Stress Analysis Of The Prestressed Concrete Arched Web Trough Girder In Railway And Study On Prestressed Stretching Control In The Construction Process

In the traffic infrastructure construction,as a new type of bridge structure,trough girder is favored by engineers and is widely used in Rail transit route because of the advantages of its large stiffness in the verticle direction.At present,the research on the force analysis of trough girder is mainly focused on the form of uniform section and beam without cross-piece,but there is not much research on the trough girder with variable section and cross-piece.In this paper,a prestressed concrete trough girder with variable section in a railway construction is taken as the research object.The finite element analysis of the whole structure in the force is carried out in different construction stages.The main work is as follows:(1)By reviewing the relevant literatures at home and abroad,the development application background,analysis methods and research status of the trough girder are reviewed.In this paper,the solid model of the trough girder is building by professional finite element software MIDAS-FEA and analyse the influence of adding longitudinal and transverse beam in the main beam on internal force and deformation.It is proved that setting the longitudinal and transverse beam can effectively enhance the longitudinal and transverse bending stiffness of the road bed,and then reduce the thickness of the road bed and the weight of the main beam,it can improve stress and linear performance of the road bed at the same time.The analysis shows that the vertical deformation of the girder floor(road bed + beam)is larger than that of the web,so the determination of the clearance under the bridge should be based on the elevation of the lower edge of the beam.(2)For the trough girder structure with longitudinal and transverse beam system,the prestressed steel strands are concentrated at the intersection of the main web and the girder,the main beam and the cross beam,the secondary girder and the cross beam,and the stress concentration is obvious.So in the process of design and construction we should pay more attention to the location of these structural links to ensure the safety and reliability of the beam.In any case,the web of the trough beam,where there is a restraint in the lateral direction of the bearing,has a bigger lateral deformation.Therefore,the internal force of the web with lateral restraint at the bearing is designed as the basis for web reinforcement design.(3)In the single-track train operation,trough girder shows obviously the coupling effect of bending and torsional.The "shear lag" phenomenon of the trough girder road bed with longitudinal and transverse beam system is not obvious.Combining with force analysis under dead load and live load for the "three legs" phenomenon in the project,the overall stress analysis of the main beam is carried out.The results show that the "three legs" phenomenon has little influence on the internal force of the main beam under dead load and live load.(4)During the tensioning process of the prestressed prestressing tendon in the construction stage,the internal forces and deformations of the main beam are analyzed and compared on the basis of the two cases of tensioning and interval tensioning and web tensioning in sequence.The latter is a reasonable tensioning scheme.(5)Combining the analysis of the super-tension and under-tension for the prestressed steel strands construction of the web,longitudinal and transverse beam.The result shows that the super-tension is beneficial to the deformation control of the main beam,but the additional overpressure and tensile stress will be generated in the structure;under-tension is bad for linear control of the main beam.Therefore,the control of pre-stress super-tension is usually less than 10% in the prosess of the structural design,and under-tension should be avoided.With the decrease of tension level for the transverse prestressed steel strands of the trough girder,the transverse compressive stress of the road bed and the web of the main girder is in the trends of decrease,and the compressive stress of the road in the transverse direction changes in the dentation shape.