Study on Snow Load on long span structure

在日本，由于膜结构的分析方法和施工技术的进步，膜结构以前只是作为临时结构在展览等场所使用，现在被用作永久性结构。自1988年以来，在日本所有地区，包括北道、东北和北陆地区等大雪地区，各种规模的永久性膜结构的建设迅速增加。在降雪量大的地区，必须通过自然的雪滑或融化的方法不断地从屋顶上清除积雪，以便光线能够穿过薄膜。膜结构屋面雪荷载的计算方法与其他类型建筑物相同。也就是说，除了特殊情况（即根据日本建筑荷载第38条，建筑省批准了较低雪荷载的屋顶设计的情况）外，膜屋盖和支撑膜屋盖的主框架…在降雪量为1米的地区，根据该地区降雪量产生的荷载对屋面的影响，设计了膜结构。在新的日本建筑协会荷载准则（1993年）中，只有在屋顶安装了可靠的融雪装置的情况下，才承认雪荷载的减少。然而，由于这些指南没有提供足够的数据来将控制雪荷载纳入结构设计，因此“可靠性”没有定义。这是因为大多数关于膜结构屋顶积雪的研究都集中在利用膜的材料特性来清除屋顶积雪，而在多雪地区建造膜结构的历史还很短。讨论膜结构屋盖雪荷载评价的资料尚未获得。目前雪区膜结构设计假定屋面积雪，这与膜结构设计的主要目的背道而驰；也就是创造一个明亮的空间。在本研究中，为了使强降雪地区的膜结构设计合理化，研究了现有膜结构屋顶上的积雪以及这些结构的除雪方法的有效性。在此基础上，提出了一种新的膜结构雪荷载评估方法。少

Membrane structures, which were previously used only as temporary structures in Japan in such places as expositions, are now being used as permanent structures due to the progress in analytical methods used for membrane structures and in construction techniques. Since 1988, construction of permanent membrane structures of all sizes has increased rapidly in all areas of Japan, including regions with heavy snowfall, such as Hokkado, Tohoku and Hokuriku areas. In regions with heavy snowfall, snow must be constantly removed from the roof by a natural snow-sliding or melting method so that light can pass through the membrane.The snow load on the roof of a membrane structure is evaluated in the same way as that for other types of buildings. That is, except for special cases (i.e., cases in which a roof design with a lower snow load has been approved by the Ministry of Construction according to Article 38 of the Japanese building coad), the membrane roof, and the main frame supporting the mem … More brane roof and secondary members, of membrane structures constructed in regions with snowfall of one meter are designed according to the effect that the load produced by the amount of snowfall in the region has on the roof. In the new Japan Construction Society Load Guidelines (1993), a reduction of snow load is recognized only in the case where a reliable snow-melting device has been installed on the roof. However, as these guidelines do not provide sufficient data for incorporating controlled snow load in the structural design, "reliability" is not defined. The reasons for this are that most studies on snow accumulation on the roof of a membrane structure have focused on the utilization of material properties of the membrane for removal of snow from the roof and that the history of construction of membrane structures in snowy regions is still short. Data for discussing the evaluation of snow load on the roof of a membrane structure has not been obtained yet. Snow accumulation on the roof, which is assumed in the current design of membrane structures for snowy regions, runs counter to the primary objective in the design of membrane structures ; i.e., the creation of a bright space.In the present study, in order to rationalize the design of membrane structures in regions with heavy snowfall, the accumulation of snow on the roofs of currently existing membrane structures and effectiveness of the methods used for removing snow from these structures have been investigated. Based on the results, a new method for evaluating the snow load on a membrane structure are proposed. Less