Deterioration Modelling of Timber Utility Poles

Abstract

Timber utility poles are extensively used in power distribution and telecommunication sectors to support the overhead cables and other attachments. These utility poles are designed to have sufficient inherent capacity to withstand the imposed actions. However, timber poles deteriorate with time losing the strength and toughness mainly due to weathering, decay and termite attacks. Therefore, pole failures occur when the imposed stresses on the pole exceed the remaining strength of the pole. It is essential to avoid pole failures which will have severe safety concerns and significant economic impacts. This paper presents a brief review of the currently available timber deterioration models and proposes a framework for evaluating the residual strength of the in-service timber utility poles. The developed framework permits the asset managers to evaluate the structural reliability of these assets and to determine the optimum pole replacement rates. The residual strength of an in-service pole is directly related to the remaining section modulus of the pole at its critical section which is the ground line region of the pole. Hence, this paper presents the evaluation of the remaining section modulus for sectioned pole specimens which were condemned from service due to pole replacements. Further, the variation of section modulus with the service life is illustrated for the analysed Australian pole specimens and compared with the predictions of the current deterioration models.