and the 1.0 second ordinates for Ground Motion A or
B, or for the MCE. The calculation of the effective
(2) Linear Static Procedures.
damping is estimated as follows:
(a)
Displacement-dependent device.
The
∑W
Linear Static Procedure (LSP) may be used to
j
implement
displacement-dependent
energy
βeff = β +
i
(8-18)
4π k
W
dissipation devices, provided that the following
requirements are satisfied:
where $ is the damping in the framing system, and is
set equal to 0.05, unless modified. Wj is work done
1. The ratio of the maximum resistance in
by device j in one complete cycle corresponding to
each story, in the direction under consideration, to the
floor displacements *i, the summation extends over
story shear demand calculated using Equations 5.3.4-
all devices j, and Wk is the maximum strain energy in
1 and 5.3.4-2 in FEMA 302, shall range between 80
the frame, determined using Equation 8-19.
percent and 120 percent of the average value of the
ratio for all stories. The maximum story resistance
shall include the contributions from all components,
1
∑ Fi di
Wk =
(8-19)
elements, and energy-dissipation devices.
2 i
2. The maximum resistance of all energy-
where FI is the inertia force at floor level I, and the
dissipation devices in a story, in the direction under
summation extends over all floor levels.
consideration, shall not exceed 50 percent of the
resistance of the remainder of the framing, where said
(b) Velocity-dependent devices.
resistance
is
calculated
at
the
displacements
anticipated in the MCE. Aging and environmental
1. The LSP may be used to implement
effects shall be considered in calculating the
velocity-dependent
energy-dissipation
devices,
maximum resistance of the energy dissipation
provided that the following requirement is satisfied:
devices.
The maximum resistance of all
3.
The base shear and story forces
energy-dissipation devices in a story, in the direction
calculated by Equations 5.3.4-1 and 5.3.4-2 in FEMA
under consideration, shall not exceed 50 percent of
should be reduced by the damping modification
the resistance of the remainder of the framing, where
factors in Table 8-2 to account for the energy
said resistance is calculated at the displacements
dissipation (damping) affected by the energy
anticipated in the MCE. Aging and environmental
dissipation devices.
Figure 8-8 indicates how the
effects shall be considered in calculating the
response spectrum is modified by the damping
coefficient Bs and B1 in Table 8-2. In Figure 8-8, the
spectral ordinates Sxs and Sx1 represent the 0.2 second
8 - 32
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