Effective Configurations of Active Controlled Devices for Improving Structural Seismic Response - Design Optimization of Active and Passive Structural Control Systems - page 236

mal control with variable gains and fuzzy logic
control shows that the second is superior to the
other in 50% of the investigated cases, while the
third performs well for earthquakes with large
accelerations. The first is effective in minimiz-
ing the acceleration of the superstructure that is
subject to moderate excitation. Nonlinear model
based control algorithms are developed recently
to monitor the magnetorheological damper volt-
age (Ali, 2009). These techniques are effective
under a set of seismic excitations, compared to
the performances obtained with a fuzzy based
intelligent control algorithm and a widely used
clipped optimal strategy.
Many state of the art publications on control
applications are published. These publications
provide a review of base isolation systems (Kelly,
1986), active control (Soong, 1988, 1990, 1994,
Datta, 2003), structural control concepts and strate-
gies (Housner, 1997, Spencer, 2003), etc. In most
cases active control systems are designed based
on the linear quadratic regulator (LQR) theory or
H ∞ control theory, and the state feedback control
laws are converted into output feedback ones
(Ikeda, 2004).
Structural control should be based on economic
principles. With this aim inexpensive control
devices should be developed and number of such
devices, required for obtaining optimal control,
should be minimized. In most structural applica-
tions passive or active devices in are connected
to diagonal or Chevron braces. When a damper is
connected to Chevrone braces the interstory drift
and drift velocity are transferred to the damper.
If a damper is connected to diagonal braces, the
displacement and velocity, transferred to the
damper are lower, compared to the interstory drift
and drift velocity, respectively.
Several efforts are undertaken to improve the
damper efficiency. Various amplification devices
are proposed to magnify the displacements and
velocities, transferred to dampers, in order to
increase energy dissipation in each damper and

decrease the number of dampers. Different ampli-
fying devices are developed and proposed to be
used for increasing energy dissipation (Hanson,
2001). Such amplifiers include toggle braces
(Taylor, 2000, Constantinou, 2001) lever arms
(Ribakov, 2000, 2003), scissor jack (Gluck, 1999,
Sigaher, 2003, Ribakov, 2006), displacement am-
plification device based on a gear-type mechanism
(Berton, 2005), cables and other configurations
(Choi, 2010).
Effective placement of active and passive
devices has also high importance. Many tech-
niques were developed to find optimal locations
of passive dampers. Parameters of linear viscous
dampers that should be connected in each floor
of a structure can be obtained using an optimal
method based on LQG control (Gluck, 1996).
The single mode approach is a special case of this
method and it is suitable for structures with one
dominant vibration mode. A method for finding
the optimal damper locations, minimizing the
dynamic compliance of a planar building frame,
was developed ( Takewaki , 2000). It allows finding
an optimal damper positioning sequentially for
gradually increasing total damper capacity levels.
Certain locations are advantageous also for
placement of actuators in the structure for effective
reduction of its dynamic response. Optimal loca-
tion of actuators in an actively controlled structure
was studied in the frame of zero-one optimiza-
tion problem with a constraint on the number of
actuators (Rao, 1991). An optimization scheme,
based on genetic algorithm was developed. The
maximization of energy dissipated by an active
controller was used as the objective function.
Locations of the electro-rheological dampers in
structures can be also obtained by placing virtual
dampers at the locations of interest and computing
the power dissipation in the dampers (Chen, 2003).
A general method for optimal application of
dampers and actuators in seismic-resistant struc-
tures is developed by Cheng (2002). The study
includes development of a statistical criterion,