CK
Coen Kortendijk
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1
Smart Aggregates and Wave Interferometry in Short-Term Static Load Tests on Zeeland Bridge
Insights from an Ongoing Two-Year Field Lab
The Zeeland Bridge (Zeelandbrug) is a 5 km multi-span prestressed-concrete bridge in the Province of Zeeland, the Netherlands, completed in 1964. To reduce the uncertainties inherent in structural re-assessment, a dedicated two-year field lab has been established, focusing on long-term monitoring and targeted load testing. Within this field lab, four cross-sections across two typical spans have been instrumented with Smart Aggregates (SA) (embedded piezoelectric transducers), Fiber Bragg Grating (FBG) strain sensors, and numerous temperature and humidity sensors. The latter enables compensation for environmental effects. Static load tests were conducted using a 50-tonnes truck at different positions across the spans. Wave Interferometry (WI) was applied to the SA signals to extract wave velocity changes; these changes are potential indicators of microstructural changes or stress redistribution. The preliminary results obtained during the static load tests at different loading conditions revealed changes in wave velocity in the concrete. These findings are compared with local strain measurements from co-located FBG sensors. This enables combined analysis of both wave velocity changes and strains under static loads. The outcomes of this research will not only improve the understanding of the structural behaviour of typical spans of the Zeeland Bridge under static load conditions, but also assess the feasibility of using SAs and WI technology for long-term structural health monitoring of concrete bridges.
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The Zeeland Bridge (Zeelandbrug) is a 5 km multi-span prestressed-concrete bridge in the Province of Zeeland, the Netherlands, completed in 1964. To reduce the uncertainties inherent in structural re-assessment, a dedicated two-year field lab has been established, focusing on long-term monitoring and targeted load testing. Within this field lab, four cross-sections across two typical spans have been instrumented with Smart Aggregates (SA) (embedded piezoelectric transducers), Fiber Bragg Grating (FBG) strain sensors, and numerous temperature and humidity sensors. The latter enables compensation for environmental effects. Static load tests were conducted using a 50-tonnes truck at different positions across the spans. Wave Interferometry (WI) was applied to the SA signals to extract wave velocity changes; these changes are potential indicators of microstructural changes or stress redistribution. The preliminary results obtained during the static load tests at different loading conditions revealed changes in wave velocity in the concrete. These findings are compared with local strain measurements from co-located FBG sensors. This enables combined analysis of both wave velocity changes and strains under static loads. The outcomes of this research will not only improve the understanding of the structural behaviour of typical spans of the Zeeland Bridge under static load conditions, but also assess the feasibility of using SAs and WI technology for long-term structural health monitoring of concrete bridges.
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.
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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.
Characterizing the effect of environmental variability on local vibrations
Experiences on the Haringvlietbrug
When employing vibration-based damage detection methods for monitoring the structural health of bridges, it is often possible to increase damage feature sensitivity by focusing on local as opposed to global vibrations. This heightened sensitivity, however, comes at a cost: by moving towards the higher frequency ranges and more local behavior, the effects of environmental variability become increasingly pronounced. In an attempt to characterize and quantify the effect of specifically temperature variations on the local vibrations, an extensive long-term monitoring campaign was performed on the Haringvlietbrug, a steel box-girder bridge in the Netherlands. Temperatures were measured on various components of the bridge, including the top and bottom of the asphalt layers. It was found that complex temperature gradients are formed especially in situations where the radiation from the sun strikes the bridge at oblique angles. More importantly, the temperature variations in the asphalt layers were found to strongly impact the natural vibration properties of the bridge in the targeted high-frequency ranges. The obtained results provide valuable indications as to the environmental parameters to monitor when designing vibration-based structural health monitoring systems for local damage detection in bridges.
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When employing vibration-based damage detection methods for monitoring the structural health of bridges, it is often possible to increase damage feature sensitivity by focusing on local as opposed to global vibrations. This heightened sensitivity, however, comes at a cost: by moving towards the higher frequency ranges and more local behavior, the effects of environmental variability become increasingly pronounced. In an attempt to characterize and quantify the effect of specifically temperature variations on the local vibrations, an extensive long-term monitoring campaign was performed on the Haringvlietbrug, a steel box-girder bridge in the Netherlands. Temperatures were measured on various components of the bridge, including the top and bottom of the asphalt layers. It was found that complex temperature gradients are formed especially in situations where the radiation from the sun strikes the bridge at oblique angles. More importantly, the temperature variations in the asphalt layers were found to strongly impact the natural vibration properties of the bridge in the targeted high-frequency ranges. The obtained results provide valuable indications as to the environmental parameters to monitor when designing vibration-based structural health monitoring systems for local damage detection in bridges.