Geotechnical fragility analysis of monopile foundations for offshore wind turbines in extreme storms

Offshore wind turbines (OWTs) must withstand harsh environmental loads over their 20- to 30-year design life. Fragility analysis investigates the probability of damage a range hazard intensities and is integral performance-based engineering approach. The focus this paper on monopiles, which are widely used support OWTs in water depths up around 40m. presents fragility monopiles extreme storms terms geotechnical performance, measured by permanent rotation foundation. Geotechnical has so far not been comprehensively addressed due challenge predicting soil behaviour under cyclic loading estimating responses. On latter, develops efficient Karhunen-Loeve representations wave that can be combined with inexpensive probabilistic methods compute fragility. framework was demonstrated using representative scenario 5 MW OWT installed clay. Non-linear foundation response captured dynamic 3D finite element model. curves were generated subset simulation for return periods (RPs) from 1 100 years. during (with 50- 100-year RPs) significantly higher than RPs 10 years or less.