Deflections and Natural Frequencies as Parameters for Structural Health Monitoring

Abstract

The Dutch road infrastructure contains a large number of concrete bridges and viaducts. Malfunction of these bridges and viaducts has large financial consequences. To avoid malfunctions of bridges, bridges need to be inspected frequently and actions should be taken when required. The reliability of the inspections of the health of a bridge could be increased by monitoring the deflections and/or the vibrations of the bridge. The main idea of a Structural Health Monitoring system is that degradation of a bridge results in detectable changes in the deflections and in the modal properties of the bridge.
The results of data-driven modal calculations of an existing concrete bridge have been compared with the results of Finite Element modal calculations of this bridge to investigate whether this comparison can be used to predict damage in the bridge. The effect of fatigue and localized corrosion damage on the deflections of a Reinforced Concrete beam was investigated by laboratory tests. The effect of fatigue and localized corrosion damage on the deflections and on the first natural frequency of a Reinforced Concrete beam was predicted by Finite Element calculations and probabilistic calculations. It was concluded from the tests and from the calculations that deflections and natural frequencies cannot be used as indicator for fatigue damage in concrete bridges.