| 梯度锚固预应力NSM CFRP板条加固梁破坏模式与影响因素试验研究 |
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| 引用本文： | 龚爽,张建仁,林福宽,粟淼.梯度锚固预应力NSM CFRP板条加固梁破坏模式与影响因素试验研究[J].中国公路学报,2022,35(2):169-180. |
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| 作者姓名： | 龚爽 张建仁 林福宽 粟淼 |
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| 作者单位： | 1. 长沙理工大学 土木工程学院, 湖南 长沙 410014;2. 桥梁工程 安全控制教育部重点实验室, 湖南 长沙 410014 |
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| 基金项目： | 国家自然科学基金项目(52178186,51578078);湖南省研究生科研创新项目(QL20210187) |
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| 摘 要： | 为探索梯度锚固预应力表层嵌贴(Near Surface Mounted,NSM) CFRP板条加固梁的破坏模式,完成了1片普通预应力和7片梯度锚固预应力加固梁的弯曲性能试验,研究了端部梯度锚固设置、加固长度、混凝土保护层厚度和钢筋表面特性对结构力学性能的影响,分析了加固梁的破坏模式、特征荷载、延性、预应力和外荷载作用下FRP-混凝土界面黏结应力,采用《中国结构设计规范》(GB 50010-2010)、《行业技术标准》(CTT/T 280-2018)和《美国混凝土协会规范》(ACI 440.1R-15)分别计算了加固梁裂缝间距。结果表明:梯度锚固预应力技术在抑制裂缝开展、延缓纵筋屈服和提高加固梁承载力等方面的表现均优于普通预应力技术,且能够避免加固梁发生端部混凝土保护层剥离;加固梁抗弯承载力显著提升,最大提升幅值达35.48%;同时,加固梁延性大幅提高,破坏时极限挠度增大100.33%。梯度锚固设置相同时,减少总加固长度、增加保护层厚度和使用光圆纵筋都会降低加固梁的承载能力,钢筋表面特性仅在端部裂缝出现水平分支后对加固梁性能产生影响。预应力和外荷载引起的黏结应力都在距FRP端部400 mm范围内出现峰值。GB 50010-2010、ACI 440.1R-15计算的裂缝间距结果稍显不安全;CTT/T 280-2018的计算结果则偏保守;而基于GB 50010-2010提出的裂缝间距修正公式,通过考虑FRP加固长度梯度锚固预应力和保护层厚度的影响,能更准确计算混凝土齿状模型中板端保护层剥离破坏时的CFRP应力。
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| 关 键 词： | 桥梁工程 梯度锚固预应力 模型试验 破坏模式 表层嵌贴 CFRP |
| 收稿时间： | 2021-06-16 |
Experimental Study on Failure Modes and Influence Factors of RC Beams Reinforced with Gradually Anchored Prestressed Near-surface-sounted Carbon-fiber-reinforced Polymer |
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| GONG Shuang,ZHANG Jian-ren,LIN Fu-kuan,SU Miao.Experimental Study on Failure Modes and Influence Factors of RC Beams Reinforced with Gradually Anchored Prestressed Near-surface-sounted Carbon-fiber-reinforced Polymer[J].China Journal of Highway and Transport,2022,35(2):169-180. |
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| Authors: | GONG Shuang ZHANG Jian-ren LIN Fu-kuan SU Miao |
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| Affiliation: | 1. School of Civil Engineering, Changsha University of Science & Technology, Changsha 410114, Hunan, China;2. Key Laboratory for Safety Control of Bridge Engineering, Ministry of Education and Hunan Province, Changsha 410114, Hunan, China |
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| Abstract: | A gradually anchored prestressed method for beams reinforced with near-surface-mounted (NSM) carbon-fiber-reinforced polymer (CFRP) strips is proposed. Bending tests of one ordinary prestressed reinforced beam and seven gradually anchored prestressed reinforced beams were completed, and the effects of the gradient prestress, reinforcement length, concrete protective layer thickness, and round bar on the mechanical properties of the structure were studied. The failure mode, characteristic load and ductility of the reinforced beam, and bonding stress of the fiber-reinforced polymer (FRP)-concrete interface under prestress and external load were analyzed. The crack spacing of the reinforced beam was calculated according to the Chinese structural design code GB 50010-2010, industry technical standard CTT/T 280-2018, and American Concrete Institute code ACI 440.1R-15. The results show that the gradually anchored prestressed reinforcement is superior to ordinary pre-stressed reinforcement in restraining fracture development, delaying the yield of longitudinal reinforcement, improving the bearing capacity of the reinforced beam, and avoiding end concrete cover separation. The bending capacity of the strengthened beam was significantly improved up to 35.48%; the ductility of the strengthened beam was greatly improved; and the failure deflection was increased by up to 100.33%. The performance of the reinforced beam increased with an increase in the end gradually anchored prestressed length. When the end gradually anchored prestress is set the same, reducing the total length of reinforcement, increasing the thickness of the protective layer, and using plain round reinforcement can reduce the bearing capacity of the reinforced beam. However, the surface characteristics of the reinforcement only affect the performance of the reinforced beam after the fracture exhibits horizontal branching. The peak value of the bond stress caused by the prestress and external load is within 400 mm of the FRP end. The fracture spacings calculated by GB 50010-2010 and ACI 440.1R-15 are slightly unsafe. The calculation results of CTT/T 280-2018 are conservative. Based on the crack spacing correction formula proposed in GB 50010-2010, by considering the influence of the FRP bond length, prestress of the gradient anchored, and thickness of the protective layer, the CFRP stress can be calculated more accurately when the protective layer of the concrete cover is separated. |
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| Keywords: | bridge engineering gradually anchored prestressed model test failure mode NSM CFRP |
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