Institute for Transportation

There is considerable interest in using hardwood species in engineered structures. Recently the USDA Forest Products Laboratory (FPL) conducted a series of laboratory and field studies to examine use of mechanical grading procedures
to enhance the use of hardwoods for structural lumber. Our first laboratory efforts revealed that for most domestic hardwood species the relationships between bending strength and the strength in tension and compression parallel to the grain
is similar to those for softwood species. Thus, the procedures used to assign allowable design properties to machine stress rated (MSR) lumber are also applicable to hardwood species. Further research at the FPL and West Virginia University
showed that significantly higher properties could be obtained through mechanical grading of red oak than is currently possible through visual grading. These encouraging results prompted us to conduct a demonstration study of machine stress rating hardwood lumber at the Spencer, W. Va.
division of the Burke-Parsons-Bowlby Corp. Using the transverse vibration technique to measure modulus of elasticity (MOE), 800 2 by 8s were graded as 1650f-1 .4E MSR lumber by the Northeastern Lumber. Manufacturer‰Ûªs Association with
the assistance of the Southern Pine Inspection Bureau. The lumber was used to construct a 40-foot span timber bridge in Jackson County, W. Va.