Concept of Buckling Restraint of Steel Braces with Fiber Reinforced Polymers: Fid-Bau Portal

Concept of Buckling Restraint of Steel Braces with Fiber Reinforced Polymers

Dusicka, Peter / Wiley, Ben

Buckling restrained braces were recently developed for seismic design as stiff and ductile structural members. These braces have the advantage of exhibiting symmetric ductile hysteretic behavior in tension and compression making them well suited for resisting reversed or cyclic loading. The compression strength of these members is governed by material yielding rather than global buckling, which is typically achieved by restraining the steel core by encasing in a steel tube filled with mortar. The buckling restrained brace technology has been rapidly adopted, especially in performance based building designs, and is now also part of the AISC Seismic Design Provisions as one of the ductile lateral load resisting systems. This paper outlines the buckling restrained brace concept with the use of fiber reinforced composites and presents results from a pilot cyclic test on a mild steel angle wrapped with glass fiber composite. Eliminating the steel tube and mortar and using fiber reinforced composites significantly reduced the brace weight improving handling during installation. This method can also be used for retrofit of in-place steel braces. In a pilot test, the wrap shifted the mode of failure from global buckling to hinging near the connection, illustrating the potential for this innovative concept while also highlighting the importance of the brace transition and connection details.