FRP strengthening of lean duplex stainless steel hollow sections subjected to web crippling

• Lean duplex stainless steel hollow sections were strengthened with FRP.
• 53 web crippling tests under four loading conditions were conducted.
• Different surface treatments, adhesives, FRPs and web slenderness were investigated.
• The web crippling strength was increased up to 76%.

This paper presents the experimental and numerical investigations of lean duplex stainless steel hollow sections subjected to web crippling. The test specimens were strengthened with different fibre-reinforced polymer (FRP). The web crippling tests were conducted under end-two-flange, interior-two-flange, end-one-flange and interior-one-flange loading conditions. A series of web crippling tests was conducted. The investigation was focused on the effects of surface treatment, web slenderness, different adhesives and FRPs for the strengthening of lean duplex stainless steel hollow sections against web crippling. The lean duplex stainless steel type EN 1.4162 was used in the investigation. Two different surface treatments, three different adhesives and six different FRPs were investigated in this study. The tests were performed on five different sizes of square and rectangular hollow sections that covered a wide range of web slenderness ratio from 8.1 to 57.3. Three different failure modes were observed in the tests of the strengthened specimens, namely the adhesion, interlaminar failure of FRP plate and combination of adhesion and interlaminar failure of FRP plate. Finite element models have been developed and verified against the test results of the specimens subjected to two-flange loading conditions.