Relationship between Timber Grade and Local, Global, and Dynamic Modulus of Elasticity in Red Oak and Red Maple Structural Lumber

Abstract

The modulus of elasticity (MOE) of structurally graded one-inch-thick red oak (Quercus rubra) and red maple (Acer rubrum) lumber was measured in this work. The center-point, third-point static loading tests, and the stress wave timer methods were used. The objective was to determine if there are statistical differences between three structural lumber grades based on their MOE values. The study considered both the within separated grades and the across combined grades. For red oak and red maple, significant differences in MOE values from center-point static loading tests were observed solely between Select Structural and Below-grade lumber. With the dynamic method, no significant differences were found between any visual grades, including Below-grade lumber. Regardless of the MOE determination method used, the MOE value was not useful for distinguishing the structural, No. 2, and No. 3 visual grades. The strongest correlation existed between the global MOE and the dynamic MOE, which was even higher when the analyses were conducted on separated visual grades. In the case of red maple, stronger correlations between the dynamic MOE, local MOE, and global MOE were observed when separated by visual classes, compared to the analysis conducted on the combined grades. The global MOE was found to be a better predictor of the local MOE than the dynamic MOE.