钢管混凝土拱桥极限承载力分析的自适应方法

Self-adaptive Approach for Analysis of Ultimate Load Bearing Capacity of Concrete-filled Steel Tubular Arch Bridges

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。

Aimed at the complexity,inefficiency and difficulty in meeting the requirements of engineering design and analysis of current incremental nonlinear finite element method（INFEM）for evaluation of the ultimate load bearing capacity（ULBC）of the concrete-filled steel tube（CFST）,employed the nonlinear iterative algorithm on the basis of the elasto-plastic constitution of the CFST,a self-adaptive method of elastic modulus reduction was presented for evaluation of the ULBC of concrete-filled steel tubular arch bridges.Firstly,the united theory and the correlation equation of bearing capacity for the cylindrical CFST member with different mechanical properties at different loading conditions were employed to develop the correspondinggeneralized yield function（GYF）,and the scheme of fitting points at the generalized yield surface were figured out by means of the comprehensive testing method,refining the collocation points around the extreme points and the discontinuity points of the GYF.Then the homogeneous GYF（HGYF）was developed by regressive analysis.Therefore,the element bearing ratio（EBR）,degree of uniformity of the EBRs,reference EBR were defined,and a self-adaptive criterion was proposed to distinguish the highly stressed elements of the HGYF.Secondly,the elastic modulus adjustment strategy was given in terms of strain energy equilibrium principle,and the ULBC of CFST arches was determined by a series of linear elastic iteration,in which the stiffness damage of the arch structure was simulated by adaptively reducing the modulus of highly stressed elements.Finally,the influences of numbers of discrete elements,load distribution,and GYF or HGYF on the ULBC of concrete-filled steel tubular arch bridges were investigated,and the comparison of results from the proposed method with those from model experiments and those from the INFEM was performed.The results show that by employing the approach proposed in this paper,self-adaptive adjustment capacity of different material fibers in the CFST is presented and higher accuracy and efficiency by means of self-adaptive simulation of the damage of the arch structure is achieved.