Performance of CFRP Confined Circularized Square Solid RC Columns under Bi-axial Bending (Theoretical Investigation)

This paper investigates theoretically the performance of square solid reinforced concrete (RC) columns circularized with concrete segments and strengthened with Carbon Fiber Reinforced Polymer (CFRP) under bi-axial load eccentricities. The layer-by-layer method is presented to calculate the axial load and bi-axial bending moment. The theoretical results were first verified with experimental results of uni-axially loaded circularized and CFRP confined square solid RC columns. Also, they were verified with experimental results of bi-axially loaded square solid RC columns that exist in the literature. It was proved that the adopted theoretical models and layer-by-layer method were in good agreement with the experimental results. After validating the reliability of the theoretical model, this study theoretically examined the performance of CFRP confined circularized square solid RC columns under bi-axial load eccentricities subjected to the effect of the number of layers of CFRP and the effect of unconfined concrete strength. It was found that circularization increased the performance of CFRP confined square solid RC columns under bi-axial eccentricity for the axial load and bi-axial moments. However, the performance was less than that of the corresponding columns subjected to uni-axial load eccentricity. Also, the performance of CFRP confinement increased with the number of CFRP layers and the unconfined concrete strength. Furthermore, the CFRP confinement performance was less significant with higher bi-axial eccentricity.