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Thanks to the capabilities of distributed fibre optic sensors (DFOS), a significant increase in their applications within civil and geotechnical engineering has been observed during the last few years. In contrast to conventional spot gauges, the main advantage of this technology is direct damage detection, as the information is gained over the entire measurement path. This diagnostic solution is especially suitable for safety-critical infrastructure, including bridges. However, to utilise the benefits of the DFOS approach, appropriate interrogators, sensors, and installation methods must be adopted. The article briefly discusses possible solutions available on the market, indicating their specific advantages and limitations. Then, several practical case studies related to bridge monitoring in Poland are presented. The review shows various possible applications, from long measurement sections over entire spans to small-size structural components. Some are truly new and pioneer solutions, solving different technical problems in bridge engineering. Presented applications supported by in situ data proved the possible high-quality performance of DFOS-based systems for measurements of concrete, steel and composite bridges in actual operating conditions. [ABSTRACT FROM AUTHOR]

Kościuszko Mound in Cracow is earthen structure particularly susceptible to deformations, among other things, due to the unfavourable physical and mechanical properties of the ground and a significant tilt of slopes. Since the beginning of its existence to the present day, structural failures were repeatedly occurred, and the biggest took place after 1997, when heavy rains led to the greatest destruction of the entire mound solid ever. Overall renovation, however, did not produced the expected results and did not stop negative atmospheric influences on the monument behaviour. Therefore, in 2012, structural health mo nitoring was installed on-site, providing remote, continuous and automatic measurements of selected physical quantities, which are important from mound technical condition point of view. System is measuring, among other things, changes in vertical displacements, circumferential and radial deformations, ground pore pressure of water within a mound body and humidity of its surface layers. Correlation of results from geodetic, inclinometer and meteorological (derived from the weather station which is part of the monitoring system) measurements will enable a comprehensive assessment of ground layer work mechanisms within the whole mound solid and will be one of the bases for effective strengthening design in the future.

This article presents laboratory tests, with the purpose being to verify the suitability of standard optical fibres in a tight jacket for advanced strain analysis within concrete members. An optical reflectometer was used to enable the optical signal to be processed on the basis of the Rayleigh scattering phenomenon, so that strains and/or temperature changes were determined along the length of the measuring fibre. The measurements were carried out continuously in a geometrical sense (distributed measurements), with a spatial resolution starting from as fine as 5 mm. The arrangement of optical fibres inside the heterogeneous concrete medium and on its surface allowed for the identification and detailed analysis of local phenomena such as cracks. Remote and early location of structural damage with an estimation of its scale provides new opportunities for the monitoring of the structural health of reinforced concrete structures, facilitating the interpretation of its behaviour as well as failure risk management based on comprehensive and reliable measurement data. If traditional spot techniques are used, this approach is not possible. The aim of the initial studies was to analyse the strain distributions over compressed and tensioned measurement sections located on the surface of a cylindrical specimen of concrete. In the tests which followed, the reinforced concrete rod was eccentrically tensioned with fibre optics installed inside. Qualitative and quantitative verification of crack widths was made, with a narrow range up to 0.05 mm and a wider one to 0.30 mm. The results of the studies show very good accuracy of optical fibre sensor technology as a reference technique during the analysis of microcracks and narrow cracks, and moderate accuracy in the case of wider cracks. Despite using optical fibres in a tight jacket which mediates in strain transfer, the results obtained can be very suitable for the assessment of the structural condition of the member under consideration. It is also worth noting that the tests conducted indicate the effectiveness of distributed optical fibre technology for the analysis of concrete homogeneity and its structural behaviour within compressed areas, as it is possible to calculate strains over measuring bases that start from lengths as short as 5 mm. [ABSTRACT FROM AUTHOR]

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The creep of concrete is a phenomenon that is often the cause of excessive deformation of the structure in serviceability limit state. In fact, creep strains are generally larger than elastic strains which occur on the application of load. Creep is affected by many factors both internal - related to the properties of specific concrete and external - related to the operating environment. In addition, attention should be paid to the fact that in real structures concrete almost always interacts with the reinforcement. This article examines the rheological phenomena that occur in the reinforced concrete cross-section of the Rędziński Bridge pylon in Wrocław, using in situ measurements from an automated structural health monitoring system. [ABSTRACT FROM AUTHOR]

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Technical Transactions / Czasopismo Techniczne is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)