Distributed Operational Modal Analysis of Multispan Bridges

A method is presented for estimating the mode shapes of multispan structures based on the distributed optical fiber strain sensors. The dynamic mode decomposition method was employed to decompose the spatial–temporal strain data into strain modes. The approach was developed and verified through laboratory experiments on a three-span 15-m-long steel beam, field tests on a five-span bridge, and numerical modeling based on the finite-element analysis of the bridge. A Brillouin-based distributed optical fiber sensor system was utilized in laboratory and field settings. In addition, conventional piezoelectric-based accelerometers were employed to compare with the modal parameter estimations based on the distributed strains. The bridge’s first three flexural vibration modes were extracted by using the introduced methodology. Further testing and analysis are necessary to evaluate its feasibility across different bridge designs, such as single-span, cable-stayed, arch, and suspension bridges.