Dynamic Time History Analysis for Fixed Offshore Platforms One of the challenges in the structural integrity assessment of existing platforms is to determine the DAF value, especially where the platform’s natural period is higher than 3 seconds after all brownfield modification and/or structural deterioration is considered. In this case, it is required to perform dynamic analysis. As per API RP 2A, for structural natural periods above 3 s, dynamic amplification is important, particularly for the lower sea states that may contribute the most to long-term fatigue damage. In these cases, it is recommended to perform a dynamic wave analysis to get the structural response accurately. One of the advantages of USFOS that I like is that it allows you to perform a dynamic time history analysis with full pile and soil included in the model. The maximum loads generated as per Maximum Overturning Moment (OTM), or Base Shear (BS) can be then recalled to perform a pushover analysis and derive the platform's Reserve Strength Ratio (RSR). Below is an illustration of the dynamic analysis performed in USFOS as part of the structural integrity assessment for a four-legged jacket. #StructuralIntegrityAssessment #OffshorePlatform #DynamicTimeHistoryAnalysis #DynamicAmplificationFactorDAF #USFOS
How to model wave loads as dynamic time history parameters?
Thank u so much for sharing the results. May i ask that do u consider the Wave in Deck effects in the analysis?
Fulbright Awardee, Faculty at ITS Surabaya
9moThis is very interesting. How can we be sure about the model's natural period compared to the actual natural period? Did you do the actual measurement? And how would you fine-tune the model to match the actual?