# The Influence of Restraints on the Stability of Beams

*The development of satisfactory design rules for beams of slender proportions, which are prone to lateral instability, has taken place gradually since the introduction of the first rolled sections, over a century ago. Until the presentation of rational data in the recently revised B.S. Code of Practice for the "Structural Use of Steel in Buildings", design formulae have been of an empirical nature. These were based on the
conception that lateral buckling was entirely due to collapse of the compression flange of a beam, as a strut under variable end load. In consequence the formdlae
gave estimates of load carrying capacity which were often considerably in error, as a result of neglecting the torsional stiffness of the member.' The new design rules
are based on the mathematical theory of stability and will give reasonable estimates of the limiting stresses in beams whose slenderness ratios exceed a certain minimum value, in the same way that the Euler formula proves satisfactory in calculating the critical stresses in slender struts.
A.R. Flint*

Author(s): Flint, A R

Keywords: stability;slender beams;cp113;steel