Four-Inch Southern Pine Lumber; Seasoning Factors for Modulus of Elasticity and Modulus of Rupture

The objective of this study was to evaluate the changes in bending properties of 4-inch-thick beams of southern pine when dried to 12 percent moisture content, and to relate these changes to quality or grade of lumber. Modulus of elasticity increased by an average of 23 percent. Modulus of rupture increased proportionally with strength ratio, a measure of quality. The increase ranged from an average of 52 percent for clear beams down to an average of zero for beams with a 28 percent strength ratio. The results of this work show that at least in the range of the relatively high-quality lumber, traditional increases in mechanical properties with drying may be too low. Application of these results can lead to monetary savings in the utilization of thick lumber. The tests were made on 55 rough-sawed, 16-foot long, 8- by 8-inch pith-centered cants of southern pine. Strength ratio was determined according to ASTM D-245 for bending members. Moisture contents for shells of the beams ranged from 10 to 14 percent with an average of 11.5 percent. Core moisture contents ranged from 11 to 17 percent and averaged 13.4 percent.

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