Evaluation of the Fatigue Performance of a Fixed Offshore Platform with Steel Group Piles under Combined Soil Effects

Öz

Fatigue occurs in the steel pile elements of jacket-type platforms because the piled foundations of offshore platform structures are exposed to cyclic dynamic loads. In this study, the fatigue behavior of platform steel piles was investigated under realistic environmental loads with return periods of 1 year (operational), 100 years (extreme), and 10,000 years (extraordinary).In addition, layered soil classes ZU1-ZU4, with different strength and stiffness values reflecting the soil type behavior of the Caspian Sea region, were modeled.Following the structural analyses, fatigue damage and fatigue life were determined in accordance with the DNV-RP-C203 (2016) and ISO 19902 (2007) standards.The equivalent stress ranges (Δσ) and the total fatigue damage (D_total) were obtained from the critical hot spots and calculated according to Miner’s linear damage accumulation rule method.All pile elements showed a fatigue strength performance exceeding 100 years, remaining below the design limit value of D = 0.04 for fatigue damage.The increase in cumulative damage under environmental loads with a 10,000-year return probability was found to be limited, suggesting that the effect of infrequent cyclic loads on the overall fatigue performance of the steel elements is low.Due to the stiffness differences and load transfer mechanisms between the soil classes, the stress and fatigue damage parameters were higher for the corner piles (B2, B6) compared to the interior piles (C2, C6).The study concludes that the pile elements provide good fatigue performance throughout their 25-year design life for the examined pile-foundation interactions.

Anahtar Kelimeler

• Steel pile foundations
• cyclic dynamic loads
• fatigue performance
• offshore pile foundations
• return-period waves

Kaynakça

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