基于规范对比的女儿墙屋面雪荷载实测分析

Analysis of measured data of snow loads on roof with parapets based on comparison of foreign codes

在女儿墙屋面雪荷载计算时,日本、美国及欧洲规范中充分考虑了风场对完全暴露屋面雪荷载的侵蚀作用、风力对积雪的搬运作用、上游积雪宽度对下游阻碍物处堆雪量的补充作用和降雪量对堆雪的补充作用。除此之外,也引入了室内采暖、雨雪联合等因素来更真实地实现对屋面雪荷载的估算。相较之下,我国规范仅考虑女儿墙高度的影响。故基于对带女儿墙屋面积雪分布的多年实测结果,参考国外规范中的影响因素,对哈尔滨地区女儿墙屋面积雪分布特征进行了分析。结果显示:风场作用下,积雪会更多地堆积于迎风向女儿墙处;随着上游屋面宽度增加,下游迎风向女儿墙处漂移积雪的峰值深度存在递增趋势,且随着风速增加,搬移堆积作用会增强;上游屋面宽度和地面降雪量对女儿墙处峰值雪深有较大影响,风速对于峰值雪深的影响依赖于地面降雪量,降雪越大,风速的影响越大,反之减小;女儿墙处堆雪长度与女儿墙高度比值多维持在3. 75左右,建议我国规范中堆雪长度与女儿墙高度比值取4. 0。

In the calculation of the snow load on the roof with parapets,standards of Japan,America,and Europe have given full consideration to the erosion effect on the snow load of the fully exposed roof caused by wind field,the movement of snow induced by wind,the supplementation of upstream snow to snow heaped up around downstream obstruction. In addition,factors such as the indoor heating and the combined effect of rain and snow are introduced to realize an accurate estimation of snow load on building roofs. By contrast,the Chinese code only considers the influence of the parapet height. Therefore,based on the measured snow distribution on an actual parapet roof on ages and the influencing factors in foreign codes introduced above,the snow distribution characteristics on the parapet roof were analyzed. The results show that: more snow is blown downstream towards the parapet;the peak snow depth close to the downstream parapet is proportional to the upstream roof width,and with an increasing wind velocity,the drifting effect is enhanced;the upstream roof width and the ground snow load have a great influence on the peak snow depth at the parapet,and the influence of wind velocity depends on the ground snow load;the larger the ground snow load is,the greater influence the wind velocity has;the ratio of the snowdrift length to the parapet height is around 3. 75,and it is suggested to adopt a value of 4. 0 in Chinese code.