基于数值模拟的在役钢筋混凝土桥梁承载力分析

发布时间：2018-05-09 22:05

本文选题：裂缝 + 刚度折减　；参考：《武汉理工大学》2014年硕士论文

【摘要】：我国桥梁众多，但是随着时间的流逝及现代交通量的不断上升，这些桥梁呈现出各种病害，使得结构的功能不断退化。在我国公路桥梁中，以钢筋混凝土梁桥居多，而病害在该桥型中是最为普遍的。在钢筋混凝土梁桥长期运营的过程中，会出现开裂。随着裂缝的发展，会使结构的刚度下降，在同等荷载作用下结构挠度变大，而挠度的增加又会使裂缝发展的更为迅速，使得结构的使用性能下降，并且很可能导致结构在一定的使用期后将成为危桥而面临损毁、垮塌的危险，因此必须对在役的钢筋混凝土梁桥的承载力进行分析。本文的研究工作主要有： (1)本文针对裂缝这一病害，归纳总结混凝土结构的裂缝种类，分析各种裂缝形成机理及其特征，，并选取裂缝中的正裂缝进行深入分析。通过正裂缝的宽度、高度、开裂范围，建立裂缝的特征参数，根据截面分析方法计算各开裂段的有效刚度，并求得刚度折减系数。然后根据开裂范围，对不同特征参数的裂缝分段折减刚度。 (2)在对混凝土空心板的实体建模中，研究了钢筋混凝土建模的几种方法，深入探讨混凝土的本构关系模型和破坏准则及钢筋的本构关系，研究了钢筋混凝土模型在开裂时的模拟方式，介绍了solid65单元和link8单元在模拟钢筋混凝土结构的方法。对带裂缝的混凝土空心板进行破坏性试验，对试验结果整理分析求得极限承载力；通过对该混凝土空心板的非线性全过程模拟，对比了折减不同项后承载力，得到有效的刚度折减方法。将有限元计算得到的挠度和应变随荷载变化的规律与试验结果对比，论证本文采用的对初始裂缝模拟方法准确性和合理性。 (3)选取一预应力空心板，在建模时研究初始预应力如何施加，选取不同的裂缝宽度建立模型，进行非线性全过程分析，对比不同裂缝宽度时的荷载—挠度曲线和极限承载力，分析得出随着裂缝宽度的增加，结构的刚度减小，在极限荷载下挠度增加，而裂缝对结构的极限承载力并没有影响。通过对带裂缝的预应力空心板梁进行承载能力的非线性分析，对比不同裂缝宽度下有限元计算结果，定性的分析了裂缝对结构的影响。通过以上研究的内容可知,在模拟初始裂缝对结构的影响时,采用刚度折减的方法是有效可行的，并且所采用的钢筋和混凝土的本构关系在进行极限承载力分析时是合理的；不同裂缝参数的有限元计算结果表明裂缝会降低结构的刚度，随着裂缝宽度的增加，极限承载力不变，挠度增加。
[Abstract]:There are many bridges in our country, but with the passage of time and the rising of modern traffic volume, these bridges show various diseases, which make the function of the structure degenerate. The reinforced concrete beam bridge is the most common highway bridge in China, and the disease is the most common in the bridge type. In the long-term operation of reinforced concrete beam bridge, cracking will occur. With the development of cracks, the stiffness of the structure will decrease, the deflection of the structure will become larger under the same load, and the increase of the deflection will make the crack develop more rapidly, and the performance of the structure will decline. And it is very likely that the structure will become a dangerous bridge after a certain period of service and face the danger of damage and collapse. Therefore the bearing capacity of the existing reinforced concrete beam bridge must be analyzed. The main research work of this paper is as follows: In this paper, the types of cracks in concrete structures are summarized, the formation mechanism and characteristics of various cracks are analyzed, and the positive cracks in the cracks are selected for further analysis. According to the width, height and crack range of the normal crack, the characteristic parameters of the crack are established, and the effective stiffness of each crack segment is calculated according to the section analysis method, and the stiffness reduction coefficient is obtained. Then, according to the crack range, the stiffness of cracks with different characteristic parameters is reduced. 2) in the solid modeling of concrete hollow slab, several methods of reinforced concrete modeling are studied, and the constitutive relation model and failure criterion of concrete and the constitutive relation of steel bar are discussed in depth. The simulation method of reinforced concrete model during cracking is studied, and the methods of simulating reinforced concrete structure by solid65 element and link8 element are introduced. The ultimate bearing capacity of concrete hollow slabs with cracks is obtained by finishing and analyzing the test results, and the ultimate bearing capacity is compared by simulating the whole nonlinear process of the concrete hollow slabs with different items. An effective stiffness reduction method is obtained. By comparing the variation of deflection and strain with the experimental results obtained by finite element method, the accuracy and rationality of the initial crack simulation method used in this paper are demonstrated. 3) choose a prestressed hollow slab, study how to apply initial prestress in modeling, choose different crack width to establish model, carry out nonlinear whole process analysis, compare load-deflection curve and ultimate bearing capacity with different crack width. It is concluded that with the increase of crack width, the stiffness of the structure decreases and the deflection increases under the ultimate load, but the crack has no effect on the ultimate bearing capacity of the structure. Through nonlinear analysis of the bearing capacity of prestressed hollow slab beams with cracks, the effect of cracks on the structure is analyzed qualitatively by comparing the finite element results under different crack widths. The results show that the stiffness reduction method is effective and feasible when simulating the effect of initial crack on the structure, and the constitutive relation of steel bar and concrete is reasonable in the analysis of ultimate bearing capacity. The finite element calculation results of different crack parameters show that the crack will reduce the stiffness of the structure. With the increase of the crack width, the ultimate bearing capacity is unchanged and the deflection is increased.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441

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