Seismic Performance-Based Design of Offshore Foundations: Insights from Predictive Modeland Fragility Curves

This study evaluates the role of effective factors on the seismic performance of offshore wind turbines supported by suction caisson foundation using probabilistic analysis. The probabilistic analyses incorporate data and the predictive models developed by the second author to estimate liquefaction-induced settlement in these structures. Fragility curves and surfaces aredeveloped to assess the probability of exceeding settlement limit states under varying seismic conditions. The analysis considers key factors such as contact pressure (Q) and shaking intensity rate(SIR). The results indicate that Q and SIR can significantly influence the probability of settlement damage. However, sensitivity analyses demonstrated that the settlement probability is more sensitive to variations in SIR compared to Q. Moreover, fragility surfaces highlighted the multivariate nature of settlement probability based on the combination of Q and SIR effects. The proposed fragility surfaces can provide valuable insights for the design and seismic risk assessment of suction caisson foundations in offshore wind farms.

Keywords: Fragility curves, Probabilistic analysis, Offshore wind turbine, Suction caisson foundations.