【作者】 叶苏荣；

【导师】 熊光晶；

【作者基本信息】 汕头大学 ， 结构工程， 2011， 博士

【摘要】 纤维增强复合材料（FRP）加固混凝土结构是当前土木工程中的一个研发热点。FRP与混凝土界面的粘结质量是加固成败的关键，迄今仍有两个难点尚未得到较好地解决：(1) FRP加固混凝土梁梁端和跨中粘结界面剥离破坏的分析方法；(2)FRP-混凝土粘结-滑移本构关系的测试方法。本文先对上述两个问题的既有研究进行了较系统的综述；进而进行了针对性研究。(1) FRP加固混凝土梁梁端和跨中粘结界面剥离破坏的分析方法针对以整根梁作为有限元模型的繁琐和困难，以及因此而未能进行FRP-混凝土界面剥离破坏参数分析的现状，本文分别提出了简单的以混凝土梁上裂缝作为边界的梁端、剪弯段和纯弯段的“梁段”模型。然后通过圣维南原理以及数值检验分别证明各个“梁段”模型的合理性和可靠性，从而化解了整梁计算的困难。基于这些“梁段”模型，使用通用有限元软件ANSYS，第一次对FRP加固混凝土梁的界面剥离破坏问题进行了参数分析。结果显示：FRP拉应力和层数是加固梁各部位FRP-混凝土界面剥离破坏的最主要的影响因素。FRP-混凝土粘结滑移本构关系反应粘结质量的优劣，对加固梁各部位界面剥离破坏有重要的影响。斜裂缝到支座的距离对梁端界面剥离破坏影响很大。剪跨比λ和裂缝间距对剪弯段界面剥离破坏的影响相对较小。由于对称性，纯弯段FRP-混凝土界面层不会发生整片剥离破坏。经与收集的55根FRP加固混凝土梁的对比表明，本文提出的各个“梁段”模型的剥离计算结果与既有实验结果的误差在-12.33%和+32.80%之间。由于尚未见到可同时分析加固梁梁端和跨中FRP-混凝土剥离破坏的整梁有限元模型，本文基于“梁段”模型，提出了简单可靠的、可同时分析全梁不同部位剥离破坏的新分析方法—分段综合法。算例表明，除FRP拉应力和层数外，梁端斜裂缝到支座的距离对剥离破坏最为敏感。为此本文提出了一种新的缺口梁试验方法以深入探讨斜裂缝位置对梁端剥离破坏的影响。(2) FRP-混凝土粘结-滑移本构关系的测试方法针对既有FRP-混凝土粘结-滑移本构关系测试试件均从一侧对FRP进行加载，在FRP-混凝土相对滑移量较小时就易发生突然性的界面整片剥离破坏,导致无法测得粘结-滑移本构关系的下降段的缺点,提出了一种新式FRP-混凝土粘结-滑移本构关系的实验方法。借鉴“梁段”模型的特点设计出一种改进的从两侧对FRP进行加载的―双拉‖试件及其水平加载装置。共进行了6个试件的测试,均实测到完整的粘结滑移关系曲线,表明新实验方法圆满成功。受“梁段”模型和“双拉”试件的启发,本文提出一种测量FRP-混凝土粘结-滑移本构关系的梁式试件的改进设想,即在FRP加固混凝土梁的纯弯段预设裂缝,一次形成多个“双拉梁段”试件,以提高实验效率。综上本文的主要创新和贡献有:(1)可靠、简单的FRP加固混凝土梁剥离破坏计算方法及其影响因素分析。a)提出并验证了可靠、简单的梁端与跨中“梁段”模型,且使计算结果更接近实际。b)第一次对FRP-混凝土界面剥离破坏影响因素进行了较全面细致的分析,有限元计算结果与大量的实验结果吻合较好。c)提出了可同时对全梁不同部位进行剥离分析的简单、可靠的新方法。d)提出了一种适合研究梁端剥离破坏的缺口梁实验方法。(2)可实测完整的FRP-混凝土粘结-滑移本构关系的实验方法。a)改进了可实测完整的FRP-混凝土界面粘结-滑移本构关系的“双拉”试件及其实验方法。b)测量FRP-混凝土粘结-滑移本构关系的梁式试件的改进设想有可能提高实验效率。更多还原

