Non-destructive Techniques for Condition Assessment of Timber Utility Poles

Abstract

Timber poles are extensively used in power and telecommunication networks all around the world. Timber utility poles have high initial strength, but susceptive to fungus and termite attacks which results in deterioration with time. It is difficult to observe the defects by looking from outside and in most of the cases, defects are observed below the ground. Power distribution and telecommunication companies conduct routine inspections on utility poles to assess the structural integrity and to avoid failure of poles which will have serious safety concerns. But most of the present pole inspection techniques are subjective methods and highly qualified personnel are required for inspection. In comparison, non-destructive testing (NDT) methods can be effectively used to assess the condition of timber utility poles. This paper provides a brief review on in-service assessment methods and focuses on stress wave propagation technique as a non-destructive test for the condition assessment of timber utility poles. Theory behind stress wave propagation technique is the observation of reflection patterns of stress waves generated by an impact load on timber pole. Longitudinal waves or transverse (shear) waves may be generated depending on the direction and location of the impact. Resulting signals due to the response of the pole are processed in time and frequency domains to obtain important information about the condition of the utility pole. Wavelet transformation is used as an effective tool for processing the signals obtained from numerical models and practicality of the mentioned method is verified using the signals obtained from field testing.