Fatigue behavior of damaged steel beams repaired with CFRP strips

This paper presents the flexural behavior of damaged steel beams repaired with carbon fiber reinforced polymer (CFRP) strips. The damage is intentionally created by notching the tension flange of the beams. Six beams are tested to evaluate the static and fatigue performance of the repaired beams with emphasis on local plasticity and the CFRP–steel interface. A three-dimensional finite element analysis (FEA) is conducted to predict the experimental behavior. A modeling approach is proposed to simulate the fatigue response of the repaired beams, based on the strain-life method and cumulative damage theory. CFRP-repair results in a recovery of static load-carrying capacity of the damaged beam to that of an undamaged beam. The stress range at the damage influences the fatigue life, damage propagation, and plastic strain development of the repaired beams. Fatigue-crack propagation across the web of the beams is not significant up to 50% of their fatigue life, whereas brittle web fracture follows beyond the threshold. A bilinear fatigue response is observed at the CFRP-steel interface, whose magnitudes are dependent upon the number of fatigue cycles and the applied stress range. An empirical model is proposed to predict the fatigue behavior of the interface.