Cyclic Testing of Tubular Steel Braces with CFRP Reinforced Net Sections

Tubular steel braces with carbon fiber reinforced polymer (CFRP) reinforced net sections are proposed and experimentally investigated. Quasi-static reversed cyclic testing protocol is applied to compare the inelastic performances of these braces with and without net section reinforcement. Special emphasis is placed on hysteretic energy dissipation. Three near fullscale specimens were designed and tested to fracture. Experimental results show that the use of CFRP members (both laminates and sheets) to improve the hysteretic behavior of tubular braces is promising as a retrofit technique in steel framed buildings lacking ductile brace to gusset connections. Repaired braces, when compared to the reference brace, reached larger story shear strength (or larger axial tension and compression capacities) up to 15%. This resulted in larger (4.3% more) cumulative dissipated energy at a prescribed drift ratio, and 82.5% more at fracture. Note that no significant change (max. 10%) in the brace stiffness was observed, which could be desirable in seismic retrofit applications.