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Structural Engineering and Mechanics Volume 88, Number 3, November10 2023 , pages 263-271 DOI: https://doi.org/10.12989/sem.2023.88.3.263 |
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Assessment of a dual isolation system with base and vertical isolation of the upper portion |
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Sasan Babaei, Panam Zarfam, Abdolreza Sarvghad Moghadam and Seyed Mehdi Zahrai
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| Abstract | ||
| Base isolation is a widely used technique for the seismic control of structures as it reduces the structural seismic demand. However, displacement of the isolation layer is not economically feasible in congested urban areas. To resolve the issue, an innovative system is proposed here to isolate both horizontally at the base and vertically in the upper portion of the structure. A simplified linear three degree-of-freedom (3DOF) model of the system that considers the mass and stiffness ratios of the substructure has been introduced and analyzed in MATLAB by spectrum analysis. The 3DOF model results revealed that, when the period of the soft substructure reaches 2.5 times that of the stiff substructure, the isolation and the lower substructure responses decrease by 65% and 51%, respectively. Time-history analysis of a MDOF system at three frequency ratios under a wide range of ground motions indicated that, at the expense of accepting a certain large drift by the soft substructure in the upper portion of the structure, base isolation displacement can be decreased by 10%. | ||
| Key Words | ||
| base isolation; dual isolation; response spectra; structural control; time-history analysis; vertical isolation | ||
| Address | ||
| Sasan Babaei, Panam Zarfam: Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran Abdolreza Sarvghad Moghadam: Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, Iran Seyed Mehdi Zahrai: School of Civil Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran, Iran; Civil Engineering Department, University of Ottawa, Canada | ||