Fragility analysis of an ultra high voltage transmission tower in saline soil subjected to wind loads

Abstract

The wind resistance of transmission towers is not only affected by wind load, but also by service environment. This study uses the world’s second Ultra High Voltage Direct Current transmission project – Xinjiang ±800 kV Tianzhong Line UHV DC transmission project – to develop a fragility analysis method for transmission towers in saline soil under wind loads to investigate the change of wind loads fragility of transmission towers in long-term service in the saline soil environment. It develops a tower-line-foundation (3 T-2L-F) system model considering soil-structure interaction. In addition, this research addresses the durability damage of the transmission tower using field investigation data and material degradation models and analyzes the influence of various durability damage components on the natural vibration mode of the basic of 3 T-2L-F model. Finally, it builds the structure-wind samples utilizing a Latin hypercube sampling method and explores the time histories analysis, the pushover analyses, and the time-varying fragility analyses considering the uncertainty of materials and wind loads. The findings indicate that the 3 T-2L-F model accurately simulates the actual situation of the transmission tower. The fragility of a transmission tower subjected to wind loads is proportional to the degree of material damage and the strength of wind loads.