Finite Element Modeling and Modal Testing of a Wind Turbine Lattice Tower Component with Interference Pin Connections

Fatigue failures at fastener holes in operating structures are undesirable as they can lead to catastrophic mechanical failures and casualties. Interference pins create interference fits with joined components to reduce stresses around fastener holes and extend the fatigue life of operating structures. In this chapter, a novel method for finite element (FE) modeling of interference pin connections in a wind turbine lattice tower component is developed. Installation of interference pins is modeled as a multistage process. It causes local changes in stiffness in joined members of the component. The local stiffness changes are accounted for in the FE model of the component through the creation of cylinders to represent interference pins. An experimental setup, including a three-dimensional (3D) scanning laser vibrometer and a mirror, was used to measure out-of-plane and in-plane natural frequencies and mode shapes of the component. Ten out-of-plane modes and one in-plane mode from the FE model are compared with the experimental results to validate the accuracy of the FE modeling approach. The maximum percent difference between the theoretical and experimental natural frequencies of the component is 3.21%, and the modal assurance criterion (MAC) values between the theoretical and experimental mode shapes are 0.92 or greater.