Structural Response of a Large Transmission Tower to a Tornado in East China

Structural analyses of transmission towers against tornados, which are of vital practical significance in design and maintenance of the structures in regions suffering from the convective weather, were rarely reported by the wind engineering community up to today. To balance the computing efficiency and the simulation accuracy, numerical calculations based on Wen's tornadic velocity model are employed to analyze the tornado-induced structural responses of a 131-meter-high free-standing transmission tower in east China in this article. Results suggest that both the tornadic load and the structural response are noticeably greater in the lateral direction than in the longitudinal direction, and they are found to be highly nonstationary due to the traveling nature of the tornado. In addition, according to the present study, the transmission tower is not prone to the strength failure during the tornadic event and slight fatigue damages are accumulated on the tower body due to the tornadic action which can be timely warned using the structural health monitoring strategy based on field measurements of low-order structural natural frequencies. Besides the points mentioned above, the innovations of the present research additionally include the following: (1) tornado-induced structural responses and atmospheric boundary layer wind-induced structural behaviors have been compared to provide conclusions of theoretical significance; (2) a novel fatigue damage assessment method based on the high-circle fatigue damage accumulation theory has been applied to the analysis of tornado-induced structural damage; (3) the structural configuration of a key joint on a main chord has been optimized against the tornado based on the advanced response surface optimization method.