Assesment of Multiple Base Isolation System Performance

Safarzadeh, Fatemeh and Mohebbi, Mohtasham and Gholizad, Amin (2016) Assesment of Multiple Base Isolation System Performance. Masters thesis, University of Mohaghegh Ardabili.

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Abstract

In this thesis, seismic behaviour of the multiple base isolated structures using lead rubber bearing isolators is investigated. In order to verify the modelling process and also verification of the software results, a five story laboratory benchmark structure is considered under fixed and base isolated conditions. Mode shapes, peak acceleration and drift of stories are compared between experimental data and model results. Seismic behaviour of a 12 story concrete structure is investigated under fixed base (F.B), base isolated (B.I) and multiple base isolated (M.B.I) conditions. The structure is designed based on Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800) and isolators are designed based on NZS3101 code. In M.B.I condition, the structure is devided into three segments. Non-linear time history analysis showed that the base shear of the B.I tall building has not been decreased compared to the F.B case. In M.B.I case, displasement of a single isolator is less than the displacement of the B.I case. Story acceleration is decreased in both of the single isolator and multiple isolators at different stories. Furthermore, reduction of the story acceleration in M.B.I case is considerably less than the B.I case. Comparison of the results obtained by sensitivity analysis showed that the effect of the initial stiffness of the base isolator is higher than the stiffness ratio (ratio of the secondary stiffness to the initial stiffness).

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