Pedestrian bridge Jan Linzelviaduct – Tuned Mass Dampers for Pedestrian Vibration
The Cycling and Pedestrian bridge Jan LinzelViaduct in the Netherlands has a length of 345 meters and crosses over the highway A4. The bridge is a multi-span bridge, with the longest span being 85 meters.
To prevent unallowable vibrations by pedestrians, Flow Engineering designed a cascade of Tuned Mass Dampers installed throughout the length of the bridge. The first and second modes of vibrations needed to be damped, which are primarily present at the span over the highway. The fourth mode also needed additional damping, which was located at the smaller span at the other side of the bridge.
A video about the result of the Tuned Mass Damper can be seen here.
The Tuned Mass Dampers (TMDs) installed on the Jan Linzelviaduct on May 26, 2020, significantly improved the bridge’s dynamic stability, effectively reducing vibrations caused by dynamic loads by pedestrian traffic.
The project’s initial phase involved modal analyses by ABT to establish fundamental vibration modes and assess pedestrian loadings. Flow Engineering subsequently calculated the optimal size of the TMDs, ensuring their suitability for the bridge.
Before installation, precise measurements of the bridge’s frequencies and damping characteristics provided crucial insights into its dynamic behaviour. The preliminary measurement facilitated the optimal tuning of the TMDs at the workshop, thereby maximizing their performance. Additionally, the favourable measured higher material damping enabled a reduction in the number of required TMDs.
Post-installation measurements conducted on May 28, 2020, verified the anticipated effectiveness of the TMDs. Modes 1, 2, and 4 notably exhibited increased damping due to the additional damping provided by the TMDs. It has to be noted that during the measurement without the TMD, the load was stopped before reaching its maximal amplitude to prevent large vibrations of the bridge. It has been established that without damper systems, the second mode of vibration would vibrate up to 120 mm under high pedestrian loads, and now has been limited to a mere 18 mm under worst-case conditions.
This successful implementation and verified performance demonstrate the efficacy of these TMDs in enhancing the Jan Linzelviaduct’s dynamic stability, underscoring the success of this engineering endeavor.
