Vibration Measurements on a Cable-Stayed Cyclist Arch Bridge for Assessment of the Dynamic Behaviour

Vibration Measurements on a Cable-Stayed Cyclist Arch Bridge for Assessment of the Dynamic Behaviour

Verdenius, S.A.
Bronkhorst, A.J.
Geurts, C.P.W.

2023

The new cable-stayed arch bridge Tegenbosch (Eindhoven, the Netherlands) needed an assessment of its dynamic behaviour under wind loading due to its slender design. Because of wind-induced vibration issues on a number of bridges in the Netherlands with similar designs, it was decided to examine if vortex excitation, wind-rain induced vibration, galloping or parametric excitation might occur. Measurements were performed to determine the natural frequencies and damping ratios of the 32 cables and the deck. All cables were individually assessed, by measuring the vibrations of the cables induced with a step relaxation excitation by pre-tensioning and releasing a lashing strap. The natural frequencies of the cables were determined by evaluating the transfer functions of the measured excitation force and acceleration; damping ratios were obtained with the half-power bandwidth method. To determine the natural frequencies of the deck, 12 accelerometers were placed at different locations on the deck, after which the deck was excited using a 250 kg impact hammer at five locations. The first natural frequency of the cables varied between 2.11 Hz for the longest cable and 8.51 Hz for the shortest cable. The lowest value of the logarithmic decrement for damping found was 0.0059. Based on the damping values, a lowest Scruton number of 58 was determined using NEN-EN 1991-1-4, meaning that vortex excitation will not lead to any problems. Using the measured natural frequencies it is shown that the critical wind velocity for galloping is larger than the occurring wind speed. The same conclusion holds for wind-rain induced vibrations, where the critical velocity is calculated using the natural frequency and the damping value. The lowest horizontal natural frequency of the deck was found to be 0.41 Hz; the lowest vertical natural frequency is 2.05 Hz. Since the natural frequencies of some of the cables coincide with the natural frequencies of the deck, parametric excitation might occur. In case parametric excitation is indeed a problem in practice, it is advised to add extra damping to the system.

Cable-stayed bridge
Damping
Natural frequency
Parametric excitation
Wind-induced vibrations
Buildings and Infrastructures
2015 Urbanisation

http://resolver.tudelft.nl/uuid:ce5f0bf9-569f-4cb3-ab88-281ac324b545

https://doi.org/10.1007/978-3-030-93236-7_12

976747

Springer Science and Business Media Deutschland GmbH

9783030932350

2366-2557

Lecture Notes in Civil Engineering, 9th International Conference on Experimental Vibration Analysis for Civil Engineering Structures, EVACES 2021, 17 September 2021 through 20 September 2021, 125-135

conference paper