.32 M High-speed Rail Simply Supported Box Girder Structure Optimization Design Study

The thesis mainly focuses on the existing problems such as mechanical index is conserved,deadweight is too large etc of 32m concrete simply supported box girder which is used in high-speed railway.Combining the design of the 32m concrete simply supported box girder used in Changji intercity railway,the thesis optimize the structural parameters. By building analytical model,analysis the structural force and the deformation features, verify the feasibility and the rationality of the optimum design and do further discussion to several key problems such as the local compression of the beam end and the spatial mechanical effect of the box girder for the optimized structure .The main works state as follows:(1).The technical ideas that using the large tonnage prestressing tendon instead of the small tonnage prestressing tendon is put forward,it greatly decreases the web thickness and reduces the structural deadweight;(2). Integrated and partial models are built by finite element software such as ANSYS, PRBP and SB. During the process, actual constraint mode of simply supported box girder is simulated and equivalent prestressed load of bar effect and train live load are simulated according to the criterion;(3). Partial structure parameters such as the width of box girder, the height of box girder, the parameter of web and supports disposal are extracted. These parameters are compared and selected ,the optimization model is recommended and the optimization suggestion of partial structure is given.The mechanical analysis verifys the feasibility and the rationality of the optimum design;(4). According to the over local stress problem in the stressing end of Changji 32m concrete simply supported box girder, by means of the force analysis of local model, the structure parameters of anchor end and anchorage are compared and selected, the suggestion to improve the local stress under the anchorage, the problem of the local stress under the anchorage is better solved;(5). The spatial stress of the web and the roof is analysed, and the results of the spatial stress analysis and plane stress analysis are compared and analysed, thereby the influence degree of mechanical factors that are neglected during the plane design process is analysed.The influence degree is large for the principal tensile stress and the shear stress of the L/8 section, it leads to the decrease of safety degree of the structure.This can be the reference for the design of the box girder;(6).The results of the thesis realizes the target to optimize the box girder, the deadweight of the optimized structure is decreased 8.3% for the qinhuangdao-shenyang passenger special line etc,and the consumption of steel material is equal,the economic benefit is significantly.