Floating structures such as spar platforms are typically designed to be compliant or move with environment loadings, rather than resisting them. Hence they are designed so that there is no dynamic amplification in wave frequency response. However, higher order nonlinear effects are produced in low frequency wind excited regions, especially in Spar platforms. It is difficult to separate the nonlinear behavior of the model response from the loading using conventional methods. In this paper, Empirical Mode Decomposition and Hilbert Transform (EMD/HT) is used to identify the nonlinear response of a spar from the model test results. From the measured response the dynamic parameters are estimated as follows: 1) The multi-component response of the floating structure is decomposed into IMF components. 2) Hilbert transform of the input and the IMF signal in the time domain is done to extract the instantaneous dynamic characteristics. 3) Amplitude and frequency dependent frequency response function is used to represent the result of HT identification. The EMD method can identify any changes in system properties in real time and can be effectively used for repair and retrofit.
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ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering
June 15–20, 2008
Estoril, Portugal
Conference Sponsors:
- Ocean, Offshore and Arctic Engineering Division
ISBN:
978-0-7918-4818-0
PROCEEDINGS PAPER
Non Linear System Identification of Offshore Floating Structures
Nadathur P. Varadarajan,
Nadathur P. Varadarajan
J. Ray McDermott Engineering, LLC, Houston, TX
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Satish Nagarajaiah
Satish Nagarajaiah
Rice University, Houston, TX
Search for other works by this author on:
Nadathur P. Varadarajan
J. Ray McDermott Engineering, LLC, Houston, TX
Satish Nagarajaiah
Rice University, Houston, TX
Paper No:
OMAE2008-57161, pp. 197-204; 8 pages
Published Online:
July 27, 2009
Citation
Varadarajan, NP, & Nagarajaiah, S. "Non Linear System Identification of Offshore Floating Structures." Proceedings of the ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. Volume 1: Offshore Technology. Estoril, Portugal. June 15–20, 2008. pp. 197-204. ASME. https://doi.org/10.1115/OMAE2008-57161
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