American Society of Civil Engineers

Lateral Stability of Beams on Seats

by Mark A. Bradford, (Research Student in Civ. Engrg., Univ. of Sydney, N.S.W., Australia) and Nicholas S. Trahair, M.ASCE, (Prof. of Civ. Engrg., Univ. of Sydney, N.S.W., Australia)

Journal of Structural Engineering, Vol. 109, No. 9, September 1983, pp. 2212-2215, (doi:

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Document type: Technical Note
Abstract: The effect of web distortion on the lateral buckling of I-beams whose top flanges are unrestrained at seat supports is studied by using a finite element method. The theoretical predictions are shown to agree well with available experimental results. The results of the study are used to evaluate present design code approximations, which are found to be unconservative for short length beams, and over-safe for long length beams. An improved approximation is suggested for beams in uniform bending which buckle in a symmetric mode.

ASCE Subject Headings:
I beams