Evaluating the Relative Bending Strength of Crossarms

Abstract

Over a million crossarms are produced annually in the United States. In the open wire lines of the Bell System alone there are now about 20 million arms in use. It is natural, therefore, that public utility engineers should have an interest in the strength of such an important item of outside plant material; and, consequently, an interest in any tool or means of evaluating the strength of such material. It is believed that the moment diagram is a convenient and reasonably reliable tool for estimating the loads an arm will support, for measuring the effect of knots of various sizes and of pinhole locations on arm strength, and for answering similar questions relating to the bending strength of crossarms under vertical loads.