Nonlinear Response of Wind Turbines Under Wind and Seismic Excitations With Soil–Structure Interaction

Abstract

The objective of this paper is to present an efficient beam formulation based on the boundary element method (BEM), for the nonlinear dynamic analysis of wind turbine towers of variable cross section founded either on surface or on monopile foundation system. The whole structure may undergo moderately large displacements, taking into account the effect of soil–structure kinematic and inertia interaction. The tower is subjected to the combined action of arbitrarily distributed or concentrated transverse wind loading as well as to seismic excitation together with axial loading arising from the self-weight of the tower and the mechanical parts. The Blade element momentum theory is taken into consideration in order to produce the wind load time histories, while the site seismic response is obtained through one dimensional shear wave propagation analysis. The soil–surface foundation system is formulated as equivalent lateral and rotational springs, while the case of monopile system is treated as a prismatic beam on elastic foundation assigning the corresponding springs and dashpots along its length. An extensive case study is carried out on a wind turbine tower–foundation system employing the generated wind velocity time histories and recorded earthquake accelerograms, providing insight to several structural phenomena. The results of the proposed model are compared wherever possible with those obtained from a commercial finite elements software package, illustrating the validity and the efficiency of the developed method. From the obtained results, the strong influence of the nonlinear effects on the dynamic response of the wind turbine tower is verified.

Analysis of seismic behaviour of an offshore wind turbine with a flexible foundation

“…The resulting aerodynamic loads are generally neglected or simplified as rotor thrust forces. Based on this simplification, a multi-body dynamic method is employed for an efficient assessment of the responses of wind turbines subjected to earthquake 4 / 41 loadings [16][17][18][19]. As prescribed in existing certification guidelines, seismic loading demand is treated as a linear combination of earthquake and wind loads that are calculated individually [20][21][22].…”

Investigation on the sensitivity of flexible foundation models of an offshore wind turbine under earthquake loadings

“…Environmental loads acting on wind turbines along with earthquake loadings have a significant influence on the accuracy of the seismic analysis of wind turbines. Dynamic behaviours of wind turbines under earthquake excitations have been studied over the past decades but with simplifications on the model geometries [2][3][4][5][6][7][8][9]. In these studies, the rotor and nacelle were either completely ignored or simplified as a lumped mass.…”

Dynamic behavior of wind turbines influenced by aerodynamic damping and earthquake intensity

“…Very commonly, the aerodynamic loads are ignored or simplified as thrust loads that are applied at rotor . On the basis of this simplification, Zhao and Maisser and Sapountzakis et al used a multibody dynamic method for assessing the behavior of wind turbines under seismic excitation more effectively. However, aerodynamic loads play an important role on the dynamic behavior of towers of wind turbines especially for the case of large diameter wind turbines .…”