Cyclic behavior of RC beams strengthened with carbon fiber sheets bonded by inorganic matrix

The objective of this paper is to study the fatigue performance of concrete beams strengthened with carbon fiber sheets bonded by an inorganic matrix. Large size reinforced concrete (RC) beams were strengthened with three layers of carbon fiber sheets and tested under fatigue loading. The relationship between fatigue strength, crack width, and number of cycles was studied and analyzed. Results showed that both load capacity and number of cycles of the RC beams were significantly increased with carbon fiber sheets. The fatigue strength increased by as much as 55% as compared with that of the control beams. Fatigue failure of the RC beams strengthened with carbon fiber sheets bonded with an inorganic matrix started with steel rupturing followed by fiber rupture. It was observed that the fatigue cracks developed during the first few cycles. With increasing number of cycles, the crack width and crack depth increased during the first half million cycles of loading, and thereafter the crack width and depth tended to stabilize.