2005 Fiscal Year Final Research Report Summary
Research on Evaluation Method of Snow Slid-off in sloped roof
| Project/Area Number |
16560509
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Building structures/materials
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| Research Institution | Hokkaido Institute of technology |
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Principal Investigator |
ITO Tshiyuki Hokkaido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (20223167)
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| Project Period (FY) |
2004 – 2005
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| Keywords | sloped roof / snow cover on roof / snow slid-off / history of outside temperature / decrease of snow load / snowfall region |
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| Research Abstract |
We investigated a method for evaluating the snow slide-off performance of coated steel sheet, which are widely used for roofs in areas subject to heavy snowfall. The method utilized the coefficient of friction between the snow and the panels. To this end it was necessary to conduct measurements in a slide-off experiment that simulated the coefficient of friction under conditions ranging from dry friction at low temperatures to wet friction that prevails when snow is in the process of melting. The value of the coefficient of friction is stable under dry conditions and also when snow is completely wet, but it is highly variable when snow is partially wet.
We conducted outdoor exposure tests using three kinds of sloped roofs having the slide-off performance of coated steel sheet. We analyzed the slide-off conditions for a range of pitches that are relevant for slide-off performance and evaluated the effects of roof pitch and outdoor air temperature on snow slide-off. Consequently, we were
… More
able to quantitatively determine the effects of roof pitch and outdoor air temperature on roof snow slide-off.
Next, we investigated the factors that influence an observed phenomenon, namely that the longer time it takes for snow to accumulate on a roof, the higher the outdoor air temperature needs to be for snow slide-off to occur. In a simulation experiment conducted in a low-temperature chamber, we confirmed that the effective frozen surface contact area between the snow and the roof surface increases with repeated melting and freezing of the accumulated snow and that this influences snow slide-off.
On the basis of the above findings, we proposed a method for determining snow slide-off from roofs that utilizes local weather data. We found the basic elements of a method for determining the outdoor temperature conditions required to achieve snow slide-off, utilizing the slide-off performance of the roofing material, the roof pitch and the temperature change over the period of snow accumulation. Less
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