基于有限断裂力学的FRP—混凝土界面粘结强度研究

发布时间：2018-10-22 11:47

【摘要】：纤维增强复合材料(fiber reinforced polymer,简称FRP)作为一种新型的建筑材料,由于其具有较高的强重比和刚重比、良好的耐久性、施工便捷等特点,受到建筑工程领域的广泛关注。从FRP加固结构的破坏模式来看,发生FRP与加固材料的界面剥离是常见的破坏形式,FRP加固效果与界面粘结性能有着密切的关系。因此在研究FRP-混凝土结构中,FRP与混凝界面粘结性能成为研究的重要课题。本文通过实验的方法对影响FRP-混凝土界面粘结性能的各种因素开展研究和对比,并用新近的力学理论模型加以分析,以期在不增加材料成本和施工难度的前提下充分挖掘FRP的优越性能。设计了24个外贴FRP的混凝土单剪试验,以CFRP板材与混凝土的粘结界面作为研究对象,考查了混凝土强度等级、粘结长度、板材厚度、粘接剂厚度以及种类对粘结性能的影响,为FRP加固混凝土构件的研究和设计提供了实验依据,主要的研究工作如下:1)采用了一套自主研发的单剪试验装置,研究了各种控制参数影响下的极限荷载、平均粘结应力及试件的破坏形态,尤其针对混凝土强度、胶层厚度及种类三者对FRP-混凝土界面应变的分布、界面应力的传递、界面滑移的演变规律以及界面粘结—滑移机理的共同影响进行了深入探讨和分析。2)实验材料制备这一环节突破性的使用了VARI工艺(真空辅助树脂灌注)制作CFRP板材,在制作的初期不断总结经验对当中的某些流程和工艺提出改善措施,成型后的CFRP板材无论外观还是机械性能完全符合要求。3)引入了一类新的失效准则,该准则基于有限断裂力学框架来表征准脆性材料的失效,假定裂缝扩展的有限距离假设为结构参数而非材料参数,其值由能量与应力(应变)相匹配条件确定,在该准则的基础上建立了FRP-混凝土界面的有限断裂力学模型,利用MATLAB编程计算得到该模型下试件的理论极限荷载值、裂纹扩展的有限长度及界面的有效粘接长度,与实验值相对比验证了有限断裂力学模型对于精确预测FRP-混凝土界面粘结强度的有效性。
[Abstract]:Fiber reinforced composite (fiber reinforced polymer,), as a new type of building material, has attracted wide attention in the field of construction engineering because of its high ratio of strong weight to rigid weight, good durability, convenient construction and so on. From the view of the failure mode of FRP strengthened structure, the interface peeling between FRP and strengthening material is a common failure form, and the effect of FRP reinforcement is closely related to the bond property of the interface. Therefore, in the study of FRP- concrete structure, the bond behavior between FRP and coagulation interface has become an important research topic. In this paper, various factors affecting the bond properties of FRP- concrete interface are studied and compared by experimental method, and analyzed by recent mechanical theory model. In order to fully excavate the superior performance of FRP without increasing material cost and construction difficulty. Twenty-four concrete shear tests with FRP were designed. The bond interface between CFRP sheet and concrete was used as the research object. The effects of strength grade, bond length, plate thickness, adhesive thickness and type of adhesive on the bond properties were investigated. This paper provides experimental basis for the research and design of FRP reinforced concrete members. The main research work is as follows: 1) A set of self-developed single shear test device is used to study the limit load under the influence of various control parameters. The average bond stress and the failure form of the specimen, especially for the distribution of strain and the transfer of interfacial stress of FRP- concrete by the strength of concrete, the thickness of adhesive layer and the type of concrete. The evolution law of interfacial slip and the mutual influence of interfacial bond-slip mechanism are discussed and analyzed. 2) the VARI process (vacuum assisted resin perfusion) is used to fabricate CFRP sheet through the preparation of experimental materials. In the early stage of production, we have continuously summed up experiences and put forward some improvement measures for some of the processes and processes. The formed CFRP sheet, whether in appearance or mechanical properties, fully meets the requirements. 3) A new kind of failure criterion is introduced. The criterion is based on the finite fracture mechanics framework to characterize the failure of quasi-brittle materials. The finite distance assumption of crack propagation is assumed to be a structural parameter rather than a material parameter, and its value is determined by the matching condition of energy and stress (strain). On the basis of this criterion, the finite fracture mechanics model of FRP- concrete interface is established. The theoretical limit load value, the finite length of crack propagation and the effective bonding length of interface are obtained by MATLAB programming. Compared with the experimental data, the finite fracture mechanics model is proved to be effective in accurately predicting the bond strength of FRP- concrete interface.
【学位授予单位】：华东交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O346.1;TU528

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