Seismic vibration control of CFDST composite wind turbine towers with TLCDs

Abstract

As MW-class wind turbine towers (WTT) continue to grow in size, traditional steel tube structures are inadequate to meet the seismic requirements of large-scale towers. Concrete-filled double-skin steel tube (CFDST) towers, known for their lightweight and high lateral stiffness, are showing promising prospects for use in MW-class wind turbine towers. This study takes the NREL 5 MW WTT as a prototype and designs four 1:20 scaled wind turbine tower models-two concrete-filled double-skin steel tube (CFDST) towers and two conventional steel towers. One CFDST tower and one steel tower are equipped with a tuned liquid column damper (TLCD) at the nacelle, while the other two serve as control specimens without TLCDs. Shaking table tests were conducted on all models, with the influence of the blades taken into account. Acceleration, displacement, and strain responses under seismic excitation were obtained. Based on these results, the dynamic response characteristics of the CFDST composite tower were compared with those of the conventional steel tower. Furthermore, the feasibility of implementing TLCDs in CFDST towers was assessed, and the combined effect of cross-sectional optimization and damping devices was investigated. The findings indicate that, under identical seismic conditions, the displacement, acceleration, and strain in the Concrete-Filled Double-Skin Steel Tube (CFDST) WTT are significantly lower than those in the traditional steel structure WTT. The effectiveness of the TLCD in reducing vibrations not only increases with the peak ground acceleration (PGA) but also varies according to the type of seismic wave and the direction of seismic loading. Moreover, the combined application of cross-sectional optimization and TLCD installation yields the most substantial vibration reduction, achieving a maximum decrease in acceleration of 66.7 % and displacement of 57.5 %. These results confirm that employing TLCD damping devices in CFDST WTT is both feasible and advantageous, enhancing the operational stability and safety of WTTs under extreme seismic conditions.