Assessment of the Structural Integrity of Timber Utility Poles Using Ultrasonic Waves

Jad El Najjar ,Samir Mustapha

doi:10.21741/9781644901311-16

Abstract

Abstract. In this study, guided stress waves were used to evaluate the conditions of a timber utility pole experimentally and numerically using COMSOL Multiphysics. Macro Fiber Composites (MFCs), due to their flexibility and convenience to install on curved surfaces, were used to actuate and sense guided waves along the tested specimens. Based on the wave propagation characteristics in these types of structures, an MFC actuator ring, which was developed in the previous work, was applied to tune and enhance the propagating wave modes of interest. The designed ring was used to excite longitudinal ultrasonic wave modes, mainly L(0,1), for the purpose of determining the embedded length of the pole. For the damage localization a single MFC excitation was used which proved to be more efficient than the actuator ring. Embedding the timber in soil had minimum impact on the wave propagation characteristics, given that the waves were confined in the timber pole with minimal leakage to the surrounding. The embedded length was determined accurately for sound and damage timber, using both experimental and numerical data with an error of less than 3 %. The deterioration in the timber structure, within the embedded region, was also evaluated with high accuracy of 93 %. Based on the obtained results, guided waves have high potential to be used as a non-destructive tool for the assessment and evaluation of timber utility poles.

Highlights

The use of timber has commenced thousands of years ago and is still being used today in numerous applications
The embedded length corresponds to the distance between the Macro Fiber Composites (MFCs) sensor and bottom edge of the pole, and the damage location corresponds of the distance between the sensor and the damage
The testing was only performed on the bottom end of the pole, which was the location of interest, to evaluate the embedded section and acquire less reflections from the top end of the pole

Summary

Introduction

The use of timber has commenced thousands of years ago and is still being used today in numerous applications. Surface non-destructive techniques are the most common in timber structures where longitudinal (compressional) and flexural (bending) stress waves are used for the evaluation process. These techniques include sonic echo (SE) and impulse response (IR) tests, where the embedded length and health state of the timber can be evaluated. Condition assessment of timber poles can be performed using guided waves where the presence of decay or damage can be detected. Various studies on this matter have been conducted with the use of machine learning techniques.

Methods

Results

Conclusion