Experimental Investigation of High Precision Bidirectional FBG Displacement Sensor for Structural Health Monitoring

In practical engineering applications, structural deformations generate displacement variations that are not simple unidirectional tension or compression, but rather complex bidirectional movements with cyclic and randomly distributed characteristics. Traditional unidirectional displacement sensors cannot effectively measure such bidirectional displacement patterns. To address this issue, this paper proposes a novel double-cantilever sensitivity-enhanced uniform-strength beam (SESM) sensing structure. The opto-mechanical displacement governing equation for the sensitized beam was derived, and a high-precision bidirectional fiber Bragg grating (FBG) displacement sensor was developed. Calibration tests and static performance analysis demonstrate that the sensor is characterized by a high sensitivity of 63.446[Formula: see text]pm/mm and an accuracy of 1.676%, with a wide bidirectional measurement range of [Formula: see text][Formula: see text]mm, respectively, showing significant advantages compared to similar commercial displacement sensors. Furthermore, when applied in pseudo-static tests of a two-story steel frame structure, the FBG displacement sensor exhibited excellent monitoring performance through comparison with conventional displacement sensors, thereby verifying its practical applicability in field measurements.