Hello forum participants,

I understand the reasoning behind the tabulated allowable stress values in the B31.1 and 31.3 Codes; the lesser of (a) one quarter of the ultimate (b) five eights of yield (c) 1% strain in 100,000 hours (or .1% in 10,000 hours or .01% in 1,000 hours) (d) the average of three samples that rupture in 100,000 hours etc … My question is “what is the historic basis for the 1% strain and what is the historic basis for the 100,000 hours”?