CFRP布与钢板复合加固的钢筋混凝土梁受弯疲劳性能试验研究

Experimental research on flexural fatigue behavior of RC beams strengthened with combination of CFRP and steel plates

通过对6根采用CFRP布与钢板复合加固的钢筋混凝土梁和2根未加固梁进行静载和等幅疲劳试验,研究了粘贴CFRP布和钢板加固对钢筋混凝土梁受弯疲劳性能的影响和作用。试验中对比了加固与未加固试件的破坏形态、跨中挠度、应变发展等情况,分析了在不同的疲劳荷载上、下限作用下复合加固梁的挠度和疲劳寿命等。结果表明：复合加固后试件的疲劳变形有所减小,复合加固梁的跨中挠度、残余挠度和各材料应变均随疲劳循环次数的增加呈现三阶段发展规律,且均随着疲劳循环次数及疲劳荷载幅值的增大而增大;循环荷载引起材料的累积损伤,使复合加固梁在200万次循环荷载后的静载受弯承载力和延性均有下降。与未加固梁相比,复合加固梁显著降低了钢筋的应力和应力幅,破坏始于钢板断裂,此后梁仍可继续承受1~2万次循环荷载才发生钢筋断裂,破坏时表现出双重保护机制且疲劳寿命得到延长。疲劳荷载幅值越低,钢板的应力幅越小,梁的疲劳寿命越长。

The effects of composite strengthening by carbon fiber reinforced polymer（ CFRP） and steel plates on the fatigue behavior of reinforced concrete（ RC） beams were studied. Six beams strengthened with CFRP and steel plates were tested under monotonic and constant amplitude cyclic loading,with two non-strengthened beams tested as reference. The failure modes,mid-span deflection and strain evolution of strengthened and non-strengthened beams were compared,and the fatigue life and deformation of composite strengthened beams under different maximum and minimum applied fatigue loads were also investigated. Results show that fatigue deformation reduces through this composite strengthening technique. As fatigue cycles increase,the mid-span deflection,residual deflection and material strain increase and three-phase behavior is shown,and their values increase with the fatigue load amplitude increasing. After two million cycles,the load-carrying capacity and ductility decrease due to the damage accumulation in materials resulted from the cyclic loading. Compared with non-strengthened beams,composite strengthened beams significantly reduce the stress and stress amplitude in rebar. The failure initiates from the fracture of steel plate,and develops further until the fracture of rebar after 10 to 20 thousand fatigue cycles,indicating a double protection mechanism. The fatigue life of strengthened beams is also extended,increasing when the amplitude of fatigue load and steel plate stress level is decreased.