Prediction of critical tornado load effects on multi-span transmission line–insulator systems: A framework integrated with analytical and optimization methods

Abstract

Predicting the wind load effects on a multi-span transmission line-insulator system (MSTLIS) during tornado conditions presents challenges due to its unique characteristics, including localized size, three-dimensional wind profiles, and the time-varying, uncertain positions of components resulting from tornado translation. This study focuses on predicting critical tornado-induced reactions transmitted to transmission towers, which are the key factors for controlled load cases in structural design. A nonlinear analytical method is introduced, integrating deformation compatibility and equilibrium equations for conductors and insulators to evaluate the quasi-static dynamic responses of MSTLIS under non-uniform, time-varying tornado loads. The accuracy of this method is validated against numerical results from the finite element method (FEM). Additionally, a pattern search optimization algorithm is utilized to efficiently identify critical tornado load cases under any tornado and structural parameters, outperforming traditional grid search methods. This framework is further employed in a parametric analysis to explore the influence of various parameters on critical load cases. This paper provides novel insights for enhancing the prediction of critical load cases for MSTLIS reactions on towers under moving tornado conditions.