Similitude Laws and Small-Scale Model Experiments Characterizing Dynamic Failures of Flawed Utility Poles

The principles of similitude were employed to scale the equations of motion of wood utility poles to small, practical laboratory size. The derived dimensionless system parameters were used to design experiments in which model pole bending moments at failure were measured in response to simulated steady and gusting wind loads. Measured were the effects of artificial flaws on a pole's integrity under these loads, with flaws represented as radial holes. Modeled in static and dynamic tests to failure were shallow pole holes at the base designed to deliver termite and rot control chemicals in a prototype; shallow holes to simulate loose knots and through holes needed for utility hardware attachments. The groundline moment data for both static and dynamic tests showed either shear or tensile failure. An application illustrates the use of small-scale model data to explain the wind-induced base failure of a generic prototype utility pole.