Integrated Structural Monitoring Method of Photogrammetry and Fiber Bragg Grating Sensors With Two Cases Study

This study proposes a novel monitoring method that combines photogrammetry and fiber Bragg grating (FBG) sensors, which provide overall shape measurement and high-precision strain sensing, respectively. A system was built and tested on a cantilever structure and a gantry crane model; it used two industrial cameras and six or 11 FBG sensors pasted along the beam. Formulas are derived and finite-element simulations of beam strain are presented, along with theoretical derivations of the relationship between image-point displacement (IPD) and 3-D spatial displacement. A series of monitoring experiments were conducted, combining FBG sensing and photogrammetry to monitor the beam under various loads. The strain and deflection curves of the beam based on FBG sensors and photogrammetry were obtained and compared. The bendings measured by photogrammetry were consistent with the strains measured by FBG sensors. To describe the relationship between the beam’s displacements at the marked points monitored by photometry and local strains, an H matrix is proposed. The proposed system allows real-time and long-term monitoring of critical structures, thereby increasing their safety.