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针对现行钢管混凝土结构极限承载力分析的增量非线性有限元法主要依据钢管混凝土的弹塑性本构关系建立非线性迭代计算公式,其计算原理复杂、效率低,难以满足工程设计和分析要求的状况,建立了钢管混凝土拱桥结构极限承载力分析的自适应弹性模量缩减法。首先对不同受力条件下材性差异较大的圆形截面钢管混凝土构件,根据统一理论和承载力相关方程确定了构件的广义屈服函数,进而利用全面试验法在广义屈服面上设置配点,并在极值点附近加密配点,通过回归分析建立了齐次广义屈服函数,据此定义了单元承载比、承载比均匀度和基准承载比,提出了钢管混凝土拱桥高承载单元的自适应识别准则。然后,利用变形能守恒原则建立了弹性模量调整策略,通过自适应缩减高承载单元的弹性模量模拟结构在加载过程中的刚度损伤,并利用线弹性迭代分析计算钢管混凝土拱桥的极限承载力。最后讨论了离散单元数量、荷载分布方式以及广义屈服函数的齐次性对结果的影响,并将该方法与模型试验及增量非线性有限元法的计算结果开展了对比分析。研究表明:该方法能够体现钢管混凝土不同材料纤维在受力变形过程中的自适应调整能力,并通过对拱桥结构损伤演化的自适应模拟取得较高的计算精度和计算效率。
The incremental nonlinear finite element method for the analysis of the ultimate bearing capacity of CFST structures is mainly based on the elastoplastic constitutive relationship of the concrete-filled steel tube to establish the nonlinear iterative formula. The computational principle is complex, inefficient and difficult to meet the engineering design and analysis requirements Condition, the adaptive elastic modulus reduction method is established for the analysis of the ultimate bearing capacity of CFST arch bridge. First of all, the generalized yield function of the member is determined according to the unified theory and the bearing capacity correlation equation, and then the full test method is used to set the matching point on the generalized yield surface The distribution points are encrypted near the extremum points, and the homogeneous generalized yield function is established by regression analysis. Based on this, the unit bearing ratio, bearing ratio uniformity and bearing capacity ratio are defined, and the adaptive identification criterion for high load carrying units of CFST arch bridge is proposed. Then, based on the principle of conservation of deformation energy, the elastic modulus adjustment strategy is established. By means of adaptively reducing the elastic modulus of high load bearing elements, the stiffness damage of the structure during loading is simulated and the linear elastic iterative analysis is used to calculate the ultimate bearing capacity of CFST arch bridge . Finally, the influences of the number of discrete elements, the distribution of loads and the homogeneity of generalized yield function on the results are discussed. The results of this method are compared with those of model tests and incremental nonlinear finite element method. The results show that this method can reflect the self-adaptive capacity of different materials of CFST under stress and deformation, and achieve higher accuracy and efficiency through adaptive simulation of damage evolution of arch bridge.