FLEXURAL AND TENSILE PROPERTIES OF 2 x 6 AND 2 x 10 SOUTHERN PINE LUMBER

Bending modulus of elasticity (MOE) and tensile properties parallel to the grain were studied on 702 pieces of 2 x 6 and 285 pieces of 2 x 10 No. 2 visually graded southern pine lumber. The overall rings per inch (RPI) in 2 x 6 pieces was 4.82, whereas 2 x 10 had an RPI average of 3.82. For latewood percentage (LW), 2 x 6 pieces found 45.88% of LW and 45.02% for 2 x 10 pieces. Bending MOE (E-b) mean for 2 x 6 was 10,615 MPa, whereas for 2 x 10 lumber, the mean was 13,665 MPa. The tension MOE (Et) mean for 2 x 6 lumber was 11,339 MPa, whereas for 2 x 10 the mean was 9735 MPa. The ultimate tensile stress (UTS) mean for 2 x 6 lumber was 28.42 MPa and the overall mean UTS for 2 x 10 lumber was 24.51 MPa. Linear regression models were useful to explain the relationship between Eb and Et. Strong coefficients of determination (r(2) =0.70 and r(2) =0.74) were found for both lumber sizes between these two properties. Moderate relationships (r(2) =0.43 up to r(2) =0.51) between Eb and UTS were also found for both lumber sizes. However, weaker relationships were found between Et and UTS (r(2) =0.32 up to r(2) =0.40). Three distributions were fit to the Eb, Et, and UTS data and evaluated for goodness of fit. The results suggest that Eb of 2 x 6 lumber might be adequately modeled by a normal distribution, and tensile properties of 2 x 10 lumber might be adequately modeled by a lognormal distribution.