Acoustic Emission Signal Entropy as a Means to Estimate Loads in Fiber Reinforced Polymer Rods

Douglas Thomson,Maha Ghaib,Mohammadhadi Shateri,Dagmar Svecova

doi:10.3390/s21041089

Douglas Thomson, Maha Ghaib + Show 2 more

Open Access

https://doi.org/10.3390/s21041089

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Journal: Sensors	Publication Date: Feb 5, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: University of Manitoba, McGill University

Abstract

Fibre reinforced polymer (FRP) rods are widely used as corrosion-resistant reinforcing in civil structures. However, developing a method to determine the loads on in-service FRP rods remains a challenge. In this study, the entropy of acoustic emission (AE) emanating from FRP rods is used to estimate the applied loads. As loads increased, the fraction of AE hits with higher entropy also increased. High entropy AE hits are defined using the one-sided Chebyshev’s inequality with parameter k = 2 where the histogram of AE entropy up to 10–15% of ultimate load was used as a baseline. According to the one-sided Chebyshev’s inequality, when more than 20% (k = 2) of AE hits that fall further than two standard deviations away from the mean are classified as high entropy events, a new distribution of high entropy AE hits is assumed to exist. We have found that the fraction of high AE hits. In glass FRP and carbon FRP rods, a high entropy AE hit fraction of 20% was exceeded at approximately 40% and 50% of the ultimate load, respectively. This work demonstrates that monitoring high entropy AE hits may provide a useful means to estimate the loads on FRP rods.

Highlights

The acoustic emission (AE) signals collected during an Fibre reinforced polymer (FRP) tensile test under ramping loads were used, where AE hits were identified using RMS hit detection algorithm
When the load was less than 10–15% of the ultimate load, the AE entropy had approximately a normal distribution
When loads exceeded 10–15% of the ultimate load, AE hits with higher entropies were observed where the one-sided Chebyshev’s inequality showed to be useful in detecting the emergence of a new entropy distribution

Summary

Introduction

Fiber reinforced polymer (FRP) rods have been widely used for reinforcing in civil structures including concrete structures and steel structures [1,2]. High strength-to-weight ratio and high resistance to the corrosion make FRP rods a good replacement for steel reinforcing rods [2]. FRP rods can be used as reinforcing as long as the allowed service load is not exceeded. Standards for the use of FRP bars such as ACI440.1R and CAN/CSA-S806-12 recommend maximum stress levels under service loads should not exceed 20–25% and 55–65% of the ultimate strength for glass FRP (GFRP) and carbon FRP (CFRP). One of the main drawbacks of the FRP rods compare to the steel reinforcing rods is their lack of ductility (see Figure 1)

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