Method for assessing the effect of knots in the conversion of logs into structural lumber

A theoretical procedure is described by which the effect of knots in the conversion of logs into structural lumber can be assessed. The procedure features a mathematical algorithm that predicts the outcome of visual stress-grading of lumber carried out in accordance with ASTM D 245. Knots are treated as void areas and logs as perfect cylinders. Log diameter, knot shapes, and the position of sawing planes are used as input parameters. A numerical example is carried out to quantify the possible improvements in lumber quality from knowledge of the internal knot structure of the log. This example showed significant differences in structural grade yield due to circumferential log orientation.