Modelling fatigue degradation of the compressive zone of concrete in onshore wind turbine foundations

Abstract Embedded rings are widely used in onshore wind turbine foundations to resist uplift and compressive forces at the interface of steel towers and concrete foundations. These embedded rings are subjected to high-cycle fatigue loading due to the high ratio of the live load to dead load in such structures. The properties of concrete in the anchorage zone of the embedded ring change with time and its strength deteriorates under the effects of the cyclic loads. Therefore, research has been initiated to investigate the local deterioration of foundations and its effect on the whole structure. This paper presents a numerical study on the fatigue behaviour of the concrete foundation of onshore wind turbines. A constitutive model was developed for the onshore turbine foundation at the section level for fatigue loading. The model in the initial state was verified against strain data from nonlinear finite element simulations with regard to the strain distribution characteristics in the cross section. The fatigue theoretical model provided a realistic description of concrete foundation fatigue processes and their redistribution characteristics. A parametric study was performed to investigate the effects of different parameters that would influence the fatigue life of the foundation. The results of this study may help explain the fatigue behaviour of foundations under repeated loads and thus lead to a more accurate depiction of the actual long-term behaviour of foundations.