The use of externally-bonded fiber-reinforced polymer (FRP) sheets has been successfully used in the repair and strengthening of both the shear and flexural capacities of reinforced concrete (RC) beams, slabs and columns since the 1990s. However, the externally-bonded FRP reinforcements still present many disadvantages, such as poor performance in elevated temperature and fire, lack of permeability and strength degradation when exposed to ultraviolet radiation. To remedy such drawbacks, the fiber-/fabric-reinforced cementitious matrix (FRCM) has been recently introduced. The FRCM system consists of a fiber mesh or grid embedded in a cementitious bonding material. The present research investigates the flexural strengthening of reinforced concrete (RC) beams with FRCM. The experimental testing included eight large-scale concrete beams, 150 mm × 250 mm × 2400 mm, internally reinforced with steel bars and strengthened in flexure with FRCM. The investigated parameters were the internal steel reinforcement ratio and the FRCM systems. Two steel reinforcement ratios of 0.18 and 0.36 of the balanced reinforcement ratio, as well as three FRCM systems using glass, carbon and PBO fibers were investigated. Test results are presented in terms of load-deflection, load-strain and load-crack width relationships. The test results indicated that the PBO FRCM significantly increased the ultimate capacity of the strengthened RC beams with both low and moderate internal reinforcement ratios compared to the glass and carbon FRCM.

Precast, prestressed hollow-core (PHC) slabs are widely used in floor and roof decks because of their economic benefits. Because no shear reinforcement can be provided because of fabrication restraints, designers have to opt for deeper profile or filling PHC slab cores with concrete when the load demand exceeds the limited concrete shear capacity of PHC slabs. This research project is exploring an innovative technique for strengthening the web-shear capacity of PHC slabs by bonding external fiber-reinforced polymer (FRP) sheets along the internal perimeter of the slab voids. Experimental testing and numerical simulation on full-scale single web, I-shaped beam specimens cut out longitudinally from full-width hollow-core slabs have been performed during the first phase of this research to investigate the feasibility and effectiveness of this new technique. The influence of several design parameters, including the length and the width of the strengthened zone, the thickness of applied FRP sheets, and the prestressing level of PHC, have been investigated. Results show that once the minimum required strengthened zone length and FRP sheet thickness are satisfied, the proposed novel shear strengthening technique would provide a considerable enhancement on the shear capacity and ductility to the strengthened specimens.

Strengthening of both aging and modern infrastructure has become necessary as a result of increased load demand and/or to restore the capacity of a member. For example, flat slabs (commonly utilized in parking garages) are subjected to an aggressive environment and increased traffic loads and additionally require strengthening and/or repair. Fiber-reinforced polymer (FRP) sheets and laminates externally bonded to concrete slabs around the slab-column joint are widely used to enhance the strength of flat slabs. Slab-column connections are most often subjected to eccentric loading; however, most reported studies have focused on retrofitted slab-column connections subjected to concentric loads. This paper aims to fill this knowledge gap and experimentally investigate the effect of eccentric loading on the behavior of slab-column connections retrofitted by externally bonded carbon fiber-reinforced polymer (CFRP) sheets. Six full-scale (2,000×1,000×150-mm) interior slab-column connections subjected to ...

In accelerated bridge construction, precast concrete girders are connected to cast-in-place concrete slab using shear transfer reinforcement across the interface plane to ensure the composite action. The steel transverse reinforcement is prone to severe corrosion due to the extensive use of de-icing salts and severe environmental conditions. As glass fiber-reinforced polymer (GFRP) reinforcement has shown to be an effective alternative to conventional steel rebars as flexural and shear reinforcement, the present research work is exploring the performance of GFRP reinforcements as shear transfer reinforcement between precast and cast-in-place concretes. Experimental testing was carried out on forty large-scale push-off specimens. Each specimen consists of two L-shaped concrete blocks cast at different times, cold joints, where GFRP reinforcement was used as shear friction reinforcement across the interface with no special treatment applied to the concrete surface at the interface. The investigated parameters included the GFRP reinforcement shape (stirrups and headed bars), reinforcement ratio, axial stiffness, and the concrete compressive strength. The relative slip, reinforcement strain, ultimate strength, and failure modes were reported. The test results showed the effectiveness and competitive shear transfer performance of GFRP compared to steel rebars. A shear friction model for predicting the shear capacity of as-cast, cold concrete joints reinforced by GFRP reinforcement is introduced.