Analysis Of The Design Parameters And Structural Behavior Of Long-span High-speed Hybrid Girder Cable-stayed Bridge

This paper takes a large-span high-speed railway hybrid-girder cable-stayed bridge as the engineering background to analyze the design parameters and structural behavior of the hybrid-girder cable-stayed bridge.High-speed railway hybrid-girder cable-stayed bridges are different from ordinary highway bridges.Due to the requirements of high-speed train running safety and passenger comfort,they have higher requirements for the accuracy of the bridge alignment.The alignment of the bridge depends on the characteristics of the structure itself and the construction process.The hybrid-girder cable-stayed bridge has a complex structure and obvious differences in the rigidity of the main girder.If we want to control the alignment of hybrid-girder cable-stayed bridge,we need pay attention to both design and construction process.So it is necessary to analyze the design parameters and structural behavior of the high-speed railway hybrid cable-stayed bridge.The main contents of this article are as follows:(1)A simulation calculation model for the construction of a mixed-beam cable-stayed bridge was established in Midas Civil,and more than 10 parameters such as concrete weight,stiffness,steel beam stiffness,elastic modulus of stayed cables,and unstressed length of stayed cables were analyzed for sensitivity.The analysis results show that the shrinkage and creep of concrete have a significant effect on the completed state of the hybrid-beam cable-stayed bridge,while the steel beam stiffness and the weight of the stay cable have no obvious effect on the completed state of the structure;The alignment of the concrete main beam is not sensitive to parameters,and the alignment of the steel beam is sensitive to the unstressed length(cable force)of the stay cable and the elastic modulus of the stay cable.(2)A step-by-step optimization process for optimizing the cable force of a hybrid-beam cable-stayed bridge is given,and the cable force is optimized by taking a large-span high-speed railway hybrid-girder cable-stayed bridge as an example.The cable force obtained by the optimization is close to the design cable force,and the cable force value is the maximum difference is 15%,most of the cable force is within 5% of the design cable force,and the cable force optimization results are consistent with the design cable force.(3)Taking the unstressed cable length of the stayed cable as the link,the iterative calculation process of the initial tension of the stayed cable and the adjustment cable force of the completed bridge is given,and a large-span high-speed railway mixed-girder cable-stayed bridge is taken as an example.The optimized state of the completed bridge obtained above was taken as the goal,and the cable tension in the whole construction process was solved.The bridge state and the target state were compared and analyzed.It was found that the difference among the bridge cable force,alignment,and main girder stress of the two was small.The bridge state is closed to the target state,which verifies the effectiveness of the cable force optimization during the construction process.(4)In the design of a large-span high-speed railway mixed-beam cable-stayed bridge,the concrete roof of the mid-span steel beam has a gap of 2cm every 5m,and shrinkage-compensating concrete is used.This paper compares the two similar concrete slab designs with the actual design,and calculates the differences among the three in the completed bridge state.The calculation results show that when the concrete slab is not provided with a gap,the stress distribution of the main beam is more uniform.After the gap is set,the stress of the steel beam at the gap increases suddenly;after three years of operation shrinkage and creep,the main beam deflection increases in different design states similar,the effect of shrinkage and creep on the deflection of the main girder in different design conditions is basically the same.