Study On Stress Characteristics And Segmental Model Test Of Steelconcrete Composite Girder Of Highspeed Railway Cable-Stayed Bridge

The composite girder cable-stayed bridge can make full use of the material characteristics of steel and concrete,which is the key part of the cable-stayed bridge.At present,the application of the composite girder cable-stayed bridge with large span high-speed railway is relatively few,and the research on the steel-concrete composite beam is relatively few.New railway nanchang to ganzhou passenger line ganjiang bridge is the first high-speed railway 300m-span hybrid girder cable-stayed bridge which laying ballastless track and the running speed is 350公里in the domestic,the main girder with open steel box girder is first used in long-span high-speed railway cable-stayed bridge,the stress and stiffness of steel-concrete composite box girder are complex,the composite beam is the key and difficult point of the bridge research.Based on the engineering background of the ganjiang bridge,the experimental research on the steel-concrete composite beam is carried out,and the main research contents and results are as follows:1.The three-dimensional finite element model of steel-concrete composite beam of high speed railway ganjiang bridge is established by ansys software,and the stress state and stress distribution of steel box girder and bridge slab are studied under the most unfavorable load conditions;the characteristics and regularity of the deformation and stiffness of the concrete slab under the load of high speed train are studied,and the safety of the composite beam is evaluated.The results show that the stress distribution of each plate is uniform,the maximum stress is 113.2MPa and the overall stress of the structure is less than 100 MPa,the bridge deck deformation is small,the maximum vertical deflection is 4.14 mm,the longitudinal bridge to the deflection ratio is 1/2899,the transverse bridge to the deflection ratio is 1/2112,and the bridge deck stiffness is good.2.According to the characteristics of steel-concrete composite beam of ganjiang bridge and the model design similarity theory,the static load model test scheme is designed,the experimental model and the original bridge segment model are compared with the stress equivalent analysis,combined with the processing technology,laboratory conditions and other factors,the final full section static load test model which has a similar ratio of 1:3 with 8.43 m long,5.43 m wide and 1.49 m high is designed.The load and test scenarios are determined to test the stress level of the model and the deformation state of the bridge deck.3.The experimental research on the steel-concrete composite beam segmental model of ganjiang bridge is carried out,the test results show that the measured data of the main plate parts of the steel-concrete composite beam conform well with the theoretical data of the finite element analysis,the test model is in the elastic working state at loading stage,and the concrete bridge slab has no cracks,the stress value of top and bottom plate is large,the maximum value is 125.9MPa appearing at the loading end which is the key area of the force,the overall displacement level of the combined beam is small,the maximum vertical displacement is 1.52 mm,and the longitudinal(1/2631)and transverse(1/2123)deflection ratio of the concrete slab is less than that of the specification of high speed railway design in the load condition of high speed railway train.Therefore,the strength and stiffness of steel-concrete composite beam of ganjiang bridge have sufficient safety reserve.