Effect of FRP strengthening on the SHS brace collapse mechanism

During an earthquake, diagonal braces are designed to dissipate energy by yielding in tension and buckling in compression. However, local buckling occurring in the middle of the brace leads to immediate fracture. Aiming to strengthen braces against local buckling, this study proposes wrapping FRP sheets in the transverse direction. The effect of FRP strengthening on the post-buckling behavior of Square Hollow Section (SHS) tubes has not been investigated. A numerical model was generated and verified by other previous researches. Then, a comprehensive parametric study was conducted, and the effects of slenderness ratio, the number of FRP layers, and FRP coverage percentage on post-buckling response of the strengthened brace were explored within this study. Results indicated that utilizing FRP was certainly successful in mitigating local buckling mode of long SHS braces. Moreover, for short braces, applying enough FRP layers can change the mode of buckling from local to overall. Finally, an optimized length of FRP was proposed for brace strengthening in accordance with their slenderness ratio.