FRP-混凝土界面粘结性能理论研究

发布时间：2018-05-11 03:18

本文选题：FRP + 混凝土　；参考：《华南理工大学》2013年硕士论文

【摘要】：纤维增强复合材料（Fiber Reinforced Polymer/Plastic，简称FRP）具有优异的物理和力学性能，其在诸多领域都具有广阔的应用前景，其中一个重要的领域是应用于加固、修复老旧钢筋混凝土结构。由于FRP材料属于脆性材料，将其应用于混凝土结构的加固工程中，还存在很多需要进行深入研究的问题，其中比较突出的一个问题就是FRP材料与混凝土界面之间的粘结性能以及剥离破坏的研究。 FRP与混凝土界面之间的粘结性能以及剥离破坏是FRP加固混凝土结构，乃至FRP加筋混凝土结构技术应用的关键问题，对构件的整体性能起着决定性作用。本文针对FRP-混凝土界面在面内剪切试验条件下的剥离特性进行了系统的研究，提出了相应的数值计算方法，较深入地分析并揭示了FRP-混凝土界面的剥离破坏机理。在此基础之上，提出了包括能够预测面内剪切剥离承载力、FRP粘结长度以及自动追踪剥离界面深度等功能的计算方法。本文的主要研究工作和创新性成果有： 1.基于精细有限单元法，充分考虑了混凝土单元在开裂情况下的尺寸效应，依据Bazant提出的裂缝带模型，提出了正确估计混凝土单元开裂软化模量的方法。同时对混凝土单元开裂后的性能进行了细致的分析研究，发现对开裂后的混凝土单元赋予一定剪切刚度有助于改善非线性有限元计算的收敛性，同时更符合实际情况。另外，本文还提出了一个全新的裂面剪力保持模型，该模型较之前的学者提出的模型，，显得更加适用于小尺度的混凝土有限单元计算。经计算对比，本文的模型能够很好地计算FRP面内剪切承载力，预测FRP有效粘结长度，并且能够自动追踪FRP剥离界面的深度，对界面粘结应力的全过程变化也有较好地控制作用。其对进一步的理论研究以及相关界面单元的开发起到指导性作用。 2.对精细单元法的结果进行了深入、细致的研究，经过大量的数值分析，提出了能够较好地预测FRP-混凝土界面剥离的界面破坏能模型。基于该模型，提出了全新的FRP-混凝土界面本构模型，并编制了相应的界面单元。将其导入通用有限元软件MSC.MARC中进行计算，计算结果与试验结果吻合较好。 3.基于试验结果、数值计算结果以及所得到的界面破坏能模型，提出了全新的FRP-混凝土界面剥离承载力计算公式以及FRP片材有效粘结长度计算公式。所提出的计算公式较其他学者提出的计算公式相比，除具有更好的计算精度之外，其计算稳定性也优于以往的模型，且具有更加严密的理论依据，适合用于FRP加固混凝土结构构件的相关分析和设计。
[Abstract]:Fiber Reinforced Polymer-Plastics (FRP) has excellent physical and mechanical properties, and it has broad application prospects in many fields. One of the important fields is to strengthen and repair old reinforced concrete structures. Because FRP is a brittle material, there are still many problems that need to be deeply studied when it is applied to the reinforcement of concrete structure. One of the outstanding problems is the bond behavior and debonding failure between FRP material and concrete interface. The bond behavior and debonding failure between FRP and concrete interface are the key problems in the technical application of FRP strengthening concrete structures and even FRP reinforced concrete structures, and play a decisive role in the overall performance of members. In this paper, the delamination characteristics of FRP- concrete interface under in-plane shear test are systematically studied, and the corresponding numerical calculation method is put forward. The mechanism of debonding failure of FRP- concrete interface is deeply analyzed and revealed. On the basis of this, a calculation method including the function of predicting in-plane shear peeling capacity and FRP bond length and automatically tracing the depth of the delamination interface is proposed. The main research work and innovative results of this paper are as follows: 1. Based on the fine finite element method, the size effect of concrete element under crack condition is fully considered. According to the crack zone model proposed by Bazant, a method to estimate the crack softening modulus of concrete element is put forward. At the same time, the behavior of concrete element after cracking is analyzed and studied in detail. It is found that it is helpful to improve the convergence of nonlinear finite element calculation and accord with the actual situation by assigning a certain shear stiffness to the cracked concrete element. In addition, a new shear retention model for crack plane is proposed in this paper, which is more suitable for the calculation of small scale concrete finite element than that proposed by previous scholars. Through calculation and comparison, the model in this paper can well calculate the in-plane shear capacity of FRP, predict the effective bond length of FRP, and can automatically trace the depth of the FRP peel interface, which can also control the whole process of the bond stress change of the interface. It plays a guiding role in further theoretical research and the development of related interface units. 2. The results of the fine element method are studied deeply and meticulously. After a lot of numerical analysis, a model for predicting the interface failure energy of FRP- concrete interface is put forward. Based on this model, a new constitutive model of FRP- concrete interface is proposed, and the corresponding interface unit is worked out. It is introduced into the general finite element software MSC.MARC for calculation, and the calculated results are in good agreement with the experimental results. 3. Based on the experimental results, numerical results and the interface failure energy model, a new formula for calculating the peeling capacity of FRP-concrete interface and the effective bond length of FRP sheet are proposed. Compared with the formula proposed by other scholars, the proposed formula has better calculation accuracy, and its computational stability is better than that of the previous models, and it has a more rigorous theoretical basis. It is suitable for the analysis and design of concrete structural members strengthened by FRP.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU375

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