Research On Structure Parameters And Mechanical Properties Of Long-span Rail-road Suspension Bridge

At present,many rail-road suspension bridges with the span over 1000m are relatively rare.And design standard or reference has not been published and the design is still in exploration.For large-span rail-road suspension bridge,the rigidity index is a key factor,consequently,investigating the effect of design parameters for the stiffness of suspension bridges is quite critical.In addition,to consider several factors such as traveling wave effect,multipoint excitation and nonlinearity,the seismic response of large-span rail-road suspension bridge can be quite complex.There is no uniform design specification for seismic design,so that the seismic design can is complex.Therefore,the research of the seismic effect of large-span rail-road suspension bridge is of great value for the concept design of earthquake resistance.Firstly,the influence of the structural parameters on the bridge stiffness sensitivity and the frequency ratio of torsion and bending were studied in this paper.Secondly,the paper also researched on the displacement response regularity of the stiffening girder of different structure design parameters under the reaction spectrum load,and the change of stiffness was summarized.Thirdly,the effect of traveling wave effect under different seismic waves on the seismic response of the bridge was compared.Fourthly,the anti-earthquake structures were set up,and the earthquake response was analyzed.Last but not least,the change of non-linearity dynamic characteristics in the construction phase of the bridge was investigated.The main details of the research are as follows:(1)The development history of suspension bridges and the main research status of rail-road suspension bridges had been summarized.In addition,the static and dynamic calculation theory of suspension bridges have been reviewed,which laid the foundation for later work.(2)The static calculation of rail-road suspension bridge with the span over 1000m had been researched in this chapter.The mechanical properties of the integral cast construction condition,as well as the conditions under the live load and the horizontal wind load had been given.The paper compared how these main factors which include the rise-span ratio,the main cable section,and the stiffening arix load influence the vertical and lateral stiffness of rail-road suspension bridges,which provided the reference for design.(3)This chapter is mainly about the dynamic characteristics of rail-road suspension bridges with the span of over 1000m.The changes of torsion and bending frequency ratio and influence on the dynamic characteristics of design parameters,including rise-span ratio,main cable section,stiffening arix load,are analyzed.At the same time,under different response spectrum conditions,the way how displacement of main girder changes with rise-span ratio,depth of the beam,width of the beam had been researched.Considering the traveling wave effect,the mechanical property of suspension bridge under seismic load condition and seismic response of the system are researched and compared with consistent encouragement.Besides,the influence of the central buckle and absorber to the earthquake response are discussed in this chapter.(4)Due to the long construction period of suspension bridges,the probability of earthquake and wind attack for suspension bridges is higher.The structural behavior and dynamic characteristics during construction are further investigated in this paper,which provide the reference for the resistant design of wind and earthquake.