Structural Health Monitoring Based on Acoustic Emissions: Validation on a Prestressed Concrete Bridge Tested to Failure.

Daniel Tonelli,Placido Migliorino,Francesco Rossi,Michele Luchetta,Daniele Zonta

doi:10.3390/s20247272

Abstract

The increasing number of bridges approaching their design life has prompted researchers and operators to develop innovative structural health monitoring (SHM) techniques. An acoustic emissions (AE) method is a passive SHM approach based on the detection of elastic waves in structural components generated by damages, such as the initiation and propagation of cracks in concrete and the failure of steel wires. In this paper, we discuss the effectiveness of AE techniques by analyzing records acquired during a load test on a full-size prestressed concrete bridge span. The bridge is a 1968 structure currently decommissioned but perfectly representative, by type, age, and deterioration state of similar bridges in operation on the Italian highway network. It underwent a sequence of loading and unloading cycles with a progressively increasing load up to failure. We analyzed the AE signals recorded during the load test and examined how far their features (number of hits, amplitude, signal strength, and peak frequency) allow us to detect, quantify, and classify damages. We conclude that AE can be successfully used in permanent monitoring to provide information on the cracking state and the maximum load withstood. They can also be used as a non-destructive technique to recognize whether a structural member is cracked. Finally, we noticed that AE allow classifying different types of damage, although further experiments are needed to establish and validate a robust classification procedure.

Highlights

An increasing number of civil infrastructures are approaching or exceeding their initial design life
The benefit of structural health monitoring (SHM) to bridge management has been extensively analyzed in the literature, see for instance [3]; SHM allows the early detection of possible damages resulting from the natural deterioration of structural materials, and to optimize decision over maintenance, repair, and reconstruction of the bridge asset [4,5]
Results from acoustic emissions (AE) acquired during the loading phase P4 confirm that the AE technique can effectively discriminate whether a prestressed concrete structure is affected by pre-existent cracks and identify the maximum load withstood by the structure

Summary

Introduction

An increasing number of civil infrastructures are approaching or exceeding their initial design life. The average age of bridges in the USA is estimated to be 46 years [1]; 70% of highway bridges in Italy were reportedly built around the 1970s [2]. The effort required by operators to identify unsafe structural conditions increases. The benefit of structural health monitoring (SHM) to bridge management has been extensively analyzed in the literature, see for instance [3]; SHM allows the early detection of possible damages resulting from the natural deterioration of structural materials, and to optimize decision over maintenance, repair, and reconstruction of the bridge asset [4,5]. The growing interest in SHM for infrastructure operators and the recent technological progress have encouraged the research community to study and develop innovative sensors and monitoring. An incomplete list includes the Ground Penetration Radar (GPR), or Georadar [6,7], the Reflectometric Impulse Measurement Technology (RIMT) [8,9,10], the Time Domain Reflectometry (TDR) [11,12], the Strand-Cutting test [13,14,15], the Core Drilling Method (CDM) [16,17], and the Acoustic

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Results

Discussion

Conclusion