or
more,
the
mathematical
model
shall
be
C1 = modification factor to relate expected
redesigned, and the pushover procedure repeated
unless the overdesign can be justified as being cost-
maximum inelastic displacement to displacements
effective or otherwise beneficial.
calculated for linear elastic response.
1.0 for Te ≥ Ts
(2)
Target displacement.
The target
=
displacement *t for a building with rigid diaphragms
at each floor level shall be estimated using an
[1.0 + (R - 1) Ts/Te]/R for Te < Ts
=
established procedure that accounts for the likely
but need not exceed:
nonlinear response of the building.
Actions and
C1 = 1.5 for Te < 0.10 sec.
deformations corresponding to the control node
displacement equaling or exceeding the target
C1 may be interpreted between Te = 0.10 sec and
displacement shall be used for component checking
Te = Ts.
in Chapter 7.
The procedure for evaluating the
target displacement is given by the following
Ts = a characteristic period of the response
equation:
spectrum, defined as the period associated with the
transition from the constant acceleration segment of
2
Te
the spectrum to the constant velocity segment of the
*t = C0 C1 C2 C3 Sa
(5-5)
4Π 2
spectrum.
where:
R =
ratio of elastic strength demand to
calculated yield strength coefficient. See below for
Te = effective fundamental period of the
additional information.
building in the direction under consideration
C2 = modification factor to represent the
C0 = modification for C0 can be calculated
effect of hysteresis shape on the maximum
using one of the following:
displacement response. Values for C2 are established
in Table 5-2.
the first modal participation factor at
the level of the control node
C3
=
Modification factor to represent
increased displacement due to dynamic P-) effects.
the modal participation factor at the
For buildings with positive post-yield stiffness, C3
level of the control node calculated using a shape
shall be set equal to 1.0. For buildings with negative
vector corresponding to the deflected shape of the
post-yield stiffness, values of C3 shall be calculated
building at the target displacement
using Equation 5-7.
the appropriate value from Table 5-1.
5-14
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