Strength enhancement of rectangular reinforced concrete columns using fiber-reinforced polymer

The strength enhancement of concentrically loaded columns bonded with external fiber-reinforced polymer (FRP) systems arises from two sources. First, the confinement effect of transverse fiber sheets leads to an increase in the uniaxial compressive strength of the confined concrete, resulting subsequently in an increase in the contribution of concrete to the load-carrying capacity of the column. Second, the longitudinal fiber sheets contribute directly to the load-carrying capacity of the column. The confinement effect of the externally bonded FRP systems in rectangular columns is known to be less than that in circular or square columns. This study specifically examines the case of rectangular reinforced concrete columns with a section aspect ratio of 3.65, which are typical in construction of monolithic housing apartments. A total of 52 half-scale, short columns were fabricated and tested to failure under a concentric load to investigate the effect of fiber type and configuration and fiber anchors on the strength enhancement of the columns. The effect of the presence of plaster finishes was also examined. A simple analytical approach is proposed for the evaluation of the axial load capacity of the strengthened columns.