CFRP-Strengthened HSS Columns Subject to Eccentric Loading

Abstract

Carbon fiber–reinforced polymer (CFRP) laminates are widely used in strengthening reinforced concrete slabs, beams, and columns. However, the application of this advanced composite material to strengthen steel structures is still evolving, and more research is needed to facilitate deployment. This paper presents the results of an experimental program aimed at investigating the behavior of steel columns subject to eccentric loading and strengthened using bonded high-modulus CFRP laminates. Thirty hollow steel section (HSS) column specimens (48×48×2 mm) were eccentrically loaded to failure using load eccentricity values of 25, 5, and 1 mm. The efficiency of bonding the CFRP laminates to the HSS column in enhancing the column’s capacity was evaluated for different column slenderness ratios (kL/r) ranging between 68 and 131. Depending on the slenderness ratio and the load eccentricity, it was found that the increase in axial load capacity of the CFRP-strengthened columns ranged between 4 and 17%, and the increase in the ultimate moment ranged between 34 and 135%; the maximum increase in a column’s capacity corresponded to the medium column slenderness ratio. Two successive failure modes for the strengthened HSS columns were encountered: CFRP laminates debonding and flexural buckling of the column. Flexural buckling was the dominant mode of failure for all the unstrengthened columns (control specimens). On the other hand, debonding of CFRP laminates was observed either before or after flexural buckling for the strengthened columns depending on the load eccentricity value and the slenderness ratio.