Buckling strength of slender circular tubular steel braces strengthened by CFRP

Although the application of carbon fibre reinforced polymer (CFRP) on strengthening of concrete structures have been reported widely, there are relatively few applications to steel structures, especially to tubular steel structures. In order to investigate the performance of circular tubular steel braces retrofitted with CFRP, long hot finished circular hollow steel braces (88.9 mm × 4 mm) wrapped with CFRP sheets are tested to study the effects of CFRP on overall buckling behavior. Based on the experimental results, a numerical model has been developed to predict the axial load capacity, lateral and axial displacements accounting for the initial out-of-straightness, material and geometric nonlinearities. It is found that CFRP layers could increase both the strength and stiffness of the brace considerably.