FRP约束混凝土本构关系及FRP加固混凝土梁断裂过程分析

发布时间：2018-03-01 11:36

本文关键词： FRP约束混凝土本构关系受压断裂能断裂粘聚区模型剥离　出处：《大连理工大学》2014年博士论文　论文类型：学位论文

【摘要】：在钢筋混凝土结构的服役过程中,由于年限、周围环境影响等原因,其结构性能出现退化。主要的表现有承载能力与刚度的降低、延性降低。另外一方面,随着对结构安全等级认识的提高,一些按照原有规范设计的结构物已经不能适应新规范的要求。此外,结构使用用途的改变也有可能造成既有结构不能满足使用要求。这些问题导致结构需要进行拆除重建或者加固改造。由于纤维增强复合材料具有轻质高强、耐腐蚀等优点,近年来大量应用于加固工程结构的各种构件尤其是梁、柱。各国研究人员对FRP加固结构的性能进行了大量的实验与理论研究,取得诸多成果。本文在前人研究的基础上,重点对FRP约束混凝土的本构关系以及FRP加固混凝土梁的断裂及FRP混凝土界面剥离过程进行了分析。得到了以下结果： (1)修正了Lam和Teng基于设计的应力-应变关系。首先通过Jefferson的混凝土破坏面方程推导了FRP约束混凝土的强度预测模型。该模型直接仅需混凝土单轴抗压强度以及FRP拉断应变；推导了基于损伤的应变公式。在强度与应变预测模型的基础上,提出了修正的Lam和Teng应力-应变模型。与搜集的试验数据比较表明,对于强度模型,本文模型与Rousakis和Karabinis模型、Wu和Zhou模型与试验数据吻合最好；对于应变模型,本文模型、Wu等模型与Teng等模型与试验数据吻合最好。进一步比较表明,本文提出的修正的Lam和Teng模型能够很好地表达结构的整体行为。本模型可用于实际构件截面的应力分析。 (2)在Suzuki等以及Teng等工作的基础上,基于受压断裂能的概念,提出了一种确定基于分析FRP约束混凝土应力-应变关系的数值方法。与试验结果比较表明,该方法与试验结果整体吻合良好。另外,分别对强约束小破坏应变、弱约束小破坏应变、弱约束大破坏应变三种情况研究了试件长度对FRP约束混凝土应力-应变关系的影响。分析结果表明,对于强约束类型FRP约束混凝土,其应力-应变关系不需要考虑试件长度的影响；对于弱约束类型FRP约束混凝土,其应力-应变关系必须考虑试件长度的影响。 (3)提出了一种断裂力学方法来模拟FRP加固梁的断裂与FRP-混凝土界面剥离过程。该方法采用虚拟裂缝模型模拟混凝土的断裂过程,采用粘聚区模型模拟FRP混凝土界面的剥离,采用应力强度因子叠加原理与权函数方法建立了整体控制方程与裂缝口张开位移协调方程。通过本课题组的试验数据验证了本方法的有效性。另外,还对影响梁承载能力的各个因素进行了详细的研究。研究结果表明,初始缝高比、梁高、混凝土强度等级对FRP加固混凝土梁的第一峰值荷载影响较大,FRP的厚度与高度对FRP加固混凝土梁的第二峰值荷载影响较大。研究还表明,相对于FRP厚度,FRP的宽度对FRP加固混凝土的承载能力影响更大。
[Abstract]:During the service of reinforced concrete structures, the performance of reinforced concrete structures is degraded due to the years of service and the influence of the surrounding environment. The main performance is the reduction of bearing capacity and stiffness, and the decrease of ductility. On the other hand, With the improvement of the level of structural safety, some structures designed according to the original code can no longer meet the requirements of the new code. The change in the use of the structure may also cause the existing structure to fail to meet the operational requirements. These problems lead to the need for demolition, reconstruction or reinforcement of the structure. Because fiber reinforced composites have the advantages of light weight, high strength, corrosion resistance, etc. In recent years, a large number of members, especially beams and columns, have been used in strengthening engineering structures. Many experimental and theoretical studies have been carried out on the performance of FRP reinforced structures by researchers from all over the world, and many achievements have been obtained. The constitutive relation of FRP confined concrete, the fracture of concrete beam strengthened by FRP and the process of FRP concrete interface exfoliation are analyzed in detail. The following results are obtained:. (1) the stress-strain relationship of Lam and Teng based on design is modified. Firstly, the strength prediction model of FRP confined concrete is derived by using the concrete failure surface equation of Jefferson. The model requires only uniaxial compressive strength of concrete and FRP tensile strain directly. The strain formula based on damage is derived. On the basis of strength and strain prediction model, the modified Lam and Teng stress-strain models are proposed. The model agrees well with the experimental data of Rousakis and Karabinis models Wu and Zhou models, and the model Wu et al., Teng model and experimental data of strain model are in good agreement with the experimental data. The further comparison shows that the proposed model is in good agreement with the experimental data. The modified Lam and Teng models proposed in this paper can well express the global behavior of the structure. This model can be used for the stress analysis of the actual member section. 2) based on the work of Suzuki et al and Teng, and based on the concept of compressive fracture energy, a numerical method for determining the stress-strain relationship of concrete confined by FRP is proposed. The method is in good agreement with the experimental results. The influence of specimen length on the stress-strain relationship of FRP confined concrete is studied in three cases of weak constraint and large failure strain. The results show that for FRP confined concrete with strong confinement, The stress-strain relationship does not need to consider the influence of specimen length, but for weakly constrained type FRP confined concrete, the influence of specimen length must be taken into account in the stress-strain relationship. In this paper, a fracture mechanics method is proposed to simulate the delamination process between the fracture and the interface of FRP strengthened beams. The virtual crack model is used to simulate the fracture process of concrete, and the cohesive zone model is used to simulate the exfoliation of the interface of FRP concrete. The stress intensity factor superposition principle and the weight function method are used to establish the integral control equation and the crack opening displacement coordination equation. The validity of the method is verified by the experimental data of our group. The factors that affect the bearing capacity of beams are also studied in detail. The results show that the initial joint height ratio, the beam height, The influence of concrete strength grade on the first peak load of FRP reinforced concrete beam is greater than that of the thickness and height of FRP-strengthened concrete beam. The study also shows that the thickness and height of FRP-strengthened concrete beam have great influence on the second peak load of concrete beam strengthened by FRP. Compared with the thickness of FRP, the width of FRP has more influence on the bearing capacity of concrete strengthened by FRP.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU37

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