Correspondence on U-Frame Restraint Against Instability of Steel Beams in Bridges by Mr. E. Jeffers
Mr J. A. Baird (F) (Swedish Finnish Timber Council)
Some years ago when I was involved with the design of lattice tubular steel portals with the Taylor Woodrow Group, I evolved a method of considering the U-frame effect of two portals connected by steel purlins at regular intervals. The effect was small but usually enough to limit the number of knee braces required to the bottom chord when in compression.