Non destructive assessment of in service timber utility poles

Timber poles have high initial strength but they often experience deterioration and decay over their design life due to fungus or termite attacks. In most cases the damage is not visible and often below ground. To ensure the structural integrity of poles, electricity distribution companies conduct specific regular inspections. The paper reviews common and new in-service assessment methods including drilling, sounding and stress wave propagation technique which is emerging to be very effective in detecting damage above and below ground. The presence of decay greatly affects stress wave propagation velocity in timber. In this paper results from stress wave testing of timber poles in-service, removed from service with different damage conditions and new poles before introduced into service are reviewed