Damage Detection at a Reinforced Concrete Specimen with Coda Wave Interferometry

Grabke, Stefan; Clauß, Felix; Bletzinger, Kai‐Uwe; Ahrens, Alexander; Mark, Peter; Wüchner, Roland

doi:10.3390/ma14175013

Cited by 13 publications

(10 citation statements)

References 32 publications

(43 reference statements)

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“…The coda is scattered several times and thus interacts with larger regions. It is known to be sensitive to small changes in mechanical strain (compressive and tensile) [9][10][11][12][13][14][15], temperature [16][17][18], moisture [19][20][21] as well as cracks or other discontinuities in the concrete [22][23][24][25][26]. Since strain is the fundamental state variable of RC [27]; it seems most promising to establish a direct correlation between it and the coda to infer the health of structures.…”

Section: Introductionmentioning

confidence: 99%

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

et al. 2022

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The integral collection of information such as strains, cracks, or temperatures by ultrasound offers the best prerequisites to monitor structures during their lifetime. In this paper, a novel approach is proposed which uses the collected information in the coda of ultrasonic signals to infer the condition of a structure. This approach is derived from component tests on a reinforced concrete beam subjected to four-point bending in the lab at Ruhr University Bochum. In addition to ultrasonic measurements, strain of the reinforcement is measured with fiber optic sensors. Approached by the methods of moment-curvature relations, the steel strains serve as a reference for velocity changes of the coda waves. In particular, a correlation between the relative velocity change and the average steel strain in the reinforcement is derived that covers 90% of the total bearing capacity. The purely empirical model yields a linear function with a high level of accuracy (R2 = 0.99, RMSE≈90μstrain).

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Section: Introductionmentioning

confidence: 99%

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

et al. 2022

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“…Reinforced concrete, however, poses a special challenge for NDT techniques due to the material’s heterogeneity, which complicates the separation between naturally present scatterers and undesired material changes, or damage. To this end, the evaluation of ultrasonic signals by means of Coda Wave Interferometry (CWI) is a promising and exceptionally sensitive method to detect even weak changes in the material and has been subject to previous studies on both the laboratory [ 2 , 3 , 4 , 5 , 6 ], and the structural scale [ 7 , 8 , 9 , 10 ]. It is suitable for application as a permanent monitoring system with the focus on the early warning of microcrack initiation, and possibly providing the impulse for further in-depth inspections at alarming locations.…”

Section: Introductionmentioning

confidence: 99%

Impact of External Mechanical Loads on Coda Waves in Concrete

et al. 2022

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During their life span, concrete structures interact with many kinds of external mechanical loads. Most of these loads are considered in advance and result in reversible deformations. Nevertheless, some of the loads cause irreversible, sometimes unnoticed changes below the macroscopic scale depending on the type and dimension of the impact. As the functionality of concrete structures is often relevant to safety and society, their condition must be known and, therefore, assessed on a regular basis. Out of the spectrum of non-destructive monitoring methods, Coda Wave Interferometry using embedded ultrasonic sensors is one particularly sensitive technique to evaluate changes to heterogeneous media. However, there are various influences on Coda waves in concrete, and the interpretation of their superimposed effect is ambiguous. In this study, we quantify the relations of uniaxial compression and uniaxial tension on Coda waves propagating in normal concrete. We found that both the signal correlation of ultrasonic signals as well as their velocity variation directly reflect the stress change in concrete structures in a laboratory environment. For the linear elastic range up to 30% of the strength, we calculated a velocity variation of −0.97‰/MPa for compression and 0.33%/MPa for tension using linear regression. In addition, these parameters revealed even weak irreversible changes after removal of the load. Furthermore, we show the time-dependent effects of shrinkage and creep on Coda waves by providing the development of the signal parameters over time during half a year together with creep recovery. Our observations showed that time-dependent material changes must be taken into account for any comparison of ultrasonic signals that are far apart in time. The study’s results demonstrate how Coda Wave Interferometry is capable of monitoring stress changes and detecting even small-size microstructural changes. By indicating the stated relations and their separation from further impacts, e.g., temperature and moisture, we anticipate our study to contribute to the qualification of Coda Wave Interferometry for its application as an early-warning system for concrete structures.

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“…The solid line shows the best linear fit regression curve, R 2 indicates the closeness of the fit, and the linear correlation between ∆v/v and ∆L/L is evident for each group. All fitted curves can be represented uniformly by Equation (9), where α θ δv/v denotes the slope at θ. Figure 8 shows the relationship between the Kd and the crack length growth, and the dots indicate the variation of the Kd with the crack length, while the solid line is the best quadratic regression fit.…”

Section: Dependence Of Cwi Observations On the Variation Of Crack Lengthmentioning

confidence: 99%

“…In fact, the coda waves that are scattered several times are extremely sensitive to small changes inside complex media. Coda wave interferometry (CWI) is known as a highly sensitive method for small changes in heterogeneous media and has shown significant advantages in laboratory studies in the field of damage growth monitoring [7][8][9][10]. In laboratory experiments, experimental results for monitoring the crack propagation process in materials are influenced by a combination of factors such as external loads [11] and ambient temperature [12].…”

Section: Introductionmentioning

confidence: 99%

“…Numerical simulation experiments have unparalleled advantages over laboratory experiments in terms of variable control. However, the existing numerical simulations of multiple scattering media are still not perfect: the coarse aggregate is not modeled [9] or only the reflection of the aggregate is considered instead of the transmission of the aggregate [13], which does not provide a realistic simulation of the propagation of ultrasonic waves in real media.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Parametric Study of Coda Wave Interferometry Sensitivity to Microcrack Change in a Multiple Scattering Medium

Liu

et al. 2022

Materials

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The expansion of cracks in 3D printing concrete materials may lead to structural failure, so it is essential to monitor crack propagation development. Coda wave interferometry (CWI) has been proven to be sensitive to microcracks, however, the evolution pattern of ultrasonic coda waves during crack growth is still not clear. This paper reports a numerical study of the sensitivity and feasibility of CWI for monitoring microcrack growth in heterogeneous materials. A two-phase concrete model, which contains microcracks with different angles and lengths, was developed using the finite element analysis software ABAQUS. The relative velocity change (Δv/v) and the decorrelation coefficient (Kd) at different crack increments were quantitatively analyzed. The numerical simulation results show that coda waves are sensitive to microcrack length as well as the crack angle. The Δv/v increases linearly with the increase of the length of a single microcrack, and the Kd could be linked to the crack length quadratically. Furthermore, a quantitative functional relationship between the CWI observations (Kd, Δv/v) and the angle of the crack to the source/receiver and the relative length growth of the crack are established. In addition, the nonlinear relationship between slope and angle can be fitted with a sinusoidal function. The reported results quantitatively assess the coda wave variation pattern during crack propagation, which is important for the promotion and application of CWI technology.

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Damage Detection at a Reinforced Concrete Specimen with Coda Wave Interferometry

Cited by 13 publications

References 32 publications

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves

Impact of External Mechanical Loads on Coda Waves in Concrete

Numerical Parametric Study of Coda Wave Interferometry Sensitivity to Microcrack Change in a Multiple Scattering Medium

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