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Non-contact surface wave testing of pavements: comparing a rolling microphone array with accelerometer measurements
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.ORCID iD: 0000-0002-5665-8288
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.ORCID iD: 0000-0003-0889-6078
2016 (English)In: Smart Structures and Systems, ISSN 1738-1584, E-ISSN 1738-1991, Vol. 17, no 1, 1-15 p.Article in journal (Refereed) Published
Abstract [en]

Rayleigh wave velocity along a straight survey line on a concrete plate is measured in order to compare different non-destructive data acquisition techniques. Results from a rolling non-contact data acquisition system using air-coupled microphones are compared to conventional stationary accelerometer results. The results show a good match between the two acquisition techniques. Rolling measurements were found to provide a fast and reliable alternative to stationary system for stiffness determination. However, the non-contact approach is shown to be sensitive to unevenness of the measured surface. Measures to overcome this disadvantage are discussed and demonstrated using both forward and reverse rolling measurements.

Place, publisher, year, edition, pages
2016. Vol. 17, no 1, 1-15 p.
Keyword [en]
Non-destructive testing, seismic testing, Lamb waves, surface waves, material characterization
National Category
Geotechnical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-155908DOI: 10.12989/sss.2016.17.1.001ISI: 000373916400002Scopus ID: 2-s2.0-84957577517OAI: oai:DiVA.org:kth-155908DiVA: diva2:763329
Note

QC 20160412

Available from: 2014-11-14 Created: 2014-11-14 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Air-coupled microphone measurements of guided waves in concrete plates
Open this publication in new window or tab >>Air-coupled microphone measurements of guided waves in concrete plates
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Quality control and quality assurance of pavements is today primarily based on core samples. Air void content and pavement thickness are parameters that are evaluated. However, no parameter connected to the stiffness is evaluated. There is a need for fast and reliable test methods that are truly non-destructive in order to achieve an effective quality control and quality assurance of pavements. This licentiate thesis presents surface wave testing using air-coupled microphones as receivers. The measurements presented in this work are performed in order to move towards non-contact measurements of material stiffness. The non-contact measurements are compared to conventional accelerometer measurements in order to compare the noncontact measurements to a “reference test”. The two appended papers are focused on evaluating one parameter in each paper. In the first paper all equipment needed to perform non-contact measurements are mounted on a trolley in order to enable measurements while rolling the trolley forward. It is shown that rolling measurements can provide rapid and reliable measurements of the Rayleigh wave velocity over large areas. However, the measurements are shown to be sensitive to misalignments between the microphone array and the measured surface. An uneven surface can thus cause major errors in the calculated results. The second paper presents an alternative method to evaluate the thickness resonance frequency of a concrete plate. It is demonstrated how the established Impact Echo method can give erroneous results when aircoupled microphones are used as receivers. Instead a method based on backward wave propagation is introduced. It is demonstrated how waves with negative phase velocities can be identified in a narrow frequency span close to the thickness resonance.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. ix, 32 p.
Series
TRITA-TSC-LIC, ISSN 1653-445X ; 14-004
Keyword
Non-destructive testing, Lamb waves, surface waves, air-coupled microphones, non-contact measurements
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:kth:diva-155912 (URN)978-91-87353-51-2 (ISBN)
Presentation
2014-12-08, B25, Brinellvägen 23, Stockholm, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20141128

Available from: 2014-11-28 Created: 2014-11-14 Last updated: 2014-11-28Bibliographically approved
2. Non-contact surface wave measurements on pavements
Open this publication in new window or tab >>Non-contact surface wave measurements on pavements
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, nondestructive surface wave measurements are presented for characterization of dynamic modulus and layer thickness on different pavements and cement concrete slabs. Air-coupled microphones enable rapid data acquisition without physical contact with the pavement surface.

Quality control of asphalt concrete pavements is crucial to verify the specified properties and to prevent premature failure. Testing today is primarily based on destructive testing and the evaluation of core samples to verify the degree of compaction through determination of density and air void content. However, mechanical properties are generally not evaluated since conventional testing is time-consuming, expensive, and complicated to perform. Recent developments demonstrate the ability to accurately determine the complex modulus as a function of loading time (frequency) and temperature using seismic laboratory testing. Therefore, there is an increasing interest for faster, continuous field data evaluation methods that can be linked to the results obtained in the laboratory, for future quality control of pavements based on mechanical properties.

Surface wave data acquisition using accelerometers has successfully been used to determine dynamic modulus and thickness of the top asphalt concrete layer in the field. However, accelerometers require a new setup for each individual measurement and are therefore slow when testing is performed in multiple positions. Non-contact sensors, such as air-coupled microphones, are in this thesis established to enable faster surface wave testing performed on-the-fly.

For this project, a new data acquisition system is designed and built to enable rapid surface wave measurements while rolling a data acquisition trolley. A series of 48 air-coupled micro-electro-mechanical sensor (MEMS) microphones are mounted on a straight array to realize instant collection of multichannel data records from a single impact. The data acquisition and evaluation is shown to provide robust, high resolution results comparable to conventional accelerometer measurements. The importance of a perfect alignment between the tested structure’s surface and the microphone array is investigated by numerical analyses.

Evaluated multichannel measurements collected in the field are compared to resonance testing on core specimens extracted from the same positions, indicating small differences. Rolling surface wave measurements obtained in the field at different temperatures also demonstrate the strong temperature dependency of asphalt concrete.

A new innovative method is also presented to determine the thickness of plate like structures. The Impact Echo (IE) method, commonly applied to determine thickness of cement concrete slabs using an accelerometer, is not ideal when air-coupled microphones are employed due to low signal-to-noise ratio. Instead, it is established how non-contact receivers are able to identify the frequency of propagating waves with counter-directed phase velocity and group velocity, directly linked to the IE thickness resonance frequency.

The presented non-contact surface wave testing indicates good potential for future rolling quality control of asphalt concrete pavements.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 70 p.
Series
TRITA-JOB PHD, ISSN 1650-9501 ; 1025
Keyword
seismic testing, asphalt concrete, dynamic modulus, non-contact measurements, rolling measurements, surface waves, Lamb waves, MEMS microphones
National Category
Geotechnical Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-201147 (URN)978-91-7729-263-0 (ISBN)
Public defence
2017-03-08, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170209

Available from: 2017-02-09 Created: 2017-02-09 Last updated: 2017-02-13Bibliographically approved

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Bjurström, HenrikBirgisson, Björn

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