钢管初应力对CFST拱桥极限承载力影响的线弹性迭代分析

LINEAR ELASTIC ITERATION ANALYSIS OF THE ULTIMATE BEARING CAPACITY OF CFST ARCH BRIDGE UNDER INITIAL STRESS OF STEEL TUBE

  • 摘要: 通过齐次广义屈服函数在钢管混凝土(CFST)构件层面考虑钢管初应力影响,建立CFST拱桥极限承载力分析的线弹性迭代方法,并结合工程实例对钢管初应力限值进行研究。搜集建立了考虑钢管初应力的轴心受压和偏心受压CFST构件试验数据库,并遴选确定了钢管初应力折减系数,在此基础上,结合无初应力作用的CFST构件承载力相关方程,建立考虑钢管初应力影响的CFST构件齐次广义屈服函数;利用齐次广义屈服函数定义CFST拱桥单元承载比,反映单元的承载状态,并将钢管初应力作用作为恒荷载,结合活荷载系数调整法和弹性模量缩减法,建立了钢管初应力作用下拱桥极限承载力分析的线弹性迭代方法;通过与模型试验结果及增量非线性有限元法对比,验证了该文方法的计算精度和效率,并将该方法推广应用于某超大跨CFST拱桥。研究结果表明:该文建立的齐次广义屈服函数和线弹性迭代方法,能够准确预测钢管初应力作用下CFST构件和拱桥的极限承载力,且具有较高的计算精度和更高的计算效率;文中算例表明钢管初应力对拱桥极限承载力有一定影响,根据规范的相关规定,可将钢管初应力影响幅度控制在10%以内。

     

    Abstract: A linear elastic iteration method for ultimate bearing capacity analysis of CFST arch bridges is developed using the homogeneous generalized yield function to consider the initial stress of the steel tube at the component level of CFST, and the limits of the initial stress of steel pipes were discussed with engineering examples. The test database of CFST members under axial or eccentric compression considering the initial stress of steel tube was established, and the initial stress reduction coefficients of steel tube were compared and determined. Combined with the bearing capacity correlation equation of CFST members without initial stress, the homogeneous generalized yield function of CFST members under the initial stress of steel tube is presented, which is further used to define the element bearing ratio of the CFST arch bridges representing the bearing state of the element with the initial stress being regarded as a constant load. The linear elastic iteration method was proposed for evaluating the ultimate bearing capacity of CFST arch bridges under the initial stress of steel tube on the basis of the live load coefficient adjustment method and the elastic modulus reduction method. The accuracy and efficiency of the proposed method were verified by comparing with the results of model tests and incremental nonlinear finite element methods. The proposed method was applied to a super-span railway concrete-filled steel tube arch bridge. The results show that the proposed homogeneous generalized yield function and linear elastic iteration method can evaluate the ultimate bearing capacity of CFST members and arch bridges under the initial stress of steel tube accurately with high efficiency. When the initial stress ratio is within the allowable range of the current specification, the influence of the initial stress of steel tube on the ultimate bearing capacity of arch bridges is less than 10%.

     

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