Modelling of electrical transmission tower line systems under wind-induced quasi-static and dynamic occurrences utilising the finite element technique
摘要
The Electrical Transmission Tower System (ETTLS) supports substantial electrical conductors at an adequate and secure elevation above the ground. In addition to their weight, they must endure several natural pressures, including high winds, earthquakes, and snow loads. Consequently, ETTLS must be engineered concerning both structural and electrical specifications to ensure safe and cost-effective construction. ETTLS, with uniformly distributed mass, possesses an infinite number of natural frequencies. The free-vibrational characteristics of ETTLS, including natural frequencies and modal forms, are essential for understanding their fluctuating behaviour. Furthermore, mitigating vibrations from wind and earthquakes is essential to preserving the stability of the ETTLS. Additional investigation of the static, modal, and dynamic properties of ETTLS is needed to assess and regulate vibrations. Nonetheless, there exists a paucity of material concerning the modal and dynamic characteristics of ETTLS. This research attempts to build a comprehensive ETTLS model that incorporates several efficient components to evaluate its static, modal, and dynamic behaviour. Additionally, ascertain the static response and associated stress resultants of the ETTLS construction resulting from wind load at a specific static moment, considering both vertical and transverse positions of the tower. The present study developed an extensive 3D FEM simulation for an ETTLS and contrasted its natural frequencies with those identified in prior research. A model of the ETTLS employed efficient element types for the static and dynamic examination of its numerous components. The primary purpose is to ascertain the static response of wind load and the resultant stress effects on the tower in both vertical and transverse orientations. The factors include deflection, directed deformation, shear force, and bending moments. The modal form computation attributes of the ETTLS were assessed by calculating frequency components and mode forms in ANSYS and corroborating the FEM results with a closed-form solution. The simulation’s validity was confirmed through a mesh-convergence study, and the ETTLS geometry was validated in accordance with the pertinent codal regulations. A complete examination of the dynamic modelling of ETTLS using ANSYS, concentrating on the evaluation of the fluctuating response of ETTLS under time-dependent wind loads at different wind velocities, incorporating displacement and axial force. The accumulated mass participation element in the modal evaluation shows that 90% of the modal mass, across all tower system degrees of freedom, is contributed by the top 10 modes. Analytical calculations of the first ten natural frequencies reveal a frequency range of 1.7–5 Hz. Eigenmode analysis is used to determine ETTLS’s principal natural frequencies in the longitudinal and lateral orientations: 1.745 Hz and 1.775 Hz, respectively. Peak displacement and axial force were recorded at 0.338 m and 17.9361 × 105 N, respectively, during the dynamic analysis phase. Compared with the uncontrolled situation, the tower with an ideal TMD curve has a displacement response that is reduced by about 7.6%. With a reduction ratio of about 12.9%, the ideal TMD dramatically reduces axial force. This study provides essential guidance for structural engineers on determining the most effective design and maintenance procedures for ETTLS. This study exclusively examines the dynamic performance of ETTLS under wind loading conditions. Furthermore, it may provide a foundation for future evaluations of fatigue life, considering various dynamic loads affecting ETTLS.