典型单跨低坡度双坡屋面的风致雪堆试验研究

Experimental studies of wind-induced snowdrifts on typical single-span low-slope gable roofs

为研究低坡度双坡屋面的风致积雪分布特性及雪荷载分布模式,设计研发了一套风吹雪联合试验装置,以高密度的石英砂颗粒模拟雪粒子,分别开展有无降雪条件下6种来流风速(有降雪1.5~2.5 m/s,无降雪4.6~6.1 m/s)、4种屋面坡度(5°、10°、15°、20°)的风吹雪风洞试验,共计24个试验工况,并就屋面中剖面积雪深度系数、积雪深度系数最大值及所在位置、雪荷载不均系数和雪颗粒净捕获系数等展开分析。结果表明:在多数工况下,低坡度双坡屋面积雪分布仍然呈明显的非均匀性,且降雪会显著影响积雪形态。对于迎风屋面,有无降雪条件下积雪深度系数均随来流风速的增大而减小,随坡度的增大而增大;积雪深度系数最大值点位置随风速增大逐渐远离屋檐,随屋面坡度的增大则呈近似线性移近屋檐。对于背风屋面,屋脊遮蔽效应容易导致积雪堆积,且积雪深度系数随风速增大而增大。随着坡度增大,背风屋面的雪颗粒净捕获系数增大,表明迎风屋面被输运的雪颗粒更容易在背风面沉积,从而加重屋面积雪分布的不均匀性。基于分析结果,归纳有无降雪影响下屋面雪荷载的典型不均匀分布模式,可为类似屋盖的抗雪设计提供参考。

To investigate the wind-blown snowdrifts and snow loads on the typical low-slope gable roofs,a wind-snow combined experiment device was designed and carried out a series of tests with or without snowfall,where the heavy-density silica sand particle was used to mimic snow particle and the six incoming wind speeds(1.5~2.5 m/s for snowfall cases,4.6~6.1 m/s for no-snowfall cases)with four roof slope(5°,10°,15°,20°)variations were considered,and the total cases were 24,and the snow depth coefficient of cross-sectional,maximum snow depth coefficient and its location,uneven snow load coefficient,and net capture coefficient of snow particles on the roof were to be analyzed.The results showed that,in most cases,low-slope double-pitch roofs had a non-uniform snow distribution,significantly influenced by snowfall.For windward roofs,the snow depth decreased with higher wind speed and increased with a steeper slope.The maximum snow depth point moved away from the eaves as the wind speed increased,approaching linearly with a higher roof slope.Leeward roofs,due to the ridge sheltering effect,accumulated more snow with higher wind speeds.With an increased slope,the snow particle net capture coefficient on leeward roofs rose,indicating that snow particles transported over windward roofs were more likely to deposit on the leeward side,intensifying the non-uniformity of snow distribution on the roof.Based on the results,three brief snow load distribution patterns for low-slope gable roof,to provide a useful addition to the snow load design for such roofs.