Analysis On Internal Force Of Prestressed Concrete Continuous Beam Of Xianhe Bridge

The prestressed concrete continuous beam bridge has been widely used in the bridge engineering due to many advantages such as high structural stiffness,convenient construction and better smoothness of car running,etc.The full scaffold construction,the hole construction by moveable formwork,simple-supported to continuous girder construction,incremental launching method,cantilever casting construction,cantilever installation construction and rotation construction are common methods adopted in the construction of the prestressed concrete continuous beam bridges.In term of the middle span continuous beam bridge,the simple-supported to continuous girder construction is often used.Based on the prestressed concrete five-span continuous beam of Xian He Bridge which is built by the simple-supported to continuous girder construction method,this paper analyzed the permanent load internal force during the construction stage with Midas/Civil,the finite element analysis software of bridge structure,and used analytic method to analyze the effect of support settlement and temperature change of this bridge.The main work of this paper is as follows:(1)This paper made a summary of the overseas and domestic research status of simple-continuous prestressed concrete continuous beam bridge,which include the construction process and technology improvement,the system transformation and redistribution of internal force,the prestressed reinforcements tension sequence and the calculation of internal force.(2)Based on the construction process of Xian He Bridge,the permanent load internal force was calculated by means of the finite element analysis software Midas/Civil.The self-heavy of the precast beam was loaded on the simple-supported structure,and the self-heavy of post-cast section and the secondary dead load was loaded on the continuous structure.In order to make a contrast with the internal force generated by the full scaffold construction and research their concrete differences,Midas Civil was used to calculate the force when all loads were loaded on the continuous structure.(3)The most dangerous internal force of the five-span prestressed concrete continuous beam of Xian He Bridge is calculated by the analytical method considering the influence of concrete creep on the settlement internal force.On the basis of the hypothesis that the support settlement has the same law with the concrete creep,conversion elastic modulus method and the principle of force method were used to derive the expressions of the creep internal force of support settlement.The results show that the creep internal force is in direct proportion to the flexural rigidity of the girder cross section and in inverse proportion to the span.The actual moments considering the concrete creep is only 0.45 times as much as the elastic ones.The most dangerous moments of this prestressed concrete five-span continuous beam bridge occurs in the section on the middle span support.(4)In accordance with the current highway bridge design general specification,the temperature internal force of Xian He Bridge was calculated.The results show that the largest moment induced by solar temperature occurred on the supports of the second span.The moments in the middle span is constant and only 0.75 times of the largest one.