Limitations of FRP Jacketing in Confining Old-Type Reinforced Concrete Members in Axial Compression

The efficacy of fiber-reinforced polymer (FRP) confinement as a means of repairing/strengthening reinforced concrete members with nonductile details is explored in this paper with particular emphasis on the interaction between jacket and the embedded longitudinal compression reinforcement at the onset of bar buckling. To this end, a total of 27 short prismatic specimens were tested to failure under concentric compression subsequent to application of FRP jackets; four additional specimens were tested as controls. Specimens had a square cross section and most were detailed according to former practices with the exception of few specimens that contained the minimum transverse reinforcement as specified by modern provisions. Parameters of the experimental study were the extent of initial damage prior to jacketing, the jacket material, and the number of layers. Response variables included ductility at failure, deformation capacity, strength increase, and mode of failure of the repaired/strengthened member. Confinement effectiveness was quantified using the degree of lateral dilation as the primary performance index. Deformation capacity as limited by embedded longitudinal bar buckling and jacket rupture/debonding strains was evaluated from the experimental results and analytical considerations.