预应力CFRP板加固混凝土结构的力学性能及温差与冻融影响研究

发布时间：2018-03-25 09:23

本文选题：预应力CFRP　切入点：力学性能　出处：《湖南大学》2014年博士论文

【摘要】：预应力CFRP加固钢筋混凝土结构技术能够较充分地利用CFRP的高强性能,改善被加固结构在工作阶段的使用性能,因此近年来得到了广泛的关注,众多学者开展了大量研究工作。但这些工作大多集中于预应力CFRP加固混凝土结构的受力性能,并且所用试件的尺寸往往较小,与真实结构存在一定差距。作为一种新型技术加固的结构,预应力CFRP加固的混凝土结构其在温度、冻融等环境因素作用下工作性能随时间变化的规律仍有待进一步认识。因此,本文针对预应力CFRP板加固混凝土结构的力学性能及温差与冻融影响开展了系统性的研究工作,包括： (1)通过模型试验研究,系统考察了预应力CFRP加固大尺寸混凝土构件的力学性能：对比了非预应力FRP、预应力FRP加固梁的力学性能差异；分析了设计参数对加固桥梁受力性能的影响；探讨了初始应力、粘结性能等引起的加固桥梁破坏形态的演变规律及内在机理；提出了加固结构承载能力、刚度等的设计计算公式。 (2)通过加固实桥的现场长期监测研究,系统考察了温度作用下预应力CFRP板加固混凝土桥梁的力学性能：通过对已加固桥梁预应力CFRP板应变及梁顶、梁底温度变化的昼夜观测,在平截面等假设基础上,将温度变化下的混凝土应变按产生的原因分为温度自由应变、自约束应变和外约束应变,利用叠加原理推导得到了预应力CFRP板温度应变的计算公式。 (3)系统研究了冻融循环作用下预应力CFRP板加固钢筋混凝土梁的受力性能变化规律,探索了冻融循环和预应力水平对加固梁破坏形态、承载能力等的影响,并深入分析了冻融循环次数、混凝土强度、初始应力大小等影响因素对冻融环境下碳纤维片材-混凝土界面粘结性能的影响规律,明确了预应力碳纤维加固混凝土结构在冻融侵蚀环境下退化机理,提出了预应力CFRP加固钢筋混凝土梁的承载能力随冻融循环作用的计算模型。 (4)通过试验研究考察了CFRP-混凝土的界面粘结极限承载力、界面应力分布等界面粘结性能,分析了粘结长度等因素对界面粘结性能的影响；在试验研究基础上,建立了CFRP-混凝土界面粘结的有限元分析模型,通过有限元分析提出了界面粘结-滑移本构关系的拟合方法,比较了本文试验结果与目前主要几种粘结滑移本构关系的吻合程度,得到了符合本文试验的CFRP-混凝土界面粘结滑移本构模型。
[Abstract]:The reinforced concrete structure strengthened by prestressed CFRP can make full use of the high strength performance of CFRP and improve the performance of the strengthened structure in the working stage, so it has been paid more and more attention in recent years. Many scholars have carried out a lot of research work, but most of these work focus on the mechanical behavior of concrete structures strengthened by prestressed CFRP, and the size of the specimens used is often smaller. There is a certain gap between the structure and the real structure. As a new type of structure strengthened by technology, the working performance of prestressed CFRP reinforced concrete structure under the action of temperature, freeze-thaw and other environmental factors still needs to be further understood. In this paper, the mechanical properties, temperature difference and freeze-thaw effects of prestressed CFRP slab reinforced concrete structures are studied systematically, including:. 1) the mechanical properties of large-sized concrete members strengthened by prestressed CFRP are systematically investigated through model test. The differences of mechanical properties of non-prestressed CFRP and prestressed FRP strengthened beams are compared. The influence of design parameters on the mechanical behavior of strengthened bridge is analyzed, the evolution law and internal mechanism of the failure form of strengthened bridge caused by initial stress and bond performance are discussed, and the bearing capacity of strengthened bridge is put forward. Design and calculation formula of stiffness etc. 2) the mechanical properties of concrete bridge strengthened by prestressed CFRP slab under the action of temperature are systematically investigated through the long-term monitoring study on the consolidation of the bridge. The strain of prestressed CFRP slab and the temperature change of the top and bottom of the beam are observed day and night through the observation of the strain of the prestressed CFRP slab and the temperature change of the beam bottom of the strengthened bridge. On the basis of the assumption of plane cross section, the concrete strain under temperature change is divided into temperature free strain, self constrained strain and external constrained strain according to the causes. The formula for calculating the temperature strain of prestressed CFRP slab is derived by using the superposition principle. In this paper, the variation of mechanical behavior of reinforced concrete beams strengthened by prestressed CFRP slab under freeze-thaw cycle is systematically studied, and the effects of freeze-thaw cycles and prestress levels on the failure form and bearing capacity of strengthened beams are explored. The influence of the factors such as the times of freeze-thaw cycle, the strength of concrete and the magnitude of initial stress on the interfacial bond properties of carbon fiber sheet and concrete in freeze-thaw environment are analyzed. The degradation mechanism of prestressed carbon fiber reinforced concrete structure under freeze-thaw erosion environment is clarified, and the calculation model of the load-carrying capacity of reinforced concrete beams strengthened by prestressed CFRP with freeze-thaw cycle is put forward. 4) through the experimental study, the interface bond properties of CFRP- concrete such as the ultimate bearing capacity of interface bond, the distribution of interfacial stress, and the influence of bonding length on the interfacial bond properties are investigated, and based on the experimental study, the interfacial bond behavior of CFRP- concrete is studied. The finite element analysis model of CFRP- concrete interface bond is established. Through the finite element analysis, the fitting method of the interface bond-slip constitutive relation is put forward, and the experimental results are compared with the main bond-slip constitutive relations. The bond-slip constitutive model of CFRP-concrete interface is obtained.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U445.72;U441

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