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

oth steel and concrete structures (3M 1995). However, since the VE damper’s properties (storage
and loss moduli analogous to spring and dashpot constants, respectively) are dependent on
vibrational frequency and environmental temperature, the system may manifest varied performance
based on the particular situation. Research indicates, though, that the damper properties
remain somewhat constant with strains below 20% for a given temperature and frequency (Chang
et al. 1992, Oh et al. 1992).
6.2.2 Applications of Viscoelastic Dampers
To date, VEDs have been installed in four buildings in the United States for the minimization of
wind-induced vibrations, with the earliest installation being the World Trade Center Towers in
New York. These applications are summarized in Table 8 (3M 1995):
Table 8. US Applications of VEDs to Reduce Excitation Due to Wind
Building
(Location)
World Trade Center
Towers (Mahmoodi et
al. 1987)
Columbia SeaFirst
Building (Mahmoodi
& Keel 1986)
Two Union Square
Building
Torishima Riverside
Hill Symbol Tower
Location &
Installation
Date
New York
1969
Seattle
1982
Seattle
1988
Japan
1999
Number of
Units Location in Structure Performance
10,000/tower installed in lower chord of
trusses that support the floors
260 parallel to main diagonal
braces of building
16 parallel to four columns on
one floor of bldg
224 8 VED/floor on first 19 floors
4 VED/floor on 20-38 floors
ξ=2.5-3% in
Hurricane Gloria
ξ=3.2% at
design wind and
upto 6.4% in
storms
Wind acceleration
response:
80%
In Japan, VEDS have been used to reduce the wind-induced response of several buildings: Seavans
South Tower in Tokyo (1991), the Old Wooden Temple, Konohanaku Symbol Tower
(1999), ENIX Headquarter Building, the Sogo Gymnasium in Chiba (1993), the Goushoku
Hyogo Port Distribution Center (1998) with viscoelastic joint dampers which reduce the seismic
response by one half, and the Torishima Riverside Hill Symbol Tower, whose 1999 installation
features 8 VEDs per story for the 1st to 19th floors and reduces to 4 VEDs per story for the
20th to 38th stories. In addition, the Chientan Railroad Station in Taipei, Taiwan has also been
equipped with 8 viscoelastic units to control the wind-induced vibrations of its unique suspended
dragon boat roof (Cermak et al. 1998).
Although the use of VEDs to control excitations due to wind has been commonplace for over 20
years, their use in seismic applications has just begun to flourish (Samali & Kwok 1995). Their
installation in the form of rubber-asphalt attached to the walls in one direction of every floor of a
24 story building was found to improve the structural responses under earthquake conditions by
30% (Maebayashi et al. 1993). There have been numerous other seismic applications, particularly
in the area of retrofitting, in the United States, including the Santa Clara Civic Center Office
Mitigation of Motions of Tall Buildings with Specific Examples of Recent Applications 22