循环载荷下碳纤维薄板增强RC梁的疲劳性能试验研究

以碳纤维薄板(CFL)增强RC梁为研究对象,通过对循环载荷作用下增强梁的三点弯曲疲劳试验研究,得到了增强梁的线性对数疲劳寿命曲线和跨中挠度的演化规律,外推得到了极限疲劳强度和抗弯刚度的演化规律,揭示了增强梁的疲劳破坏机理。循环载荷下CFL增强RC梁的破坏模式包括混凝土开裂、碳纤维薄板与混凝土界面剥离、主筋屈服等模式,疲劳破坏过程具有明显的损伤成核、稳定扩展、失稳扩展三阶段发展规律。与普通RC梁相比较,CFL增强RC梁的裂缝分布较均匀、密集,粘贴CFL对增强梁的初始抗弯刚度提高幅度较小,对疲劳损伤阶段的抗弯刚度则提高了约一倍。根据CFL增强RC梁的疲劳寿命曲线得到其极限疲劳强度为25.42 kN,为三点弯曲静载下极限承载力的58.5%。

Experimental Study on Fatigue Behavior of RC Beam Strengthened with Carbon Fiber Laminate under Cycle Loading

Three point bending experiments of carbon fiber laminate(CFL) strengthened RC beams under cycle loading were performed.The linear logarithmic fatigue life curve was obtained and the histories of midspan flexibility of strengthened beams were recorded and the ultimate fatigue strength and bending rigidity of the beams were deduced further.Then fatigue failure mechanism of CFL strengthened RC beams was studied.The failure modes of the beams under cycle loading include concrete cracking,carbon fiber laminate debonding from concrete and steel bars yielding.And their fatigue failure process shows evident three stages of damage nucleation,steady expansion and failure at last.Compared with the normal RC beams under cycle loading,CFL strengthened RC beams scatter more symmetrical and denser cracks.And external bonded CFL increases the original bending rigidity of strengthened beam a little,but doubles its bending rigidity at fatigue damage stage.The ultimate fatigue strength is 25.42 kN obtained from fatigue life curve of CFL strengthened RC beams,which is about 58.5 percent of the ultimate loading under static loading.