Condition Assessment of Foundation Piles and Utility Poles Based on Guided Wave Propagation Using a Network of Tactile Transducers and Support Vector Machines.

Ulrike Dackermann,Ernst Niederleithinger,Jianchun Li,Herbert Wiggenhauser,Yang Yu

doi:10.3390/s17122938

Abstract

This paper presents a novel non-destructive testing and health monitoring system using a network of tactile transducers and accelerometers for the condition assessment and damage classification of foundation piles and utility poles. While in traditional pile integrity testing an impact hammer with broadband frequency excitation is typically used, the proposed testing system utilizes an innovative excitation system based on a network of tactile transducers to induce controlled narrow-band frequency stress waves. Thereby, the simultaneous excitation of multiple stress wave types and modes is avoided (or at least reduced), and targeted wave forms can be generated. The new testing system enables the testing and monitoring of foundation piles and utility poles where the top is inaccessible, making the new testing system suitable, for example, for the condition assessment of pile structures with obstructed heads and of poles with live wires. For system validation, the new system was experimentally tested on nine timber and concrete poles that were inflicted with several types of damage. The tactile transducers were excited with continuous sine wave signals of 1 kHz frequency. Support vector machines were employed together with advanced signal processing algorithms to distinguish recorded stress wave signals from pole structures with different types of damage. The results show that using fast Fourier transform signals, combined with principal component analysis as the input feature vector for support vector machine (SVM) classifiers with different kernel functions, can achieve damage classification with accuracies of 92.5% ± 7.5%.

Highlights

Structural Health Monitoring (SHM) is a wide and multi-disciplinary field dealing with innovative methods for monitoring structural safety, integrity and performance without affecting the operation of the structure [1]
This paper presented a novel testing system for foundation piles and utility poles using a network of tactile transducers and accelerometers alongside an advanced signal processing technique for condition assessment and damage classification
The innovative testing system uses tactile transducers in a ring configuration to excite narrow-band frequency stress waves, in order to generate axisymmetric guided waves and thereby reduce the appearance of multi-wave types and modes typically encountered with broadband hammer excitation

Summary

Introduction

Structural Health Monitoring (SHM) is a wide and multi-disciplinary field dealing with innovative methods for monitoring structural safety, integrity and performance without affecting the operation of the structure [1]. While visual inspection is undoubtedly one of the oldest assessment methods, it is limited to accessible areas and surface damage, and like sounding and resistance drilling, its reliability and accuracy is highly dependent on the experience of the operator [2]. As an alternative to these limited low-tech condition assessment methods, guided wave-based methods, such as pile integrity testing, are established testing methods for concrete piles and deep foundations that provide objective quantitative data, and are able to potentially detect internal damage and evaluate the health condition of non-accessible areas such as embedded sections of foundation piles and utility poles [3,4,5]. In pile and pole structures, the wave types generated through guided wave testing are longitudinal, bending and Rayleigh waves. Due to the dependency of the wave’s velocity to the modulus of elasticity, Poisson’s ratio, density and geometry of the structure, analyzing stress waves can give indications of a structure’s soundness condition [7,8]

Results

Discussion

Conclusion