| Research Abstract |
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
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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
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