the various performance objectives.
For most
The building has a non-orthogonal lateral-
moment frame systems, the contribution of panel
force-resisting system.
zone deformations to overall story drift may be
assumed to be adequately represented by the use of
c.
Implementation of the Procedure shall be in
centerline-to-centerline
dimensions
in
the
accordance with the provisions of Section 5.3 of
mathematical model. This analytical procedure is
FEMA 302, with exceptions or modifications as
considered acceptable for all structures and all
noted in the following paragraphs.
performance objectives designed in accordance with
(1) Performance Objective 1A. In accordance
this
document,
except
for
the
structures
with Section 5.3 of FEMA 302, except that I = 1.0.
incorporating the use of a supplemental energy
This is the prescribed analysis in FEMA 302 for
dissipation system and some types of base isolation
standard occupancy structures, and is prescribed in
systems. For specific analysis procedures applicable
this document as a preliminary analysis for all
to those structures, refer to Chapter 8. The ELF
seismic use groups to satisfy the Life Safety
procedure described in Paragraph 5-2 may be more
Performance Objective.
appropriate for some regular or rigid (one or two-
story) structures. Unusual or complex structures in
(2) Performance Objective 2A, 2B, and 3B.
Seismic
Use
Groups
II
and
III,
with
the
In accordance with Section 5.3 of FEMA 302, except
characteristics described in Paragraph 5-4b, may
that R = 1.0, I = 1.0, and the base shear is modified
require a nonlinear elastic static procedure for
to represent the pseudo-lateral load described in
confirmation
of
the
enhanced
Performance
paragraph 6-3a(2). The m modification factors used
Objectives 2A, 2B, and 3B.
in these analyses are defined in Paragraph 6-3a.
5-4.
Nonlinear Static Procedure.
Exception: Buildings with enhanced performance
objectives in Seismic Design Categories A and B
a.
General.
Nonlinear procedures directly
may be analyzed by the ELF procedure, or the modal
account for the redistribution of forces and
analysis procedure described in the following
deformations that occur in a structure as it undergoes
paragraph, with the appropriate ground motions, the
inelastic response. Consequently, they are generally
R factors from Table7-1, and the applicable I factor
capable of providing a more accurate estimate of the
from FEMA 302.
demands produced in a structure than either of the
5-3.
Linear Elastic Dynamic Procedure.
linear procedures.
However, the nonlinear static
procedure is not able to predict accurately the higher
This procedure, also known as the "Modal Analysis
mode response of flexible structures and a nonlinear
Procedure," shall be performed in accordance with
dynamic procedure should be considered for tall
the requirements of Section 5.4 of FEMA 302, with
buildings (i.e. in excess of six stories) or buildings
the exceptions noted in Paragraph 5-2c for use with
with significant vertical irregularities.
5-3
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