(2.风电装备与电能变换协同创新中心, 湖南湘潭 411104)
【基金资助】 国家自然科学基金项目(51678430); 湖南省自然科学基金项目(2017JJ4016,2018JJ4042);
A new innovation of research on the interface slip of concrete beam strengthened with near-surface mounted fiber reinforced plastics bars
(2.CIC of Wind Power Equipment and Energy Conversion, Xiangtan, Hunan Province, China 411104)
【Abstract】Bonding performance of the interface between FRP bars and concrete is the key of mechanics properties in the concrete structure strengthened with FRP bars. The constitutive relations of the interface bonding performance are described by the interface bond–slip model of FRP–concrete, which predict the stripping damage of FRP–concrete and must determine the appropriate bond–slip model. For the establishment of an interface bond–slip model, a four-point bending test of 11 concrete beams was carried out on the basis of a new test method to study the interface characteristics of reinforced concrete beams with embedded CFRP bars. Based on the shear stress model of the interface between resin bolt and anchoring agent in rock, the analytical expression of the axial normal stress of CFRP bar along the anchorage length of CFRP bar in the cross-section was derived, and the elongation of CFRP bar anchorage segment was obtained. In combination with the measured slip of the specified section of CFRP bar and the elongation of exposed CFRP bar, the slip of the interface between CFRP bar and concrete is obtained, and the bond–slip curve of the interface between CFRP bar and concrete is plotted. The test and analysis of the wide-notch beam show that the bonding shear stress and the slip properties are easy to obtain by the testing system. Bar stress is clear and the average interface shear stress of the CFRP is convenient to obtain. The slip and bond–slip curve is accurate and simple, and the interference of strain gauges is eliminated, so it has demonstrative guidance to the research on the interface properties of CFRP–concrete.
【Keywords】 near-surface mounted fiber reinforced plastic; concrete; interface; constitutive relation; new innovation;
【Funds】 National Natural Science Foundation of China (51678430); Natural Science Foundation Project of Hunan Province, China (2017JJ4016, 2018JJ4042);
 LI Huimin, DING Yahong. Experimental study on flexural strengthening of RC beams with near surface mounted prestressing helical rib–steel wire [J]. Journal of Building Structures, 2013, 34 (6): 137–142 (in Chinese).
 LI Ke, CAO Shuangyin, PAN Yi, et al. Fatigue test program selection for FRP-to-concrete interfacial bonding properties [J]. China Civil Engineering Journal, 2013, S2: 185–189 (in Chinese).
 HE Xiaobing, YAN Bo, SHEN Qiang. Interface shear performance of interply hybrid GFEP//CFRP composite and concrete [J]. Journal of Building Materials, 2013, 16 (6): 1004–1011 (in Chinese).
 YE Surong, SUN Yanhua, XIONG Guangjing. Analysis on end debonding failure of FRP strengthened RC beams based on a‘beam segment’model [J]. Engineering Materials, 2012, 29 (2): 101–106 + 113 (in Chinese).
 XU Tao, TANG Chunan, ZHANG Yongbin, et al. Parallel simulation of FRP–concrete debonding failure process [J]. Chinese Journal of Solid Mechanics, 2011, 32 (1): 88–94 (in Chinese).
 ZHANG Tuo. Study on Interface Shear Failure Forms and Rules of GFRP Reinforced Concrete Compound Beam [D]. Chongqing: Chongqing Jiao Tong University, 2013 (in Chinese).
 Nakaba K., Toshiyuki K., Tomoki F. Hiroyuki Y.. Bond behavior between fiber-reinforced polymer laminates and concrete [J]. ACI Structural Journal, 2001, 98 (3): 359–367.
 Ueda T., Dai J. G., Sato Y. A nonlinear bond stress-slip relationship for FRP sheet–concrete interface. Proc [C] ∥International Symposium on Latest Achievement of Technology and Research on Retrofitting Concrete Structures, Kyoto, Japan, 2003: 113–120.
