This paper presents experimental and theoretical investigations on flexural CFRP strengthening/repairing of pretested (i.e., damaged) beams reinforced using prestress rebars. Six beams were fabricated and tested under a four-point bending system to failure. The internal longitudinal tensile and transverse steel reinforcements of these beams were reinforced using prestress and mild steel rebars, respectively. After the application of load, these pretested (i.e. damaged) beams were repaired and tested using externally bonded Carbon Fibre Reinforced Polymer (CFRP) reinforcement. This study investigated the effects of number of CFRP plies, three different grades of concrete, and wrapping layouts. The results confirm that the CFRP repaired beams reinforced with prestress rebars efficiently increased the flexural capacity, however the trend of ductility was inadequate as in damaged-unstrengthened beams. Experimental results show that the flexural capacity of the repaired beams increased to a maximum enhancement of 172.4% over the damaged-unstrengthened beam. It was experimentally observed that CFRP repaired beams with low grade of concrete could provide better performance as compared to higher grades of concrete. The comparison of experimental and theoretical results had good agreement for higher grades of concrete, whereas, in case of low grade concrete, the experimental results were relatively greater than the theoretical results.

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This study proposes using glass fibre-reinforced polymer (GFRP) as stay-in-place structural formwork for casting bridge decks with ultra-high performance concrete (UHPC). The GFRP stay-in-place formworks completely replace the bottom layer of rebars, and the top steel reinforcement is also replaced by a GFRP mesh to mitigate the corrosion damage. The formworks were either a flat GFRP plate with square hollow section (SHS) stiffeners or a flat GFRP plate with new Y-shape stiffeners.Concentric static tests on five 1:2.75 scale decks were performed to investigate the effect of stiffener's configuration and the influence of the concrete strength on the performance of bridge decks. Rotational fixity support was used to simulate a real bridge deck connection of supporting girders. All specimens with stay-in-place formwork exhibited punching shear failure. It was found that the use of Y-shape stiffeners significantly improved the load-carrying capacity of the proposed deck. Replacing normal concrete with UHPC further improved the loading capacity of the deck. The decks demonstrated excellent performance, with the load-carrying capacity 3.8 to 9.5 times higher than the established equivalent service load depending on the concrete strength and configuration of the GFRP stay-in-place formwork. Deflection at service load was less than span/1,600 for all the decks. Compared with normal strength concrete (34 MPa), UHPC improved the maximum load-carrying capacity of the deck from 91.4 kN to 149 kN.

This paper aims to investigate the effect of bond strength of corroded steel rebar embedded in concrete cylinders enveloped externally using hybrid and non-hybrid fiber reinforced polymer (FRP) reinforcement. A series of 16 concrete cylinders (i.e. 100 mm  200 mm) embedded with steel rebar were prepared in the laboratory condition. The test variables were types of fiber reinforced polymer wrapping (i.e. hybrid and non-hybrid fiber reinforced polymer reinforcement), duration of corrosion activity, and percentage of mass loss in steel rebar. The specimens were immersed in 5% NaCl solution at a depth of 170 mm and anodic current was impressed through the rebar for accelerating the corrosion activity. After the exposure period of 24 days, the embedded steel rebar in concrete cylinder was pulled out monotonically to failure. The bond strength, percentage of mass loss in embedded steel rebar, and effect of different periods of corrosion activity on concrete cylinders enveloped with hybrid and non-hybrid fiber reinforced polymer reinforcement are addressed. Test results show that the observed bond strength of hybrid fiber reinforced polymer confined specimens was the highest as compared to the non-hybrid CFRP and GFRP confined specimens. Moreover, the bond strength performance of hybrid FRP confined specimens was slightly better than the non-hybrid CFRP confined specimens.