Condition assessment of utility timber poles using Hilbert Huang transform

Timber poles play an important role in Australia's infrastructure especially for power distribution and telecommunication networks. Routine inspections are carried out to monitor pole condition which deteriorates with time due to fungal and termite attacks, climate and soil condition. Currently practiced pole inspection techniques available in the market are mostly inaccurate and unreliable that results into often unnecessary replacement and sometimes unexpected failure. Vibration based non-destructive testing (NDT) technique is implemented by many researchers for assessing health state of pole or pile structures. However, captured vibration signal is highly affected by the uncertainty on timber material, structure and environment. Therefore, advanced signal processing technique is essential in order to determine the pole condition accurately. In this study, Hilbert Huang Transform (HHT) is adopted as an efficient time-frequency analysis technique for analysing the captured field data from vibration testing of one serviceable and one unserviceable pole. The raw signal is primarily subjected to empirical mode decomposition process before computing instantaneous frequencies of the decomposed signals using HHT. The anomalies in the instantaneous frequency plots are efficiently utilized which are vital for determining pole condition. The results of the study showed that HHT has great potential for the condition assessment of utility timber poles.