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Earthquakes and Structures
  Volume 8, Number 5, May 2015, pages 1091-1111

Simplified procedure for seismic analysis of base-isolated structures
Mohammed H. Serror, Sherif O. El-Gazzar and Sherif A. Mourad

    Base isolation is an effective method for protecting structures against earthquake hazard. It elongates the period of vibration and introduces supplemental damping to the structural system. The stiffness, damping and displacement are coupled forcing the code seismic design procedure to be unnecessarily complicated. In addition, the force reduction factor -a key parameter in the design procedure- has not been well addressed by seismic design codes at the high levels of damping due to the pronounced difference between pseudo and actual accelerations. In this study, a comparison has been conducted to evaluate eight different methods, in the literature, for calculating the force reduction factor due to damping. Accordingly, a simplified seismic analysis procedure has been proposed based on the well documented N2 method. Comprehensive analysis has been performed for base-isolated structure models for direct application and verification of the proposed procedure. The results have been compared with those of the European code EC8, the nonlinear time history analysis and investigations in the literature, where good agreement has been reported. In addition, a discussion has been elaborated for the resulted response of the base-isolated structure models with respect to the dynamic characteristics of the base isolation system.
Key Words
    base isolation; force reduction factor; damping; seismic analysis
Mohammed H. Serror, Sherif O. El-Gazzar and Sherif A. Mourad: Department of Structural Engineering, Faculty of Engineering, Cairo University, Egypt

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