Axial strength of FRP-confined rectangular RC columns with different cross-sectional aspect ratios

This paper aims to contribute to a better understanding of the axial behaviour of rectangular reinforced concrete (RC) columns with large cross-sectional aspect ratios (section depth to width ratios) confined by carbon-fibre-reinforced polymer (CFRP). Three series of rectangular RC columns with cross-sectional aspect ratios of 2·25, 2·0 and 1·8 were tested under monotonic uniaxial compressive loads until failure. The effects of aspect ratios and CFRP anchors on the confinement effectiveness of CFRP wraps for rectangular RC columns were evaluated. The test results indicate that CFRP wraps enhanced the compressive strength of CFRP-confined rectangular RC columns even with a large aspect ratio of 2·25; however, the strength enhancement levels decreased with an increase in aspect ratio. CFRP anchors were effective in restraining concrete from bulging out and thus improved the confinement effectiveness of the CFRP wraps. Based on the test results regarding medium- and large-scale CFRP-confined rectangular RC columns available in the literature and this study, some existing confinement models for rectangular RC columns were assessed and a new analytical model was developed through regression analysis of the database. The proposed analytical model was found to be in good agreement with the test results in the database.