Design-parameter study on seismic performance of chevron-configured SCBFs with yielding beams

Abstract

Special concentrically braced frames (SCBFs) designed to meet the 2016 American Institute of Steel Construction Seismic Provisions for Structural Steel Buildings require beams in chevron configurations to develop expected brace forces associated with large lateral deformations. The braces are assumed to fully yield in tension and buckle and deteriorate in compression. These brace forces impose axial forces, shear forces, and bending moments in beams that usually require relatively deep and heavy beam cross sections in comparison to gravity framing and beams in other bracing configurations. A research study was undertaken to develop a new design approach that permits the use of smaller beams engaged as secondary yielding mechanisms. The proposed design approach was developed from previous large-scale experiments and nonlinear response-history analyses. However, the variety of brace sizes and frame geometries used in research to-date is limited. Therefore, two studies were conducted using nonlinear analysis to consider practical design parameters that could impact seismic performance. First, a large parametric study was conducted on three-story chevron SCBFs under static cyclic loading. Second, different methods were used to design typical three-story chevron SCBF buildings for a site in Seattle, WA, which were then subjected to response-history analysis using earthquakes representative of the 2%/50-year hazard level. The studies indicate that low-rise buildings designed by the proposed method have equal or improved seismic performance compared to those designed by conventional design methods, and in conjunction with previous research, they help support future use of the proposed method in practice.