无粘结预应力U形CFRP加固混凝土梁抗剪试验

发布时间：2018-08-10 21:32

【摘要】：针对外贴纤维布抗剪加固钢筋混凝土梁极易发生纤维剥离破坏、纤维利用率低且被动受力等问题,开发了一套U形纤维带预应力系统,包括侧面端部自锁锚固装置、角钢和底部连接及张拉装置.为验证该系统的可行性及探讨碳纤维带预应力大小对抗剪加固效果的影响,完成了5个较大截面矩形梁段试件的单点加载抗剪试验,其中1个未加固,4个采用无粘结预应力U形碳纤维带进行抗剪加固.试验结果表明:该系统能给U形纤维带提供可靠预应力,并把常见的纤维剥离破坏转变为拉断破坏,大大提高纤维利用率;施加预应力的纤维带对梁裂缝的产生与发展及开裂后梁刚度的退化均有明显的抑制作用;预应力大小对主斜裂缝倾角及直接参与抗剪的纤维带数量影响较大,但对这些纤维带的有效应变影响不大;并非预应力越大,抗剪加固效果越好,本试验中,仅将纤维带预应变张拉至0.001就能最大幅度提高梁的抗剪承载力.基于试验结果分析,从考虑竖向平均预应力对主斜裂缝倾角的影响入手,提出了无粘结预应力U形碳纤维带加固混凝土梁抗剪承载力公式,其计算值与试验值符合良好.
[Abstract]:In order to solve the problems of fiber stripping failure, low fiber utilization ratio and passive force, a prestressing system of U-shaped fiber strip is developed, including self-locking anchoring device at the side end. Angle steel and bottom connection and tensioning device. In order to verify the feasibility of the system and to discuss the influence of the size of prestressed carbon fiber on the effect of shear reinforcement, the single point loading shear tests of five specimens with large section rectangular beams have been completed. One of them was not strengthened, and four were unbonded prestressed U-shaped carbon fiber strip for shear reinforcement. The test results show that the system can provide reliable prestressing force for U-shaped fiber strip, and transform the common fiber stripping failure into tensile failure, which greatly improves the fiber utilization ratio. The prestressed fiber band can obviously restrain the generation and development of beam cracks and the degradation of beam stiffness after cracking, and the size of prestress has a great influence on the inclination angle of the main oblique crack and the number of fiber bands directly involved in shear resistance. But there is little effect on the effective strain of these fiber bands, but not the more prestressing, the better the effect of shear strengthening. In this experiment, the shear capacity of the beams can be greatly improved by only stretching the pre-strain of the fiber strips to 0.001. Based on the analysis of test results and considering the influence of vertical average prestress on the inclined angle of the main oblique crack, a formula for shear bearing capacity of unbonded prestressed U-shaped carbon fiber reinforced concrete beams is put forward. The calculated values are in good agreement with the experimental values.
【作者单位】：中南大学土木工程学院;广州地铁设计研究院有限公司;
【基金】：国家自然科学基金(51378507) 湖南省自然科学基金重点项目(2013JJ2005) 中南大学教师研究基金(2013JSJJ019)
【分类号】：TU317;TU375.1

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