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title

DAMAGE DETECTION IN JOINTS LOCATION OF OFFSHORE JACKET PLATFORMS

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Year: 2018
COI code: ICOPMAS13_108
Paper Language: English

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Authors DAMAGE DETECTION IN JOINTS LOCATION OF OFFSHORE JACKET PLATFORMS

  Amin Rahimzadeh - Faculty of Civil Engineering, Sahand University of Technology, Tabriz, Iran
  Ahmad Reza Mustafa Gharabaghi - Faculty of Civil Engineering, Sahand University of Technology, Tabriz, Iran
  Mohammad Reza Chenaghlou - Faculty of Civil Engineering, Sahand University of Technology, Tabriz, Iran

Abstract:

The fixed offshore jacket platforms are always at exposure of the sever environment condition of sea. Because of the high importance of these structures, earlydetection of damages, when they are minor, and their repair can prevent from further serious dangers. According to a report from the damages caused to the jacket platformsin the NFS1 from 1974 to 2016, mostly damages are of crack type at the joints [1]. The purpose of the paper is to detect damages in jacket platforms with respect to minordamages at the joints. Among different methods of damage detection, signal processing methods have better performance in health monitoring of complex structureswith nonlinear behavior. By studying the researches of Kim and Melhem, Byissa et al., Rakowski, Zhu and Huang et al. [2-6], it is found that the wavelet transform methodhas a high ability to detect minor damages. In this paper, the wavelet packet transform is used to extract the wavelet packet energy rate to damage detection at the joints.However, these detects have errors. Therefore, a target function formulated based on the wavelet packet energy rate index (WPERI). Then, the LSE2 optimizationoptimizes target function to obtain a new index (WPTLSE) to reduce the errors and improve the results. 2. Modeling and Verification For modeling, the SPD16 platform of the South Pars Gas Field Development Phase 12 in the Persian Gulf was simulated in Abaqus. According to Figure 1, for substructure modeling, the Wire element based on thecross section characteristics, and for deck modeling, Shell element based on its loading characteristics is used. For the pile-soil interaction the equivalent length of pile with fixitypoint at the end was used. Water effect is considered as an added mass and hydrodynamic damping. To verify the structure modeling, the natural frequencies of the first three modes were compared to the original designed structure frequency that has acceptable difference below 8%. 3. Identification Method The principles of damage detection methods are oftenbased on the comparison of a structural system in two different states (damaged and undamaged). Accordingly, structure signals must be available in the two phases, andthen processed. Wavelet packet transform is one of the signal processing approaches provides level by level decomposition of signal. However, processed signalproperties should be extracted to be comparable in two different states. Wavelet packet energy, Ef, at the level j of signal decomposition is the extracted property calculatedaccording to the following equation

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COI code: ICOPMAS13_108

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Rahimzadeh, Amin; Ahmad Reza Mustafa Gharabaghi & Mohammad Reza Chenaghlou, 2018, DAMAGE DETECTION IN JOINTS LOCATION OF OFFSHORE JACKET PLATFORMS, 13th International Conference on Coasts, Ports and Marine Structures, تهران, سازمان بنادر و دريانوردي, https://www.civilica.com/Paper-ICOPMAS13-ICOPMAS13_108.htmlInside the text, wherever referred to or an achievement of this article is mentioned, after mentioning the article, inside the parental, the following specifications are written.
First Time: (Rahimzadeh, Amin; Ahmad Reza Mustafa Gharabaghi & Mohammad Reza Chenaghlou, 2018)
Second and more: (Rahimzadeh; Mustafa Gharabaghi & Chenaghlou, 2018)
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Paper No.: 3496
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