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Abstract
Round timbers, ties, and lumber sawn from a log, regardless of species and size, are quite variable in mechanical properties. Pieces may differ in strength by several hundred percent. For simplicity and economy in use, pieces of wood of similar mechanical properties are placed in categories called stress grades, which are characterized by (a) one or more sorting criteria, (b) a set of properties for engineering design, and (c) a unique grade name. The most familiar system is that for lumber. Sorting criteria have also been established for round timbers and ties. This chapter briefly discusses the stress grades and design properties for lumber, round timber, and ties.
Keywords
Wood grading,
lumber grading,
grading,
mechanical properties,
lumber,
timber,
timber grading,
railroad ties,
standards,
bending,
elasticity,
modulus of elasticity,
wood quality,
flexure,
stress grading,
nondestructive testing,
engineering design,
wood defects,
structural timbers,
roundwood,
round timbers,
wood strength,
logs,
bending strength,
LRFD,
load factor design,
allowable stress design,
ASD,
design properties
Citation
Kretschmann, David E. 2010. Stress grades and design properties for lumber, round timber, and ties. Wood handbook : wood as an engineering material: chapter 7. Centennial ed. General technical report FPL ; GTR-190. Madison, WI : U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory, 2010: p. 7.1-7.16.
