<title>Real-time health monitoring of a scaled-down steel truss bridge by passive-quadrature 3x3 fiber optic Michelson sensors</title>

Abstract

The quadrature phase-shifted 3x3 fiber optic Michelson sensors were tried to monitor the health status of a steel truss bridge which was scaled down to 1/15 of the real bridge for the laboratory experiments. The fiber optic sensors and electrical strain gages were bonded on the surface of some frames to sense the strain pattern induced by the abnormal structural behavior. The fiber optic signals were immediately processed by personal computer for the strain determination. In order to confirm the strain sensitivity of the fiber optic sensors, these fiber optic strains were compared with the strains of the strain gages. The static behavior of the bridge was analyzed by finite element analysis with SAP2000. These finite element analysis results were compared with the structural strain pattern obtained by the electrical strain gages and were arranged with the database for the determination of the bridge health condition. It was shown that the breakage of some frames could be detected from the changes in strain pattern.