Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

Golafshani, Ali Akbar; Ebrahimian, Hossein; Bagheri, Vahid; Holmås, Tore

doi:10.1016/j.jcsr.2011.01.005

Cited by 31 publications

(8 citation statements)

References 18 publications

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“…The conventional run of pushover analysis only considers the 100-year design crest height for the ultimate collapse. However, when the RSR is higher, the wave height will also become higher [38]. However, no comprehensive study is carried out as to the effects of the wave-in-deck load, which are excluded during the RSR determination [38] as shown in Figure 3a.…”

Section: Wave-in-deck Load and Reserve Strength Ratiomentioning

confidence: 99%

“…However, most of the collapse wave height was higher than the platform deck, and this led to the wave-in-deck scenario. Based on Golafshani et al [38], the wave-in-deck load was ignored during the determination of RSR in the pushover analysis. In the conventional pushover analysis using USFOS software, the 100-year return period environmental load is incremented until the platform is collapsed and generate the ultimate resistance of the jacket.…”

Section: Introductionmentioning

confidence: 99%

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Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Azman¹,

Husain²,

Zaki³

et al. 2021

JMSE

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The structural integrity of offshore platforms is affected by degradation issues such as subsidence. Subsidence involves large settlement areas, and it is one of the phenomena that may be experienced by offshore platforms throughout their lives. Compaction of the reservoir is caused by pressure reduction, which results in vertical movement of soils from the reservoir to the mud line. The impact of subsidence on platforms will lead to a gradually reduced wave crest to deck air gap (insufficient air gap) and cause wave-in-deck. The wave-in-deck load can cause significant damage to deck structures, and it may cause the collapse of the entire platform. This study aims to investigate the impact of wave-in-deck load on structure response for fixed offshore structure. The conventional run of pushover analysis only considers the 100-year design crest height for the ultimate collapse. The wave height at collapse is calculated using a limit state equation for the probabilistic model that may give a different result. It is crucial to ensure that the reserve strength ratio (RSR) is not overly estimated, hence giving a false impression of the value. This study is performed to quantify the wave-in-deck load effects based on the revised RSR. As part of the analysis, the Ultimate Strength for Offshore Structures (USFOS) software and wave-in-deck calculation recommended by the International Organization for Standardization (ISO) as practised in the industry is adopted to complete the study. As expected, the new revised RSR with the inclusion of wave-in-deck load is lower and, hence, increases the probability of failure (POF) of the platform. The accuracy and effectiveness of this method will assist the industry, especially operators, for decision making and, more specifically, in outlining the action items as part of their business risk management.

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Section: Wave-in-deck Load and Reserve Strength Ratiomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Azman¹,

Husain²,

Zaki³

et al. 2021

JMSE

View full text Add to dashboard Cite

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“…In another study, Dolsek [27] used the strategy to propagate uncertainty in a reinforced concrete building and evaluate its seismic performance through IDA. This approach was applied by Golafshani et al [28] in 2011 to propagate uncertainty in an existing jacket type offshore platform and to assess it under extreme waves through a probabilistic incremental wave analysis.…”

Section: A Brief Overview Of Seismic Performance and Reliability Techmentioning

confidence: 99%

Probabilistic seismic analysis of offshore platforms incorporating uncertainty in soil–pile–structure interactions

Ajamy

Zolfaghari

Asgarian

et al. 2014

Journal of Constructional Steel Research

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“…Despite the fragility analysis has been commonly adopted in the performance-based assessment of buildings under seismic loads, it is still possible to encounter the use the similar analysis for other structure types. Golafshani et al (2011) assessed the performance of a jacket offshore platform under extreme waves. Golafshani et al (2011) based the assessment on a framework named probabilistic incremental wave analysis, which has considerable similarity with the incremental dynamic analysis and the applied framework considers the uncertainties associated with the sea state parameter, structural response, and collapse capacity.…”

Section: Introductionmentioning

confidence: 99%

“…Golafshani et al (2011) assessed the performance of a jacket offshore platform under extreme waves. Golafshani et al (2011) based the assessment on a framework named probabilistic incremental wave analysis, which has considerable similarity with the incremental dynamic analysis and the applied framework considers the uncertainties associated with the sea state parameter, structural response, and collapse capacity. Zeinoddini et al (2018) also assessed the structural integrity of offshore platforms against extreme irregular waves where the stochastic nature and the uncertainties in the ocean waves were taken into account.…”

Section: Introductionmentioning

confidence: 99%

Fragility analysis of an ageing monopile offshore wind turbine subjected to simultaneous wind and seismic load

Yeter

Tekgoz

Garbatov

et al. 2020

Saf. Extreme Environ.

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The loads induced as a result of seismic activities may jeopardize the serviceability of offshore wind turbines or may even lead the structure to reach the ultimate strength. The maximum load-carrying capacity of a support structure can be estimated by performing a structural assessment which accounts for the nonlinear effects arising from the material and geometry. The present work aims to analyze the fragility of a 5 MW monopile offshore wind turbine structure subjected to seismic activities accounting for soil interactions and time-variant structural degradation. The offshore wind turbine structure is subjected to different ground motions with different intensity. The nonlinear full transient dynamic structural analysis is carried out based on the finite element method, and the nonlinear monopile structural response during the different seismic activities is discussed. Finally, the fragility curves associated with the serviceability limit state design and the ultimate strength limit state are developed.

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Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

Cited by 31 publications

References 18 publications

Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Probabilistic seismic analysis of offshore platforms incorporating uncertainty in soil–pile–structure interactions

Fragility analysis of an ageing monopile offshore wind turbine subjected to simultaneous wind and seismic load

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