Nondestructive Strength Assessment of In-Place Wood Utility Poles

Abstract

In-place nondestructive simulation evaluation of the remaining bending strength of wooden utility poles is vital to the continued and successful operation of the poles, viability of the electrical transmission and delivery system, and reduction of system disruption potential. A methodology for nondestructively assessing the strength of in-place wood utility poles was developed and is proposed in this paper. Because of the nonhomogeneous and anisotropic nature of wood and the variability of in-place utility poles, a deterministic approach does not seem feasible. The proposed method combines multiple variables to statistically predict the breaking strength, or modulus of rupture, of wood poles. The full-scale testing methodology was tested on real life poles. Results from in-field simulation tests were correlated to data from failure testing of the full-scale poles. The proposed static bending approach is quite accurate, utilizing a device that applies a horizontal force on an in-place utility pole and measures the resulting deflection. The slope of the force-deflection curve and the pole moment of inertia from a regression analysis correlate well to the breaking strength of the poles. Additionally, a method for measuring and adjusting for the tilt of the utility pole under test was determined. Full-scale field simulated testing and break testing data that provide significant insight into nondestructive wood pole testing are provided in this paper. Recommendations for increasing the validity of the proposed model with additional test data, together with implementation of additional relevant parameters, are made.