Most flyovers in the Dutch road network are now some fifty or sixty years old, which means they are near the end of their design lives. TNO is using specially adapted sensors to find out how long these structures could actually last. The measurement results are input for computational models that work out the structural state, serviceability and remaining operating life at a given traffic load
The traffic load on flyovers has increased throughout the past half century as heavy goods traffic has intensified and commercial vehicles become heavier. Meanwhile, the concrete quality has been suffering from years of weathering and the salt strewn on icy roads. Although there is no cause for alarm, the parties responsible for the ageing flyovers need a clear picture of the actual structural state.
TNO is keeping down the costs of this information by adapting standard sensors for use in monitoring the flyovers. For instance, we assess corrosion in the steel reinforcement of concrete with a modified medical ECG sensor. An airbag sensor normally used in the car industry has been adapted to measure the vibrations in a flyover caused by heavy traffic. TNO also has sensors for tracking the rate of crack growth and sagging.
Our numerical computational models use all the measurements to pronounce an extension to operating life, flag required maintenance, or warn of the need for replacement.