Abstract
In recent years, the field of structure monitoring has been making increasing use of systems based on fiber-optic technologies. Fiber-optic technology offers many advantages, including higher quality measurements, greater reliability, easier installation and maintenance, insensitivity to the environment (mainly to the electromagnetic field), corrosion resistance, safety in explosive and flammable environments, the possibility of long-term monitoring and lower cost per lifetime. We have used SOFO fibre-optic strain gauges to perform measurements to check the overall relative deformation of a real reinforced concrete structure. Long-term monitoring of the structure revealed that the measurement readings obtained from these fibre-optic strain gauges differed from each other. Greater attention was therefore paid to the calibration of the fibre-optic strain gauges, and to determining their measurement accuracy. The experimental results show that it is necessary to calibrate SOFO strain gauges before they are used, and to determine their calibration constant.
Highlights
During the lifespan of building structures, changes take place in the volume of the structure due to the effects of external loads from the surrounding environment
The displacements as a function of time obtained from the inclinometer, ∆LH, were plotted against the displacements obtained from the SOFO fibre-optic strain gauge, ∆LSOFO, for the repeated measurements of ±0.5 mm displacement in 0.1 mm steps for each initial stress length
The values obtained in the calibration of six fibre-optic strain gauges of varying active lengths (0.5 m, 1 m and 2 m) have been plotted as graphs depicting the spread of calibration constants together with a 95 % reliability interval as a function of the initial stress length — see Figures 6 to 8
Summary
During the lifespan of building structures, changes take place in the volume of the structure due to the effects of external loads from the surrounding environment. This enables deformations in the structure to be monitored right from the concrete casting operation Other advantages of these sensors are their higher quality, reliability and measurement accuracy, easier installation and maintenance, electromagnetic resistance, resistance against corrosion, and the opportunity to carry out long-term monitoring of the structure. Strain gauges of this type can be used for monitoring the behaviour of a whole range of building structures, e.g. bridges, tunnels, dams, power stations, buildings, piping systems, interactions between old and new concrete, etc. Greater attention was paid to the calibration of these fibre-optic strain gauges, and to determining their measurement accuracy
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