Offshore Wind Turbines Subjected to Simulated Earthquakes: From Point Source to Finite Fault Effects

Govind, C.V and Somala, S N (2021) Offshore Wind Turbines Subjected to Simulated Earthquakes: From Point Source to Finite Fault Effects. PhD thesis, Indian institute of technology Hyderabad.

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Abstract

Offshore wind turbine (OWT) has become a new renewable energy source choice even at a high seismic region. This modern facility is primarily installed in the European region in its initial phase, where fewer seismic activities are observed. Hence unlike other conventional structures, not much attention is given to the seismic performance of the OWT. The literature review shows that the seismic loads strongly influence the performance of OWT structures. However, most of the past work talks about the coseismic performance of the OWT structure considering the generic earthquake aspects. The work done in the past evaluated the performance of OWT essentially for earthquake load, yet, they have considered the set of ground motions from different sources that can have significant variations due to fault mechanism, heterogeneity of soil strata, source site distance. Hence simulated ground can be adopted. In this study, the wind turbine response is computed by incremental dynamic analysis. To perform the nonlinear dynamic analysis, the numerical model is developed in the open-source software OpenSees. Finally, fragility curves are derived for serviceability and ultimate limits of wind turbines. The seismic performance of OWT is evaluated for typically generated ground motions through an open-source finite element simulation and closed-form equations. The various attributes of the earthquakes studied are the influence of ground motion pulse characterises, fault rupture speed and directivity, and the effect of the seamount in the subduction zones. The earthquake duration is one aspect that hasn't been studied for OWT, hence the influence is studied using the real ground motions data

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