Tuned Liquid Column Gas Damper in Structural Control - Design Optimization of Active and Passive Structural Control Systems - page 176

For practical purposes the liquid column
length has to be in the range of several meters to
thirty meters and more for large structures, caus-
ing the classical TLCD's natural frequency to be
far below 1Hz. The invention of the gas spring
effect by properly sealing and pressurizing the
rigid pipe not only has extended the practical
frequency range say up to 5Hz, but also renders
an easily accessible tuning parameter, namely
the static equilibrium gas pressure in the sym-
metrically arranged gas containers above the
inclined pipe sections. Furthermore, additional
desired properties were obtained, particularly the
passive protection against overload and excessive
liquid column strokes and the reduced sensitivity
against parametric excitation. The simple tuning
mechanism allows for very promising applications
of TLCGD in case of continuous adjustment of
the frequency e.g. in the course of the cantilever
method of bridge construction. Den Hartog's opti-
mal tuning is recommended for preliminary modal
design, before splitting the TLCGD into smaller
units in parallel action to achieve an additional gain
in structural damping and a more robust control
of the response in the neighborhood of resonance
frequencies by fine tuning in state space. As a
general rule the TLCGD should be installed at the
position of largest modal displacements. For the
low vibration modes of a building the top floor
is appropriate, for higher modes an intermediate
floor might be equally adequate. For strongly
asymmetric buildings a redesigned torsional
TLCGD (TTLCGD) is recommended. Applying
the device to increase the effective damping of a
lightly damped base isolation mode, the base slab
is proposed for TLCGD placement because it is
easy to meet the requirements for the additional
mass load as well as the space specifications for
the TLCGD piping system. Besides the classi-
cal V-or U-shaped TLCGD a novel design of a
VTLCGD is analyzed that mitigates dominating
vertical vibrations, e.g., of bridges and large floor-
plates. For a practical design of the symmetric
VTLCGD unit and to safely avoid unsymmetric

flows and sloshing, two separate TLCGDs are to
be combined, Ziegler et al. (2013).
The advances made in the last decade have led
to an increased insight and the understanding of
TLCGD has grown in C.E. practice a great deal.
As a result simple guidelines for optimal place-
ment and tuning are readily available for buildings,
bridges and recently even for large arch-dams. So
far, all research results indicate that the TLCGD
is more competitive when compared to TMD so
that it should replace the TMD (possibly except
the pendulum-dashpot type) in almost any struc-
tural application.

REFERENCES

Bachmann, H. (2010). Seismic upgrading of a fire-
brigade building by base isolation in Basel, Switzer-
land. Structural Engineering International , 20 (7),
268-274. doi:10.2749/101686610792016880

Den Hartog, J. P. (1956). Mechanical vibrations
(4th ed.). New York, NY: McGraw-Hill.

Fu, C. (2008). Effective damping of vibrations
of plan-asymmetric buildings. Doctoral disserta-
tion, Vienna University of Technology, Austria.
Retrieved from http://www.ub.tuwien.ac.at/ diss/
AC05037516.pdf

Fu, C., & Ziegler, F. (2010). Vibration prone
multi-purpose buildings and towers effectively
damped by tuned liquid column-gas dampers.
Asian Journal of Civil Engineering , 10 (1), 21-56.

Hochrainer, M. J. (2001). Control of vibrations
of civil engineering structures with special
emphasis on tall buildings . Doctoral disserta-
tion, Vienna University of Technology, Austria.
Retrieved from http://www.ub.tuwien.ac.at/ diss/
AC03322409.pdf

Hochrainer, M. J. (2005). Tuned liquid column
damper for structural control. Acta Mechanica ,
175 (1-4), 57-76. doi:10.1007/s00707-004-0193-z