风致不均匀积雪的大跨网架结构工作状态分析

Working state analysis of long-span grid structure considering wind-induced uneven snow cover

为了保证结构服役安全,有必要对不均匀积雪荷载作用下网架结构工作状态进行分析。采用CFD数值模拟技术,基于准动态网格划分方法,以一正放四角锥网架结构为研究背景,分析了网架结构在持续降雪24 h中的屋面不均匀积雪分布变化情况,并详细探讨了不同风向角和不同风速对网架屋面积雪分布变化情况的影响;最后建立了该网架结构的有限元模型,分析了不同雪荷载工况的结构工作状态。结果表明:与其他有风条件下的工况相比,风速为12 m·s^(-1)、风向角为90°时的结构屋面平均雪压和积雪沉积区域占比最大,因此它是结构的最不利工况,该工况的平均雪压是无风条件下均布积雪平均雪压的88.9%,但结构杆件的最大应力值及挠度值却较均布积雪作用时有所增加,而且部分杆件从受拉杆变为受压杆;风致不均匀积雪是网架结构在服役期间的安全隐患,应在工程设计中予以重视。

In order to ensure the service safety of structure,it is necessary to analyze the working state of grid structure under uneven snow cover load.Taking a square pyramid grid structure as the research background,the CFD numerical simulation technology and quasi dynamic grid division method were adopted to investigate the changes of uneven snow cover distribution on the roof of grid structure during continuous snowfall for 24 h.The effects of wind angles and wind speeds on the changes of snow distribution on the roof of grid were discussed in detail.Finally,the finite element model of the grid structure was established.The working states of the structure under different snow load conditions were analyzed.The results show that compared with other working conditions under windy conditions,the average snow pressure and proportion of deposition area are the largest when the wind speed is 12 m·s^(-1) and the wind angle is 90°,therefore it is the most unfavorable working condition of the structure.The average snow pressure under this working condition is 88.9%of the average snow pressure of uniformly distributed snow under no wind condition.The maximum stress and deflection of structural members are increased compared with those under the action of uniformly distributed snow,and some members change from tension rod to compression rod.Wind-induced uneven snow cover is a potential safety hazard of grid structure during service,which should be paid attention to in engineering design.