My paper at the SAHC conference concerns a broader and vaguer topic than Marieta’s. Thorough analysis of an old building can give reasonably precise guidance about load capacity, but what do we do for a fast answer? In other words, engineering analysis and design is often iterative and how do we get a rough idea of the capacity of, say, a steel column from 1910? Here’s the 1901 New York City Building Code on steel column design [as always, click to enlarge]:
Those values show a straight-line formula, where the allowable stress is reduced linearly from the allowable compressive stress in a flat piece of steel. (Longer columns have lower allowable stresses because of the possibility of sideways buckling under load.) My paper compares the allowable stresses in steel columns from 1900 until the present, in an effort to develop some simple rules to allow comparison of steel columns designed under old codes to the capacity that current codes give us now.