RC Beams and Slabs Externally Reinforced with Fiber Reinforced Plastic (FRP) Panels

摘要

Considerable experimental and analytical studies concerning the external reinforcement of RC beams and slabs using fiber reinforced plastic (FRP) strips and panels have been accomplished in the past ten to twelve years. This paper will review the pertinent work in this area and in particular will review and present both experimental and analytical studies conducted by the United States Air Force at Wright Laboratory's Pavements and Facilities Section (WL/FIVCO), Tyndall Air Force Base, Florida. Both experimental and analytical studies at WL/FIVCO have shown that RC beams and slabs retrofitted with carbon fiber reinforced plastic (CFRP) and Aramid fiber reinforced plastic (AFRP) show considerable flexural strength increases when compared to control beams without the FRP panels. These studies have been conducted on structural response to static loads, drop weight dynamic loads and blast loadings from conventional explosives. In all cases considerable strength enhancement has been observed. For beams retrofitted with bottom tensile CFRP strips the largest strength enhancement occurred for RC beams with steel reinforcing ratios of 1.5 percent or less. This corresponds to a ratio of steel area (tension only) to CFRP area of approximately 4.0 or less. In cooperation with WL/FIVCO, the University of Florida developed a vacuum bond technique to apply prefabricated FRP panels to concrete surfaces using a commercial high performance epoxy adhesive. In addition to beam and slab structural response, WL/FIVCO has conducted tests of freeze-thaw cycling, ultraviolet exposure, heating, cooling, wetting and drying on concrete samples with and without various FRP strips. No detrimental effects were observed for these tests. Fatigue strength of externally reinforced beams (no steel) was also studied at WL/FIVCO using a non-reversed fatigue loading of 80 and 10 percent of static maximum load applied at a rate of 20 Hz for 2,000, 000 cycles.