Rate of Loading Influence on Southern Pine 2 By 4’S in Bending

Approximately 400 southern pine No. 2 Dense, kiln-dried 2 by 4’s were tested in third-point, edgewise bending to determine the influence of an increased rate of testing on strength and stiffness. One-half of the specimens were tested at a rate of cross head travel of 0.2 in./min., the suggested ASTM Standard rate of loading. The other half of the specimens were tested at a rate of cross head travel of 5.0 in./min., consistent with the rate used in the U.S. In-Grade Testing Program. No significant differences were found for the modulus of elasticity (MOE) distributions, modulus of rupture (MOR) distributions, or MOR-MOE (regression) relationships between the specimens tested at 0.2 in./min. and those tested at 5.0 in./min. Trends in the data indicated that there was a greater influence of test rate on the stronger pieces of lumber while the weaker specimens were relatively unaffected.

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