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In this paper, the effect of cyclic loading on punching strength of flat slabs strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets is studied. Experimental results of ten slab specimens under monotonic and cyclic loading are analyzed. Eight specimens were strengthened with CFRP sheets on the tensile face of the slabs and the two other specimens were kept un-strengthened as control specimens. The width of CFRP sheets varied in different specimens. After the tests, the punching shear strength of specimens under cyclic loading was compared with those with monotonic loading. The comparison of results shows that cyclic loading decreases the effect of CFRP sheets on punching shear strengthening. This decrease was more for the specimens with a larger value of reinforcing steel ratio. Therefore, it can be concluded that for specimens with large reinforcing steel ratios, cyclic loading may completely eliminate the effect of CFRP sheets on shear strengthening of slabs.

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The use of epoxy-bonded FRPcomposite for structural repair is emerging as an efficient and cost-effective technique for restoring and upgrading the capacity of concrete structures. Considerable researches have been reported in the last decades on the mechanical behavior and failure modes of the FRPstrengthened RC elements but actual data on its durability are scarce. This study intends to examine the durability of concrete specimens strengthened with FRP laminates under accelerated laboratory conditions and mimic harsh environmental situation which is the penetration of chloride ions. In this study three groups of specimens were examined. Each of these groups includes several concrete cylindrical specimens full confined with FRP laminates for investigating different types of fiber (Glass and Carbon), number of fiber layers and temperature influences. Furthermore, an apparatus was fabricated to simulate wetting and drying cycles for the second group of specimens. Moreover group III specimens were placed in a marine environment for 3 years to monitor their performance. Test results show that addition of FRP laminates reduces chloride ions penetration up to 70 percent. Results also indicate that although chloride ions penetration decreased the ultimate strength of cylindrical specimens up to 11 percent but FRP strengthened specimens achieved their initial strengths. Moreover wetting and drying cycles reduced the strength of cylinder specimens up to about ten percent especially in the high temperature laboratory condition.

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The effect of steel plate thickness on the repair effectiveness of RC beam is presented in this paper. A total of four beams were tested, one beam repaired by CFRP with a thickness of 1.2 mm and used as a control beam, and three beams repaired by a steel plate. Steel plates with a thickness of 2 mm, 3 mm, and 4 mm were used in repairing the beams. The maximum load-carrying capacity, deflection at mid span and edge of the opening, strain in steel bars, strain in externally bonded plates, crack patterns, and failure modes were observed on each beam. The externally bonded CFRP sheet and steel plates were found to be effective in the repairing of RC beams with large rectangular web opening. The results show that increasing steel plate thickness has little effect on the maximum load capacity. The CFRP plate is more effective than steel plate in increasing the load capacity of beams.