Research On Line Control And Force Performance Of Railroad Hybrid Girder Cable-stayde Bridge Construction

Hybrid girder cable-stayed bridges are rapidly developing with the advantages of large span,high strength and economy,but the structure of this type of bridge is complex and difficult to construct,so it is necessary to control the alignment and force state of the construction process in order to ensure the rationality and safety of the construction process.Based on the Qingpu Special Bridge as the background of the project,this paper analyzes the optimization methods of the hybrid girder cable-stayed bridge and the construction stage,and verifies the reasonableness of the optimization methods with the optimized structural alignment and force,followed by the analysis of the effects of shrinkage creep and temperature effect on the structure of the cable-stayed bridge during the construction process,and finally establishes a complete construction control system to control the whole construction process.The main research of this paper are as follows:(1)The finite element software MIDAS was used to build the model of the whole bridge and the construction stage model of the Qingpu Special Bridge,and to optimize the bridge cable force by the minimum bending energy method and the influence matrix method at the same time the structural condition of the optimized bridge under the action of the cable force is verified and the fabrication alignment and installation alignment of the steel girders are calculated.The calculation of the bare tower construction stage is carried out by the positive loading iterative method to ensure the safe topping of the tower column;meanwhile,the stress-free state method is combined with the stress-free length of the diagonal cable to optimize the cable force in the construction stage,and the results of the maximum cantilever state are used for verification.The results show that the optimized cable force of the completed bridge is within ±5% of the design cable force,and the iterative construction stage cable force is within ±3% of the target cable force.(2)Analysis of structural alignment and force effects of hybrid girder cable-stayed bridges after 10 years of operation due to the effect of contraction creep in the bridge-forming state;Analysis of the maximum cantilever state overall lift temperature,main tower temperature difference effect,main beam temperature gradient,and the effect of the diagonal cable and main tower main beam temperature difference conditions on the main beam elevation and cable force during the construction process;The results show that shrinkage creep has a large impact on structural alignment and force construction should take shrinkage creep into full consideration;annual temperature difference has a small impact on the construction stage cable force and main beam alignment,while the temperature gradient has a large impact,so avoid tensioning the cable and assembling the steel beam at noon during actual construction.(3)According to the design and construction characteristics of the double-tower hybrid girder cable-stayed bridge combined with the existing construction control experience,a construction control system based on the adaptive method is established,and measurement points are arranged at the key positions of deformation and force during the construction of the main tower and main girder,and the tensioning cable force is monitored by the frequency method;the construction process is tracked and controlled,and the model is corrected to guide the construction control by combining the actual measurement data with the theoretical data errors.