Fatigue crack propagation behaviour of RC beams strengthened with prestressed CFRP under cyclic bending loads

Abstract

Numerical and experimental methods were applied to investigate the fatigue crack propagation behaviour of the reinforced concrete (RC) beams strengthened with prestressed carbon fibre laminate (CFL). On the one hand, a theoretical analysis method was presented to calculate the stress intensity factor K of the main crack on RC beam strengthened with prestressed CFL. On the other hand, fatigue crack propagation tests were carried out to obtain the crack propagation rate on RC beams strengthened with CFL, which had different prestressing levels (0%, 15%, and 22%). For accurate description of the fatigue crack propagation and fatigue life prediction, the digital image correlation method was used to capture the fatigue crack pattern. Based on the numerical and experimental method, a modified version of Paris' law was proposed. Compared with RC beams strengthened with nonprestressed CFL, the main crack propagation rates on RC beams strengthened with prestressed CFL having prestressing levels of 15% and 22% were decreased by 28% and 33%, respectively. The effectiveness of the proposed modified version of Paris' law was verified.

Interfacial properties of CFRP sheets and concrete subjected to variable amplitude fatigue loading

“…[18][19][20][21][22] It is found that interfacial fatigue life can be expressed by some other parameters such as the stress intensity factor for the interfacial fatigue cracks, interfacial shear stress and residual strains at the edge of concrete compression zone. [23][24][25] Moreover, the stress level of the reinforcing steel is critical in predicting fatigue life of FRP strengthened RC beams. 26 The first loading cycle dissipates more energy than any other cycle through cracking.…”

“…In the research of constant amplitude fatigue loading, the types of fiber and concrete, the form of FRP, the method of bonding, the scheme of loading, the size effect and the service environment have a great influence on the fatigue life 18–22 . It is found that interfacial fatigue life can be expressed by some other parameters such as the stress intensity factor for the interfacial fatigue cracks, interfacial shear stress and residual strains at the edge of concrete compression zone 23–25 . Moreover, the stress level of the reinforcing steel is critical in predicting fatigue life of FRP strengthened RC beams 26 .…”