环境损伤作用下CFRP布加固混凝土梁力学性能研究

发布时间：2018-07-28 14:31

【摘要】：因受到各种环境作用、工程建设质量问题及使用时间等因素的影响,建筑物的性能逐渐衰退。对受损建筑的加固修复,既能保证受损建筑不断适应人类社会的发展,又可以节约工程建设成本,但现有的混凝土结构加固方法大都存在一定缺陷。碳纤维增强复合材料(CFRP)具有轻质高强、耐腐蚀、抗疲劳等诸多优良性能,正被越来越广泛地应用于建筑的维修与改造。因此,本文开展环境损伤作用下CFRP布加固混凝土梁的力学性能研究,主要内容包括:开展环境损伤作用下CFRP布加固混凝土梁力学性能试验研究,分析配筋率、CFRP布加固量和环境损伤对试件破坏形态、承载力、变形能力及裂缝开展的影响,结果表明,试件主要发生两种破坏模式:CFRP布拉断破坏、中部裂缝开展引起的CFRP布局部剥离破坏。随着配筋率的增大,试件承载力逐渐增大,承载力提高幅度降低,刚度退化速度和截面曲率增长速度减小,跨中挠度、裂缝宽度和平均裂缝间距减小。随着CFRP布加固量的增大,试件承载力和承载力提高幅度逐渐增大,刚度退化速度和截面曲率增长速度减小,跨中挠度、裂缝宽度和平均裂缝间距减小。随着环境损伤作用的增大,试件的承载力和承载力提高幅度逐渐降低,刚度退化速度和截面曲率增长速度增大,跨中挠度、裂缝宽度和平均裂缝间距增大。应变分析结果表明,沿梁高测得的截面应变分布符合平截面假定。在加载初期,CFRP布应变增长趋势与纵筋基本一致,试件屈服后,CFRP布应变增长速度逐渐大于纵筋应变增长速度,CFRP布逐渐承担主要拉应力。随着配筋率和CFRP布加固量的增大,纵筋和CFRP布应变增长速度减缓,随着环境损伤作用的增大,纵筋和CFRP布的应变增长速度加快。从试件加载初期到试件破坏,U型CFRP布锚固箍应变持续稳定增长,U型锚固箍可有效抑制CFRP布与混凝土之间的剥离。在试验研究基础上,根据截面应变关系和静力平衡条件,考虑配筋率、CFRP布加固量、环境损伤的影响,引入CFRP布强度折减系数和环境损伤系数,推导出环境损伤作用下CFRP布加固混凝土梁开裂、屈服、极限承载力计算公式,并给出其正截面受弯承载力计算的设计方法。根据普通混凝土梁的粘结滑移裂缝计算模型,考虑配筋率、CFRP布加固量、环境损伤的影响,引入CFRP布加固影响系数和环境损伤影响系数,推导出环境损伤作用下CFRP布加固混凝土梁的裂缝计算公式。根据曲率法,考虑CFRP布层数和环境损伤的影响,引入CFRP布层数影响系数和环境损伤影响系数,推导出环境损伤作用下CFRP布加固混凝土梁的挠度计算公式,并给出CFRP布加固混凝土梁的变形验算方法和CFRP布U型锚固箍宽度计算公式。
[Abstract]:Due to the influence of various environmental factors, engineering construction quality problems and service time, the performance of buildings is gradually declining. The reinforcement and restoration of damaged buildings can not only ensure that the damaged buildings can adapt to the development of human society, but also save the construction cost. However, most of the existing reinforcement methods of concrete structures have some defects. Carbon fiber reinforced composite (CFRP) has been widely used in building maintenance and renovation because of its high strength, corrosion resistance, fatigue resistance and many other excellent properties. Therefore, the mechanical properties of concrete beams strengthened with CFRP sheets under environmental damage are studied in this paper. The main contents are as follows: the experimental study on mechanical properties of concrete beams strengthened with CFRP sheets under environmental damage is carried out. The effects of reinforcement ratio and CFRP reinforcement amount and environmental damage on the failure form, bearing capacity, deformation capacity and crack development of the specimens are analyzed. The results show that there are two kinds of failure modes: 1 / CFRP brac fracture. Central crack development caused by the CFRP layout of the peeling damage. With the increase of reinforcement ratio, the bearing capacity of the specimen increases gradually, the increase of bearing capacity decreases, the velocity of stiffness degradation and the growth rate of sectional curvature decrease, the deflection of span, the width of crack and the average crack spacing decrease. With the increase of CFRP reinforcement, the bearing capacity and bearing capacity of the specimens increase gradually, the stiffness degradation speed and section curvature growth speed decrease, the mid-span deflection, crack width and average crack spacing decrease. With the increase of environmental damage, the bearing capacity and bearing capacity of the specimen decrease gradually, the stiffness degradation speed and section curvature increase, the deflection of span, the width of crack and the average crack spacing increase. The results of strain analysis show that the cross section strain distribution measured along the beam height accords with the assumption of plane section. At the beginning of loading, the strain growth trend of CFRP cloth is basically consistent with that of longitudinal steel bar, and the strain growth rate of CFRP cloth is gradually larger than that of longitudinal reinforcement strain growth rate after the specimen yield, and the CFRP cloth gradually bears the main tensile stress. With the increase of reinforcement ratio and CFRP reinforcement amount, the strain growth rate of longitudinal reinforcement and CFRP cloth slowed down, and the strain growth rate of longitudinal reinforcement and CFRP cloth increased with the increase of environmental damage. From the initial loading stage of the specimen to the failure of the specimen, the strain of the U-type CFRP cloth Anchorage hoop increases steadily and the strain of the U-type Anchorage hoop can effectively restrain the peeling between the CFRP cloth and the concrete. On the basis of experimental study, according to the strain relation of section and static equilibrium condition, considering the influence of reinforcement ratio and environment damage, the strength reduction coefficient and environmental damage coefficient of CFRP cloth are introduced. The formula of crack, yield and ultimate bearing capacity of concrete beams strengthened with CFRP sheets under environmental damage is derived, and the design method of flexural bearing capacity of normal section is given. According to the calculation model of bond slip crack of ordinary concrete beam, considering the reinforcement ratio and the influence of environment damage, the influence coefficient of CFRP sheet reinforcement and environment damage is introduced. The formula for calculating the cracks of concrete beams strengthened with CFRP sheets under the action of environmental damage is derived. According to curvature method, considering the influence of CFRP layer number and environmental damage, the influence coefficient of CFRP layer number and environmental damage coefficient is introduced, and the deflection calculation formula of concrete beam strengthened by CFRP cloth under environmental damage is deduced. The method of checking the deformation of concrete beams strengthened with CFRP sheets and the calculation formula of the width of U-type Anchorage hoop of CFRP cloth are given.
【学位授予单位】：安徽工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU37

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