Vibration-based FE-model updating for strain history estimation of a 3MW offshore wind turbine tower

At present, the fatigue-life design of Offshore Wind Turbines (OWTs) is based on design assumptions accounting for significant uncertainties both on loading and fatigue-resistance of different vulnerable structural details. Monitoring of strain histories can potentially have a significant positive impact when estimating the remaining life of OWTs, as the uncertainties are reduced. However, strain-based monitoring approaches present the important drawbacks, that only instrumented locations can be assessed and that there tend to be accessibility issues associated with the installation process. In this paper, the initial results of a novel methodology developed to estimate strain time histories are presented. The underlying idea of such an approach is to combine an updated FE model with the vibration response histories acquired with only a few sensors to estimate the strain histories at any location of an OWT tower.