酒杯型输电铁塔曲臂风荷载风洞试验研究

Wind tunnel tests for wind loads of crank arms of cup-type transmission towers

酒杯塔是1 000 k V特高压输电线路工程中的常用塔型,设计时曲臂风荷载计算存在使用模型不统一的问题,而目前还没有针对曲臂风荷载的专门研究。完成了15 m/s和20 m/s来流风速下酒杯型输电铁塔曲臂模型的风洞试验,得到了11种风向角下的风轴和体轴平均阻力系数,获得了曲臂模型迎风面、背风面体型系数和背风面风荷载降低系数η,分析了酒杯型输电铁塔曲臂角度风荷载系数和有效投影面积,将试验确定的曲臂风荷载计算参数与国内外规范值进行了对比分析,提出了酒杯型输电铁塔曲臂角度风荷载的设计建议。按中国规范"塔身"模型计算曲臂风荷载满足安全要求,风向角为90°时曲臂风整体风荷载取值偏于保守;风向角为45°、60°和90°时,按中国规范"横担"模型计算的曲臂风荷载远低于风洞试验值,将低估曲臂风荷载并使结构抗风设计存在安全隐患。

Cup-type transmission towers are frequently used in 1 000 k V UHV transmission lines. However,different calculation models are used for wind loads calculation of crank arms in design. Until now there has been no specialized study on wind loads of cranks arms. Wind tunnel tests were conducted on crank arm models of a cup-type transmission tower under 15 m/s and 20 m/s wind velocities. The drag coefficients along wind direction axis and body-fitted axis for 11 skewed angles were obtained. The models' shape coefficients over the windward surface and the leeward one,respectively and the leeward surface shielding factor η of the models were obtained. The skewed wind load factors and the effective projected areas( EPA) of the models were analyzed. The parameters determined with the wind tunnel tests for the wind loads calculation of crank arms were compared with standard values in Chinese and foreign codes.Some design suggestions for the wind loads calculation of crank arms of cup-type transmission towers were proposed. It was shown that the wind loads of crank arms calculated according to the tower body model of Chinese code can meet safety requirements,but the total wind loads of crank arms calculated for 90° wind incidence angle are conservative; the wind loads of crank arms calculated according to the cross-arm model of Chinese code are much lower than the wind tunnel test values for 45°,60° and 90° wind incidence angles,so the wind loads of crank arms are underestimated and there is a safety hazard in anti-wind design of structures.