考虑拱肋病害影响的钢管混凝土拱桥力学行为研究

Concrete-filled steel tube (CFST) arch bridges are widely used in China, since these bridges have advantages such as long-span, high bearing capacity, convenience and beautiful appearance. However, during their maintenance, many diseases occur such as separation, arch rib deflection, etc, which cause significant damage to more and more CFST bridges in China. So it is necessary to analyze the existing problems in order to evaluate the structure safety of the CFST bridges in service. In this project, the influence of rib diseases on mechanical properties and ultimate bearing capacity of CFST arch bridge is studied. .Firstly, according to the ratio of eccentric confining force with axial confining force, a modified constitutive relation for filled concrete under eccentric load is proposed. A simplified model for bond-slip constitutive relationship is also presented. The nonlinear spring element using this constitutive model is adopted to simulate the bond-slip behavior between the steel tube and concrete. Then computer simulation of the whole process for ultimate bearing load of CFST bridge considering separation effect is carried out on the platform of the universal finite element software ANSYS..Secondly, in order to verify the accuracy of the computer simulation, a total of 20 CFST truss columns and 20 CFST dumbbell shaped columns are tested with the experimental parameters being separation ratio and eccentricity. The load-deflection curves, ultimate load carrying capacity and behavior of specimen components are analyzed through testing results and computer simulation results..Thirdly, the basic creep component of RELEM B3 model is proposed to predict the creep of the concrete in CFST due to the sealing properties of the concrete. Preconditioning conjugate gradient (PCG) is employed to fit the equation of RELEM B3 model for the concrete creep as a common degenerate-kernel Dirichlet series expression, based on which the creep recurrence formula is established. The user creep model is implemented through UPFs secondary exploitation technique of ANSYS software, so the calculation of creep effect for CSFT structure is carried out step by step. .Finally, the carrying capacity of CFST bridges in service is evaluated with the finite element model considering the arch rib disease and the shrinkage and creep of the core concrete in the steel tube. It can be used as guidance for maintenance and strengthening of CFST arch bridges in service.

钢管混凝土拱桥是我国应用较为广泛的桥型之一，其因病害和损伤积累而出现破坏的现象呈增长趋势，但关于病害对其承载能力的影响目前仍缺乏充分的认识。本项目针对钢管混凝土拱桥的拱肋病害问题展开研究。采用"等效紧箍力"的方式对钢管混凝土的本构关系进行修正，提出钢管混凝土界面粘结－滑移本构关系的简化模型，从而建立考虑脱空影响的钢管混凝土拱桥三维有限元数值计算模型，深入分析脱空对其受力性能和极限承载能力的影响。分别设计20组不同脱空率的桁式和哑铃型构件模型试验，对本方法数值模拟结果的正确性进行验证。根据钢管混凝土的密闭特性，提出采用B3模式的基本徐变来预测钢管混凝土的徐变，并采用预处理的共轭梯度法对B3模式的基本徐变表达式进行Drichilet级数拟合，建立徐变效应计算的递推公式。最后，计入拱肋缺陷和管内混凝土收缩徐变的影响，对服役期钢管混凝土拱桥的承载能力进行全面的评估，为大桥的维护与加固对策提供指导。

本课题以钢管混凝土拱桥为研究对象，采用理论推导、数值模拟和试验研究的方法对其病害机理及其对承载能力的影响进行了深入研究。主要研究内容及成果如下：. 1.按“等效紧箍力”与轴压紧箍力的比值对套箍系数进行修正，得到了改进的考虑偏心影响的钢管混凝土本构关系。提出了钢管与核心混凝土粘结－滑移本构关系的简化模型，并采用该模型，通过在钢管与混凝土之间设置弹簧单元来模拟界面之间的粘结程度，在大型通用有限元软件ANSYS平台上实现了考虑脱空影响的钢管混凝土拱桥受力全过程仿真分析。. 2.设计制作了多组钢管混凝土桁架试件，对其粘结界面进行了不同程度的处理，分别进行了钢管内壁抹油脂和刮毛处理的对比试验，考察其对钢管混凝土界面粘结性能的影响；为了研究高度脱空率对钢管混凝土桁架结构极限承载力和结构刚度的影响，还进行了考虑完全粘结和高度脱空率为20%的对比试验；在试验研究的基础上，对圆形钢管混凝土桁架的荷载-变形全过程进行了深入研究，建立了钢管混凝土桁架的非线性有限元计算模型并与试验结果进行了对比分析，验证了本课题提出的考虑脱空影响的钢管混凝土结构受力全过程分析方法的正确性。. 3.根据钢管混凝土的密闭特性，提出采用B3模式的基本徐变来预测钢管混凝土的徐变。并采用预处理的共轭梯度法对B3模式的基本徐变表达式进行了Drichilet级数拟合，建立了徐变计算的递推公式。然后通过UPFs二次开发技术，在大型通用软件ANSYS上通过自定义徐变模式的方式，实现了钢管混凝土结构徐变效应的计算。. 4.提出了钢管混凝土界面脱空率和高度脱空率的概念。研究了脱空率对不同含钢率、不同矢跨比以及不同荷载作用方式钢管混凝土拱肋受力性能的影响。并以三山西大桥、丫髻沙大桥及桂江大桥为实例，研究了脱空对桁式及单圆管钢管混凝土拱桥极限承载力的影响。结果表明，脱空将明显降低桁式钢管混凝土拱桥的极限承载力。但脱空基本不影响单圆管钢管混凝土拱桥的极限承载能力。