Geology Reference
In-Depth Information
INTRODUCTION
thing along with the developed control algorithms
and control devices is the mechanism of optimal
placement of control devices and sensors within
structures. However, the optimal placement of
control devices/sensors has not been much inves-
tigated even though it can significantly contribute
to the improvement of control performance. With
this in mind, we propose three new different
multi-objective optimization algorithms of not
only finding minimum distributions of both actua-
tors and sensors, but also minimizing the seismic
responses of structures.
To date, the impact of optimal placement of
control devices in large-scale civil structures has
been investigated. Arbel (1981) found optimal
locations of actuators in an oscillatory dynamic
system using controllability measures. DeLorenzo
(1990) optimized the placement of actuators and
sensors in a solar optical telescope system using
successive approximation-based weight-selection
technique. Chen et al (1991) used simulated an-
nealing (SA) for finding optimal placement of
active/passive members of truss structures. GA
was applied to an active truss structure for finding
optimal locations of actuators (Rao et al. 1991).
Onoda and Hanawa (1992) applied GA to an actua-
tor placement optimization for correcting statisti-
cal static distortion of truss structures. Furuya and
Haftka (1995) applied GA to optimization prob-
lems of finding optimal actuator locations within
large space structures. Dhingra and Lee (1995) ap-
plied a hybrid gradient based GA to an across-four
space structure for finding actuator locations and
minimum weights of structures. Liu et al. (1997)
used SA to solve an integrated structural topology
and actuator placement problem of structures.
Agrawal and Yang (1999) studied a variety of
heuristic search algorithms for optimal placement
of energy dissipative devices within buildings,
including Sequential, Worst-Out-Best-In, and
Exhaustive Single Point Substitution methods.
Linear quadratic Gaussian-based Pareto optimal
trade-off curves have been proposed by Brown
et al. (1999) for various placements of actuators
In recent years, structural control technology
has attracted a great attention from the society
of civil engineering because the properties of
structural systems can be modified in real time
without adding too much mass to mitigate severe
damage and protect structural poverty and human
lives from attacking strong natural hazards such
as winds, waves, and earthquakes (Kobori et al.
1991; Soong and Reinhorn 1993; Housner et al.
1994; Adeli and Saleh 1999; Kim et al. 2009;
2010a; 2010b; Cha and Agrawal 2011). As a re-
sult of this, a lot of control strategies have been
proposed. In general, structural control systems
can be classified into three different categories:
passive, active, and semi-active control systems
(Spencer and Nagarajaiah 2003). It is generally
said that the passive control system is the most
stable and reliable control method because it does
not require external power supply, but utilizes
material yielding forces or viscosity of fluids or
friction forces. Representatives of the passive
control devices include viscous fluid damper,
viscoelastic damper, friction damper, tuned mass
damper, tuned liquid damper, tuned liquid column
damper, base isolation systems, etc. Although it
is relatively easy and cheap to install into civil
structures, the parameters of the passive systems
cannot be adjusted during earthquake events. On
the other hand, active control systems can adjust
control forces according to the maginitude and
spectrum of external loads and structural respons-
es. Thus, active control systems are more effective
in mitigating natural hazards of large-scale civil
structures than the passive systems. However, the
active control system requires large external power
supply to offer desired control forces that derive
actuators. Although semi-active control systems
have been proposed to compenstate the drawbacks
of the active and passive systems, it is beyond the
scope of this topic chapter. This study focuses on
the application of structural active control systems
to large-scale civil structures. Another important
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