抗剪加固用U形纤维布条带预应力系统设计及试验

Design and Experiment Study of Prestressing System for U-shaped FRP Sheet in Shear Strengthening

针对传统纯粘贴纤维增强复合材料(FRP)抗剪加固钢筋混凝土梁技术中,FRP强度利用率低、端部极易发生剥离和被动受力等问题,自主研发了抗剪加固用U形纤维布条带预应力系统.它由锚固装置、张拉装置和转角圆钢3部分组成.详细给出了各部件尺寸的设计方法和预应力施工工艺.设计制作了适用于2层50mm宽FRP的预应力系统,分别进行了1组直线条带的承载力试验和8组抗剪U形条带的预应力损失试验研究.结果表明:预应力系统能够有效锚固FRP并实现拉断破坏,使其强度利用率最大可达到96.1%;各部件尺寸设计方法是安全可靠的;施工工艺能够在确保FRP两侧应力的均匀性和对称性的基础上施加不同大小的预应力值;预应力系统适用于施加244.84 MPa以上预应力值的抗剪FRP,其长期预应力损失比约为15%.

In the shear strengthened reinforced concrete （RC） beams by externally bonded fiber rein- forced polymer （FRP） composite, there are some main shortcomings including low fiber utilization, pre- mature debonding, and stress hysteresis of the FRP, etc. In order to address these problems, this paper independently developed a novel prestressing system for U-shaped FRP sheet in shear strengthening, which consists of three parts： anchor device, tension device, and steel angle. The design method of com- ponent size and the prestress construction technology were presented. Furthermore, a prestressing system for 2-ply and 50-ram-wide FRP sheet was designed and manufactured. One bearing capacity test of linear FRP sheet and eight prestressing loss tests of shear-strengthened FRP strips were conducted in this sys- tem. The test results show that： the prestressing system can effectively anchor FRPand result in rupture failure; fiber strength increases up to 96.1-; design method of component size is safe and reliable; pres- tressing construction technology can exert different prestress values to FRP strip based on the uniformity and symmetry of the strip stress; the system is applicable to exert the prestress more than 244.84 MPa to the FRP; and the long-term prestress loss ratio is about 15%.