Roof Snowdrifts due to Blizzards

Abstract

The evaluation of structural loads due to drifted snow on a multilevel roof is considered. A detailed case history is presented that highlights the two types of drifts that form on multilevel roofs. The two types of snowdrift are triangular drifts, which typically form at backward‐facing steps, and quadrilateral drifts, which typically form at forward‐facing steps. Thirty‐five case histories of large triangular drifts on multilevel roofs are used in developing an empirical relation for predicting drift size. The empirical relationship is the result of multiple‐regression analysis involving pertinent roof‐geometry parameters as well as environmental factors. The environmental factors considered are snowfall, wind speed and wind direction. The combination of wind and snowfall is an attempt to characterize blizzard intensity. The writers feel that the empirical relationship presented herein is an improvement over previous relationships in that wind in general and blizzard intensity in particular are included in the model.