【作者】 李知兵；

【导师】 尚守平；

【作者基本信息】 湖南大学 ， 结构工程， 2014， 博士

【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。更多还原

【Abstract】 The technique of strengthening reinforced concrete structure with prestressed CFRP laminates can make full use of the high tensile strength of CFRP and improve the service performance of the strengthened structure, and attracted much attention from researchers in recent years. However, these studies were conducted on the load-carrying behavior of the reinforced concrete structures strengthened with prestressed CFRP laminate, and the dimension of the specimens in the experimental works is often small, which results in the difference in the load-carrying behavior between the specimens and the actual structures. As the structures applied a new technique, the influence of temperature and freeze-thawing on the behavior of the reinforced concrete structures strengthened with prestressed CFRP plates needed be further studied. Therefore, in the presented paper the experimental studies of the reinforced concrete beams strengthened with prestressed CFRP plate were conducted. The mechanical behaviorin and influence on Temperature difference and freeze-thawing of the strengthened beams were researched as the following.(1) Based on the test studies with the large-size specimens, the load-carrying behavior of the large-size reinforced concrete members was researched. The difference in the behavior of the beams strengthened with prestressed and non-prestressed CFRP plate was analyzed, and the effect of the initial stress and the bonding capacity of the CFRP-concrete interface on the failure mode of the strengthened beams were discussed. Moreover, the calculation formulas of the load-carrying capacity and the flexural stiffness of the strengthened beams were presented.(2) Through on-the-spot long-term monitoring study on strengthening real bridge, the mechanical property of prestressed CFRP plates strengthening concrete bridge under the temperature was investigated. Through diurnal observation of strain of prestressed CFRP plates of the reinforced bridge, and the temperature variation of beam top and beam bottom, based on the plane surface assumption, the concrete strain under temperature changes was divided into temperature free strain, self-constrained strain and external constrain strain according to the causing reasons. Furthermore, by using superposition principle, the calculation formula of prestressed CFRP plates temperature strain was derived. (3) The stress behavior variation law of prestressed CFRP plates strengthening steel bar concrete beams under the effect of freeze-thaw cycles was studied. Rechered the effects of freeze-thawing cycles and prestress level on the failure mode and load capacity of strengthened, beams The influential law of freeze-thawing cycles frequency, concrete intensity, magnitude of stress and other factors on carbon fiber plate-concrete interface bonding performance was analyzed. The degradation mechanism of prestressed carbon fiber strenthening concrete structure under the freeze-thaw erosion environment was determined. The calculation model of the loading capacity of prestressed CFRP strenthening steel bar concrete beams functioning with freeze-thaw cycles was presented.(4) Through experimental research, the CFRP-concrete interface bonding behavior of ultimate loading capacity, interface strain distribution and others was examined and the effects of factors of bonding length and others on interface bonding behavior were analyzed. Based on the experimental research, the finite element analysis model of CFRP-concrete interface bonding was built. With the finite element analysis, the fitting method of interface bond-slip relations was given to compare the coincide degree of experimental results of this paper with the main bond-slip relations at present, from which a CFRP-concrete interface bond-slip model in accordance with the experiments in this paper was calculated.更多还原