Investigation of the shear behaviour of unbonded Fiber Reinforced Elastomeric Isolators (FREIs) with modified support geometry

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Conference Proceeding

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Proceedings, Annual Conference - Canadian Society for Civil Engineering





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The use of fiber reinforcement in lieu of traditional steel reinforcement for elastomeric seismic isolators has the potential for widespread application in developed and developing countries. If mechanical fasteners are not used when installing a Fiber Reinforced Elastomeric Isolator (FREI) between the supports, a unique roll-over deformation will occur when displaced horizontally. This roll-over deformation is a consequence of the lack of flexural rigidity of the fiber reinforcement and the unbonded application of the isolator. Unbonded FREIs have a non-linear shear relationship due to the roll-over behaviour. The non-linear relationship is a desirable feature as it allows the response of the isolator to be tailored depending on the horizontal force. Methods of predicting and modelling the non-linear relationship range from simplified analytical equations to complex finite element analysis. Three analytical models are reviewed and compared, outlining the fundamental assumptions and implications of each model. Shear relationships are compared against experimental results for two unbonded FREIs from the literature. Of the three models considered, only one provides an estimate of the deformed shape of the roll-over. This model is adapted to show the influence of modifications to the support geometry that can be used as an additional design parameter. Recommendations are made based on model results and areas requiring further investigation are identified and discussed.

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