Study on the wind effect and reinforcement reliability of cathead tower under downbursts

Downbursts, as a typical type of extreme wind weather, pose a serious threat to the operational reliability and structural safety of transmission line systems due to the suddenness and high destructiveness, often triggering large-scale progressive collapse. To quantify the effectiveness of reinforcement measures in enhancing the structural reliability of transmission towers, the 220ZM33 cat-head transmission tower was taken as the research object and a multi-scale numerical model coupling B31 beam elements and C3D8R solid elements was established based on Advanced Simulation for Engineering and Sciences(ABAQUS) software. Research indicates that the “single row” alternating reinforcement method significantly improves system reliability. Under the most critical downburst condition, the maximum tower top displacement is reduced by 11.4% compared to the unreinforced scenario; stresses in critical regions are substantially reduced, with a 50% decrease in the central region, effectively suppressing the failure probability of key components and thereby enhancing the overall structural robustness. Results from the reliability index calculation model based on the First-Order Second-Moment (FOSM) method show that the reliability index for tower top displacement increases by 32.8%, while those for the main members in the central and end regions increase by 125% and 51.7%, respectively. The Translator Connector element effectively simulates the transfer of bolt pre-tension forces; however, the end members did not achieve the ideal stress reduction due to stress concentration, indicating a local reliability weakness. It is recommended to increase the number of connectors to distribute stress and provide redundant load paths. The method combining Multi-point Beam constraints (MPC BEAM constraints), surface-to-surface contact, and bolt pre-tension forces adopted in this study constructs a reliable multi-scale coupled connection system, providing key technical references for reliability-based reinforcement design and assessment in similar projects.