DS 2-8 Earthquake Protection for Water-Based Fire ... - FM Global

Earthquake Protection 2-8
FM Global Property Loss Prevention Data Sheets Page 47
National Institute of Standards and Technology (NIST), U.S. Department of Commerce. Analysis of Fire
Sprinkler System Performance in the Northridge Earthquake. NIST-GCR-98-736.
Structural Engineering Institute/American Society of Civil Engineers (SEI/ASCE). Minimum Design Loads
for Buildings and Other Structures. Standard SEI/ASCE 7.
APPENDIX A GLOSSARY OF TERMS
Allowable Stress Design (ASD): A method of designing structural members such that computed stresses
produced by normal gravity design loads (e.g., the weight of the building and usual occupancy live loads)
do not exceed allowable stresses that are typically below the elastic limit of the material (e.g., in steel these
are typically well below the yield stress, F y). Although not common currently, in the past normal allowable
stresses were often increased by a factor (often a one-third increase was used) when design included extreme
environmental loads such as earthquakes. (Also called working stress design or elastic design).
Elastic: A mode of structural behavior in which a structure displaced by a force will return to its original state
upon release of the force.
Elastic Design: See allowable stress design.
FM Approved: References to ‘‘FM Approved’’ in this data sheet mean the products or services have satisfied
the criteria for FM Approval. Refer to the Approval Guide, an online resource of FM Approvals, for a complete
listing of products and services that are FM Approved.
Four-way bracing: Sway bracing intended to resist differential movement of the piping system in all horizontal
directions. Most often used on vertical pipe. When applied to horizontal piping, it is essentially a lateral and
a longitudinal brace in the same location.
Importance factor: A factor used in building codes to increase, for example, the usual wind or earthquake
design forces for important or essential structures or equipment, tending to make them more resistant to those
phenomena.
Lateral brace: A sway brace intended to resist differential movement perpendicular to the axis of the pipe.
Sometimes referred to as a transverse brace.
Load and Resistance Factor Design (LRFD): A method of designing structural members such that computed
stresses produced by service design loads multiplied by load factors do not exceed the theoretical nominal
member strength multiplied by a strength reduction (resistance) factor. (Also called strength design or
ultimate strength design).
Longitudinal brace: A sway brace intended to resist differential movement parallel to the axis of the pipe.
Strength Design: See load and resistance factor design.
Sway brace: An assembly, consisting typically of a pipe attached component (PAC), a brace member and
building attached component (BAC),used to resist the seismic forces imparted to the sprinkler system and
prevent excessive differential movement of the piping system.
Transverse brace: See lateral brace.
Two-way bracing: Either lateral or longitudinal sway bracing intended to resist the perpendicular or the parallel
two-way differential movement with respect to the axis of the pipe. Where a single sway brace acts as a
two-way brace, it must resist both tension and compression forces.
Ultimate Strength Design: See load and resistance factor design.
Working Stress Design: See allowable stress design.
Yield point: The stress (usually designated by F y) at which there is a decided increase in the deformation
or strain without a corresponding increase in stress. The strain is inelastic resulting in permanent deformation.
APPENDIX B DOCUMENT REVISION HISTORY
May 2010. This data sheet has been revised in its entirety to provide a consistent format. Editorial corrections
(such as revising metric sizes) were made throughout the document. Several technical revisions were made
as well, the most significant of which include the following:
• Clarified that design basis is Allowable Stress Design (Section 1.0).
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