CFRP管约束受压区的钢筋混凝土梁受弯性能试验研究

发布时间：2018-04-28 10:00

本文选题：钢筋混凝土梁 + CFRP约束混凝土　；参考：《湖南大学》2015年硕士论文

【摘要】：钢筋混凝土梁的延性变形能力对混凝土结构抗震性能有着重要影响,为了保证梁的延性变形能力,我国《建筑抗震设计规范GB50011-2010》对配筋率进行了限制,但实际工程设计中,由于层高限制或荷载过大等原因,设计人员不得不把混凝土梁设计成高配筋率梁或超筋梁。延性可以从结构、构件、截面、材料四个层面来评判,构件的延性与截面和材料的延性密切相关。钢筋混凝土梁的主要材料为混凝土和钢筋,钢筋具有良好的变形能力,因此钢筋混凝土梁的延性变形能力主要由受压区混凝土的延性控制。对混凝土进行侧向约束可以提高混凝土的强度和极限压应变,因此对梁的受压区混凝土进行侧向约束可以提高梁的延性性能。CFRP(Carbon Fiber Reinforced Plastic)材料具有轻质、高强、高弹模、耐腐蚀等优点,CFRP约束混凝土在试验中展现出良好的变形能力。在这种背景下,本文提出了一种新型的CFRP管约束受压区的钢筋混凝土梁(以下简称CFRP约束梁),通过9根CFRP约束梁和3根对比梁的四点受弯试验,研究了CFRP约束梁的受弯性能。本文主要包括以下几方面的内容:(1)对本文试验中所使用的材料进行材料力学性能试验,包括CFRP单向拉伸试验,钢筋拉伸试验,C50和C35混凝土配合比设计及其抗压性能试验等,为CFRP约束梁的试验研究与理论分析提供依据。(2)通过四点受弯加载试验,以混凝土强度等级、配筋率、CFRP层数、约束区长度与形状为试验参数,对CFRP约束梁的受弯性能进行试验研究,试验结果显示:对受压区混凝土进行CFRP管约束对钢筋混凝土梁的极限承载力影响不大,但能有效地提高梁的延性;梁的混凝土强度等级越低,或配筋率越高,梁的延性提高幅度也越大;增加CFRP层数对延性的进一步提高效果不明显,但能有效地延缓CFRP管应变的开展;就提高钢筋混凝土梁延性而言,采用矩形CFRP管对受压区混凝土进行约束比圆形CFRP管更有效;CFRP约束区长度大于纯弯段长度时,增大约束区长度对进一步提高梁的受弯性能效果不明显;为了节约CFRP材料,CFRP管的高度可以小于受压区高度。(3)根据材料力学性能试验结果和简化的应力-应变关系,结合已有的CFRP约束混凝土应力-应变模型 Wei模型,采用数值法,对CFRP约束梁进行受弯全过程非线性分析,主要分析CFRP约束梁截面的荷载-曲率关系和CFRP约束梁的荷载-位移关系,并与试验值进行对比,发现两者比较吻合。
[Abstract]:The ductile deformation ability of reinforced concrete beams has an important effect on the seismic behavior of concrete structures. In order to ensure the ductile deformation capacity of the beams, the reinforcement ratio is restricted by the Code for Seismic Design of buildings in China (GB50011-2010), but in the practical engineering design, the reinforcement ratio is limited. Because of the limit of floor height or the excessive load, the designers have to design the concrete beam into high reinforcement ratio beam or super reinforced beam. Ductility can be judged from four aspects: structure, member, section and material. The ductility of the member is closely related to the section and the ductility of the material. The main materials of reinforced concrete beams are concrete and steel bars, so the ductility of reinforced concrete beams is mainly controlled by the ductility of concrete in compression zone. Lateral confinement of concrete can improve the strength and ultimate compressive strain of concrete. Therefore, lateral restraint of concrete in compression zone can improve the ductility of beam. CFRP carbon Fiber Reinforced Plastic) material has light weight, high strength and high elastic modulus. Corrosion resistance and other advantages of CFRP confined concrete in the test showed a good deformation capacity. In this context, a new type of reinforced concrete beam (CFRP confined beam) in the confined zone of CFRP pipe is proposed. The flexural behavior of CFRP confined beam is studied by four point bending tests of 9 CFRP restrained beams and 3 contrast beams. The main contents of this paper are as follows: (1) the mechanical properties of the materials used in this paper are tested, including CFRP uniaxial tensile test, steel bar tensile test, C50 and C35 concrete mix ratio design and compressive performance test, etc. Through four-point flexural loading test, the concrete strength grade, reinforcement ratio and the number of CFRP layers, the length and shape of the confined zone are taken as the test parameters, which provides the basis for the experimental study and theoretical analysis of CFRP restrained beams. The flexural behavior of CFRP confined beams is studied. The experimental results show that the ultimate bearing capacity of reinforced concrete beams is not affected by CFRP pipe confinement, but it can effectively improve the ductility of RC beams. The lower the concrete strength grade of the beam is or the higher the reinforcement ratio is, the greater the ductility of the beam is. The further improvement of the ductility by increasing the number of CFRP layers is not obvious, but it can effectively delay the strain development of the CFRP pipe. In order to improve the ductility of reinforced concrete beams, when the concrete confined by rectangular CFRP tube is more effective than the circular CFRP tube, the length of confined zone is larger than that of pure bending section. In order to save the height of CFRP tube, the height of CFRP-tube can be smaller than that of compression zone, according to the experimental results of mechanical properties of materials and the simplified stress-strain relationship, the effect of increasing the length of confined zone is not obvious. Combined with the existing stress-strain model of CFRP confined concrete and Wei model, the nonlinear analysis of the whole bending process of CFRP confined beams is carried out by using numerical method. The load-curvature relation of CFRP confined beam section and the load-displacement relation of CFRP constrained beam are analyzed and compared with the experimental results. It is found that the two relations are in good agreement with each other.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU375.1

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