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1.
Quasi-distributed long-gauge fiber optic sensor system
Matjaž Linec, Denis Đonlagić, 2009, original scientific article

Abstract: This paper presents a quasi-distributed, long-gauge, sensor system for measurement optical path length variation. This system can be directly applied to long gauge strain and/or temperature sensing. The proposed sensor system is comprised of sensing fiber, which is divided into the sensorćs segments separated by semi reflective mirrors made out of standard optical connectors. Short duration radio-frequency modulated optical bursts are launched into the sensing fiber and phase differences among individual reflected bursts are measured to determine the optical path-length variations among neighboring mirrors. Twenty sensing fiber segments were successfully addressed by a single-signal processor, while relying on standard telecommunication PIN diode, and a Fabry Perot laser diode. The resolution of a fiber-length variation better than 5 ìm was demonstrated in practice. Since the long sections of fiber can be employed for constructing individual sensors within the sensor's array, a microstrain resolution can be achieved in practice. The drift of the sensorćs system can be predominantly attributed to the temperature sensitivity of the electronic components, which proved to be below 20 um/°C. The entire system relies on simple and widely-used components that are low-cost.
Keywords: fiber optic systems, fiber optics sensors, sensing fiber, long-gauge, strain sensing, temperature sensing, optoelectronics
Published: 31.05.2012; Views: 1299; Downloads: 69
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2.
Vertical displacements measuring methods during bridge load tests
Boštjan Kovačič, Ante Marendić, Rok Kamnik, Mikhail Volkov, Vera Roy, 2016, published scientific conference contribution

Abstract: This article introduces the use of the GNSS method for the load testings of bridge structures. We know that there area lot of methods by which you can determine vertical displacement. However, as new bridge constructions are constructed over almost impossible and inaccessible gorges and valleys, the classic measurements method do not allow us to determine vertical displacement so reliably any more or they are very time-consuming. The GNSS method is well known but there are difficulties when determining the altitude component of this method, which is rather questionable. For this purpose, the methods were tested as practical examples in which some difficulties were encountered, so subsequently another test recording was performed of altitude changes using this method.
Keywords: bridges, measurements, strain gauge, load test, deformation, strain, signal processing
Published: 29.08.2016; Views: 618; Downloads: 193
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3.
The different methods of displacement monitoring at loading tests of bridges or different structures
Boštjan Kovačič, Rok Kamnik, Andrii Bieliatynskyi, 2016, published scientific conference contribution

Abstract: By measuring the displacements and deformations at different structures we deal in the Faculty of Civil Engineering, transportation Engineering and Architecture in University of Maribor for about 20 years. At that time we measured over 600 structures. Most loading tests of bridges and Viaducts were made. The measurements of movements needed to be as precise and accurate as possible. To do that laboratory test of instruments were made to see which instrument gives us reliable results. Displacements can be determined by geodetic and physical methods, depends of the construction. The use of geodetic methods are still preferable. In the paper the measurements with the total station, the level and rotation level, photogrammetry and solutions on the field by physical methods with inductive transducers are presented. We need to measure displacements as quick as possible but efficiently because we can not repeat the measurements under the same conditions. Also the surveying on the bridge and in the lab with the comparison of methods is presented under the different hard terrain conditions - water beneath the construction, big height of the structure, unapproachability, large span structures.
Keywords: bridges, measurements, strain gauge, load test, deformation, strain, signal processing
Published: 02.08.2017; Views: 364; Downloads: 155
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