Seismic performance of steel chevron braced frames designed according to Japanese practice

Six steel braced-frame specimens and nine isolated brace specimens were tested to examine the seismic behavior of steel chevron braced frames designed and constructed according to the current Japanese practice. The braced-frame specimens placed a pair of braces in a “chevron” arrangement, in a single-bay, single-story moment-resisting frame. The braces had either a round-HSS or I section. The bracing connections adopted either slip-critical bolted connections as is the norm in Japan or a field-welded connection following U.S. recommendations. The specimens were subjected to a cyclic loading sequence that is similar in severity to the protocol specified for steel moment-resisting frames in the U.S. seismic provisions. The test results suggest that chevron braced frames with compact braces and using moment-resisting beam-to-column connections can safely develop large story drifts exceeding 0.03 rad. The force unbalance between the tension and compression braces led to large beam deflection and, in some cases, torsion, which in turn limited the tensile axial forces in the braces. The lateral resistance at key limit states matched the strength computed based on plastic analysis.