The technique of strengthening or repairing reinforced concrete (RC) structures with externally bonded steel plates or composite sheets has been successfully applied in civil engineering. The RC structure is often strengthened in flexure. This work studies the effect of the shear strengthening of RC beams on the stress distribution, initial cracks, crack propagation, and ultimate strength. Five types of beams with different strengthening carbon-fiber-reinforced plastic sheets are used. The experimental results show that it is not necessary to strengthen the entire concrete beam surface. The general and regional behaviors of concrete beams with bonded carbon-fiber-reinforced plastic sheets are studied with the help of strain gauges. The appearance of the first cracks and the crack propagation in the structure up to the failure is monitored and discussed for five different strengthened beams. In particular, for one of the strengthened RC beams, the failure mode and the failure mechanism are fully analyzed.
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