Long Span Prestressed Concrete Continuous Beam Bridge Deformation Control By Cantilever Construction Method

Based on the Beijing-Hangzhou Canal Bridge,this paper studies the deformation control of long-span prestressed concrete continuous beam bridge during cantilever construction.Deformation control problems studied in this paper include foundation settlement monitoring and control,vertical prestress loss and web inclined crack control,setting of prebias of movable support,construction simulation analysis and deformation monitoring,adaptive cantilever construction control,midspan deflection control,and verification of the accuracy of finite element calculation of live load in pre-arch of completed bridge.Through the study of the above deformation control problems,the following results are obtained:(1)Through observation,the settlement of foundation tends to be stable before the midspan closure of the Beijing-Hangzhou Canal Bridge.It is a necessary condition for bridge closure to ensure that the settlement of foundation tends to be stable.(2)The loss of prestressing force caused by the use of finely rolled threaded steel as vertical prestressing tendons is about 15.6%.It is more appropriate to use steel strand with low retraction secondary tensioning anchorage as vertical prestressing tendons.(3)For the Beijing-Hangzhou Canal Bridge,the calculation result of the prebias of the 14# pier bearing reaches 43.5mm.(4)The influence of the inclination angle of each section on the deformation of the cradle can not be neglected in cantilever construction.(5)In the early stage of cantilever construction,the difference between measured and theoretical values is very small.In the later stage,the difference is biger and biger.It is necessary to adjust the parameters of finite element model in the later stage of cantilever construction.(6)There are two main direct reasons for midspan deflection,one is overweight,the other is the rotation of pier top beam section.(7)By comparing the data of finite element analysis and field loading test,it is found that the calculation results of live load part in pre-arch of completed bridge by finite element method are very accurate.The data in this paper are obtained through three ways: finite element analysis,observation and test in the construction process.Because of the large span,the monitoring of Jinghang Canal Bridge is different from that of this kind of bridge with smaller span.The above research results can provide reference for the monitoring of other prestressed concrete continuous girder bridges with this span.