Effect of load eccentricity on the capacity of CFRP-strengthened HSS beam-columns

Abstract

“Retrofitting steel structures is gaining a high demand in many cases. Such as the increase in applied load or corrosion and fatigue problems. Retrofitting steel structural elements using adhesively bonded Carbon Fibres Reinforced Polymers (CFRP) has attracted more research attention worldwide. Due to their high elastic modulus carbon fibres are preferred to glass fibres. This thesis presents the results of an experimental study into the behaviour of slender HSS steel columns retrofitted using standard-modulus CFRP plates (E = 205 GPa). Thirty slender HSS column specimens, 48×48×2 mm, were eccentrically loaded until failure using eccentricity values of 25 mm (B/2), 50 mm (B) and 100 mm (2B). The effectiveness of retrofitting using CFRP laminates was evaluated for different slenderness ratios (kL / r), namely, 68, 100 and 131. The maximum gain in capacity of axial l0ad ranged between 40 and 107%, however, the maximum increase in bending moment ranged between 34 and 135%. Two different failure modes took place for the CFRP-strengthened beam-columns. Flexural buckling was the predominant mode of failure for all steel control specimens. Due to the combination of eccentricity and slenderness ratio debonding of CFRP plates was observed for all strengthened specimens either before or after the flexural buckling.