Behavior and failure modes of reinforced concrete beams strengthened with NSM GFRP or aluminum alloy bars

摘要

Although the use of near-surface mounted (NSM) fiber reinforced polymer (FRP) reinforcement satisfactorily enhances the flexural capacity of deficient reinforced concrete beams, the concrete beams strengthened with NSM FRPs typically exhibit brittle behavior. Aluminum alloy (AA) bars possess non-corrosive characteristics like FRPs but also exhibit a nonlinear tensile response with a clear yield point. This paper investigates the failure modes of reinforced concrete beams strengthened with either NSM glass FRP (GFRP) bars or AA bars. A total of six concrete beams including one control beam were tested under four-point bending. The effects of NSM reinforcement type, internal steel reinforcement ratio, and NSM reinforcement ratio on the failure behavior of the strengthened beams were examined. The ultimate flexural load capacity, ductility index, energy absorption capacity, strains in steel reinforcement and in concrete, and cracking behavior for each tested beam were determined and analyzed. The results indicated that for the same NSM reinforcement ratio, the NSM GFRP bars provided considerably higher increases in the flexural strength of reinforced concrete beams compared to the AA bars. However, the beams strengthened with AA bars showed more ductile response compared to the beams strengthened with NSM GFRP bars.