- Baker, HA; Williams, CJ; Irwin, PA
- For buildings being designed in cold regions, local building codes provide guidelines to determine loads attributed to snow accumulations. These guidelines necessarily apply to only a range of generic situations that are fairly simple. For unusual roof geometries, and/or for cases where the surrounding buildings and terrain complicate the wind flow patterns over the roof, the code provisions can be difficult to interpret and may be inaccurate. The National Building Code recommends model simulations for these cases. Model testing and computer analyses, utilizing detailed meteorological histories, have now developed to the point where the many variables that affect snow loading can be accounted for, even in complex situations, leading to more accurate loading predictions. The variables affecting snow loading include: building shape; building orientation; building insulation; wind speed; wind direction; precipitation (both snow and rain); temperature (melting, re-freezing); cloud cover; and, solar exposure. This paper will describe several case histories where detailed scale model simulations and computer simulations have been undertaken on specific projects. These simulations provide many interesting insights into the way snow loads build up and how they are affected by the climates in different regions. The application of these methods can be particularly helpful in resolving situations where the construction of a new building could potentially increase snow loads on an adjacent building. In this situation the cost of upgrading the existing roof, as would be required by application of the generic code provisions, can be magnified by the cost of lost business during the retrofit. Therefore it becomes extremely important to establish with the best possible accuracy what the expected loads will be and whether they will in truth cause an overload on the existing roof.
- December 1, 2003
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