| 1. |
- Bjurström, Henrik, et al.
(författare)
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Comparative Seismic Laboratory and Non-Contact Field Measurements of Asphalt Concrete
- 2016
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Ingår i: 2016 Structural Materials Technology Paper Summaries.
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Konferensbidrag (refereegranskat)abstract
- Non-contact acoustic field measurements are performed on a newly built highway to characterize the real part of the dynamicmodulus of the asphalt concrete (AC) top layer. The in situ measurements are performed using an array of 48 micro-electromechanicalsystem (MEMS) sensors. Cores extracted from the field measurement positions are then examined in a laboratory usingseismic modal testing for comparison. The laboratory testing allows master curves to be constructed to characterize the AC over awide temperature and frequency range. It is demonstrated that the real parts of the dynamic moduli are consistent at the fieldtemperatures using the two test methods. The in situ measurements are also shown to be highly repeatable. The presentedcomparative study indicates a possible application for assuring the quality of AC based on mechanical properties using fast noncontactin situ measurements.
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| 2. |
- Bjurström, Henrik, 1983-, et al.
(författare)
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Detecting the thickness mode frequency in a concrete plate using backward wave propagation
- 2016
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 139:2, s. 649-657
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Tidskriftsartikel (refereegranskat)abstract
- Material stiffness and plate thickness are the two key parameters when performing quality assurance/quality control on pavement structures. In order to estimate the plate thickness non-destructively, theImpact Echo (IE) method can be utilized to extract the thickness resonance frequency. An alternativeto IE for estimating the thickness resonance frequency of a concrete plate, and to subsequently enablethickness determination, is presented in this paper. The thickness resonance is often revealed as asharp peak in the frequency spectrum when contact receivers are used in seismic testing. Due to a lowsignal-to-noise ratio, IE is not ideal when using non-contact microphone receivers. In studying thecomplex Lamb wave dispersion curves at a frequency infinitesimally higher than the thickness frequency,it is seen that two counter-directed waves occur at the same frequency but with phase velocitiesin opposite directions. Results show that it is possible to detect the wave traveling with anegative phase velocity using both accelerometers and air-coupled microphones as receivers. Thisalternative technique can possibly be used in non-contact scanning measurements based on aircoupled microphones.
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| 3. |
- Bjurström, Henrik, et al.
(författare)
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Field and laboratory stress-wave measurements of asphalt concrete
- 2016
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Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 126, s. 508-516
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Non-contact surface wave measurements are performed on a new asphalt concrete (AC) pavement using 48 micro-electro-mechanical system (MEMS) sensors as receivers to estimate the real part of the dynamic moduli of the AC top layer. Laboratory measurements of core samples, extracted from the field measurement positions, are used to construct master curves for comparison with the field measurements. The real parts of the dynamic moduli from the two test methods are consistent at the field measurement temperatures, and the non-contact field measurements are highly repeatable. These results indicate a possible application for quality assurance of AC based on mechanical properties.
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| 4. |
- Gudmarsson, Anders, 1983-, et al.
(författare)
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Application of resonant acoustic spectroscopy to asphalt concrete beams for determination of the dynamic modulus
- 2012
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Ingår i: Materials and Structures. - : Springer Netherlands. - 1359-5997 .- 1871-6873. ; 45:12, s. 1903-1913
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a new application of resonant acoustic spectroscopy (RAS) is examined for constructing asphalt concrete mastercurves from seismic testing. The frequency-dependent material properties can be characterized from multiple modes of vibration through the use of RAS. Beam-shaped asphalt specimens are tested at multiple temperatures to determine the resonance frequencies of the specimens. The resonance frequencies are estimated by applying a small load impulse and measuring the resulting acceleration through the specimens. Using RAS, the material properties of the specimens are determined numerically using the measured resonance frequencies. The results presented show that the frequency-dependent dynamic modulus of the asphalt concrete specimens can be characterized using several modes of vibration at each testing temperature.
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| 5. |
- Lundqvist, Peter, et al.
(författare)
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ACOUSTOELASTIC EFFECTS ON THE NATURAL FREQUENCIES OF PRE-STRESSED CONCRETE BEAMS
- 2011
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Ingår i: Review of Progress in Quantitative Nondestructive Evaluation (AIP Conference Proceedings). - : AIP. - 9780735408883 ; 1335, s. 1379-1385
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Konferensbidrag (refereegranskat)abstract
- Abstract in Undetermined Pre-stressed concrete is used to increase the load capacity in many civil engineering structures. There is a need for non-destructive methods to estimate the potential loss of pre-stress in these structures. In this study we investigate the acoustoelastic effect on the natural resonance frequencies of a pre-stressed concrete beam. Measured resonant frequencies increase with increasing compressive stress. Results agree with predicted frequency shifts obtained from a non-linear finite element model based on Murnaghan's third order elastic theory.
