常幅循环荷载下CFL增强RC梁弯曲疲劳性能研究

通过碳纤维薄板（CFL）加固RC梁三点弯曲疲劳实验，得到了常幅疲劳荷载作用下加固梁挠度、CFL与钢筋应变的演化规律；试验过程中加固梁刚度的疲劳损伤、CFL与混凝土界面的疲劳剥离都呈现初始快速扩展、稳定扩展、失稳扩展的三阶段发展规律。通过对CFL加固梁的疲劳破坏机理的分析，指出钢筋的疲劳屈服导致CFL的剥离是加固梁最主要的破坏模式，其疲劳寿命主要取决于控制截面受拉钢筋的应力幅值，提出采用疲劳损伤第二阶段的钢筋应力幅值的△S-N曲线与国外试验结果吻合较好。

FATIGUE BEHAVIOR OF RC BEAMS STRENGTHENED WITH CFL UNDER CONSTANT AMPLITUDE LOAD

Three-point bending experiments of RC beams strengthened with carbon fiber laminate （CFL） under constant amplitude loads were performed, the evolution of mid-span flexibility of strengthened beams and strain of CFL and tensile reinforcing steel on control section were recorded. The degradation of flexural stiffness shows three stages of primary quick damage, steady linear fatigue damage and unstable damage to failure at last, CFL-concrete interracial debonding follows the same trend. By the analyses of fatigue failure mechanism, the most commonly fatigue failure mode of strengthened beams is the rupture of tensile reinforcing steel followed by FRP failure, the fatigue life is controlled by the stress amplitude of tensile reinforcing steel, the △S- N curve of tensile reinforcing steel exhibits good agreement with test datum.