Flexural and axial behaviour of CFRP strengthened steel circular hollow section beams and short columns

The use of carbon fibre reinforced polymer (CFRP) sheets for strengthening steel hollow sections is a relatively new technique and provides advantageous of lightweight and strength enhancement. There are presently few applications that concern with composite strengthening of circular tubes with larger diameter-to-thickness ratios, and in the absence of clear theoretical understanding of behaviour to guide engineers, research is much needed to develop analytical and design models for such tubes strengthened by CFRP. This paper summarises a recent investigation at Monash University on the behaviour of circular hollow section (CHS) beams and short columns with varying section slenderness ratios and strengthened by CFRP sheets. Analytical models for determining the ultimate moment capacity and for predicting the moment-curvature response of CFRP-reinforced steel CHS beams are presented. The nonlinear model accounted for material properties of the steel and CFRP, volume fractions of the fibre and adhesive, amount of CFRP, and a wider range of section slenderness. The theoretical models were validated through comparisons with the test results. Design rules for predicting the strength of composite CHS under bending and compression were also proposed.