Cyclic testing of steel-core buckling-restrained braces (BRBs) having simple end details and infilled with high strength grout

Intense research is being done in the field of Buckling-Restrained Brace (BRB) technology to seek more cost effective and reliable solutions. To investigate performance under cyclic loading, two full scale steel-core BRB specimens (labeled as TURKBRACE BRB-SCI and TURKBRACE BRB-SCII) with simple end details have been designed to AISC specification, manufactured, and cyclically tested in the Structural and Earthquake Engineering Laboratory (STEEL) of the Technical University of Istanbul. A diagonal configuration for the braces in an L-shaped testing setup was used. These specimens use single, large diameter bolted (pinned) end connections and rectangular shaped steel core plates as the core materials of S235JR and S355JR. The core is surrounded by a thin steel tube infilled with a high strength (64MPa) grout material as the buckling restraining system. A teflon based unbonded surface system was used on the core member's surface. Experimental results show that maximum drifts of 3.17% and 3.55% were obtained for BRB-SCI and BRB-SCII, respectively. Note that no fractures in the welds or any signs of local or global instability were observed during testing. Experimental hysteretic curves, behavioral values such as maximum strength in tension and compression cycles, hysteretic damping (ξ max = 40%), and cumulative hysteretic energy dissipation values are given. These observations reveal that BRB-SCI performed slightly better than BRB-SCII since this brace used a longer core length, resulting in larger dissipated energy, and better hysteretic response. A maximum displacement ductility of μ=10 was obtained for both BRBs.