June 99
is responsible for specifying the SHL not the
contractor.
B.
Bracing in SHL "A" is designed to resist 48% of the
weight of the ducts or pipes. Bracing in SHL "B" is
designed to resist 30%, and bracing in SHL "C" is
designed to resist 15% of the weight of the ducts or
pipes. In addition to the horizontal seismic force, a
vertical seismic force equal to one-third of the
horizontal force is included in the analysis.
C. Current building codes require most structures and
their components to be designed for a horizontal
seismic force that is a given percent of the supported
weight. Each code has its own method for
determining the percent. The formulas are in the form:
Fp=Cp x Wp
Where Wp is the weight of the ducts or pipes, Fp is
the seismic force, and Cs is a seismic coefficient
which represents a combination of factors that varies
with the building code. Use the more severe of the
Local Code and the Uniform Building Code (UBC) to
determine seismic force, Fp.
D.
The percent horizontal seismic factor is:
%F = (FpxWp) x 100
= Cs x 100
If %F is greater the 48, then the manual cannot be
used, and an independent analysis and design is
required for all bracing components.
E.
Use SHL "A' if %F is between 31-48, use SHL "B" if F
is between 16-30, and use "C" if %F is 15 or less.
4.3 CONFORMANCE WITH NUSIG:
A. NUSIG has developed guidelines as a service to
the design professionals. The guidelines are not
intended as a substitute for design. The design of
seismic bracing remains the responsibility of the
design professional who must review the specific
project for its applicability before using or specifying
NUSIG guidelines.
VA Design Guide -- National Cemetery Administration
Page 5 -63
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