Wind tunnel model studies of roof snow loads resulting from multiple snowstorms

Most physical model studies of roof snow loads deal with the aerodynamic influence of buildings on shaping snow accumulations during particular snowstorms. While the effects of such “single events” can be satisfactorily predicted with physical model studies in wind tunnels and/or water flumes, the evaluation of how weather events combine to produce maximum loads during a particular winter is more difficult. Numerical techniques are used in combination with physical model tests to predict maximum snow accumulations which can occur on roofs. Numerical methods are effective in evaluating the influence of temperature, solar radiation, heat loss from the building and the effects of rain. It is more difficult to use numerical methods to evaluate the accumulation and redistribution of snow on roofs. These depend on the aerodynamics of roofs and are difficult to predict without information from wind tunnel model tests. This paper describes wind tunnel experiments carried out to examine the snow accumulation on roofs which can result due to weather events during cold periods when the roof snow layer remains susceptible to drifting. Results of wind tunnel model studies of such multiple-events and those obtained for a maximum single storm are presented for a large roof.