Vertical response behaviour of Stable Unbonded Fiber Reinforced Elastomeric Isolators (SU-FREIs) with holes in the loaded surface

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Conference Proceeding

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Proceedings, Annual Conference - Canadian Society for Civil Engineering



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Base isolation is a seismic mitigation method that seeks to decouple a structure from the ground motions of an earthquake event by introducing a flexible horizontal element at the foundation level. Current base isolation practices using elastomeric isolators are generally employed in a grid pattern and require a structural system to adequately transfer the weight of the structure to these point locations. The concept of large strip isolators allows these concentrated loads to be uniformly distributed along the length of the isolator. If used in an unbonded application with fiber as the reinforcement, the strip isolator can maintain a positive tangential stiffness as the ends of the isolator roll-off. Isolators displaying this type of characteristic are denoted as Stable Unbonded Fiber Reinforced Elastomeric Isolators (SU-FREIs). It is necessary to have sufficient control over the horizontal and vertical properties of the isolator to optimize the design. One approach for this is the introduction of holes to the loaded surface of the isolator. The influence of holes on the vertical properties of the isolator is investigated through an experimental study of six SU-FREIs. Holes are introduced to five of the SU-FREIs either in the interior or exterior of the loaded area. The influence of the area removed and shape factor are discussed. The study concluded that the vertical stiffness and effective compression modulus are highly dependent on the area removed and the shape factor.



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