Designs of Special Concentrically Braced Frame 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. One new analysis section is added into AISC 341-10 to address the inelastic responses of SCBFs. Two separate structural analyses and one additional analysis are required for SCBFs in AISC 341-10. 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 three SCBFs with different heights, namely, 4, 10, and 20 stories, at different sites. Two bracing configurations, chevron and X-bracing over two stories, are considered for each braced frame. Step-by-step design procedures on typical SCBFs are completed under AISC 341-05 and AISC 341-10. The design results of studied frames are compared to discover the general trends for low-rise and medium-rise CBFs between the two design provisions.