Seismic control of concrete bridges using multiple tuned mass dampers

The magnitude-frequency response and phase-frequency response of concrete bridges appended multiple tuned mass dampers (MTMD) with difference parameters are studied. The time-historic responses of the MTMD system excited by seismic waves with different frequency characteristics are calculated. The analysis of the frequency response shows that the peak magnitude-frequency response decreased largely when the frequency bandwidth of the dampers become small, but the effective frequency ranges of the excitations become narrow. So the frequency bandwidth of the dampers should be properly selected under wide-frequency earthquake excitations. It is more effective when the prominent frequency of the construction sites approach or larger than the frequency of the controlled mode. The control effect under difference earthquake excitations and the effective frequency ranges of the excitations changed with the various parameters of the MTMD system. The optimized selection of the parameters of the MTMD system under earthquake excitations must take consideration of the practical application and the construction sites of the structures. The MTMD system can also take effect by some degrees when slight mistuning or the frequency ranges of the excitations varying. So it is more robust than the single TMD (STMD) system.