The present thesis work studies the parametrically excited vibrations on bridge stay cables when the natural frequency of the bridge tower is half of the resonance frequency of the cable. This condition is found at the longest stay cables of the resund Bridge. Experimental and numerical analysis is carried out based on a simplified scaled model (1:200) of this bridge, replacing the cables by strings made of steel. When parametrically excited vibrations are studied, certain relations between resonance frequencies of bridge tower and cable lead to high vibration levels. The most critical relation is when the tower frequency is double the cable frequency. The case studied here, where the tower frequency is half of the cable frequency, shows to be less severe.
Contents
1. Notations
2. Introduction
2.1 Background
3. Theoretical Fundamentals
3.1 Dynamics of the transverse vibration of a Taut String
3.2 Dynamics of the Lumped Mass Systems
3.3 Modal Analysis and Extraction of the Modal Parameters
3.4 Parametrically Excited Vibrations
4. Modeling a Stay Cable
4.1 A Stay Cable with one anchorage free to move
4.2 A Stay Cable interacting with the tower/deck of the bridge
4.3 A Stay Cable supported by a Cantilever Beam
5. Methodology
5.1 The Øresund Bridge
5.2 A Scaled Model of the Bridge
5.3 Experimental Setup
5.4 Characterization of the Pylon and String
5.5 Response of the system under Sinusoidal Excitation
6. Result
6.1 Characterization of the Pylon and String
6.2 Response of the system under Sinusoidal Excitation
7. Discussion and Comparison of Results
7.1 Characterization of the Pylon and String
7.2 Response of the system under Sinusoidal Excitation
7.3 The effect of the ratio Pylon Resonance-String Resonance
8. Conclusions and Recommendations
9. References
Author: Armando Enrique León Guarena
Source: Blekinge Institute of Technology
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