【作者】 胡程鹤；

【导师】 吴智敏； 吴宇飞；

【作者基本信息】 大连理工大学 ， 结构工程， 2011， 博士

【摘要】 纤维增强复合材料(FRP)被广泛用于加固钢筋混凝土(RC)结构。目前最常用的方法是将FRP片材粘贴在混凝土构件上。但是利用这种方法加固的钢筋混凝土构件容易发生FRP剥离的破坏形态。FRP剥离降低了FRP材料的抗拉强度利用率,同时使结构发生脆性破坏,影响结构安全。为了阻止FRP剥离破坏的发生,本文在香港城市大学吴宇飞提出的复合粘结技术的基础上,提出了一种改进的复合粘结技术(IHB-FRP)。该改进的复合粘结技术由外贴FRP方法(EB-FRP)和改进的机械锚固系统组成。为了给IHB-FRP技术提供一种适宜的机械连接件,首先进行了螺杆的拉拔试验,考察各种螺杆的抗滑移性能,从而选择一种具有较强抗滑移能力的螺杆作为IHB-FRP系统的机械连接件。然后对利用IHB-FRP技术加固的钢筋混凝土梁进行了三点弯曲试验,以检验该技术用于阻止FRP剥离的有效性。考察了IHB-FRP技术加固梁的破坏形态、极限承载能力、延性、裂缝分布、FRP应变分布、界面剪应力分布和螺杆的受力状态。同时对主筋配筋率、FRP的横截面面积、锚固件间距对IHB-FRP加固梁的影响进行了讨论。为了便于该技术在实际工程中的应用,本文还探讨了用于计算IHB-FRP加固梁的极限弯矩的简化的理论计算方法。试验结果表明：IHB-FRP技术非常有效地阻止了FRP加固的钢筋混凝土梁发生FRP剥离破坏,提高了FRP材料强度的利用率。当使用7层FRP片材进行抗弯加固时,IHB-FRP加固梁会发生FRP断裂破坏。IHB-FRP加固梁的极限承载能力得到显著提高,IHB-FRP加固梁的极限弯矩可以达到相应未采用FRP加固的RC梁的极限弯矩的11倍。与EB-FRP加固梁相比,IHB-FRP加固梁具有较好的延性,较小的平均裂缝间距,并且FRP应变分布更加均匀,其应变分布形状接近弯矩分布图形。IHB-FRP技术有效地增加了FRP/混凝土界面的摩擦剪切抗力。简化的理论计算方法适用于计算IHB-FRP加固梁的极限弯矩。在加载过程中,螺杆与混凝土之间的相对滑移量很小,因此在拉拔试验中选择的螺杆以及施加于螺母的扭矩在实际工程中是适用的。更多还原

【Abstract】 Fiber reinforced polymer (FRP) is widely used for retrofitting and strengthening reinforced concrete (RC) structures. Externally bonded FRP (EB-FRP) is one of the most popular techniques. However, the EB-FRP strengthened members often fail due to FRP debonding, reducing the strength utilization ratio of FRP and leading to brittle structural failure. To solve the problem and based on the original technique proposed by Yu-Fei Wu of City University of Hong Kong, an improved hybrid bonded FRP (IHB-FRP) technique is developed in this paper. The technique combines EB-FRP and improved mechanical fastening. The pull-out test was conducted first to select an appropriate mechanical fastener for the technique. The slip resistance capacity of the. threaded rod is checked in order to select a threaded rod with better slip resistance capacity for the IHB-FRP technique. Then IHB-FRP strengthened RC beams were tested under three-point bending to verify the effectiveness of the technique. The failure mode, ultimate load, ductility, crack distribution, FRP strain distribution, interfacial shear stress distribution and performance of mechanical fastener were examined. For the application of the technique, a simplified method is proposed for estimating the ultimate bending moment of the IHB-FRP strengthened beam. Based on the experimental results, the effects of the steel reinforcement ratio, the number of FRP plies, and the fastener spacing are evaluated. It is found that all the beams strengthened with the IHB-FRP technique fail due to tensile rupture of FRP strips even for seven plies of FRP strips. Thus, the IHB-FRP technique is highly effective in preventing FRP debonding, and increases FRP strength utilization ratio. The ultimate load may increase by a factor of 11 compared with the RC beam without strengthening. Compared with EB-FRP strengthened beam, the IHB-FRP strengthened beam has a better ductility, a shorter average crack spacing, and a more uniform strain distribution in the FRP strip. The shape of the strain distribution is similar to that of the bending moment. The IHB-FRP technique is effective in increasing the interfacial friction between FRP and concrete. The validity of the simplified method has been verified with the experimental results. The slip between the threaded rod and concrete is little in the three-point bending test, indicating that the selected threaded rod and the torque applied to the nut before loading are acceptable in practical applications.更多还原