Roof Collapse under Snowdrift Loading and Snowdrift Design Criteria

This paper summarizes an investigation of the roof collapse that occurred at Waterville Junior High School in Waterville, Maine, on February 9, 1978, after a heavy snowstorm. The primary cause of the collapse is found to be that load from drifting snow was not considered in the design; the physical cause is found to be severe overloading of open web joists. Had the designer followed accepted engineering practice standards for drifting snow existing at the time of design, the collapse would not have occurred. The paper also compares the snowdrifts observed at Waterville Junior High School to accepted engineering practice at the time of design, to other observations of snowdrifts, and to recent code criteria for snow drifts. The proper character of drift loads is found not to have been recognized by the structural engineering profession at the time of the collapse, and presently, the ability of the profession to predict snowdrifts and their loads is limited. Recommendations for improving predictions of snowdrift loads using recent code criteria are presented.