Civil Engineering Reference
In-Depth Information
Table G1-2
Damage Resulting from Dif erent Types of Snow Loading
Type of Snow Loading Number of Cases Percentage
Roof step drift 12 22
Parapet wall drift 6 11
Gable roof drift 12 22
Combined drift 8 15
Open air & freezer buildings 8 15
Sliding snow 1 2
Others 7 13
Total 54 100
Note: Cases are from author's forensic engineering practice covering the past 15 years.
in drifting loads at the lower roof's northwest corner. This roof drift results
partially from windward roof step drifting (wind component out of the east)
in combination with gable roof drifting (wind component out of the south).
Hence roof drifting of one kind or the other accounted for about 70% of the
failures. Other causes were nominally uniform loading on open air and freezer
buildings (15%) and sliding loads (2%). The “Other” category includes the
case of a partial collapse due to ice-dam formation at the eave of a building, a
few cases with missing fl ange braces in metal buildings, and the like.
The purpose of this guide is to provide structural engineers with a detailed
description of the snow loading provisions in Section 7 of the SEI/ASCE Stan-
dard 7-10,
Minimum Design Loads for Buildings and Other Structures
. The
guide presents the research and philosophy that underpins the provisions and
illustrates the application of the provisions through numerous examples so that
the user not only knows how to use the provisions but also knows the reason-
ing behind them. Consequently, users may be able to address nonroutine snow
loading issues that are not explicitly covered in the ASCE 7-10 provisions.
Structural engineers involved in the design, analysis, and/or review of
building structures are the intended audience for this guide. Although previous
experience calculating snow loads is not necessary to use this guide, most read-
ers will have used the ASCE 7 snow load provisions in the past, even if only in
a “cookbook” fashion. This guide could be used in graduate or undergraduate
civil engineering courses, but it was not written with that audience exclusively
in mind.
Chapters 2 through 10 of this guide are named and numbered to cor-
respond with the ASCE 7-10 snow provisions. As an example, Chapter 5 is
devoted to partial loading, which is covered in Section 7.5 of ASCE 7-10. This
guide does not contain a separate chapter for Section 7.1 because the symbols
and notations provided in that section are defi ned in this guide when fi rst
encountered. Chapter 11 corresponds to material in Sections 7.11 and 7.12 of
ASCE 7-10. Chapter 12 presents three complete snow design examples, while
Chapter 13 answers frequently asked questions (FAQs).
The examples appearing at the ends of Chapters 2 through 10 illustrate
the correct application of the ASCE 7-10 snow load provisions. Chapter 11
