Improving the seismic stability of concentrically braced steel frames

Abstract

This paper presents an analytical study on the seismic stability of multi-storey concentrically braced steel frames. The building height varies from 4 to 16 storeys and three braced frame systems are studied: conventional braced frames, buckling restrained braced frames, and dual buckling restrained braced frames. The structures are designed according to Canadian seismic provisions. Different force modification factors are used and the both the equivalent static load procedure and the modal response spectrum analysis are used. P-delta effects are included in the design of some of the buildings. The performance of the various structures is evaluated and compared by means of incremental dynamic analysis. The results show that the potential for instability for conventional braced frames is higher for taller structures or when the design loads are reduced. Tall buckling restrained braced frames and conventional braced frames offer similar resistance against instability. Dual buckling restrained braced frames exhibit a more robust response and represent a promising solution for tall braced steel frames.