Research On Torsional Performance Analysis And Design Optimization Of Steel-concrete Composite Beams

The steel-concrete composite beam is a new structure which is composed of the top concrete slab and the bottom steel beam connected by the flexible shear key.Because of its light weight and high bearing capacity,it is widely used in the field of bridge engineering.In order to find out the mechanical characteristics of composite beam torsion and promote the use of composite beam in the field of high-speed railway bridge,based on the calculation theory of thin-walled members,numerical simulation and vehicle bridge coupling analysis method,this paper gives the analytical calculation formula of composite beam torsion resistance and the recommended design scheme of composite beam by numerical simulation parametric analysis and vehicle bridge coupling dynamic analysis.The main research results are as follows:(1)Based on the torsion theory of thin-walled members,the calculation formula of free torsion theory of composite box girder is carried out.Then,based on umansky's second theory and virtual work principle,the differential equation of restrained torsion control of composite box girder is derived,and the differential equation is solved by the initial parameter method.(2)Considering the cross-section deformation of the actual composite box girder,considering the cross-section distortion to the composite girder.Under the influence of torsion,the distortion differential equation is derived by using the equivalent frame theory,the plane internal force system and external force system of each member in turn,and the distortion differential equation is solved by using the elastic foundation beam analogy method and the initial parameter method.(3)Referring to the section form of the composite beam bridge of Shanghe Hangzhou railway,the theoretical calculation formula of the single box double chamber composite beam under the action of torque is calculated by an example,and the composite beam model is established by the finite element calculation software ANSYS.The numerical calculation results are compared with the theoretical calculation results,and the correctness of the theoretical calculation formula is verified.(4)Based on the numerical analysis model of composite box girder established by ANSYS,the influence of interface slip of composite girder under the action of torque on the calculation result of section stress is analyzed.The torsional stress increasing coefficient of composite girder is defined,and the change rule of stress increasing coefficient of single box composite girder with different box section is analyzed in turn when the width,height,thickness and thickness of steel box and concrete slab are changed.(5)Based on the calculation of deflection span ratio of 48 m,56m,64 m and 72 m steel-concrete composite simple supported beam bridge and continuous composite beam bridge of high-speed railway train,the cross-section forms of composite beams with different spans meeting the design specifications are obtained.Then,the dynamic characteristics of vehicle bridge coupling are studied,and the vehicle model and bridge model are established respectively,and take the track irregularity as the external excitation of the system,Based on the standard of train speed 350 km / h,the recommended design parameters of high-speed railway composite beams are obtained.