Mitigation of Motions of Tall Buildings with Specific Examples of ...

incorporating fluid viscous dampers to control wind induced vibrations, structures may be built
with reduced lateral stiffness, as the fluid dampers alone reduce the wind deflection by a factor of
2 to 3, greatly improving occupant comfort without creating localized stiff sections (Taylor &
Constantinou 1996).
Though operating on the same premise as many of the other forms of energy dampers, the fluid
damper holds several advantages. Foremost, the performance of the VDD is essentially out of
phase with primary bending and shearing stresses in the structure. Thus, the devices may be effectively
employed to reduce both the internal shear forces and deflections. Furthermore, by requiring
no external power source and little maintenance, they have become very attractive options for
civilian applications, having proven their durability and effectiveness in over 100 years of large
scale military use (Taylor & Constantinou 1996).
6.2.6 Applications of Viscous Damping Devices
Other passive systems also exist and are gaining rapid popularity, especially in the design of seismically
vulnerable structures. In this area, the application of Viscous Damping Devices (fluid
inertial dampers) has been notable. The first use of VDDs for seismic zones was in 1993 in the
earthquake-resistant design of the San Bernadino County Medical Center in California. The
addition of VDDs to the system helped to keep displacements under 22 inches and lengthened the
effective period to 3.0 seconds (Asher et al. 1994).
Since that installation, there have been numerous other seismic applications, including the Pacific
Bell Emergency Communications Building (Sacramento, CA), Woodland Hotel (Woodland,
CA), the CSUS Science II Building (Sacramento, CA) and recently for the seismic retrofit of
bridges. In fact, they were even been installed (1984) in the North American Air Defense Command
in Wyoming for the possible loads caused by a nuclear attack and have been proposed for
use in residential structures (Taylor & Constantinou 1996).
While such devices have witnessed widespread application in seismic zones, they have also been
installed in several structures for the explicit purpose of controlling wind-induced vibrations, as
Table 10 reflects (Taylor & Constantinou 1996).
Table 10. Applications of Viscous Damping Device to Reduce Wind-Induced Excitation
Structure Location
Rich
Stadium
28 State
Street
Petronas
Twin Towers
Installation
Date
Buffalo, NY 1993 12 Fluid Dampers
Type & Number of
Dampers Additional Information
50 kN, mm stroke
Boston, MA 1996 40 Fluid Dampers
Kuala Lumpur
City
± 460
670 kN, mm stroke
1995 12 Fluid Dampers
10 kN, mm stroke
Building A 1995 80 Oil Dampers, ±60 mm
stroke
Dampers connect light poles to
stadium wall to eliminate base
plate anchor bolt fatigue
used in diagonal bracing for
serviceability issues
part of mass damping system in
skybridge legs
Increased Damping by 2.1% of
critical
Mitigation of Motions of Tall Buildings with Specific Examples of Recent Applications 24
± 25
±
50