The following blog is from the book Forest Products Laboratory 1910-2010, Celebrating A Century of Accomplishments.
This major study, preformed in the 1980s, is referred to as the “in-grade testing of structural lumber program,” and is one of the largest cooperative research programs ever undertaken by the North American wood engineering community.
It included universities, the Southern Pine Inspection Bureau, the West Coast Lumber Inspection Bureau, the Western Wood Products Association, a number of companies, and the Forest Products Laboratory (FPL).
Physical and mechanical properties information was obtained on 33 species or species groups of visually graded structural lumber. Over an eight-year period, nearly 70,000 pieces of lumber — approximately 1,000,000 board feet — were tested to destruction in bending, tension, or compression.
The information provided the basis for more accurately estimating mechanical properties of lumber and revising allowable design properties.
Thanks to FPLs statistical design for selecting the wood samples, testing them, and analyzing the outcomes, the results from the study were useful and applicable to structural lumber in general. The data garnered from this research is now part of the National Design Standard, and is still used today.