Flexural behavior of cracked reinforced concrete beams with externally bonded CFRP plates

The purpose of this thesis is to perform an experimental study of the flexural behavior of damaged reinforced concrete beams strengthened with externally bonded Carbon Fiber Reinforced Polymer (CFRP) plates. Damage have been simulated by applying different pre-load prior to installation of the strengthening system. The effect of existing cracks and different degree of damage have been evaluated from failure test under a 4-point load arrangement of the strengthened members. Same reinforcement configuration of the externally bonded CFRP plates will be used for eight different test specimens subjected do different degree of preload with corresponding different degree of crack formation in the concrete substrate. The resulting failure capacity have been evaluated and compared to theoretical predictions. Different national guidelines and codes for FRP strengthened concrete structures have been reviewed to compare different design parameters and the corresponding theoretical capacity. The experimental work will give a greater understanding of the failure behavior of concrete beams reinforced with CFRP and the accuracy of current guidelines for CFRP design can be validated with the test results. The results obtained from experimental testing revealed a lower capacity of the strengthened beams compared to the theoretical prediction. Failure mode for all the test specimen were governed by formation of flexural cracks within constant bending zone followed by sudden debonding of the CFRP plates from the concrete substrate. To prevent debonding, strain limits of the FRP are implemented in the design. During test, the developed strain in the CFRP plates were monitored and recorded with strain gauges. The results from the test revealed neither theoretical failure load nor theoretical strain limit were reached. Despite the lower ratio of experimental over theoretical result, a capacity increase between 70-80% were found for the CFRP strengthened beams and the result demonstrated the vast potential of capacity enhancement possible to attain by externally bonded CFRP reinforcement