Techno Press
Techno Press

Earthquakes and Structures   Volume 13, Number 2, August 2017, pages 103-118
Vertical isolation of a structure based on different states of seismic performance
Reza Milanchian, Mahmood Hosseini and Masoud Nekooei

Abstract     [Full Text]
    In vertical seismic isolation (VSI), a building is partitioned intentionally by vertical layers into two dynamically different substructures for seismic response reduction. Initially, a 1-story frame was partitioned into two substructures, interconnected by viscous and visco-elastic links, and seismic responses of the original and the vertically isolated structures (VIS) were obtained, considering a large number of stiffness and mass ratios of substructures with respect to the original structure. Color contour graphs were defined for presentation and investigation of large amounts of output results. Dynamic characteristics of the isolated structures were studied by considering the non-classical damping of the system, and then the effects of viscous and visco-elastic link parameters on the modal damping ratios were discussed. On this basis, three states of mass isolation, interactional state, and control mass were differentiated. Response history analyses were performed by Runge-Kutta numerical method. In these analyses, interaction of isolation ratios and link parameters, on response control of VIS was studied and the appropriate ranges for link parameters as well as the optimal ranges for isolation ratios were suggested. Results show that by using the VSI technique, seismic response reduction up to 50% in flexible substructure and even more in stiff substructure is achievable.
Key Words
    vertical seismic isolation; non-classical damping; viscous and visco-elastic dampers; Runge-Kutta method; response history analyses
Reza Milanchian, Masoud Nekooei: Department of Structural Engineering, Science and Research branch, Islamic Azad University, Tehran, Iran

Mahmood Hosseini: Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

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