Carbon-fibre strengthening of deficient hollow steel sections under combined loading

Strengthening of steel structures using carbon-fibre-reinforced polymer (CFRP) is a useful technique that has been considered by many researchers in recent years. However, most previous research studies have concerned the behaviour of structural steel members without deficiencies such as cracks and holes. The work described in this paper explored the effect of CFRP strengthening on the structural behaviour of square hollow section steel members having an initial deficiency under combined axial and lateral load. To study the effects of the strengthening, 17 specimens were tested under four loading scenarios, with 12 specimens strengthened using CFRP sheets. The deficiency was created by cutting vertical or horizontal slots in one flange. Three-dimensional modelling and non-linear static analyses were used to analyse the steel members. The results showed that the strengthening significantly improved the ultimate capacity of the deficient steel members and the effect of a transverse deficiency on the ultimate capacity of the steel members was greater than the effect of a longitudinal deficiency.