摘要
随着高速公路和城市立交的兴建以及城市建设的进一步发展,社会对交通设施的要求也越来越高,曲线梁桥的修建日益增多,准确地把握曲线梁桥的受力和变形特性对曲线梁桥的安全运营和进一步发展都具有重要的意义。本文主要针对预应力混凝土曲线梁桥抗扭设计中的相关问题进行了分析计算。
曲线梁桥最显著的受力特点是:梁截面在发生竖向弯曲时,由于曲率的影响,必然产生扭转,而这种扭转作用又将导致梁的挠曲变形,这种现象被称之为“弯—扭”耦合作用。
考虑到预应力混凝土曲线梁桥结构本身的特点,在荷载作用下弯矩与扭矩的相互耦合作用,本文针对引起主梁扭转的几个主要因素进行了研究,对曲线梁桥中的预应力钢束的配置、支承条件以及支承位置等因素对扭矩的影响进行了深入的探讨,主要进行了以下几个方面的工作:
首先,简述了曲线梁桥的形式及力学特性,综合分析了曲线梁桥的各种计算理论,讨论了各自的适用范围和优缺点。
其次,研究了预应力混凝土曲线梁桥中预应力钢束对曲线梁桥扭矩的影响。从结构上平衡外扭矩,常采用预应力混凝土结构,它既可有效地抵抗弯梁桥中的截面弯矩、剪力和扭矩,还可以提高结构刚度,减小结构尺寸和增大跨越能力。本文主要分析了预应力配筋过程中的相关计算问题,并针对具体情况对预应力束做出调整,从而使曲线梁桥的受力趋于更加合理的状态。
接着,对预应力混凝土曲线梁桥抗扭设计中的有关问题做了进一步的研究。在进行结构分析时,选择一种正确的分析计算理论,建立合理的结构模型是关键。
再次,讨论了预应力曲线梁桥预设支座偏心调整扭矩的方法,分析了支座预偏心对上部结构内力的影响。支座偏移可以改善主梁受力、减小两端扭矩、减小横桥向和顺桥向的变形,避免由于变形过大引起主梁横移或落梁现象。
最后,通过工程实例分析了曲线梁桥中的曲率、支承条件以及支承位置等因素对计算结果的影响,从计算分析中总结出了一些有益的结论。
With the construction of highways and overpasses in the cities, and the further development of urban construction, demands for facilities in transportation of our society are higher and higher. Curved girder bridges are built more and more. It is of great significance to accurately hold the stress and deformation characteristics of the curved girder bridges for its safe operation and further development. This article mainly aimed at analyzing and calculating some problems related to the torsion design of curved prestressed concrete girder bridges.The most remarkable features of curved girder bridge under the load are as follows. Due to the influence of curvature, the torsion will appear inevitably, which will also cause bending deformation. This phenomenon is called flexure-torsion coupling.Considering the own characteristics of curved prestressed concrete girder bridge structure, and the mutual coupling affect of moment of flexion and torsion under the load, this article aimed at the research on some major factors causing the torsion of main beam ,and the thorough discussion on the influence of prestressed reinforcement, supporting condition and supporting position on the torsion. I have mainly done the following jobs.Firstly, I have briefly introduced the form and mechanical characteristic of curved girder bridges, synthetically analyzed all sorts of calculational theories, and discussed respective Applicable scope, advantages and disadvantages of them.Secondly, I have researched the influence of prestressed reinforcement on the torsion of curved girder bridges. To balance the external torsion structurally, we often use prestressed concrete structure. It can effectively resist the cross-sectional moment of flexion, shear and torsion in the curved girder bridges, but also can enhance the structural rigidity, reduce the sectional dimension and increase the span. This article mainly analyzed the
problems related to the distribution of prestressed reinforcement. And make adjustments of the prestressed reinforcement on the specific conditions, thus enable the stress of curved girder bridges to tend to a more reasonable state.Thirdly, I have made a further research on the relative problems of torsion design of curved prestressed concrete girder bridges. It is the key to choose a correct calculational theory and establish a reasonable model when we analyze the structure.Fourthly, I have discussed the method to adjust torsion through presetting decentration of support abutment, and analyzed the influence on the superstructure of it. It can improve the stress of main beam, reduce the torsion of both sides, reduce the deformation of cross direction and consequent direction, and avoid the cross move or drop of the main beam.Finally, through a case study, I have analyzed the influence of some factors such as curvature, supporting conditions and supporting positions of curved girder bridges on the results, from which I have generalized some useful conclusions.
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