Tension Proof Loading for Southern Pine Beams

by Melvin Dee Strickler, Wood Technologist; Dept. of Materials Science and Engrg., Washington State Univ., Pullman, Wash.,
Roy F. Pellerin, Wood Technologist; Dept. of Materials Science and Engrg., Washington State Univ., Pullman, Wash.,


Serial Information: Journal of the Structural Division, 1976, Vol. 102, Issue 3, Pg. 645-657


Document Type: Journal Paper

Abstract: E-rating (measuring modulus of elasticity) and tension proof loading of lumber before laminating could improve stiffness characteristics and allowable design stresses for glued-laminated timber beams. Twenty-four large southern pine beams were fabricated from E-rated lumber — the high-E material located on the outside and low-E material in the core. Although average beam strength of southern pine equals Douglas fir, southern pine responds differently to tension proof loading than does Douglas fir. Southern pine may require higher proof loads (1.5 times beam Fb) than Douglas fir (1.3 times Fb) to eliminate brash pith-associated wood from the critical tension laminations. Since proof load breakage with southern pine was significantly less than with Douglas fir, a higher proof load stress for southern pine could be tolerated without causing excessive loss from breakage. Static beam modulus of elasticity is predictable from the E of the laminations with a correlation coefficient of 0.982.

Subject Headings: Ultimate strength | Light rail transit | Load tests | Load factors | Tension members | Laminated materials | Wood beams

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