Comparative seismic designs of scbf using AISC 341-05 and AISC 341-10

Abstract

Special Concentrically Braced Frames (SCBFs) are among the most common steel structures for resisting earthquake loads in high seismic regions. Concentrically Braced Frames (CBFs) are elastically designed as one vertical truss system to resist lateral loads through axial brace members when they are introduced. The explicit capacity-design approach has been fully incorporated into the newest seismic provisions for structural steel buildings (AISC 341-10, 2010). One new analysis section is added into AISC 341-10 to address the inelastic responses of SCBFs. Two separate structural analyses are required for SCBFs in AISC 341-10. Analysis one assumes that braces have their expected strength without considering cyclic strength degrading. Analysis two explicitly considers the expected post-buckling strength for compression braces. The beams/columns could be significantly increased by these analyses from the elastically designed sections. One additional analysis is such that the compression braces are removed under amplified seismic loads to alleviate the high strength demands for columns in high-rise buildings. These analysis requirements significantly increase design efforts in typical design offices, and a comprehensive study to demonstrate how such an explicit inelastic design procedure would (or would not) significantly improve seismic performance of SCBFs appears to be justified. This paper summarizes the seismic design of two SCBFs with different heights, 4-story and 10-story, at different sites. Two bracing configurations, chevron and X-bracing over two stories, are considered for each braced frames. Step by step design procedures on typical SCBFs are completed under AISC 341-05 and AISC 341-10. The design results of all studied frames were compared to discover the general trends for low- and medium-rise CBFs between the two design provisions. © 2015 Elsevier B.V., All rights reserved.