Pendulum impact tests of wooden and steel highway guardrail posts

Impact strength characteristics of southern pine, red oak, and steel highway guardrail posts were evaluated in destructive impact testing with a 4,000-pound pendulum at the Southwest Research Institute. Effects were recorded with high-speed motion-picture equipment. Comparisons were based on reactions to the point of major post failure. Major comparisons of 6x6-inch and 6x8-inch red oak and southern pine posts with W6x8.5 and S3x5.7 steel posts showed wooden posts to be equal or superior to steel. The basis for wooden-post specifications should be the amount of knot-associated grain distortion in the middle third of the tension face of the posts. Acceptable posts are those with no single knot in the middle third of the tension face that disorients the grain for more than one-third the width of the face.