This section is from the book "Safe Building", by Louis De Coppet Berg. Also available from Amazon: Code Check: An Illustrated Guide to Building a Safe House.
To Obtain the Actual Strength of Flange is Tons.
Multiply the safe uniform load (U) by the effective width of flange, that is, the total width of either flange, less the greatest number of rivet holes coming on any line drawn across the top of flange, and at right angles to same (usually two rivet holes).
Never use less than one-quarter inch thick plates.
For Steel Flanges.