【Abstract】 Fiber reinforced composites strengthened RC structure is a current hot topic in civil engineering. FRP–to-concrete interface bond quality is the key issue for a successful strengthening, so far two difficulties yet have not been solved successfully: (1) analysis method of interface debonding in the end and mid-span of FRP strengthened RC beams; (2) testing method of bond-slip constitutive law of FRP-to-concrete interface. Existing studies of these two issues above were systematically reviewed in this thesis firstly, and then targeted researches were carried out.(1) Analysis method of interface debonding in the end and mid-span of FRP strengthened RC beamsIt is difficult and cumbersome to take a whole strengthened beam as a finite element model model and consequently to carry out a parameter study of interface debonding. Noticing these, various simple "beam segment" models of beam end, shear-flexure zone or pure-flexure zone were proposed respectively in this thesis, in which concrete cracks were taken as the boundaries for each segment. The new simple―beam segment model‖was validated to be rational and reliable respectively by using Saint-Venant Principle and a numerical study. The difficulties of the whole beam calculation, thus, were resolved.Based on these "beam segment" models, parameter analysis of debonding was performed for the first time, using general finite element software ANSYS. The result shows that FRP tensile stress and the layers are the most important influence factors of debonding. FRP-concrete bond-slip constitutive law has an important impect on debonding, which is the response of bonding quality. Distance from critical diagonal crack to the bearing of beam has a great influence on debonding of beam end. The influence of shear span ratioλand the crack spacing on debonding of shear-flexure zone is relatively small. Because of symmetry, no entire interface debonding occurs in pure-flexure zone.Comparison with a large number of experimental results collected shows the various "beam segement" debonding models proposed by this thesis are in good agreement with existing experimental results.As no finite element model of the entire beam which can analyse deonding in both beam end and mid-span has been reported yet. Based on "beam segement" model, a simple and reliable new analysis method named as segmentation-synthesization method was proposed by this thesis, which can be used to analyse debonding in different zones at the same time. Calculation examples show in addition to tensile stress and the FRP layers, the distance from critical diagonal crack to the bearing of beam is most sensitive on debonding failure. In order to further investigate the fluence of the critical diagonal crack location on debonding failure, a new beam specimen desigh with an opening was proposed by this thesis.(2) Test method of FRP-to-concrete interface bond-slip constitutive curveIt is impossible to measure descending constitutive curve of FRP-to-concrete interface bond-slip by using existed specimens loaded from just one side of FRP, because of the sudden destruction of the entire FRP-to-concrete interface when FRP-concrete slip is relatively small. In light of "beam segement" model, a new test method of FRP-to-concrete interface bond-slip constitutive curve was proposed. An improved "double-pull" specimen and loading equipment were designed to load from both two sides of FRP. Complete bond-slip constitutive curve is obtained by each of 6 specimens’tests, indicating the success of the new experimental method.By "beam segement" model and "double-pull" specimen, a new beam specimen was inspired for testing FRP-to-concrete interface bond-slip constitutive curve. Preset cracks in pure-flexure section were designed to form several "double-pull beam segment" specimens, which might improve test efficiency.To sum up the main innovation and contribution of this paper are:(1) Reliable, simple debonding calculation method of FRP strengthened RC beams and analysis of influencing factors.a) Reliable, simple "beam segement" models in both beam end and mid-span were proposed, which make the calculated results more realistic.b) For the first time, a relatively comprehensive and detailed analysis for influencing factors of FRP-concrete debonding was carried out. Finite element results agree well with a large number of experimental results.c) A new method was proposed for analyzing debonding in different zons at the same time.d) An experimental method using beam with an opening was presented for the study of beam end debonding.(2) Experimental method by which complete FRP-to-concrete interface bond-slip constitutive curve can be measured.a) "Double-pull" specimen and test method are improved, by which complete FRP-to-concrete interface bond-slip constitutive curve can be measured.b) Tentative idea of improved beam specimen might improve FRP-to-concrete interface bond-slip constitutive curve test efficiency.更多还原