ABSTRACT
This paper describes an analytical study performed to evaluate the influence of the brace slenderness ratio on the seismic performance of concentrically braced steel frames. Nonlinear time history dynamic analyses have been performed on typical building structures. The brace slenderness, λ, for the braces was varied from 0.35 to 2.65 for tension-compression brace design and from 0.85 to infinite for tension-only brace design. The building height was varied from 1 to 8 storeys. The results of the analyses indicate that the inelastic demand in the tension-compression bracing systems decreases as the brace slenderness is increased. For tension-only bracing, the inelastic demand generally increases when increasing the brace slenderness. For both bracing systems, it was also found that higher inelastic demand was generally associated with a concentration of inelastic damage over the height of the structures. The results suggest that a brace slenderness limit of λ = 2.65 is appropriate for tension-compression bracing systems. Tension-only design should be allowed, provided that the brace slenderness is kept below the same limit. For both systems, building height limitations are proposed to prevent the formation of a soft-storey mechanism.
