A Low-Cost Fbg Vertical Displacement Sensor for Health Monitoring of Medium-Small Span Bridges

Abstract

A low-cost fiber Bragg grating (FBG) vertical displacement sensor was developed for medium-small bridges with a large number and limited maintenance costs. Firstly, the calibration and temperature correction of the sensor was carried out. Secondly, the influences of the fixed angle and sag effect of the sensor on measuring results were investigated. Finally, the sensor was installed in an in-service hollow slab bridge and the static and dynamic load tests were carried out. Results showed the fixed angle of this sensor was recommended to choose in the range of 15°-30° in order to obtain higher measurement accuracy; when θ = 15° and the radius of the external wire was 0.3 mm, the limit of the external wire length can be set to 19.5 m ; the sensor is feasible in vertical displacement measurement of in-service medium-small span bridge, and the relative measuring errors in field experiments were less than 5%.

Keywords: Medium-small bridge, vertical displacement, real-time monitoring, environmental temperature, fixed angle, sag effect