Study On Nonlinear Seismic Response Characteristics Of Long-span Double-thin-walled Pier Continuous Rigid Frame Bridge

In order to overcome obstacles such as high mountains and deep valleys,continuous rigid frame Bridges with long span and double thin-wall piers have been built widely in western China.The northwest region is located in minqin,the hexi corridor,qilian mountain and so on six big earthquake belt,the frequent earthquake rate is high,the strength is big,high seismic fortification intensity area,the large span continuous rigid frame bridge construction in the general with the earthquake force control design,and it is pointed out in the current specification,meet the conditions for large span,high pier bridge design to do special analysis and research.Therefore,the seismic performance of the long-span double-thin-wall continuous rigid frame bridge has always been one of the hot research issues.Continuous rigid frame bridge has very similar appearance characteristics with continuous beam bridge,but its difference lies in the consolidation of piers and beams,which belongs to the bending system with thrust,and the system is intermediate between beam and arch system,which is essentially different from continuous beam bridge.Therefore,the method of studying the seismic response of continuous rigid frame bridge is different from that of continuous beam bridge.Firstly,the numerical analysis model needs to establish the full bridge model.Secondly,before seismic response analysis,the static effect of superstructure on the pier should be considered,because the pier will be affected by transverse thrust and bending moment at the bottom of the beam(pier top)in addition to the pressure transmitted by the dead load from the upper part.Based on the past a lot of related literature at home and abroad,the upper bridge construction process affect the earthquake response of the continuous rigid frame bridge with combination of research and analysis is not common,the usual way is: the effect of the upper structure is simplified to gravity and the second phase of constant load,directly above the beam body,as the structure before the earthquake response analysis of the initial conditions.However,this approach ignores the influence of prestress,concrete shrinkage,creep and other factors on the piers of the superstructure of continuous rigid frame bridge caused by construction process.And how much difference can this influence have on the seismic response results of continuous rigid frame bridge? It is not clear whether the deviations between the different methods(with or without regard to the superstructure construction process)are within acceptable limits.Therefore,based on a(80+140+80)m large-span double thin-wall pier continuous rigid frame bridge as the research object,the two upper dead load simulation method,which does not consider the construction process of simple method and consider in detail the construction process of refinement method,the static results by two methods for seismic response initial conditions,the linear and nonlinear seismic response characteristics of the bridge are studied.Specific according to the following aspects.(1)Midas Civil finite element analysis software was used to create the static analysis model of the background bridge,and the above two upper dead load simulation methods were accurately simulated,and the difference of static influence of different methods on the long-span double-thin-wall continuous rigid frame bridge was compared and studied.(2)established by using finite element analysis software MIDAS Civil space background bridge elastic dynamic analysis model,the static results will be two methods as before the earthquake response analysis of the initial conditions,the linear dynamic analysis method was used to,choose three seismic waves from the level of the bridge longitudinal and vertical input at the same time,the contrast research E1 long span double thin-wall pier continuous rigid frame bridge under the action of earthquake response.(3)the open source earthquake engineering simulation software Open Sees background bridge space nonlinear dynamic analysis model is established,with two methods of the static results as initial conditions before earthquake analysis,USES the nonlinear dynamic time history analysis method,the three level of seismic waves from the bridge longitudinal and vertical input at the same time,the contrast research E2 earthquake under the action of nonlinear responses of large-span double thin-wall continuous rigid frame bridge differences.(4)In good nonlinear dynamic analysis model has been established,based on the three seismic peak acceleration from 0.5g(E2 level)gradually increased to 1.0g,earthquake excitation method and two methods of initial conditions are unchanged,in turn bridge nonlinear seismic response analysis to the background,finally according to the calculation results,the peak of the rarely met earthquake consider or not consider the upper structure under seismic response error caused by the construction process can estimate size and trend.