Study On The Influence Of Prestressed Tendons In Large Segment Cast-in-Place Continuous Beam On The Stress Of Support Structure

Due to the combination of the flexibility of the full support and the advantages of the beam-column support,such as low foundation requirement,good integrity and no blocking of the traffic under the bridge,the composite support has been applied more and more widely in the construction of medium and long span prestressed continuous beam Bridges.At present,most studies on the cast-in-situ support are about the relationship between the fastening force of fasteners or bowl buckles at the joints of the support and the stiffness of semi-rigid joints,as well as the influence of semi-rigid joints on the stability of the support.However,there are few studies on the influence of stress redistribution in beams caused by the tension of prestressed steel beams before closure on the internal forces of the main bearing members in the formwork support system.This paper introduces several main structure forms,collapse accidents of supports and the research status of cast-in-place supports.Based on the support construction of Chaihe bridge on Beijing-Shenyang high-speed railway,the finite element software MIDAS/FEA is used to carry out detailed construction simulation of some beam sections.At first,this paper simulates the regardless of the tension of prestressed steel beam,the bowl bracket shaft rod and horizontal rod respectively and articulated in the space of just two ways under the template support system is the main component of the stress state,and then according to the engineering of the actual construction sequence(including the corresponding construction stage tensioning of prestressed steel beam)it is concluded that the stress of the template support system’s main components are,finally,the simulation in the two different way under the stress of the major components were analyzed.In this paper,it is found that the connection stiffness of the bowl buckle has little influence on the static internal force of the members of the formwork support system after the calculation and comparison of the forces under different connection stiffness of the bowl buckle vertical bar and horizontal bar;Through the finite element simulation of the actual construction process,it is found that the tension of the prestressed steel beam will have a great impact on the support system.As a result,the internal force of the support at the middle of the beam body will be unloaded,and the internal force at the end will be significantly increased.Therefore,the support at the end should be properly encrypted.The research results of this paper can provide some references for similar support design in the future.