Distributed optical fiber sensors for deflection measurement of structure

摘要

This paper presents applications of fiber Bragg grating(FBG)sensors on the deflection measurement of structure.In the first application type,there are 18 FBG sensors were installed on some girders of a degraded RC bridge in north Taiwan to monitor the long-term variations of strain.Curvature of each cross section can be calculated from the strain data measured by two optical fiber sensors installed at this section.The deflection of a girder can be calculated by integrating the curvature distribution equation.Similar method is also used to monitor the vertical and horizontal deflections of a 200 m railway track by 123 FBG sensors.The second application type is to use optical slope-deflection meter that was built by a series of bending gauges with FBG sensors inside to measure the dynamic defection curve of structure.Applications of measuring the deflection curve of a PC bridge deck under loading test and the dynamic deflection curves of two string lines on a PC box girder under the action of high speed train are presented.From each set of 4 neighboring points on these two deflection curves of a deck,a cant value induced by transverse rotation of the bridge can be calculated.