| In the cold and snowy area, accidents of roof damaged and personnel casualty caused by snow disaster happened frequently. For snow load is the important design load in structure design, the effect of snow load to building structures should not be overlooked. Non-uniform distribution snow load related failures are more obvious especially to the large span structure, low rise structure, light-steel structure and membrane structure. Therefore, determine snow load on the roof exactly is the essence of avoiding snow related failures happen, which is also the key problem that many researchers focus on. While, research on the snow load is really late in getting started in China and the field measurements are few carried out. Compared with standards in the developed country, our standard is still simple in determining roof snow load, a lot of work need to be carried out to improve our standard. Based upon the condition above mentioned, research on snow distributions on the low-rise roof was conducted by this paper, which focused on the field measurement of snow load.Firstly, development of researches on the snow load was introduced in detail including the theory of snow-drifting, characteristics of snow particles and influence factor, snow distribution on the roof and around the building.Secondly, the snow standards of China, America, Canada, Australia, Japan, England and International were further studied. The deficiencies of our standard were put forward by comparing the equation and method of snow load determination with developed countries’.Thirdly, we conducted the field measurement of snow densities on the ground and on the roof. It can be found that snow densities increase usually associated with the rising temperature, the deeper snow layer and the high humidity. Deposited snow densities are generally larger than the new snow densities and roof snow densities are larger than the ground snow densities. Then the mean snow pressure on the roof was calculated by field measured data and compared with the results determined by snow standard.Finally, we conducted the field measurement of characteristics of snow distributions on the prototype roof and the model experiment. Snow distributions on three typical prototype roof including flat roof, arch roof and multi-level roof were studied, the ratio of the length of snow unbalanced distribution to the parapet height is about 3.0 were concluded. Five typical roof models including single-sloping roof, double-sloping roof, multi-level roof, arch roof and multi-span roof were designed and characteristics of snow distributions on the typical roof were suggest by field observation. Wind was found the main factor which influence snow distribution on the roof, the temperature, sunshine, roof orientation and drainage system was also play an important part. The most unfavorable loading location on the roof under the snow load was put forward by the field measured data and then the results were compared with the standards. |
