Measurement in Wind Tunnel
In connection with the huge Danish project construction of a combined bridge and tunnel between the two islands Zealand and Funen (app. 18 km), the Danish Maritime Institute got the assignment to investigate wind properties of the world’s longest free span, 1624 m, of the suspension bridge across the eastern part of the Great Belt. This investigation aimed to understand how wind loads would affect the bridge’s structural integrity and performance. The research involved extensive measurements in a wind tunnel, where various models of the bridge were subjected to controlled wind conditions. By analyzing the aerodynamic characteristics, engineers sought to optimize the design to ensure stability and safety, especially during storm events. The results of these wind tunnel tests were crucial for informing the final design specifications and construction methods that would ultimately protect the bridge from extreme weather conditions.
A model of the suspension part of the bridge was built in scale 1:200. The bridge deck of the model is very light, and it is therefore of great importance that the movements of the bridge caused by various influence from the wind can be measured without touching the bridge and as far as possible also without disturbing the wind flow around the bridge.
By using ODS sensors, these wishes became fulfilled. Ten small targets were mounted on the deck of the bridge and 10 sensors were mounted to measure the movements of the targets. The targets were selected as small as possible, but due to the fact that the bridge can move up to 30 mm when exposed to an exaggerated high wind velocity, they could not be made smaller that app. 55 x 20 mm. Nevertheless, the influence from the targets is negligible. The movements of the bridge were measured with an excellent resolution of 0.02 mm without any kind of contact to the model. In order not to disturb the wind flow, the sensors have been made more streamlined by means of foam and wing shaped plastic profiles. The data collected from the ODS sensors provided valuable insights into the dynamic behavior of the bridge under varying wind conditions. Each target’s movement was recorded and analyzed to create detailed models of the stress and strain experienced by the bridge structure. This information is crucial for engineering assessments, helping to inform design modifications and ensure the bridge’s stability and safety in real-world conditions. The success of this measurement technique not only demonstrated the effectiveness of the chosen sensors but also set a precedent for future studies involving fluid dynamics and structural
The comprehensive test program performed on the model of the bridge verified into very small details all calculations made during the construction phase.
