Monitoring the Concrete Slab Bridge on Balladelaan in the Netherlands using Embedded Ultrasonic Sensors

The concrete slab bridge on Balladelaan in the Netherlands was built in 1946. It is a cast-in-place concrete bridge with five spans that together form a statically indeterminate deck system. For this type of concrete bridge, shear failure often appears to be the critical failure mechanism, raising concerns about the structural capacity and remaining service life of the bridge. Additionally, the bridge has undergone several undocumented modifications over its lifetime, making it difficult to accurately assess its safety. To monitor this bridge and predict its structural capacity, 22 ultrasonic sensors, known as Smart Aggregates (SAs), and 16 temperature sensors were embedded in the bridge by drilling holes to track changes such as crack development, stress variations, and temperature fluctuations. This paper presents the initial phase measurements from the SAs and temperature sensors in the monitoring project. The main goals of this phase are (1) to ensure that the installed sensors function properly and (2) to establish a preliminary correlation between the measurements from the SAs and the temperature sensors.