Biaxially loaded RC slender columns strengthened by CFRP composite fabrics

The present study involves experimental and analytical investigations on carbon fiber reinforced polymer (CFRP) confined reinforced concrete (RC) slender columns subjected to combined axial load and biaxial bending. A total of five RC slender column specimens wrapped in layers with CFRP jackets were experimentally tested to failure. To assess the combination of wrapping techniques, the effect of CFRP sheet orientation in longitudinal and transverse directions of the column was studied. For all representative specimens, the average loading capacity gain was achieved with CFRP layers applied on four sides. The specimen lateral deflection was reduced when CFRP sheets were oriented in the longitudinal direction. The analytical study was taken one step further by using a modified computer program accounting for the stress-strain equation for CFRP-confined concrete to verify the behavior of tested columns. There is a good agreement between the analytical prediction and the experimental results for both ascending and descending branches of the load versus deflections and the moment versus curvature curves.