are classified as being either primary or secondary.
6-3.
Enhanced Performance Objectives.
Primary components and elements are those that
provide the structure' overall ability to resist
s
The minimum analytical procedure for enhanced
collapse under earthquake-induced ground motion.
performance objectives is the linear elastic static or
Although damage to these components, and some
dynamic procedure using the modification factors, m
degradation of their strength and stiffness, may be
(refer to Paragraph 5-2b(2) for the exception
permitted to occur, the overall function of these
applicable to buildings with enhanced performance
components in resisting structural collapse should
objectives in Seismic Design Categories A and B).
not be compromised. Other components and
The dynamic procedure shall be employed when the
elements are designated as secondary. For some
limitations described in Paragraph 5-2b preclude the
structural
performance
levels,
substantial
use of the static procedure. The acceptance criteria
degradation of the lateral-force-resisting strength
for all performance objectives analyzed by the
and stiffness of secondary components and elements
dynamic procedure are the same as for the Linear
is permissible; however, the ability of these
Elastic Static Procedure, except that the seismic
secondary components and elements to support
design actions, QE in Equations 6-2, 6-4a, and 6-4b,
gravity loads under the maximum deformations
for the individual structural components, are
induced by the design ground motion, must be
obtained by either square root of the sum of the
preserved.
squares (SRSS), or by the complete quadratic
combination (CQC) of the modal values for each
(1)
General.
The analysis procedure
action. The nonlinear static procedure shall be used
indicates the structure' response to the design
s
in lieu of the linear procedures when the conditions
earthquake and the forces and deformations imposed
described in Paragraph 5-4b are present. Alternative
on the various components, as well as the global drift
analytical procedures and applicable acceptance
demands on the structure.
Acceptability of
criteria not prescribed by this document will require
component behavior is evaluated for each of the
specific authorization by the cognizant design
component' various actions using Equation 6-2 for
s
authority.
ductile
(deformation-controlled)
actions,
and
Equations 6-4a and 6-4b for nonductile (force-
a.
Linear Elastic Static Procedure. For those
controlled) actions.
structures with a linear elastic static procedure
permitted in accordance with Paragraph 5-2b,
(a)
Figure 6-1 indicates typical
compliance with enhanced Performance Objectives
idealized force-deformation curves for various types
2A, 2B, and 3B shall be achieved by evaluation of
of component actions.
The Type 1 curve is
the demand on individual structural components in
representative of typical ductile behavior.
It is
accordance with the following procedures adopted
characterized by an elastic range (point 0 to point 1
from FEMA 273. Structural components or elements
on the curve), a plastic range (points 1 to 2) that may
6-3
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