Feasibility Study on Building Mass Damper Using Optimum Dynamic Response Control Algorithm for Practical Application

In a mid-story isolated building, the isolation system is incorporated into the mid-story rather than the base of the building. The effectiveness of mid-story isolation design in reducing seismic demands on the superstructure above the isolation system has been verified in many researches. But the response of substructure may be enlarged due to the flexibility and the contribution of the higher modes. Besides, tuned mass damper (TMD) system has been recognized as an effective energy absorbing device to reduce the undesirable vibrations of the attached vibrating system subjected to harmonic excitations. Therefore, the concept of building mass damper (BMD) design is to combine the tuned mass damper system and mid-story isolated design to control the seismic response of both substructure and superstructure. In BMD design, the superstructure serves as a tuned absorber mass whose stiffness and damping can be provided by the isolation system composed of elastomeric bearings and additional dampers, as the advantages of conventional tuned mass damper and mid-story isolation systems can be integrated. A simplified three-lumped-mass structure model, in which three lumped masses are respectively assigned at the building mass absorber, the control layer, and the primary structure, is rationally assumed to represent a building structure with a BMD system. The reason for doing this is so that the inherent dynamic characteristics (fundamental modal characteristics of vibration) of both the building mass absorber and the primary structure can be considered comprehensively in the simplified structure model. The feasibility of the optimum BMD (or OBMD) design method has been verified in previous studies. In this research, the 57-story steel frame is used to be a bare frame. According to 2% inherent damping ratios of the TMD, BMD and OBMD can be designed respectively. Six real earthquake records with distinct seismic characteristics adopted in this research are selected for the ground acceleration inputs along the longitudinal and transversal direction. On the other hand, the acceleration transfer functions of the simplified three-lumped-mass structural model and the FFT of each ground motion are used to describe the seismic behavior of the TMD, BMD and OBMD. Then, the seismic responses of the OBMD system are thoroughly investigated and the practicability and effectiveness of the OBMD system for seismic design are verified.