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Experimental damping assessment of full scale offshore Mono Bucket foundation

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Szymon Gres

Abstract

Fatigue loads induced by the wind and waves are usually the drivers for the design of modern offshore structures. The magnitude of the fatigue load is dependent on the site-specific environmental conditions and the dynamic properties of the system, i.e. damping ratios. In order to provide a cost-optimized design and accurately assess the fatigue lifetime of the structure, a proper description of the damping contribution from the foundation is required. This paper quantifies the system damping of a offshore meteorological mast supported by a Mono Bucket foundation based on a long-term experimental campaign. The structure is located at Dogger Bank west, North Sea, and equipped with a measurement system monitoring acceleration , strain, inclination and sea surface elevation. Natural frequencies and corresponding damping ratios are assessed using different operational modal analysis techniques, enhanced frequency domain decomposition and stochastic subspace identification. Application and results from both methods are compared and discussed. Research shows that the total damping ratio of the lowest eigenmode is normally distributed with mean value of 1.11% of critical damping. Linear correlation between the damping ratio and the significant wave height is observed.
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Dates and versions

hal-02422704 , version 1 (22-12-2019)

Identifiers

  • HAL Id : hal-02422704 , version 1

Cite

Szymon Gres, M Fejerskov, L B Ibsen, L Damkilde. Experimental damping assessment of full scale offshore Mono Bucket foundation. ISMA - The International Conference on Noise and Vibration Engineering, Sep 2016, Leuven, Belgium. ⟨hal-02422704⟩
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