Geology Reference
In-Depth Information
SEMI-ACTIVE TUNED MASS
DAMPER SYSTEM
Most of the above studies have related to the
use of dynamic vibration absorbers in mechanical
systems. While application of these systems in civil
engineering structures, frequently known as tuned
mass damper (TMD) systems, is expected to be
different. In last decades, many research studies
have been performed to show the effectiveness
of the TMD system and the other control devices,
derived from TMD, such as: semi-active tuned
mass dampers (STMDs) and active tuned mass
dampers (ATMDs) in civil engineering commu-
nity in reducing the structural responses, some of
which are reviewed in the following.
The tuned mass damper (TMD) system is a
typical form of control devices including a mass,
spring, and a viscous fluid damper, which can be
attached to the main structure at one of its degrees
of freedom. This system is one of the well-accepted
devices to control flexible structures, particularly,
tall buildings. In this passive control system, if its
damping ratio or stiffness of the spring changes
with time, then it is called a semi-active tuned
mass damper (STMD).
Wirsching and Campbell (1974) evaluated the
optimal values of the TMD parameters for one-
story, and ten story building structures. It has been
shown that the optimum values of TMD stiffness
becomes less sensitive to structural damping and
mass ratio when the number of stories increases;
and the optimum TMD damping is insensitive to
structural damping even for one-story buildings
(Soong and Dargush, 1997).
Huffmann et al. (1987) investigated the ef-
fectiveness of two separate TMDs, installed in
the center of a bridge deck, to reduce flexural
and torsional vibrations. Each TMD was tuned to
the corresponding eigenfrequency. Nobuto et al.
(1988) performed a study to suppress the coupled
flutter of long-span bridges using a 2-TMD model.
They showed that the TMD frequency should be
tuned to the frequency of the torsional mode of
the bridge.
Warburton (1982) proposed optimal design of
the TMD under different types of loads. Sadek et
The modern concept of tuned mass dampers
(TMDs) for reduction of structural vibrations,
indeed, is the development of the undamped
dynamic vibration absorber studied as early as
1909 by Frahm (Frahm 1909; Den Hartog 1956).
Frahm's dynamic absorber was consisting of a
small mass m and a spring with spring stiffness
k attached to the main mass M with spring stiff-
ness K. Under a simple harmonic load, it can be
shown that the main mass M can be kept com-
of the attached absorber is chosen to be (or tuned
to) the excitation frequency (Soong & Dargush,
1997; Grover 1996).
Den Hartog (Ormondroyd and Den Hartog,
1928) first studied the theory of undamped and
damped dynamic vibration absorbers without
considering damping in the main system, and
developed the basic principles and the procedure
for proper selection of absorber parameters.
Bishop and Welbourn (1952) continued the above
procedure by considering the damping in the main
system. Then in 1967, Falcon et al. performed an
optimization procedure to obtain minimum peak
response and maximum effective damping in the
main system (Soong & Dargush, 1997).
A translatory-rotary absorber system has been
numerically studied by Jennige and Frohrib (1977)
to control both bending and torsional modes in
a building structure. Then Ioi and Ikeda (1978)
developed empirical formulas for correction fac-
tors of these optimum absorber parameters by
considering light damping in the main system.
Warburton and Ayorinde (1980) performed another
study to introduce further optimum values of the
maximum dynamic amplification factor, tuning
frequency ratio, and absorber damping ratio for
specified values of the mass ratio and the main
system damping ratio (Soong and Dargush, 1997).
k
m
pletely stationary if the natural frequency
Search WWH ::
Custom Search