Non-destructive methodologies for assessment of the mechanical properties of new utility poles

Abstract

The application of non-destructive technologies for the assessment of mechanical properties has been increasingly used due to its reliable assessment of the condition of timber elements. The application of such methods is well established for sawn timber and small-diameter roundwood. However, regarding the assessment of the mechanical properties for roundwood with larger diameters, which are usually used for new utility poles, a fewer number of studies are available. This research considered three different methodologies for application in Maritime Pine utility poles: i) longitudinal vibration, ii) transverse vibration, and iii) ultrasound. The methodology with better results was chosen for use in the second stage of testing. Furthermore, mechanical tests were performed to compare and validate the results from the non-destructive tests. The moisture contents and densities were also determined. Simple and multiple linear regression analyses were performed between the visual, dynamic, and mechanical properties. The longitudinal vibration method achieved the best correlation within the non-destructive methods, while the ultrasound method had no noticeable correlation. The vibration frequency (f) (r = 0.51) showed a better correlation with the bending strength (MOR) than the dynamic modulus of elasticity (MOEdyn) (r = 0.45). The static modulus of elasticity (MOE) was the best property used to predict MOR because it presented the highest correlation (r = 0.79).