Seismic behavior of concentrically braced frames designed to AISC341 and EC8 provisions

Abstract

Steel concentrically braced frames (CBFs) are frequently used as efficient lateral load resisting systems to resist earthquake and wind loads. This paper focuses on high seismic applications where the brace members in CBFs dissipate energy through repeated cycles of buckling and yielding. Widely-used seismic provisions have somewhat different approaches for the seismic design of CBFs. The present study evaluates in detail the similarities and differences between the design philosophies and provisions used in the United States and Europe for these systems. The requirements of both provisions applied during a full design procedure are summarized and compared. Furthermore, X-braced, split X-Braced, and V-braced archetypes are designed accordingly and the differences in the design outcomes are investigated regarding section sizes and the weight of steel used in each design. Finally, inelastic structural models of the designed archetypes are developed and subjected to a large set of ground motions to study their seismic behaviors. The results of a total of 880 nonlinear time history analyses are then synthesized to investigate the way in which the requirements of these provisions affect the seismic behavior of the designed CBF. Notable differences are observed between the performances of the CBFs designed using American and European provisions. The similarities and differences as well as drawbacks of the provisions are thoroughly discussed. Recommendations and future research needs are suggested to enhance the seismic performance of steel CBFs designed according to these provisions.