下击暴流作用下输电铁塔荷载取值及承载性能分析

Bearing Capacity Analysis and Load Values of Transmission Towers Under Thunderstorm Downburst

下击暴流会给输电线路造成巨大危害,已引发生多起倒塔事故。基于ASCE关于高强度风区域输电线路设计的相关规定,综合考虑下击暴流尺度特征和输电线路经济性设计原则,提出了下击暴流作用下输电线路的设计荷载取值建议。采用Vicroy风速剖面模型,计算得到了内陆和沿海地区典型输电铁塔在下击暴流作用下的风荷载。建立了输电铁塔空间有限元分析模型,通过结构受力分析,确定了输电铁塔在下击暴流作用下的受力特征和破坏模式。结果表明:下击暴流作用下,输电铁塔杆件应力主要由45°大风控制。对于设计风速较低的内陆地区,尽管铁塔结构高度不在下击暴流最高风速区域,下击暴流风荷载明显高于常规风,塔腿横隔面以上主材会首先发生破坏;对于设计风速较高的沿海地区,下击暴流风荷载低于常规风,下击暴流在铁塔设计中不起控制作用。

Downbursts can cause great harm to the transmission lines and even many destroyed accidents of the towers. Based on the design regulations on the transmission lines in high intensity wind areas by ASCE, by considering the scale features of downbursts and the economic design principle of transmission lines, the design load values under downbursts for transmission lines were proposed. The wind velocity profile model by Vicroy was applied, and the wind loads of two typical transmission towers in inland areas and littoral areas were calculated separately. Spatial finite element models of the transmission towers were established and the structural analysis was completed. The bearing characteristics and the destroyed modes of the transmission towers under downburst were determined. It shows that stresses of the tower members are mainly controlled by 45~ wind load. For the inland areas with low deign wind velocity, though the structural height is not in the highest wind velocity zone of downburst, the wind load under downburst is much higher than under regular wind. The main members above the transverse separator of the legs will be firstly destroyed. For the littoral areas with high deign wind velocity, the wind load under downburst is lower than under regular wind. Transmission towers are not controlled by the wind loads from downbursts in design process.