Research On The Steel Layouts Of Continuous Rigid Frame Bridge With External Prestressed Reinforcement

In the past 30 years,the transportation industry in China has been booming accompanied by the national economic growth,while the design and construction of bridge project have been greatly improved.Among them,the prestressed concrete continuous rigid frame bridge has been widely used because of its strong spanning ability,high resistance to deformation,good stiffness,the overall stability and riding comfort and etc.But during the long-term service,the material degradation,the increase in vehicle load and not enough meticulous of structure design lead to many defects such as continuous deflection,cracks in the box girder webs and bottom slab,which are greatly reducing the stiffness and bearing capacity of the bridges and shortening the service life of the bridges and riding comfort.External prestressed reinforcement is primarily used to improve the bearing capacity of the prestressed concrete continuous rigid frame bridge,which is a kind of method of active reinforcing.It can improve the girder’s bearing capacity effectively,increase the reservation of girder’s compressive stress and prevent the development of deflection.Even though this method has become more mature than others,it still has many roblems to deal with.Therefore,it is important to solve the optimized layout of the prestressed steel so as to find the concordant cables.The main work of this paper is as follows:Firstly,this paper briefly summarized the development of prestressed concrete continuous rigid frame bridge.And it pointed out that due to the existence of secondary interior force,it had caused the statically indeterminate structure against the structure of the above factors,which always resulting in abnormal limit state of prestressed steel beam under total effect reduction.Secondly,this paper introduced related concepts such as secondary interior force,concordant cables,linear transformation,load equation,and three methods of getting concordant cables.It also deduced the equations about how to calculate secondary moments of different presrtressed steel forms with uniform cross-section and variable cross-section while using force method and compared the influence when changing related parameters.Thirdly,the paper took three-span uniform cross-section and variable cross-section bridges respectively for instance to deduce that how to carry out external prestressed reinforcement design on the basis of the concordant cables and make the scheme much more reasonable and economic.It also discussed the influence of secondary interior force at ultimate.Firstly,because of the existence of the secondary interior force,it’s quite difficult to calculate the stress in tendons at ultimate.Secondly,it also pointed out that the schemes should differ in different defects rather than blindly arranging long prestressed steels.Finally,the paper introduced the main defects of Hongling Viaduct Bridge and put forward the reinforcement scheme according to different defects in different spans.Based on the theory ahead,it carried out different schemes according to different spans and combined them into a new scheme,which is much more reasonable and economic.In the meanwhile,it simulated the reinforcement scheme using finite element model.Through comparing some main indexes of before and after reinforcement,it compared with the traditional reinforcement scheme and evaluated the effect of the reinforcement.The reinforcement scheme carried out and the train of thought in this paper could be referred by the same kind of bridges.