three groups of suitable seismic waves,including the EL Centro wave,the Taft wave and an artificial simulated seismic wave,are selected for uniform time-history seismic analysis.The seismic responses of the bridge structure under longitudinal-vertical input and lateral-vertical input are obtained and compared with the results of the response spectrum analysis.(4)The traveling wave effect of non-uniform seismic excitation on the response of the structure is discussed.The displacements and internal forces of the key bridge sections under different visual velocities are obtained and compared with the results of uniform seismic excitation.