Strengthening and strain sensing of rectangular concrete beam using composites and FBG sensors

In this paper, a state-of-art report of an experimental investigation on the mechanical properties of the laboratory size notched-concrete beams strengthened by using fibre woven composites is presented. Fibre- optic Bragg grating (FBG) sensors have been adhered on the concrete surface before laying up the composites to monitor the strain changes at the interface when the concrete beam was subjected to three-point bending load after strengthening. The electrical strain gauges were also used to measure the surface strain of the composites and compare the results from the internal sensors. The results show that the overall flexural strengths of the strengthened specimens are increased compared with its un-strengthened status. Concrete and bonding failures were observed when the thick reinforcement was used. In addition, the results obtained from the sensor reveal that the strain at the interface of bond was higher than that measured on the surface of the composite reinforcement. High strain was measured from the sensor when debond at the interface occurred.