Multi-component Reliability Analysis of Unequal Leg Transmission Tower in Steep Mountainous Areas Under Random Wind Loads
Unequal leg transmission tower is widely used in transmission line projects in steep mountainous areas.Accurately assessing the reliability level of every component will be significant for the maintenance and strengthening.In this regard,a multi-component reliability analysis of unequal leg transmission towers in steep mountainous areas under random wind loads is carried out based on the Quasi Monte Carlo method in this paper.According to the Technical Specification for the Design of Steel Supporting Structure of Overhead Transmission Lines(DL/T 5486-2020),five types of failure modes and functional functions of different components of unequal leg transmission tower are given.Considering the randomness of material and wind loads,the Quasi Monte Carlo method is used to establish a multi-component reliability analysis framework of unequal leg transmission tower.A unequal leg transmission tower in a 500 kV transmission line is used as an example for multi-component reliability assessment,and the influence law of different tower leg height difference,nominal height and design wind speed on the reliability index of unequal leg transmission towers is analyzed.The analysis results show that:the reliability index of all components of the unequal leg transmission towers are above 3.2,meeting the code requirements of the second safety level.It should be noted that the short-legged main material is the weakest component of the unequal leg transmission tower,and the reliability index is reduced by 23.25%compared to that of the long-legged main material.For every 6 m increase in tower nominal height,the maximum decrease in reliability index of unequal leg transmission towers is 3.37%.For every 1 m·s-1 increase in design wind speed,the maximum reduction in reliability index is 2.83%.The reliability index is reduced by 10.48%for every 3 m increase in tower leg height difference.It is recommended that the tower design should try to avoid too large leg height difference.
unequal leg transmission towermulti-component reliabilityQuasi Monte Carlo methodrandom wind load