Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

Vertical mass isolation (VMI) is one of the novel methods for the seismic control of structures. In this method, the entire structure is assumed to consist of two mass and stiffness subsystems, and an isolated layer is located among them. In this study, the magnetorheological damper in three modes: passive-off, passive-on, and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems. Multi-degrees-of-freedom structures with 5, 10, and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes. On each level, the displacement of MR dampers was taken into account. The responses of maximum displacement, maximum inter-story drift, and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures. According to the results, the semi-active control method can reduce the response by more than 12% compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures. This method can reduce more than 16% and 20% of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure, respectively.