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frame subjected to the ground motion recorded at
Sakaria station in the 1999 Kocaeli earthquake.
The two dimensional concrete frame model used
for the study consists of three bays and the base is
assumed to be fixed, neglecting the effect of soil-
structure interaction. The fundamental period of
the un-damped frame is 1.31 seconds. This period
falls in the range where additional damping was
found to increase the response in Figure 1. The
frame is fitted uniformly with viscous dampers
with a capacity of 9000 kN (Taylor 1999). A
uniform distribution of the dampers is adopted
as shown in Figure 2.
Assuming that the parent (i.e. uncontrolled)
frame remains elastic during the seismic event, a
linear time history analysis using the Newmark
Beta scheme is performed using SAP 2000. Both
acceleration and displacement time histories at
the top floor are recorded and the results are
presented in Figures 3 and 4. Figure 3 compares
the displacement time history at the roof for both
the controlled and the un-controlled frames.
Similarly, Figure 4 compares the acceleration time
history at the roof for both the controlled and un-
controlled frames.
Figure 3 clearly illustrates the displacement
response reduction achieved by the controlled
frame. For this specific case, a reduction of ap-
proximately 80% is achieved in the peak displace-
ment. On the contrary, Figure 4 depicts the fact
that at certain specific times, there is an increase
in the acceleration response of the controlled
frame as compared to the un-controlled frame.
For example, the acceleration response between
2 and 3 seconds is considerably higher for the
controlled frame than for the uncontrolled frame.
This reinforces the significance of optimal posi-
tioning by highlighting the fact that “a uniform
increase in damping” might not always be ben-
eficial from a response reduction point of view.
Figure 2. Controlled 20-storey frame with a uni-
formly distributed damper arrangement
PREVIOUS STUDIES
This section presents a consolidated review on
the state-of-the-art for optimal passive damper
placement. Wherever possible and relevant, com-
prehensive outlines of the contents of respective
works are presented. At the end of this section,
some limitations inherent in the current optimal
damper placement methods are pointed.
The majority of earlier research on structural
control science has primarily focused on the design
and installation techniques (i.e., the first system
uncertainty discussed in Section 1). Extensive
studies have been carried out on these aspects of
structural control and considerable progress has
been made. In comparison, studies associated
with optimal positioning (i.e., the second system
uncertainty) are very limited. Classically, optimal
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