d.
Basis of the Procedure.
Under the
(1) General. In this document, the Nonlinear
Nonlinear Static Procedure, a model directly
Static Procedure involves the monotonic application
incorporating inelastic material response is displaced
of lateral forces or displacements to a nonlinear
to a target displacement, and resulting internal
mathematical model of a building until the
deformations and forces are determined.
The
displacement of the control node in the mathematical
nonlinear-load-deformation
characteristics
of
model exceeds a target displacement. For buildings
individual components and elements of the building
that are not symmetric about a plane perpendicular
are modeled directly. The mathematical model of
to the applied lateral loads, the lateral loads must be
the building is subjected to monotonically increasing
applied in both the positive and negative directions,
lateral forces or displacements until either a target
and the maximum forces and deformations used for
displacement is exceeded, or the building collapses.
design. The relation between base shear force and
The target displacement is intended to represent the
lateral displacement of the target node shall be
maximum displacement likely to be experienced
established for control node displacements ranging
during
the
design
earthquake.
The
target
between zero and 150 percent of the target
displacement, *t, given by Equation 5-5. Acceptance
displacement may be calculated by any procedure
that accounts for the effects of nonlinear response on
criteria shall be based on those forces and
displacement amplitude; one rational procedure is
deformations
(in
components
and
elements)
presented in Paragraph 5-4f, and further described in
corresponding
to
a
minimum
horizontal
displacement of the control node equal to *t,.
Paragraph 4-8b(3) and Table 4-7.
Because the
mathematical model accounts directly for effects of
Gravity loads shall be applied to appropriate
material inelastic response, the calculated internal
elements and components of the mathematical model
forces will be reasonable approximations of those
during the nonlinear analysis. The loads and load
expected during the design earthquake. The target
combination presented in ASCE 7, as appropriate,
displacement calculated using Equation 5-5 may be
shall be used to represent the gravity loads. The
unconservative if the strength ratio of Equation 5-6
analysis model shall be discretized in sufficient
exceeds five, or if the building is located in the near
detail to represent adequately the load-deformation
field of the causative fault. Results of the Nonlinear
response of each component along its length.
Static Procedure are to be checked using the
Particular attention should be paid to identifying
applicable acceptance criteria prescribed in Chapter
locations of inelastic action along the length of a
6, and provided in Chapter 7.
Calculated
component, as well as at its ends.
displacements and internal forces are to be compared
directly with the allowable values.
(2)
Control node.
The procedure requires
definition of the control node in a building. This
e.
Modeling and Analysis Criteria.
document considers the control node to be the center
of mass at the roof of a building.
The top of a
penthouse should not be considered as the roof. The
5-9
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