The AISC Seismic Provisions include acceptance criteria and extrapolation ranges for buckling-restrained brace (BRB) tests. It is common practice to test short braces, which can be tested conveniently, and extrapolate design parameters for longer braces which are more difficult to test. This paper compares results from long (40') and short (20') braces with the same core size (7.5 in.2) and casing type (HSS12×12). Compression overstrength factors were about 30% higher for the longer braces at 2% strain, as compared to the shorter brace. It is recommended that an adjustment factor, based on the ratio of core lengths, be used to estimate appropriate compression overstrength factors, when the braces being designed are longer than those used for qualification.
展开▼