 ZENG Xiantao, REN Zhenhua. Analyses and evaluation of the problem concerning interface test and peel strength of concrete beam strengthened with fiber reinforced plastic [J]. Earthquake Resistant Engineering and Retrofitting, 2014, 36 (2): 88–93 (in Chinese).
 REN Zhenhua, ZENG Xiantao. Test research on bending capacity of π-type concrete beam strengthened with carbon fiber reinforced plastic [J]. Journal of Natural Disasters, 2013, 22 (3): 221–228 (in Chinese).
 YANG Xiaoming, WU Tianyu, CHEN Yonglin. Experimental study on the bending performance of corroded reinforced concrete beam [J]. Journal of Natural Disasters, 2018, 27 (5): 70–78 (in Chinese).
 CAO Wanlin, GONG Xiaoxue, YE Taoping, et al. Experiment of the flexural performance of recycled concrete beams with different recycled aggregate replacement ratios [J]. Jaurnal of Natural Disasters, 2017, 26 (4): 10–18 (in Chinese).
 ZHANG Haixia, HE Luyuan. Experimental study on bond–slip behavior between NSM FRP bars and concrete [J]. Fiber Reinforced Plastics/Composites, 2016, 3: 5–12 (in Chinese).
 ZHANG Yannian, LIU Xin, LIU Jinsheng, et al. The failure model of concrete beams strengthened with near surface mounted FRP bars [J]. Mechanics In Engineering, 2015, 37 (5): 612–617 (in Chinese).
 Hee Young Lee, Woo Tai Jung, Wonseok Chung. Flexural strengthening of reinforced concrete beams with pre-stressed near surface mounted CFRP systems [J]. Composite Structures, 2017, 163 (3): 1–12.
 TONG Gusheng, AI Bowen. Research advance of FRP–concrete interface bond–slip relationship [J]. Concrete, 2016, 8: 1–7 (in Chinese).
 WU Yili, YAO Jian, ZHU Xiaoxu. Analysis on bonding performance test of mounted CFRP strengthened concrete beam [J]. Architecture Technology, 2010, 41 (5): 454–456 (in Chinese).
 REN Zhenhua. Research on relationship of strain coordination and interface properties forπRC beam strengthened with carbon fiber reinforced plastic [D]. Nanjing: Hohai University, 2012 (in Chinese).
 REN Zhenhua, ZENG Xiantao, XIONG Shanming et al. Research on the interface properties of concrete beam bridges strengthened with externally bonded reinforcement carbon fiber reinforced plastic plate by using wide-notch concrete beam model [J]. China Journal of Highway and Transport, 2015, 28 (1): 71–79 (in Chinese).
 REN Zhenhua, ZENG Xiantao, ZHOU Fengjun. Research on interface properties of concrete beam bridges strengthened with near-surface mounted carbon fiber reinforced plastic bar by using wide-notch concrete beam model [J]. China Journal of Highway and Transport, 2015, 28 (7): 58–65 (in Chinese).
 KANG Hongpu, CUI Qianli, HU Bin, et al. Analysis on anchorage performances and affecting factors of resin bolts [J]. Journal of China Coal Society, 2014, 39 (1): 1–10 (in Chinese).
 LI Qingfeng, YI Hou, ZHU Chuanqu. Distribution of shear stress on resin bolt of anchoring rods and its damage model analysis [J]. Journal of Hunan University of Science & Technology (Natural Science Edition), 2016, 31 (1): 12–18 (in Chinese).
 LU Xinzheng. Studies on FRP–concrete Interface [D]. Beijing: Tsinghua University, 2004 (in Chinese).
 REN Zhenhua, ZENG Xiantao, YAN Qian. Calculation method for interface slip of wide-notch concrete beam strengthened with carbon fiber reinforced plastics plate [J]. Journal of Building Structures, 2018, 39 (11): 119–128 (in Chinese).