Development and experimental validation of an FBG-based substructure cross-sectional load measurement approach for a semi-submersible floating wind turbine

The semi-submersible floating wind turbine offers an advanced alternative for exploiting offshore wind energy in intermediate and deep waters. The cross-sectional loads of semi-submersible hulls are important for the structural design of floating wind turbines, but are difficult to be determined by experimental techniques. To gain the internal loads of the hull structure, a new Fiber-Bragg-Grating (FBG) sensor-based substructure cross-sectional load measurement approach is proposed and experimentally validated in this study. The substructure is fabricated into a multi-segment floater, in which segments are assembled together by rigid tubes with FBG sensors attached. The strain messages capture the strain variation in a wide range and are used to predict the cross-sectional loads. To validate the feasibility of this approach, a set of comparison experiments was conducted. Two physical models of floating wind turbines with an intact floater and a multi-segment floater are fabricated and tested under identical wave conditions in the wave basin. The experiment contains free decay tests, white noise tests, and wave-only tests. The experimental results confirm that the approach is feasible and effective for capturing the cross-sectional loads of floating foundations in wave basin model tests. •An FBG sensor-based substructure cross-sectional load measurement approach for a semi-submersible FWT.•The foundation is fabricated as a multi-segment platform connected by rigid tubes with sensors attached.•The approach is validated by comparisons of floating wind turbines with an intact platform and a multi-segment platform.•Several application guidelines for this approach are provided.