Strengthening of rectangular wall-type RC columns with CFRP composites and steel plates under axial compression

Confinement using fibre-reinforced polymers (FRPs) is an effective solution for strengthening reinforced concrete (RC) columns. However, the confinement of FRP is less effective for rectangular wall-type columns (WTCs) having aspect ratios greater than two, and only limited information exists on their behaviour. The effectiveness of different strengthening configurations for WTCs with higher aspect ratios was therefore evaluated. Eleven RC WTCs measuring 150 mm × 450 mm in cross-section and 1500 mm in length were cast and strengthened using ten different configurations. The different strengthening configurations included externally bonded (EB) FRP, fabric-reinforced cementitious matrix (FRCM) systems, near-surface mounted (NSM) FRP systems and steel plates. EB FRP or FRCM with NSM FRP or steel plates were considered as hybrid combinations. The influence of these strengthening configurations on the axial capacity and ductility of the column was experimentally evaluated and compared with analytical calculations. The test results showed that hybrid strengthening can provide 30% strength enhancement and a significant enhancement in deformation capacity compared with unstrengthened RC WTCs. Analytical calculations of peak strengths using simple constitutive models agreed well with the experimental results.