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.