Actual bridge verification of monitoring technique using optical fiber sensors

Japan’s Metropolitan Expressway is an expressway network linking major cities around the capital, Tokyo. In legally-mandated inspections once each 5 years, the need to construct scaffolds and individual differences between inspectors were issues in close visual inspections of RC decks. The authors investigated a method for evaluating the deterioration of deck slabs by monitoring with optical fiber sensors (length: 1000 mm). To understand the relationship between actions and responses, the strain in RC deck slabs was monitored using 245 kN and 118 kN constant load vehicles. The strain on the underside of RC deck slabs with a crack density of 9.8 m/m² was 37 μ under the action of 245 kN and 19 μ under 118 kN. In a laboratory test under live loads similar to those in actual bridges, the strain immediately before punching shear failure was 500 μ or more, indicating that failure is not urgent at present.