Numerical and analytical performance of tapered CFDST column under cyclic loading for wind turbine structures

Abstract

Tapered concrete filled double skin tubular (CFDST) member has great potential to be employed in wind turbine structures for catering to the increasing height and output power of wind turbine. However, wind turbine was often subjected to fluctuating wind loads, causing the cyclic lateral force acted on the wind turbine tower. Currently, there is still lack of related research on tapered CFDST under lateral cyclic loading. In this paper, the finite element model (FEM) of tapered CFDST was established and verified by the test results. Detailed failure mechanism of tapered CFDST with various tapered degrees were discussed, and the contributions of sandwiched concrete, inner and outer tubes and the interactions between them were analyzed in detail. It noticed that the failure position of tapered CFDST was not always near the bottom and significantly affected by the tapered degree, which induced an appreciable effect on the hysteretic performance. Subsequently, parametric analyses were performed based on the FEM considering various parameters including slenderness ratio, tapered degree and hollow ratio. Finally, a simplified hysteretic model was proposed. Three-line model was employed to describe the skeleton curve, in which the failure position was properly considered. Typical hysteretic rules were developed to simulate the hysteretic shape of tapered CFDST under various stages. The accuracy of the proposed model was validated by the numerical results. The analytical results in this paper provide a reasonable method to predict the hysteretic performance of tapered CFDST in wind turbine structures.