RC Columns Strengthened with NSM-CFRP Strips and CFRP Wraps under Axial and Uniaxial Bending: Experimental Investigation and Capacity Models

The efficiency of the use of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) strips confined with CFRP wraps to strengthen reinforced concrete (RC) columns will be experimentally and analytically investigated in this paper. A total of 15 specimens of RC columns strengthened with different numbers of NSM-CFRP strips (0, 4, and 8) and confined with different numbers of CFRP wraps (0, 2, and 4), will be prepared and tested under concentric and eccentric loading with different eccentricity ratios of 0, 0.25, 0.50, and 0.75, respectively. The axial load capacity, lateral deflection (δ), axial deflection, and longitudinal and transverse strains will be measured. The effects of NSM-CFRP strips, the number of CFRP layers, and the eccentricity ratio on the capacity of the specimen will be investigated. The strengthened specimens showed a significant increase in load-carrying capacity and ductility over the control specimens. The increase in the load-carrying capacity of the confined specimens strengthened with strips in axial and uniaxial bending reached 49% and 95%, respectively, over the control specimen. It was concluded that strengthening RC columns with NSM-CFRP strips wrapped with CFRP composite sheets enhanced both the capacity and ductility consistently, for all applied eccentricity ratios. In addition, an analytical model will be developed to predict the strength of NSM-CFRP-strengthened RC columns and will be validated using the obtained experimental results.