A Comparative Study of Alternative Approaches for Stability Design of Steel Frames

Abstract

Approaches for stability design of steel frames include the traditional and the modified effective length methods and the notional load approach. This paper presents a storey-based stability factor approach in which storey slenderness and a stability coefficient for a storey are defined, the stability of a storey is checked as a whole. Also presented are detailed comparison of the modified effective length approach, the notional load approach and the proposed storey-based method with FEM. Seven frames, with different bases or beam-to-column connections, one or two spans, one or two stories, with or without leaning columns, uniformly or unevenly loaded, are analysed. Various imperfections are considered. All frames are assumed to be axially loaded to serve as benchmark problems for checking the priority of available methods. It is found that the notional load approach is ideal for frames that are uniformly loaded, and if the modified effective length factors of columns are within 1∼2. The modified effective length is not accurate enough in considering the inter-column interaction of a storey failing in an elastic-plastic state. The proposed storey-based stability factor approach shows good agreement with FEM for all the frames analysed.

Keywords

frame stability notional load approach storey-based buckling

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