Monitoring of Bridges by a Laser Pointer: Dynamic Measurement of Support Rotations and Elastic Line Displacements: Methodology and First Test

Artese, Serena; Achilli, Vladimiro; Zinno, Raffaele

doi:10.3390/s18020338

Cited by 31 publications

(24 citation statements)

References 36 publications

(33 reference statements)

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“…The high S/N ratio, typical of these devices, strongly influences the results of dynamic tests; (7) Currently, the measurement of deflections by using laser beams is widespread. Some systems for the measurement of deflections and displacements with the use of laser beams are described in [22,23]; (8) An effective methodology for measuring displacements of large structures is offered by Ground-Based Synthetic Aperture Radar (GB-SAR).Used in RAR mode (Real Aperture Radar) it allows measurements of vibration frequency and displacements associated with dynamic loads. In SAR mode (Synthetic Aperture Radar) the instrument is mounted on a slide and allows to obtain the mapping of the area investigated at different times and to get the deflection of each point.…”

Section: Introductionmentioning

confidence: 99%

TLS for Dynamic Measurement of the Elastic Line of Bridges

Artese

Zinno

2020

Applied Sciences

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The evaluation of the structural health of a bridge and the monitoring of its bearing capacity are performed by measuring different parameters. The most important ones are the displacements due to fixed or mobile loads, whose monitoring can be performed using several methods, both conventional and innovative. Terrestrial Laser Scanner (TLS) is effectively used to obtain the displacements of the decks for static loads, while for dynamic measurements, several punctual sensors are in general used. The proposed system uses a TLS, set as a line scanner and positioned under the bridge deck. The TLS acquires a vertical section of the intrados, or a line along a section to be monitored. The instantaneous deviations between the lines detected in dynamic conditions and the reference one acquired with the unloaded bridge, allow to extract the displacements and, consequently, the elastic curve. The synchronization of TLS acquisitions and load location, obtained from a Global Navigation Satellite System GNSS receiver or from a video, is an important feature of the method. Three tests were carried out on as many bridges. The first was performed during the maneuvers of a heavy truck traveling on a bridge characterized by a simply supported metal structure deck. The second concerned a prestressed concrete bridge with cantilever beams. The third concerned the pylon of a cantilever spar cable-stayed bridge during a load test. The results show high precision and confirm the usefulness of this method both for performing dynamic tests and for monitoring bridges.

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Section: Introductionmentioning

confidence: 99%

TLS for Dynamic Measurement of the Elastic Line of Bridges

Artese

Zinno

2020

Applied Sciences

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“…The measurement error of the RCS is 1.4%. Serena Artese et al [10] proposed a bridge monitoring system, which combines camera and laser indicator; the elastic line inclination is measured by analyzing the single frames of an HD video of the laser beam imprint projected on a flat target. The inclination of the elastic line at the support was obtained with a precision of 0.01 mrad.…”

Section: Introductionmentioning

confidence: 99%

An Overall Deformation Monitoring Method of Structure Based on Tracking Deformation Contour

et al. 2019

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Featured Application: This study aims at the lack of sufficient data supporting structural damage identification, which is a general issue in traditional single-point measurement method. A novel method has been proposed for structural deformation monitoring based on digitalized photogrammetry, with improved efficiency and reduced cost. The method can be applied in the overall deformation monitoring of engineering structures, such as bridges. Furthermore, the method can provide a solid foundation for the estimation of structural health state.Abstract: In structural deformation monitoring, traditional methods are mainly based on the deformation data measured at several individual points. As a result, only the discrete deformation, not the overall one, can be obtained, which hinders the researcher from a better and all-round understanding on the structural behavior. At the same time, the surrounding area around the measuring structure is usually complicated, which notably escalates the difficulty in accessing the deformation data. In dealing with the said issues, a digital image-based method is proposed for the overall structural deformation monitoring, utilizing the image perspective transformation and edge detection. Due to the limitation on camera sites, the lens is usually not orthogonal to the measuring structure. As a result, the obtained image cannot be used to extract the deformation data directly. Thus, the perspective transformation algorithm is used to obtain the orthogonal projection image of the test beam under the condition of inclined photography, which enables the direct extraction of deformation data from the original image. Meanwhile, edge detection operators are used to detect the edge of structure's orthogonal projection image, to further characterize the key feature of structural deformation. Using the operator, the complete deformation data of structural edge are obtained by locating and calibrating the edge pixels. Based on the above, a series of load tests has been carried out using a steel-concrete composite beam to validate the proposed method, with the implementation of traditional dial deformation gauges. It has been found that the extracted edge lines have an obvious sawtooth effect due to the illumination environment. The sawtooth effect makes the extracted edge lines slightly fluctuate around the actual contour of the structure. On this end, the fitting method is applied to minimize the fluctuation and obtain the linear approximation of the actual deflection curve. The deformation data obtained by the proposed method have been compared with the one measured by the dial meters, indicating that the measurement error of the proposed method is less than 5%. However, since the overall deformation data are continuously measured by the proposed method, it can better reflect the overall deformation of the structure, and moreover the structural health state, when compared with the traditional "point" measurements.

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“…In the area of structural control and health monitoring of concrete surfaces, different targets are used in the literature, such as pseudo‐speckle patterns, laser pointers, isolated white spots, black and white blocks with random sizes, concentric rings, crosses, or roundel targets . Recently, some studies have been made in which no additional pattern was used on the concrete surface.…”

Section: Introductionmentioning

confidence: 99%

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

Espinosa

Mas

2019

Struct Control Health Monit

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Summary This paper proposes a method to measure the displacement of every point on a concrete surface using its original surface texture and digital image cross‐correlation (DICC). The main advantage is that it does not need to add or attach any particular pattern or target to the surface, contrary to the current methods based in DICC. The method is tested in a concrete probe during loading–unloading cycles under its yield limit, with no cracks appearing in the surface. The total surface of the probe was tessellated in optimal local areas, and DICC with peak refinement was performed on each local area. In order to find the optimal size for that areas, we propose here a method based on the image local entropy. We show that, with natural nonoptimized textures, the proposed technique allows to locally measure the concrete deformation due to small strains (<0.1%) with an error below 50 με. Although results are more inaccurate than those obtained by a strain gauge, our method is able to noninvasively determine the strains in a concrete surface under small loads with reasonable accuracy, thus allowing its use in unreachable or historical structures where no attachment or target painting is possible.

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Monitoring of Bridges by a Laser Pointer: Dynamic Measurement of Support Rotations and Elastic Line Displacements: Methodology and First Test

Cited by 31 publications

References 36 publications

TLS for Dynamic Measurement of the Elastic Line of Bridges

TLS for Dynamic Measurement of the Elastic Line of Bridges

An Overall Deformation Monitoring Method of Structure Based on Tracking Deformation Contour

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

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