【作者】 徐田；

【导师】 潘景龙；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2007， 博士

【摘要】 纤维增强复合材料(FRP)具有高强、轻质、耐腐蚀和施工方便等优点,近年来在混凝土结构修复加固领域已开始得到较为广泛的应用。FRP较为合理的应用形式之一是用其环向对混凝土施加约束,从而形成FRP约束混凝土,提高构件的抗压承载力以及其延性性能。目前,国内外许多学者对FRP约束混凝土进行了研究,得到了很多有用的结论和有价值的试验数据。在取得了丰硕的研究成果的同时,我们也看到现在对FRP约束混凝土的研究所存在的问题:第一,截面形状的研究以圆形截面为主,方形倒角截面研究较少,而在工程实际当中,存在大量的方形截面柱,并且FRP约束方形截面柱还存在应力集中问题,根据这种受力特点本文认为需对截面形式进行改良,对矩形或方形截面进行圆弧化处理,从而减小应力集中问题。第二,尽管对于FRP约束混凝土短柱的研究很多,但是各个学者在计算方法上尚未有统一的认识,而且对于各家提出的计算方法也很少见到关于可靠度的报道。第三,在应力-应变曲线的研究上,用哪个参数来表达FRP约束混凝土的约束量与混凝土的几何特性和物理特性之间匹配关系,以及到底采用分段式还是单一函数形式的表达式较好。第四,国内外目前的研究主要集中在短柱轴心受压的力学性能,而对中长柱轴心受压、偏心受压研究较少。而在工程中还存在大量的中长柱和偏心受压柱,因此为了更广范的应用FRP约束混凝土柱,对其开展系统的研究是十分必要的为了了解方形倒角截面的约束混凝土的基本力学性能,本文对8个FRP约束混凝土方形倒角截面轴心受压短柱进行了试验研究并结合国内外的试验资料研究分析了不同包裹量和不同混凝土强度的构件力学性能,结果表明:构件的应力-应变曲线的特点是过渡段较长,这个特点与圆形截面和圆弧化截面是有差别的。同时采用有限元计算软件ABQUS分析了方形倒角截面和圆形截面构件的力学性能,分析模拟过程考虑了不同混凝土强度、不同包裹量对构件承载力的影响,理论计算结果与试验结果吻合较好。同时对反映约束量与混凝土的几何特性和物理特性之间匹配关系的参数进行了讨论,并利用有限元计算对约束刚度比βj的适用性进行了论证。在此基础上结合大量的国内外试验数据,对FRP约束混凝土应力-应变模型中的参数进行回归分析,并得出不同截面形状约束混凝土应力-应变模型参数。把回归参数带入到Richard模型和滕锦光模型计算,并与试验应力-应变曲线进行对比,结果表明,采用本文回归的参数带入到不同的模型中,均可得到与试验结果吻合较好的应力-应变曲线。论文还利用有限元计算软件ABQUS进行了参数分析,并根据有限元计算数据回归出不同截面形状的约束混凝土的应力-应变模型参数,与根据试验数据回归的参数公式计算结果进行对比,结果吻合较好。为了了解FRP约束钢筋混凝土轴心受压中长柱的力学性能,为偏心受压中长柱的研究做铺垫,本文进行了10根FRP约束钢筋混凝土圆弧化截面轴心受压中长柱的试验研究和9根FRP约束钢筋混凝土方形倒角截面轴心受压中长柱的试验研究,分析了它的工作机理。并得到了不同截面轴心受压中长柱的稳定系数回归计算公式,从而提出FRP约束钢筋混凝土轴心受压中长柱的承载力计算公式。针对工程中存在大量偏心受压柱,本文进行了20根FRP约束钢筋混凝土圆弧化截面偏心受压中长柱的试验研究和18根FRP约束钢筋混凝土方形倒角截面偏心受压中长柱的试验研究。对其承载力进行了理论分析,讨论了偏心距增大系数的取值,并得出承载力计算公式。本文还利用经验系数法给出了偏心受压构件的承载力计算公式的简化计算方法。最后,本文利用JC法编写的MATLAB程序,对本文提出的FRP约束钢筋混凝土不同截面的轴心受压和偏心受压承载力计算公式进行可靠度分析,研究了各参数的影响,结果表明应用本文提出的中长柱承载力计算结果,其可靠度指标满足规范要求。更多还原

【Abstract】 In recent years, FRP has been widely used in the field of retrofit of concrete structures due to its excellent mechanical behavior. It is the fit using style that FRP is used to confine concrete. As a result of FRP confinement, both the compressive ability and ductility of concrete can be greatly enhanced.At present, many researchers have been studied on the FRP confined concrete and abtained many conclusions and valuable test data. At the same time, the problems of the studies on the FRP confined concrete are found. The first problem is the study on the cross section of columns, most researches have mainly concentrated on the shape of circle cross section of short columns, few square cross section studies are reported. In order to reduce the problem of stress concentrate, this paper proposed a new cross section named elliptical modified rectangular. The second problem is the study on the method of caculating and the reliability of the FRP confined concrete column, although there are many researchers studying on the method of caculating of the FRP confined concrete, they did not accord. The publications on reliability of the FRP confined concrete column are relatively few. The third problem is the study on the stress-strain curve, the problem focus on the parameter which can exactly reflect the relationship of the geometry character and the physics character of FRP and concrete. The fourth problem is that in contrast to the large available database on short RC columns wrapped with FRP, publications on slender columns under eccentric loading are relatively few. This limits the applications of RC columns wrapped with FRP. In order to investigate the behavior of slender reinforced concrete (RC) columns sufficiently confined with FRP, more research work is needed. It is, therefore, useful to study the load carrying capacity of RC slender columns sufficiently confined with FRP and thus to understand the characteristics of the columns with a large slenderness ratio.To get a better understanding of the square section reinforced concrete columns wrapped with FRP under axial loading, eight specimens were tested. The results show that the stress-strain curve of square section, which is characterized by the transition zone is longer, is different from of circle and elliptical section. At the same time, the theoretical reseach work had been done with the software ABAQUS. The ABAQUS analyses include the circle and elliptical section specimens, considering the strength of concrete and layers of FRP. The caculated results are compared with those from experiment and they agreed well with each other. The problem about the parameter which can exactly reflect the relationship of the geometry character and the physics character of FRP and concrete is present is discussed and the applicability of the confinement stiffness ratioβj is proved. Based on the above argument and a lot of test data, the fomular of parameters of stress-strain curve of different section specimens are proposed. The stress-strain curves which are caculated by bringing the proposed the fomular of parameters into the model of Richard and Teng J.G are compared well with the experiment stress-strain curves.Before the study on the behavior of slender reinforced concrete columns sufficiently confined with FRP under eccentric loading, we must get a better understanding of FRP confined concrete slender columns under axail loading. So ten elliptical section slender columns and nine square section slender columns are tested. The stable coefficient of specimens is abbtained and the fomular of load carrying capacity of FRP confined slender columns is proposed.Because of many slender columns in the structure under eccentric loading, the study on them is necessary. Twenty elliptical section slender columns and eighteen square section slender columns are tested. The augment coefficient of eccentric distant is discussed and the fomular of load carrying capacity of FRP confined slender columns under eccentric loading is proposed. The simplified fomular of load carrying capacity of FRP confined slender columns under eccentric loading is also proposed, which is deduced by the method of experience coefficient.At last, in order to analyse the reliability of the proposed fomulars of load carrying capacity of FRP confined slender columns under axial and eccentric loading, we compile a program using the software MATLAB according to the method of JC. The caculating results show that the relatility satisfy the need of the concrete criterion.更多还原