Now-a-days, the construction industry is witnessing an increased demand for taller light-weight structures. The modern high-rise steel building gains more flexibility and lower damping ratio, therefore it's more prone to vibrations due to lateral loads. Seismic and wind induced vibrations in high-rise steel buildings may cause structural damage or annoyance to the occupants. In the recent years, the researchers developed several techniques to mitigate the response of structures due to seismic and wind loads. Among of these technique is the use of tuned mass damper (TMD) to control the vibration in civil engineering structures.
A Tuned mass damper is a passive mass damper. It is a kind of passive energy absorbing translational vibrations of civil engineering structures. Tuned mass dampers (TMD) consist of a mass connected to the structures through a translational spring and a dashpot which is the simplest damper.
The objective of this research is to investigate the behavior and the effectiveness of passive mass dampers on steel structural buildings.
A detailed literature review of this passive mass damper is provided concentrating on its applications to steel structures. In addition, some discussion about the effectiveness of TMD for mitigating harmonic loads of machines, wind and earthquake induced vibrations is also presented.
A numerical analysis is proposed on the effectiveness of tuned mass damper to reduce translation structural vibration. The following 3 types of models are considered in the analysis; 2D single degree of freedom building, 2D 6-degres of freedom structure, and 2D 10-degres of freedom structure. The Finite Element of the three types of models is investigated considering the structural building is provided with and without TMD. The rigid body of motion of the tuned mass damper and the lateral vibrations of the buildings are coupled and energy is translated between them.
Three types of dynamic loading conditions are considered, named sinusoidal machine load (with different load frequency ratios), earthquake loads and wind loads. Seven natural earthquake records are used for the verification of different time history analysis. These earthquake records are as follows; El-Centro (Imperial Valley, 1940, NS component), Northridge (Canyon Country, 1994), Loma-Prieta (Cliff House, 1989), Kobe (Kakogawa, 1995), Aqaba (Hadera, 1995, EW component, Mexico (Cerro Prieto, 1980), and Whittier Narrows (Pasadena, 1987. Three wind speed time history are considered. The wind records are obtained from the Egyptian Meteorological Authority at the Abbasia and Katameya station at Cairo and the third station is Zaafarana at Red Sea.
The effectiveness of TMD in reducing structural response is studied for variation of TMD parameters, (mass ratio, frequency ratio and damping). The structural buildings are also analyzed with different damping ratios.
A case study was performed to examine the vibrations of the super tall TAIPEI 101 skyscraper. To investigate the response of Taipei tower that composed of 101 floors to wind loads, an equivalent 10-D.O.F model was performed by SAP2000. Two FEMs are created, one of them is the main structure itself as 2-D frame and the other one is the main structure with TMD. The change in the response of the tower due to a wind-induced vibration is illustrated by performing a time-history analysis with and without the TMD in a SAP2000 model.
Based on the analysis results, conclusions are drawn about the advantages and disadvantages of the TMD device and its potential to become a practical mechanism to protect structures against the devastating effects of dynamic loads, wind and earthquakes. The study indicates that the passive mass dampers can serve as a rational device to mitigate the translations and vibrations from wind, machine loads and some cases of earthquake excitations. Passive mass dampers may not be efficient in all earthquake loads, and other types of mass damper may be preferable to be equipped. TMD is efficient when the damping ratio of the structure is low. Increasing the ratio of the TMD decreases the displacement, acceleration response and base shear of the structure.
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