On the suitability of proposed equivalent linear elastic models for multi-story seismically isolated buildings

Abstract eng:
Seismic isolation is used in relatively stiff buildings to reduce the induced seismic loads, by shifting their fundamental periods outside the dangerous for resonance range. Seismic isolation systems exhibit non-linear inelastic behavior, which can be sufficiently well represented by bilinear inelastic models. However, simplified linear elastic analysis is often used, at least at the preliminary design and analysis phases of seismically isolated buildings. Therefore, it is very important to investigate the appropriateness of using such linearized models, by comparing their computed responses with those of the more accurate bilinear inelastic models. The proposed in the literature effective characteristics of equivalent linear elastic models that are used to simulate the bilinear hysteretic behavior of seismic isolation are assessed. The proposed methods and formulas are evaluated by comparing the computed peak responses with those that are computed using the corresponding bilinear inelastic models. In particular, this research work investigates whether linearized models are suitable for the analysis of seismically isolated buildings, considering the maximum relative displacements at the isolation level, the peak interstory deflections and the peak absolute floor accelerations. A number of numerical simulations and parametric studies have been performed, using a specially-developed software, to obtain an insight on the accuracy of the proposed equivalent linear elastic models. The analysis results indicate that there are several limitations to the usage of equivalent linear elastic models in the simulations of seismically isolated buildings and suggest that nonlinear inelastic analysis should be performed.

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