The use of Fiber-reinforced polymer (FRP) composite materials in new construction and repair of concrete structures has been growing rapidly in recent years. FRP provides options and benefits not available using traditional materials. The promise of FRP materials lies in their high-strength, lightweight, noncorrosive, nonconducting, and nonmagnetic properties. ACI Committee 440 has published several guides providing recommendations for the use of FRP materials based on available test data, technical reports, and field applications. The aim of these document is to help practitioners implement FRP technology while providing testimony that design and construction with FRP materials systems is rapidly moving from emerging to mainstream technology.

Precast, prestressed hollow core (PHC) slabs are among the most common concrete deck system in the world. However, due to the manufacturing constraints and the difficulty in providing internal shear reinforcement, the shear capacity of PHC slabs sometimes dictates the design and reduces the efficiency and economics of PHC slabs. The objective of this research project is to develop an innovative application of externally bonded Fiber-Reinforced Polymers (FRP) sheets by installing the sheets along the internal perimeter of the slab voids to strengthen the webshear capacity of PHC slabs. To explore the feasibility and to optimize the new technique, experimental testing was carried out on eight full-scale single web, I shape, specimens (each of 4575 mm “180 in” long, 300 mm “12 in” thick and a 284 mm “11.2 in” wide) that were cut longitudinally out of the PHC slab. Carbon FRP sheets were bonded along the full perimeter on each side of the web specimens. The test specimens were loaded monotonically until failure under single concentrated load at a shear span/depth ratio of 2.5. The investigated parameters were the width of the FRP strengthened zone (300 “12 in.”, 450 “18 in.”, and 600 mm “24 in.”) and the number of strengthening layers (2 and 4 layers). The test results showed the efficiency of the proposed technique to enhance the shear strength of PHC slabs.

Strength and fatigue testing were conducted on concrete specimens strengthened with three different epoxy systems. These specimens were conditioned in elevated water baths, subjected to fatigue loading, then tested for strength. For all three systems, the bond strength of a single conditioned specimen was at least 90 percent of the bond strength of three samples that had been fatigued but not conditioned in elevated water baths. Because of the limited data the results are anecdotal and only preliminary findings can be drawn from this work.

Experimental and analytical investigation into the performance of a special bond system was conducted on small-scale mixed-mode bending (MMB) specimens for implementation in a full-scale hybrid bridge deck system. Full-depth threaded Glass Fiber Reinforced Polymer (GFRP) rods, as a proposed replacement for commonly used GFRP shear studs, in conjunction with an epoxy bonded coarse silica sand aggregate layer, were used at the bond interface between a pultruded GFRP plate and cast-in-place Ultra-High Performance Concrete (UHPC). Findings show that the presence of the threaded GFRP rods increased the strength of the system up to 250% while utilizing 25% of the rod capacity. The full potential of full-depth threaded GFRP rods for bond and crack control can be explored in greater detail in future studies, including the application of nut tightening forces to increase initial clamping forces at the bond interface.

Flexural strengthening of Reinforced Concrete (RC) beams using fiber reinforced polymer (FRP) has become a common practice in the construction industry. Such strengthening is typically performed by attaching FRP laminates to the tension side of RC beams. In many occasions reaching the tension side of the beam can be a major challenge due to existing ducts as in buildings or the need of large scaffolds underneath the beam as in bridges. This challenge makes FRP strengthening an expensive alternative. In this paper, we suggest an alternative flexural strengthening method using a composite system made of Ultra High-Performance Concrete (UHPC) and Carbon Fiber Reinforced Polymer (CFRP) laminates for RC beams without reaching the tension side of the beam. In this technique, the accessible cover of the RC T-beam is removed, the CFRP laminates are attached to top side of the beam then a thin UHPC overlay is cast over the FRP. We show that the combination of UHPC and FRP allows the FRP to act as additional tensile reinforcement and increase the flexural capacity of the RC T-beams. The proposed method might be effective for shallow to medium RC T-beams specifically T-beams with very wide flange.