The structure is located on a Class E
The isolation system does not limit
or F site; or
maximum capable earthquake displacement to less
than SM1/SD1 times the total design displacement.
The structure is located at a site with
(c) Dynamic analysis. A dynamic analysis
S1 greater than 0.60g.
is permitted to be used for the design of any structure,
but shall be used for the design of all isolated
e.
Equivalent Lateral Force Procedure.
structures not satisfying Paragraph 8-3d(3)(b). The
dynamic lateral response procedure of Paragraph 8-3f
(1) General. Except as provided in Paragraph
shall be used for design of seismically isolated
8-3d, every seismically isolated structure or portion
structures as specified below.
thereof may be designed and constructed to resist
minimum earthquake displacements and forces, as
1.
Response-spectrum
analysis.
specified by this Paragraph and the applicable
Response-spectrum analysis is permitted to be used
requirements of FEMA 302.
for design of a seismically isolated structure,
provided that:
(2) Minimum lateral displacements.
The structure is located on a Class A,
(a)
Design displacement.
The isolation
system shall be designed and constructed to
B, C, or D site; and
withstand minimum lateral earthquake displacements
The isolation system meets the
that act in the direction of each of the main horizontal
axes of the structure in accordance with the
criteria of Item 7 of Paragraph 8-3d(3)(b).
following:
2. Time-history analysis. Time-history
analysis is permitted to be used for design of any
g S T
DD = 2 D1 D
(8-1)
4π BD
seismically isolated structure, and shall be used for
design of all seismically isolated structures not
meeting the criteria of Paragraph 1 above:
where:
3.
Site-specific design spectra.
Site-
g = acceleration of gravity. The units of the
specific
ground-motion
spectra
of
the
design
earthquake and the maximum considered earthquake
units of the design displacement, DD, are inches
developed in accordance with Paragraph 8-3f(4)(a)
(mm).
shall be used for design and analysis of all
seismically isolated structures, if any one of the
SD1 =
design 5 percent damped spectral
following conditions apply:
acceleration in g units at 1 sec period for Ground
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