Research Into Space Prestressing Analysis Theory And Application Of Curved Girder Bridges

With the rapid development of highway and urban way, overhead road and interchange project have come out more and more. The curved girder bridge can well suit the limit of terrain and culture to bridge site, reduce construction cost, and meet the design requirement of routine continuity and urban environmental beautification, so it has been adopted extensively. The most significant behavior of curved girder bridge under the load is the flexure-torsion coupling phenomenon. Due to the influence of curvature, at the same time of occurring vertical flexure, the cross section of gird occurs inevitable torsion, which complicates the mechanical analysis to curved girder bridges.In this paper, in consideration of the complexity of space mechanical analysis to curved girder bridges, a new method was put forward. Based on coordinating relations of steel and concrete, the grillage structure finite-element method was adopted to analyze the space mechanical effect of curved girder bridges. The main thoughtful way was: the upper concrete construction of curved girder bridges was divided into girder elements, and the prestressing cable was divided into some cable elements, then the coordinating relation of steel and concrete was established, finally the finite-element method was used to make mechanical analysis of curved girder bridges. The grillage structure theory is an effective and practical way of using computer to analyze upper structure of the curved girder bridge. Through the prestressing effect analytical way based on coordinating relations of steel and concrete, the prestressing cable stretching procedure can be simulated properly, and the stretching force of steel cable can be calculated effectively. At the meantime, the prestressing loss due to concrete contraction and creep and the prestressing loss due to batch stretching steel cable can be also considered automatically. If the method is adopted to analyze the curved girder bridge, design hardness can be further reduced, and design precision can be further increased. So the research work of this paper has certain realistic purpose.First, the grillage structure theory of the curved girder bridge was formulated. The mesh division and the cross-section characteristic calculation of the upper structures of three cross-section types were discussed. Second, the space prestressing effect analytical theory and method was expounded focally. The traditional prestressing effect analytical method was introduced, which is the equivalent load method. Based on coordinating relations of steel and concrete, the prestressing effect analytical method was put forward, and the relative problems of space girder element were expanded briefly. Then, according to the latest highway bridge design standards, the prestressing loss calculation of the curved girder bridge was discussed. Making use of space differential geometry method, the calculation formula of space prestressing loss due to friction was deduced. Finally, making use of the WXQ Program, a simple example and the example of the South Lake Bridge were analyzed. The feasibility and accuracy of adopting the coordinating relation way of steel and concrete to analyze the space prestressing effect were demonstrated.