Reproduction of seismic responses of wind turbine tower by hybrid tests considering shear and bending coupled boundary control

Abstract

The dynamic responses of wind turbine towers subjected to earthquakes and winds are very complex and might cause significant damages. However, the reproduction of the dynamic response in a laboratory is not easy because the specimen shall be scaled very small to meet the space limits of wind tunnels and shaking tables. Real-time hybrid testing (RTHT) is an appealing option to solve this difficulty, which takes part of a structure as the specimen, while treats the rest numerically so that large scale specimen could be used. However, the application of RTHT to a wind turbine tower requires more complex boundary coordination to reproduce the coupled shear and bending behavior. This paper proposes a shaking-table substructure testing framework, where the lower part of the tower is fixed on the shaking table at the bottom and the top of the specimen is simultaneously loaded by a two-degree-of-freedom loading device. The loading facilities communicate in real time with the numerical substructure, and the superstructure including the wind turbine and blades is numerically simulated under the external excitations. Displacements and forces at the boundary are transferred between the numerical and physical substructures to realize boundary compatibility and equilibrium. A novel boundary loading device controls two masses to realize bending and shear equilibrium at the same boundary surface. Enhanced three-variable control is proposed to improve the performance of boundary coordination and the error-response negative feedback compensation method is proposed to reduce error transmission in RTHT, as demonstrated and introduced in a series of simulations and conceptual study.