Design Ground Snow Loads: Historical Perspective and State of the Art
Publication: Journal of Structural Engineering
Volume 148, Issue 6
Abstract
This paper reviews the development of snow load research since the contemporary introduction and calibration of the ANSI A58-1982 provisions (and subsequent ASCE 7-88). The ASCE 77-88 ground snow loads were based on the data and methods available at the time and subsequently updated in 1995. The provided loads are based on 50-year mean recurrence intervals, with design loads for each category being obtained through a combination of partial safety and importance factors. Changes and improvements in snow load design over the last 40 year necessitate a reconsideration of the original calibration of these safety and importance factors. This paper discusses the need for a movement away from a uniform-hazard snow load design approach in combination with uniform load and importance factors, in favor of reliability-targeted design snow loads. This paper reviews the concept of reliability targeted loads as a means of meeting the ASCE 7 goal of uniform risk/reliability in the US. This paper further describes the incremental changes in both reliability and snow load research that will culminate in a change from uniform hazard (i.e. 50-year) loads to uniform-reliability loads. The purpose of this paper is to describe the motivation for, and historical context of E 7, the forthcoming changes to design ground snow loads in ASCE 7-22. Furthermore, the paper discusses the future of snow load prediction and its impact on the engineer and the code, particularly in regards to the implications of climate change for future snow load design.
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Data Availability Statement
All data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
This research was made possible through funding from the Structural Engineering Institute of the American Society of Civil Engineers in collaboration with several private organizations. The groups that provided significant monetary support to this effort were (in alphabetical order) Factory Mutual, Metal Building Manufacturer’s Association, National Council of Structural Engineering Associations, Nucor, Simpson Gumpertz and Heger, the State of Montana, the Steel Deck Institute, the Steel Joist Institute, Structural Engineers Association of Montana, Wiss Janney and Elstner Associates. Oversight of the work was provided by a steering committee headed by Abbie Liel and Scott Russell with members Jim Harris, Mike O’Rourke, Jim Buska, Jerry Stephens, R. Nielson, D. Jared DeBock, Johnn Judd, David Thompson, Hossein Mostafaei, John Corless, John-Paul Cardin, Sean Homem, Gary Ehlrich, Sterling Strait, Vince Sagan, Thomas DiBlasi, and chair of the Rain and Snow Load Subcommittee: John Duntemann. Additionally, results were reviewed by a steering committee led by Bruce Ellingwood, Jeanette Torrents, and Therese McAllister. The authors would like to thank all those who have generously provided their time as part of this effort. Special thanks to David Thompson for his keen observations and thoughtful questions that led to the questions that were answered by the bulk of this document.
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Journal of Structural Engineering
Volume 148 • Issue 6 • June 2022
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© 2022 American Society of Civil Engineers.
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Published online: Apr 13, 2022
Published in print: Jun 1, 2022
Discussion open until: Sep 13, 2022
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