Modelagem do comportamento estrutural dinâmico de torres de aço em sistemas de linhas de transmissão de energia submetidas à ação não determinística de cargas de vento

Abstract

The increasing demand for electricity in Brazil, along with the characteristics of its energy matrix which relies heavily on hydroelectric plants located far from consumption centres has driven the implementation of thousands of kilometres of transmission lines across the country in recent decades. With the significant expansion of the national power grid, the use of lattice steel towers to support electrical cables has become widespread due to their constructive and structural advantages, such as low self-weight, ease of transportation, and assembly. This high demand has provided designers with extensive experience in the structural analysis and design of such towers. However, reports of structural failures, even under conditions where the design wind speeds were not exceeded, raise questions about the effectiveness of traditional analysis methods and suggest that these failures may be related to the effects of dynamic loading on transmission lines. This research investigates the structural behaviour of steel towers used as supports for overhead power transmission lines, considering wind action's dynamic and non-deterministic effects. A nonlinear, non-deterministic dynamic structural analysis methodology was developed, incorporating the aerodynamic damping effects of the cables and applying appropriate statistical treatment to evaluate the structural response of steel transmission towers. The study included both isolated tower analyses and complete “tower-cable” system evaluations. The traditionally employed design methodology was compared with the proposed approach, focusing on analysing structural responses (displacements and internal forces) to identify the main qualitative and quantitative differences between the two, as well as to alert structural designers to potential issues associated with using simplified design methods in systems significantly influenced by dynamic wind action. Seven basic wind speeds (20, 25, 30, 35, 40, 45, and 50 m/s) were analysed, with 30 loading series applied to each, followed by statistical treatment of the obtained responses. Results showed variations of up to 93% in displacements and 91% in internal forces when compared to the traditional design methodology, revealing that accounting for nonlinear dynamic effects is essential for safe structural design. The proposed methodology allows for a more accurate representation of the real behaviour of these structures and provides valuable insights for improving design practices. Its purpose is to alert designers to the limitations of simplified models, especially in situations where dynamic wind action has a significant influence, potentially compromising the accuracy and safety of structural designs.