Seismic fragility analysis of jacket supported offshore wind turbine considering ground motion directionality

Abstract

Offshore wind turbines (OWT) being developed in seismically active regions imparts the necessity of understanding the risk caused by earthquake. Seismic fragility analysis considers the probability of damage over a range of hazard intensities due to earthquake loads and provides a measure of safety of the wind turbines. Knowing the importance of the seismic risk assessment of the OWTs, this study attempts to conduct the seismic fragility analysis for a 10 MW jacket supported offshore wind turbine considering the ground motion directionality. Three-dimensional numerical modelling of jacket, pile, and tower is developed in SAP2000 using non-linear beam elements. The soil-pile interaction is modelled by using American Petroleum Institute (API) based p-y springs. Incremental dynamic analysis (IDA) is performed to develop the fragility curves for various angles of seismic incidence under different limit state of critical responses of OWTs based on codified provisions. The fragility curves developed for jacket supported OWT provide significant insight into the importance of considering ground motion directionality and also provide a step for measuring the seismic performance to ensure safety and reliability.