超大跨度渡槽脉动风频率特性分析

贵州龙场渡槽是我国目前最大的拱跨渡槽,其脉动风频率特性分析对设计工作具有极其重要的指导作用。计算了龙场渡槽在有水、无水工况下的前20阶自振频率,分析了相应的振型;采用极值Ⅰ型概率分布函数,计算得到龙场渡槽所在地的50年一遇最大设计风速为17.6m/s;针对1986～2010年间的3次强风风速和50年一遇最大设计风速,计算了龙场渡槽所在地典型高程处的脉动风功率谱密度。研究表明:在同一高度,随着年平均最大风速的增加,功率谱密度最大值逐渐增大,其对应的频率也在增大;对于同一风速,随着高度的增加,功率谱密度的最大值逐渐增大,其对应的频率也在增大。通过比较龙场渡槽自振频率与脉动风功率谱密度显著值所对应的频率,认为龙场渡槽在上述风速下不会发生共振现象。

Analysis of Pulsating Wind Frequency Characteristics for Super Large-span Aqueduct

At present,Longchang aqueduct in Guizhou Province is the largest arch span aqueduct in China.The pulsating wind frequency characteristics analysis plays an important guiding role in design.The first twenty natural frequencies of the Longchang aqueduct were calculated in water and anhydrous conditions,and the corresponding vibration modes were analyzed.The maximum designed wind velocity for once in 50 years of Longchang aqueduct,which is obtained by using extreme value Ⅰ-type probability distribution function,is 17.6 m/s.For the 3 strong breeze velocities during 1986-2010 and the maximum designed wind velocity for once in 50 years,pulsating wind power spectrum density at typical elevation of Longchang aqueduct was calculated.By comparing natural frequency and the frequency corresponding to the significant value of pulsating wind power spectrum density,it is shown that the resonance phenomenon of the Longchang aqueduct will not occur at above wind velocities.