Enhancing buckling capacity of slender s-section steel columns around strong axis using bonded carbon fibre plates

Abstract

This paper investigates a strengthening technique of slender S-section steel columns against global buckling about their strong axes. Carbon fibre-reinforced polymer plates of various Young’s moduli, ranging from 168 to 430 GPa, were adhesively bonded to the steel flanges. The number of carbon fibre-reinforced polymer layers was varied to produce reinforcement ratios of 11–34%. The study comprised eight 2.6 m long pin-ended columns with a slenderness ratio of 83, including five strengthened with carbon fibre-reinforced polymer. The out-of-straightness imperfection of the columns ranged from length (L)/29,000 to L/1600. It was shown that the increase in strength ranged from 15% for the smallest out-of-straightness to 25% for the largest. Increasing reinforcement ratio of the 168 GPa modulus carbon fibre-reinforced polymer from 11 to 34% increased strength from 5 to 15%. Although a higher modulus carbon fibre-reinforced polymer would generally be favoured for achieving higher gains in buckling strength according to Euler’s buckling theory, this study showed that failure strain of such carbon fibre-reinforced polymer could be a critical limiting factor. It is important that global buckling, and hence the peak load, is achieved before carbon fibre-reinforced polymer crushing.