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| 6. |
- Lundqvist, Peter, et al.
(författare)
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Acoustoelastic Effects on the Resonance Frequencies of Prestressed Concrete Beams – Short-term Measurements
- 2012
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Ingår i: NDT & E International. - : Elsevier BV. - 0963-8695. ; 50, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- In this study resonant acoustic spectroscopy was applied during static loading and unloading of three prestressed concrete beams in the context of acoustoelasticity. At each load step multiple modes of vibration were measured using an accelerometer and a small impact source. It was found that the measured resonance frequencies increased with increasing compressive stress in a manner which can be predicted using a non-linear finite element model based on Murnaghan's third order elastic theory. Previous results from experimental studies on concrete bridges indicate that measured structural resonance frequencies increase with increasing prestress forces. These results have been difficult to explain theoretically and the results from this study can possibly provide a new theoretical basis for the observed stress dependency of the resonance frequencies of concrete structures. Furthermore, the results indicate that a change in the state of stress in a concrete structure can be detected or monitored by measuring one or several resonance frequencies.
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| 7. |
- Lundqvist, Peter, et al.
(författare)
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Short- and long-term measurements of resonance frequencies on prestressed concrete beams
- 2011
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080255 ; 43:1
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Konferensbidrag (refereegranskat)abstract
- Currently, no method exists for determining the prestress forces in prestressed concrete structures. According to the theory of acoustoelasticity, the modulus of elasticity of concrete is stress dependent, which means that the resonance frequency of a concrete structure also is stress dependent. In this study, both short-term and long-term measurements of the resonance frequencies of four prestressed concrete beams were performed. The results show that the acoustoelastic effect in concrete is measureable and that the resonance frequencies increase with the applied compressive stress and that the prestress losses can be monitored through measurements of the resonance frequencies.
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| 8. |
- Bjurström, Henrik, et al.
(författare)
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Effect of Surface Unevenness on In Situ Measurements and Theoretical Simulation in Non-Contact Surface Wave Measurements Using a Rolling Microphone Array
- 2015
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Ingår i: NDT-CE2015 proceedings. - Berlin : NDT.
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Konferensbidrag (refereegranskat)abstract
- Non-destructive seismic testing using air-coupled microphones is today an attractive alternative to the more conventional stationary accelerometer testing, in order to perform fast and reliable material characterization on pavement structures. A multichannel microphone array enables fast mobile data collection using a rolling trolley. It is essential that the microphone array and the material surface are perfectly aligned to receive a correct result. This study presents estimations of the calculation errors due to misalignments between the microphone array and the material surface. It is shown that even small misalignments can cause large errors. A realistic pavement roughness is simulated in order to quantify the errors in different situations and for different materials (stiffness). A simple solution to correct the errors under certain circumstances is also presented.
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| 9. |
- Bjurström, Henrik, et al.
(författare)
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Effect of surface unevenness on non-contact surface wave measurements using a rolling microphone array
- 2015
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Ingår i: 41ST ANNUAL REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION. - : American Institute of Physics (AIP). - 9780735412927 ; , s. 128-135
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Konferensbidrag (refereegranskat)abstract
- Surface wave velocity is measured and evaluated along a straight survey line in order to compare two different data acquisition methods. Results from a rolling microphone array are compared to data acquired using a conventional accelerometer. Results from the two different data acquisition methods are shown to be similar. However, it is demonstrated that the results are very sensitive to misalignments between the microphone array and the measured surface. Practices to overcome problems with misalignments are discussed and demonstrated.
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| 10. |
- Bjurström, Henrik, et al.
(författare)
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Non-contact rolling surface wave measurements on asphalt concrete
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Rolling surface wave measurements on a single, thin asphalt concrete (AC) layer arepresented to investigate their use in rapid nondestructive field tests. An array of 47 micro-electromechanicalsensor (MEMS) microphones is mounted on a trailer together with an automated impactsource. Multichannel recordings from single impacts are obtained at 80 equally spaced positions as thetrailer moves at a constant speed. The complete battery-powered data acquisition system enables largescaletesting of newly built pavements. Multiple sets of test results show good repeatability for theassessed shear wave velocity and demonstrate the strong temperature dependency of AC. The presentedresults indicate a possible application for quality assurance of AC using rolling surface wavemeasurements.
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