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Cooper B-Line Seismic
Restraints
What is Seismic Bracing?
Seismic forces are exerted on a building and its contents during an
earthquake. These forces act horizontally upon the  structure itself, as
well as the piping, cable trays, ductwork, and other building systems
within. Typical supports for piping, trays, and other equipment are
designed for the gravity, or vertical, loads but do not take into account
the horizontal loading caused by earthquakes. Seismic restraints (i.e.
braces) resist the horizontal forces and keep the systems in place and
secure. The main purpose of seismic bracing is safety- to minimize the
loss of life due to an earthquake.
Seismic Bracing Requirements
The rules and requirements for the seismic restraints are published in
the model building codes: The Uniform Building Code (International
Conference of Building Officials), National Building Code (Building
Officials and Code Administrators) and the Standard Building Code
(Southern Building Code Congress International). Each code is similar in
nature, and has a chapter on structural forces which defines the level of
seismic force must be used in the design of seismic restraints.
The amount of seismic force (as determined
by the building code) is given as a percent of the components’ weight,
or g-force. If the horizontal force is determined to be 50 percent of the
piping weight, for example, the seismic force is .5g. The seismic
"g-value" can vary greatly depending on the nature of the
project. Critical buildings in a high seismic zone have larger g-value
requirements than warehouses in zone 1.
Factors that govern the seismic g-values
used for design: Seismic Zone, Building Type, Elevation within
building, System being braced, Soil Type, Distance from known
faults. The design professional should use these factors and the
applicable building code requirements to determine the proper g-values to
be used for the project.
B-Line's Seismic Restraints brochure
contains seismic bracing details that can be used for seismic bracing
projects up to 1.0 g. The bracing details for the pipe hangers, trapeze
supports, structure attachments, and components are the same for any
g-value. The brace spacing charts and rod loads, however, must be
determined for the specific g-value for the project. This brochure
contains charts for a variety of g values, however, the charts can be
changed to reflect different g-values, hanger spacings, and system weights
as required for the project. Contact B-Line Engineering at 618-654-2184
with your requirements.
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