Geology Reference
In-Depth Information
BS
−
−
BS
located at
m
active floors and
BS
NDOF
is the base
shear force in a structure with optimally distributed
dampers located at all floors.
Similar criteria are proposed to examine the
effectiveness of a control system with a limited
number of active devices connected to amplifiers:
0
m AM
,
J
=
⋅
100
%
(12)
6
BS
BS
0
NDOF
where BS
m,AM
is the peak base shear force in a
structure with optimally distributed dampers,
connected to amplifiers at
m
active floors.
NDOF
NDOF
∑
∑
d
−
d
i
,
0
i m AM
,
,
i
=
1
i
=
1
AMPLIFYING DEVICES
J
=
⋅
100%
(10)
4
NDOF
NDOF
∑
∑
d
−
d
i
,
0
i NDOF
,
It is well known that during earthquakes rigid
structures have small inter-story drifts and drift
velocities. Hence the effect of energy dissipation
in damping devices connected to Chevron braces
(Figure 1a) is not always high as desired. Using
amplifying devices increases the deformations and
velocities transferred to dampers and consequently
enhances their efficiency. It was demonstrated
experimentally and analytically that the toggle
brace configuration (Figure 1b) increases energy
dissipation (Taylor, 2000, Constantinou, 2001).
A more effective amplifier called a “scissor-
jack” (Figure 1d) has demonstrated high magnify-
ing effect (Constantinou, 2000). It was reported
that using this configuration reduces the required
i
=
1
i
=
1
where
d
i,m,AM
is the peak inter-story drift at floor
i
in a structure with optimally distributed dampers
connected to amplifiers at
m
active floors.
NDOF
NDOF
∑
∑
a
−
a
i
,
0
i m AM
,
,
i
=
1
i
=
1
J
=
⋅
100%
(11)
5
NDOF
NDOF
∑
∑
a
−
a
i
,
0
i NDOF
,
i
=
1
i
=
1
where
a
i,m,AM
is the peak acceleration at floor
i
in
a structure with optimally distributed dampers,
connected to amplifiers at
m
active floors.
Figure 1. Dampers configurations: (a) Chevron brace, (b) toggle brace, (c) lever arm, (d) scissor jack
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