Date of Award
Master of Applied Science (MASc)
Michael J. Tait
The first application of the tuned liquid damper (TLD) to mitigate the
dynamic vibrations of structures was only around 20 years ago and has just been
recently applied in North America. TLDs are partially fluid filled tanks (usually
water) with a fundamental sloshing frequency tuned close to the frequency of the
dynamic mode of structural vibration to be suppressed. Water alone is
insufficient to achieve the level of damping typically required for design.
Damping devices are often submerged in the water to greatly increase the inherent
TLD damping. The damping device investigated in this study is a thin sharpedged
horizontal-slat screen. TLDs with such screens of a particular solidity are
designed for one target amplitude of structural response and have limited
efficiency over a range of structural response. To increase the efficiency, the
concept of smart screens is introduced in this study.
Smart screens is the name given to a damping screen that alters its fluid
pressure-loss characteristics at differing levels of excitation, (ideally) in a passive
state of control. Symmetric fixed-angle screens and oscillating (rotating) parallellinked
screens are experimentally investigated inside a rectangular TLD on a
shake-table under sinusoidal motion in this study.
TLDs have similar principles to common tuned mass dampers (TMD) and
are analyzed accordingly. The TLD equipped with fixed-angle screens is
modelled with linear numerical fluid models to simulate the TLD performance for preliminary design purposes. An inclined screen alters the pressure-loss
characteristics from its typical vertical position, which in turn changes the
inherent TLD damping, allowing damping to be controlled by simple screen
rotation. The analytical models, including the utilization of a pressure-loss
coefficient for an inclined horizontal-slat screen in oscillatory flow developed in
this study, are compared with experimental results to verify their accuracy and
Oscillating smart screens are investigated mainly for their practical
consideration in a preferred passive mode of control. The screens rotate
automatically with changes in fluid velocity (or excitation amplitude). Their
ability to maintain a near-constant amount of TLD damping (or resonant energy
dissipation) is examined. Other implementations of (passive) smart screens are
possible and suggestions for future study are recommended.
A TLD equipped with the mathematically modelled symmetric fixed-angle
screens is theoretically investigated in a hypothetical structure-TLD system. This
system demonstrates the ability of a smart screen to change its damping
characteristics-altering the angle of inclination in this study-over a range of
structural response thereby maintaining an optimal level of efficiency over a
range of structural response accelerations.
Cassolato, Marcus Richard B.E.Sc., B.Sc., "The performance of a tuned liquid damper equipped with inclined and oscillating damping screens" (2007). Open Access Dissertations and Theses. Paper 3873.