Abstract: In response to the issue of insufficient accuracy in cable force detection caused by the unconstrained structure of the external prestressed cables of hybrid concrete-steel wind turbine towers and the presence of steering devices, a detection technology based on local rigid coupling is proposed to improve cable force detection accuracy. By designing a local rigid coupling device and using a cable band combined with injected epoxy resin, the testing conditions of the frequency method are effectively improved. Based on the Euler beam vibration theory, a simplified dynamic model of the cable considering the effects of local rigid coupling devices and steering devices was established. The natural frequency equation was derived, and the validity of the model was verified through numerical simulation. Evidence demonstrates that the cable frequency is influenced by the steering device, resulting in the superposition of the frequencies of the two segments. When the support stiffness of the steering device exceeds 1.5×10⁷ N/m, the frequency superposition effect of the cable can be neglected, and the model can be simplified to the form of two simply supported cables. Field tests used accelerometers to capture cable vibration signals, and the simplified model was used to calculate cable forces. The measured results had an error within 1.03% of the theoretical values, satisfying the testing accuracy requirements. It was verified that the local rigid coupling device can effectively increase detection accuracy, and the proposed simplified dynamic model provides a practical technical solution for the detection of cable force in hybrid tower masts.

Key words: frequency method, wind turbine, hybrid concrete-steel tower, external prestressed cables, fundamental frequency, rigid coupling