Research On Tie Beam And Support Cooperative Stress Of Steel Tube-confined Concrete Tied Arch Bridge Based On Elastic Foundation Beam Theory

As a bridge structure with large stiffness,strong span capacity and beautiful shape,concrete-filled steel tubular tied arch bridge is more and more widely used in highway,railway and urban bridge engineering.The support design and construction of concrete-filled steel tubular tied arch bridge is the basis of the whole project.Its safety and reliability determine whether the tied arch bridge can be completed successfully.For the concrete-filled steel tubular tied arch bridge with the construction method of "beam before arch",considering the cooperative stress of the tied beam and support of the arch bridge can effectively control the construction cost and optimize the construction scheme.Based on a high-speed railway concrete-filled steel tubular tied arch bridge,this paper makes an in-depth study on the cooperative stress of tie beam and support in the construction of concrete-filled steel tubular tied arch bridge from two aspects of theoretical analysis and finite element analysis.The main work and research contents of this paper are as follows:（1）Aiming at the cast-in-situ construction scheme of the tie beam of concrete-filled steel tubular tied arch bridge,based on the elastic foundation beam theory,the vertical rod of the turnbuckle frame is regarded as a Winkler spring,and the deflection curve equation of the stress and deformation of the tie beam is deduced.The load borne when the tie beam is used as the construction platform after pouring is equivalent to the uniformly distributed load,and the analytical solution of the coordinated stress of the turnbuckle full support and the tie beam is deduced.Through the parameter sensitivity analysis of the elastic modulus of the tie beam and the stiffness of the vertical rod of the turnbuckle frame,the influence of various parameters on the cooperative stress of the tie beam and the support is studied.（2）According to the cast-in-situ construction scheme of Bailey beam steel pipe column composite support for the tie beam of concrete-filled steel tubular tied arch bridge,based on the double-layer elastic foundation beam theory,the tie beam and Bailey beam support of the arch bridge are regarded as the upper and lower beams respectively,and the square timber and distribution beam between the tie beam and Bailey beam are regarded as the elastic interlayer between the double-layer beams.Through the stress balance analysis of the upper and lower beams,the deflection curve equations of the upper and lower beams are established.The load borne when the tie beam is used as the construction platform after pouring is equivalent to the uniformly distributed load.Combined with the relevant boundary conditions and continuity conditions of the tie beam of the arch bridge and the Bailey beam support,the analytical solution of the cooperative stress of the Bailey beam steel pipe column composite support and the tie beam is derived.Through the sensitivity analysis of the elastic modulus of tie beam and Bailey beam and the stiffness of elastic interlayer,the influence of various parameters on the cooperative force of tie beam and Bailey beam is studied.（3）Through Midas/Civil,the collaborative stress finite element model of tie beam and support is established,and the numerical solution calculated by the finite element model is compared with the analytical solution to verify the correctness of the analytical solution.（4）Combined with engineering examples,the cooperative stress of tie beam and support is analyzed.The calculation results show that the load above the bridge deck can not be considered when designing the tied arch bridge support of the construction scheme of "beam before arch".Compared with the original support design,this method can reduce the amount of Bailey beam by about 19.4%,and effectively reduce the construction cost.