裂后预应力混凝土梁非线性力学行为研究

发布时间：2018-05-08 12:46

本文选题：预应力混凝土 + 力学行为　；参考：《武汉理工大学》2014年硕士论文

【摘要】：随着公路桥梁建设的不断发展，目前预应力混凝土结构应用日趋广泛，然而，由于日益增加的交通量、超载现象严重、建设初始损伤、以及养护缺位等多种因素的共同影响下，使得在役预应力混凝土结构普遍存在开裂、下挠等结构损伤，这也导致了设计意义上的预应力结构与实际运营中的结构存在明显力学性能差异，这严重影响和威胁着我国在役梁桥的使用功能和安全运营，但是，目前国内外对预应力混凝土结构开裂后的力学性能的试验研究和理论分析相对滞后，因此揭示预应力混凝土结构开裂后的力学性能和劣化机理，对于正确评价在役混凝土桥梁的技术状态极为重要。本文结合2010年江西省交通厅科技计划项目《基于开裂试验的混凝土梁结构性能研究》，课题试验研究中结合我国公路桥梁建设中常用的30米预应力混凝土T梁，并按照相似关系换算为1：5缩尺比例6片预应力混凝土模型梁，结合模型试验和三维弹塑性实体有限元数值模拟，获取预应力混凝土梁三分点加载全过程的变形、应变、裂缝等结构响应发展规律，研究裂后预应力混凝土梁非线性力学行为，主要结论如下：（1）本文采用非线性有限元理论研究了有粘结预应力混凝土T型梁的受力性能，计算结果与试验结果吻合较好，说明，模型在考虑材料、几何非线性的前提下能够深入揭示混凝土和预应力筋应力变化，从而验证了模型中采用的单元类型、材料本构和破坏准则的可行性和合理性，也进一步明确了预应力混凝土T梁的开裂后力学性能和工作机理，为理论分析提供了参考依据。（2）结合6片试验梁的荷载挠度数据，可以算出基于跨中截面的等效抗弯刚度，得出有、无粘结形式试验梁在不同开裂程度下梁体的刚度退化规律。（3）根据试验梁荷载混凝土应变的数据，可以得出临近破坏荷载，，顶缘混凝土应变达到最大，结合不同截面应变增长率可以看出，截面开裂越早，其上顶缘混凝土的应变增长率越大，并得出不同荷载阶段顶缘混凝土应变增长率-荷载的关系。（4）根据试验梁荷载的预应力筋应力增量的数据，可以得出，截面开裂越早，其截面上所布置预应力钢筋的应力增长率越大；结合不同国家规范计算无粘结预应力梁的极限应力，J GJ92-2004对极限应力增量的计算值同实测值相比有一定的安全储备，对设计而言更为安全合理。（5）根据试验梁的荷载与普通钢筋的应变增量的数据，可以得出，开裂后普通钢筋的应力重分布规律；试验梁截面开裂得越早，其截面上所布置的普通受压应变钢筋的应变增长率也越大。（6）基于试验梁荷载-挠度数据、荷载与平均裂缝宽度数据，推导出有、无粘结形式预应力梁体的剩余承载能力计算公式，并基于相似关系、相似理论推导出原型梁的承载能力评判模型，为在役预应力混凝土结构的运营和设计提供参考，具有重要的工程意义。
[Abstract]:With the continuous development of highway and bridge construction, prestressed concrete structures are widely used at present. However, due to the increasing traffic volume, serious overload phenomenon, initial damage of construction, and maintenance vacancy and other factors, The existing prestressed concrete structures are generally damaged by cracking and deflection, which leads to the obvious difference of mechanical properties between the pre-stressed structures in the design sense and the structures in operation. This seriously affects and threatens the use function and safe operation of in-service beam bridges in China. However, the experimental research and theoretical analysis on the mechanical properties of prestressed concrete structures after cracking at home and abroad are relatively lagging behind. Therefore, it is very important to reveal the mechanical properties and deterioration mechanism of prestressed concrete structures after cracking. In this paper, according to the 2010 Jiangxi Provincial Communications Department Science and Technology Project "Research on the structural performance of concrete Beams based on cracking Test", this paper combines with the 30-meter prestressed concrete T-beam, which is commonly used in highway and bridge construction in China. According to the similarity relation, 6 pieces of prestressed concrete model beams with 1:5 scale scale are converted into six pieces of prestressed concrete model beams. Combined with model test and three-dimensional elastic-plastic finite element numerical simulation, the deformation and strain of prestressed concrete beams during the whole process of three-point loading are obtained. The nonlinear mechanical behavior of post-crack prestressed concrete beam is studied. The main conclusions are as follows: In this paper, nonlinear finite element theory is used to study the mechanical behavior of bonded prestressed concrete T-beam. The calculated results are in good agreement with the experimental results, indicating that the material is being considered in the model. Under the condition of geometric nonlinearity, the stress changes of concrete and prestressed tendons can be revealed in depth, which verifies the feasibility and rationality of the element type, material constitution and failure criterion used in the model. The mechanical properties and working mechanism of prestressed concrete T-beams after cracking are further clarified, which provides a reference for theoretical analysis. 2) combined with the load deflection data of six test beams, the equivalent flexural stiffness based on the mid-span section can be calculated, and the stiffness degradation law of the beams with unbonded test beams with different cracking degree can be obtained. 3) according to the data of load concrete strain of test beam, the near failure load can be obtained, and the strain of concrete at the top edge reaches the maximum. The earlier the section cracks, the more the strain growth rate of section can be seen. The strain growth rate of the top edge concrete is larger and the relationship between the strain growth rate and the load rate of the top edge concrete in different loading stages is obtained. 4) according to the data of stress increment of prestressed tendons under test beam load, it can be concluded that the earlier the section cracking, the greater the stress growth rate of the prestressed bars arranged on the section. Combined with the code of different countries, the calculation value of limit stress increment of unbonded prestressed beam (J GJ92-2004) has a certain safety reserve compared with the measured value, which is more safe and reasonable for design. 5) according to the data of load and strain increment of normal steel bar, the stress redistribution law of common steel bar after cracking can be obtained, and the earlier the section of test beam cracks, The strain growth rate of the common compressive steel bars arranged on its section is also larger. Based on the load-deflection data, load and average crack width data of the test beam, the formula for calculating the residual bearing capacity of the prestressed beam with unbonded form is derived, and based on the similarity relationship, The model for evaluating the bearing capacity of the prototype beam is derived from the similarity theory, which provides a reference for the operation and design of the existing prestressed concrete structure, which is of great engineering significance.
【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;U448.35

【参考文献】