移动下击暴流作用下输电塔的风振响应及荷载评估方法

A dynamic responses and evaluation method of the downburst wind loads effect on a transmission tower

下击暴流是一种典型的局部强对流天气。由下击暴流风荷载导致的输电杆塔的倒塌事件时有发生,是目前造成国内外内陆地区输电线路风灾破坏的主要原因。基于下击暴流理论模型,采用准定常假设,模拟了移动下击暴流作用下输电塔的风荷载。通过输电塔的空间有限元建模与计算,考察了移动下击暴流平均风、拟静力和瞬态动力三种工况作用下输电塔在频域及时域内风振响应的规律。分析了移动下击暴流时变平均风作用下的最不利风剖面。同时,采用非平稳随机振动的极值分析理论,基于风振惯性力方法,给出了最不利风剖面作用下输电塔脉动风振响应的等效静力风荷载分布,且与有限元动力分析结果进行了对比和验证。研究为下击暴流作用下输电塔设计风荷载的评估提供了有效的探索。

Downburst is a typical local highly intensive wind all over the world,which attribute to main cause of wind damage to transmission lines in inland areas world widely.In this paper,based on the empirical model of downburst and the quasi-steady assumption,the wind load of moving downburst acting on the transmission tower was simulated.A spatial finite element model of the transmission tower was established,the wind-induced dynamic response of the transmission tower under three working conditions(mean wind,quasi-static and transient)of moving downburst was studied.The most unfavorable wind profile under the moving downburst average wind was found,and the relationship between the radial distance corresponding to the maximum structural response and the structure height and the jet diameter of the wind field was analyzed.At the same time,the wind-induced dynamic response of the transmission tower under the most unfavorable wind profile of the moving downburst was calculated by using the equivalent static wind load,and the results were compared with the time-varying analysis results.It provides an evaluation method for calculating the design wind load of transmission tower under the downburst.