An excessive deformation of railway tracks can cause malfunctioning of railway system, which manifests itself either through decreased train speed or through temporary closing the traffic.
Both effects involve economic costs. Moreover, if the excessive deformation of rails is not detectable in time, the consequences can be very serious, not only from economic point of view, but also from the point of view of passengers’ safety. Long-term monitoring of the tracks offers solutions for an early detection of excessive deformation and therefore, allows an in time planning of maintenance actions necessary to ensure safety and decrease the economical losses. In order to monitor the structural behavior of the railway tracks of high speed train in Taiwan, fiber optic technology based monitoring systems SOFO® and DiTeSt® are proposed. The standard sensors are easy and fast to install, but they require an additional protection, notably if exposed to direct sunrays, wind, rodents and vandalism. Good and safe protection can involve slowdown of installation, increase of costs and increase of size of the installation. Therefore, a new packaging for the sensor is being developed. This packaging is designed to allow fast and easy installation, but also to insure good and durable protection of the sensor over long terms, even in aggressive environments. The new packaging consist in the integration of the optical fibers into a glass-fibers reinforced thermoplastic composite profile or tape, which guarantees safe and easy installation and good long term protection of the sensor. Prototypes of the tape were tested first in the laboratory and than on-site. The sensing tape is called SMARTape and can be used with both systems (SOFO and DiTeSt). All the deformation sensors (SMARTapes and Standard SOFO Sensor) are installed by gluing, using the Araldite glue. The thermocouples were only simply fastened using the self-gluing tape (scotch). The one-meter long Standard SOFO Sensor was installed using the L-brackets. First the rust was cleaned, than the glue was applied and the L-bracket bonded to the rail. The same procedure was repeated for both L-brackets. When the glue had set, the sensor was installed. In case of the SMARTape, a special procedure was developed. As in case of the L-brackets, first the rail was cleaned. The SMARTape was first glued to the scotch tape, and then the layer of araldite was applied on it. Afterwards, both the SMARTape and the scotch tape were glued to the rails. The scotch tape was not necessary after the setting of the glue, but it was however kept, since it protected the SMARTape from direct exposure. The loading of the rail was performed using an empty wagon (W=19 tons). The wheel of the wagon was placed approximately in the middle of the sensors. The static measurements were performed once before the load was applied (zero measurement), once during the loading and once after the load was removed. The full loading test was repeated two times, in two successive days.
Aim of monitoring:
The on-site test was performed with the following aims:
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To test applicability of Standard SOFO Sensor onto the rails in real conditions
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To test applicability of SMARTape onto the rails in real conditions.
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To test the sensing performances of SMARTape
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.To compare two sensors (Standard SOFO Sensor and SMARTape)
Main results:
Thanks At the present stage static test is perfomed. The following conclusisons are carried out: ·The Standard SOFO Sensor can successfully be used for rail monitoring. The issue of the sensor protection in long-term was not considered by the tests. ·The SMARTape can successfully be used for rail monitoring. The measurements collected using the SMARTape are comparable with those collected by Standard Sensor, proving excellent resolution and transfer of strain from the rail to the sensor. ·Due to small dimensions of the cross-section and due to material combination (fiber-reinforced thermoplastic composite tape) the protection of the SMARTape in long term is not an issue. ·A curvature of 8.14×10-4 m-1 (bending radius of 1228.5 m) was successfully measured. Long term peformance testing of SMARTape continues. The quality of interaction between the rail and the SMARTape is regularly controlled. The SMARTapes will remain installed onto the rail for the purposes of their long-term testing and characterization.
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INSTALLATION PERIOD |
TYPE OF SENSORS |
NUMBER OF SENSORS |
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2002 |
SOFO |
3 |
Global view to the test from the inner side of rails
Configuration of sensors in rail cross-section
Global view to the system (SMARTapes, Standard SOFO Sensor, Thermocouples, Connection Box, Extension Cables and Central Measurement Point (CMP).
Strain diagrams before, during and after loading for the first test
Global view to the test from the inner side of rails
Configuration of sensors in rail cross-section
Global view to the system (SMARTapes, Standard SOFO Sensor, Thermocouples, Connection Box, Extension Cables and Central Measurement Point (CMP).
Strain diagrams before, during and after loading for the first test
