A method to measure small local strains in concrete surfaces using its natural texture and image cross‐correlation

Espinosa, Julián; Mas, David

doi:10.1002/stc.2410

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…In order to have some information regarding the rigid body sample movement, a second camera could be used to record images in which, at least, two sample sides be inside of the image. With a whole view, the technique applied in [8] could be used also here to obtain a full description of the rock behavior.…”

Section: Discussionmentioning

confidence: 99%

“…Figure 6 shows a flow chart with the main steps used to find the movement. The procedure is fully described in [8].…”

Section: Image Processingmentioning

confidence: 99%

“…This possibility basically relies on the imaging system and its configuration, since rock surface could have a pseudospeckle-like texture similar to speckle depending only on the magnification and the type of material. This hypothesis was tested in [8], where a DIC measurement of a concrete test specimen under loading-unloading cycles below its yield limit was done using only the concrete surface texture.…”

Section: Introductionmentioning

confidence: 99%

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Use of image correlation to measure hygric swelling in rocks

Tomás

Benavente

Mas

2020

Optics, Photonics and Digital Technologies for Imaging Applications VI

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Some materials undergo an hygric expansion when they are soaked. In porous rocks, this effect is enhanced by the pore space that allows the water to reach every part of its volume and to hydrate the most of their swelling parts. This enlargement has negative structural consequences in the vicinity since adjacent elements will support some compressions or displacements. Recently image-based methods have arisen in this field due to their advantages versus traditional methods. Among all image processing methods, digital image correlation (DIC) is one of the most used in all areas. In this work, we propose a new methodology based on DIC for the calculation of the hygric expansion of materials. We use porous sandstone, with dimensions 14x14x30 mm to measure its hygric swelling using an industrial digital camera and a telecentric objective. We took one image every 5 minutes to characterize the whole swelling process. Due the large magnification, the whole 14 mm length of one contour was not in the image and therefore we lost the image scale reference. To solve this, a 1951 USAF test was used to calibrate the imagen. The telecentric objective and a narrow deep of field allowed to have the specimen surface exactly on the same plane that the USAF test was during the calibration. The image was pointed to one corner of the specimen, to obtain information not only of its vertical displacement due to its expansion but also of its horizontal movement. Preliminary results show that the proposed methodology provides reliable information of the hygric swelling using a non-contact methodology, with an accuracy of 1 micron.

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Section: Discussionmentioning

confidence: 99%

“…Figure 6 shows a flow chart with the main steps used to find the movement. The procedure is fully described in [8].…”

Section: Image Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use of image correlation to measure hygric swelling in rocks

Tomás

Benavente

Mas

2020

Optics, Photonics and Digital Technologies for Imaging Applications VI

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“…Akbar et al [29] carried out laboratory tests to validate the performance of a UAV‐based system with an image‐stitching approach for the purpose of SHM. Ferrer et al [30] measured the full field displacement of a concrete surface by surface texture and digital image correlation.…”

Section: Introductionmentioning

confidence: 99%

Computer vision‐based monitoring of the 3‐D structural deformation of an ancient structure induced by shield tunneling construction

Jin

Ang

et al. 2021

Struct Control Health Monit

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Summary Shield tunneling is an efficient method of the tunnel construction for the system of underground transportation, but it will disturb the surrounding soil and affect the security of nearby structures. The monitoring for deformation of the structures influenced by the tunneling construction is crucial for structural safety evaluation, especially for the ancient structures. The computer vision‐based structural deformation monitoring approach is a newly developed method that has advantages such as, long‐distance, noncontact, and so on, which provides a promising tool for deformation monitoring of ancient structures. This study applied a computer vision‐based method for field monitoring of three‐dimensional (3‐D) deformation of an ancient tower under the influence of shield tunneling. The target‐free strategy was adopted to eliminate the need for installation of artificial makers on the surface of the tower. The environmental factors during the long‐term monitoring were discussed, especially the influence of temperature variation. Background modification was employed to reduce the error induced by the microchange of camera position. The long‐term 3‐D deformations of the ancient tower including vertical settlement and horizontal deformation in two directions during the shield tunneling construction were obtained. The results indicate that the proposed computer vision‐based method offers an efficient and cost‐effective approach to monitor the 3‐D deformation of the ancient structure and further for structural safety evaluation.

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“…Briefly, the technique consists of interpolating the correlation function over a local area around the maximum peak and then refining the search by fitting the peak neighborhood to an analytical function [ 8 ]. This procedure may increase peak location accuracy by almost two orders of magnitude [ 10 , 11 ]. Despite the evident improvement, the procedure also introduces a bias error, which limits its performance.…”

Section: Introductionmentioning

confidence: 99%

Influence of Neighborhood Size and Cross-Correlation Peak-Fitting Method on Location Accuracy

Tomás

Mas

2020

Sensors

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A known technique to obtain subpixel resolution by using object tracking through cross-correlation consists of interpolating the obtained correlation function and then refining peak location. Although the technique provides accurate results, peak location is usually biased toward the closest integer coordinate. This effect is known as the peak-locking error and it strongly limits this calculation technique’s experimental accuracy. This error may differ depending on the scene and algorithm used to fit and interpolate the correlation peak, but in general, it may be attributed to a sampling problem and the presence of aliasing. Many studies in the literature analyze this effect in the Fourier domain. Here, we propose an alternative analysis on the spatial domain. According to our interpretation, the peak-locking error may be produced by a non-symmetrical sample distribution, thus provoking a bias in the result. According to this, the peak interpolant function, the size of the local domain and low-pass filters play a relevant role in diminishing the error. Our study explores these effects on different samples taken from the DIC Challenge database, and the results show that, in general, peak fitting with a Gaussian function on a relatively large domain provides the most accurate results.

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A method to measure small local strains in concrete surfaces using its natural texture and image cross‐correlation

Cited by 6 publications

References 17 publications

Use of image correlation to measure hygric swelling in rocks

Use of image correlation to measure hygric swelling in rocks

Computer vision‐based monitoring of the 3‐D structural deformation of an ancient structure induced by shield tunneling construction

Influence of Neighborhood Size and Cross-Correlation Peak-Fitting Method on Location Accuracy

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