Use of tuned mass dampers for the vibration control of floors subjected to human movements.

Abstract

This thesis investigates the use of tuned mass dampers to control the vibration of floor systems caused by human movements. The application of tuned mass dampers to single degree of freedom systems is studied as related to multiple degree of freedom systems with well separated natural frequencies. Use of the equivalent single degree of freedom model to represent the vibration characteristics of multiple degree of freedom systems is discussed. The Component Mode Synthesis method is used to compute the response of the floor-tuned mass damper systems by the modal approach using only a few natural modes of the floor. It is shown that the addition of a number of static mode shapes can give a better accuracy in the responses. Using this technique and optimization software, different finite element models representing typical two and three dimensional behavior of balcony systems are analyzed. Conclusions are drawn regarding the tuning of mass dampers for different balcony characteristics. An experimental investigation of a theater balcony is performed. Tuned mass dampers for reducing the level of vibration of the existing system were manufactured using steel plates, springs and shock absorbers. Results of damper tuning and pre and post tuned mass damper installation tests are given. From this investigation it was concluded that for typical floor systems with natural frequencies separated by at least 50% using tuned mass damper effective mass ratio of maximum 5%, the equivalent SDOF model for optimization can be used. In addition, it was found that the mass dampers have to be tuned to the floor with the maximum likely mass. It was also concluded that when the location of the tuned mass dampers becomes farther from the point of maximum vibration amplitude, the system gets more out of tune. In this case, the CMS method accompanied by Static Mode Shapes to find the optimum tuned mass damper parameters can result in the reduction of the amplitude of vibration. A number of other conclusions regarding the optimum tuning of the mass dampers are mentioned. In addition, a methodology for tuning mass dampers for floor vibration control is proposed.