**FALL
2003
**

**Volume
I: Deterministic and Probabilistic Control of Seismic Vibration using TMD
**

Fahriba
Manju

This
work presents a study on the effectiveness of Tuned Mass Damper (TMD) to control
seismic vibration. Several RC buildings of different heights (2, 5, 10, 20
storied) are considered as the structural models. The so-called ‘optimized’
TMDs (obtained for White Noise excitation of SDOF systems) are installed at the
top of the structures and modifications of the structural behavior are studied
for both deterministic and stochastic ground motions.
Deterministic studies are performed with
the El Centro earthquake in USA (1940) and the Kobe earthquake in Japan (1995)
while the
stochastic analyses use the White Noise as well as the Kanai-Tajimi spectrum.
Both studies observe the effect of mass
ratio of the so-called ‘optimized’ TMD on the vibrations of the structures
and the TMD itself. Besides
the standard deviation and response spectra for the first floor motions obtained
by random simulations in the time domain are compared with the probabilistic
predictions in the frequency domain. Parametric studies are also performed
varying the properties of the TMD and observing the resulting effects of the
structural response.
Results show the
effectiveness of the TMD depending on its mass ratio, height of the structure as
well as nature of the earthquake spectrum. It is observed that since the TMD is
tuned to the first natural frequency of the structure, it is more effective in
reducing the structural motions around that frequency. Moreover, beyond a
certain mass ratio the TMD does not reduce (in fact it even increases) the
structural motions significantly.
Results from the parametric studies show that
although the so-called ‘optimized’ parameters of the TMD do not always
provide the minimum structural vibrations, the values are quite close to the
minimum. The studies also show the importance of the damping of TMD in decaying
the structural vibrations. |