Further development, testing and modeling of the Axon seismic isolation system
Fenz, Daniel Mark
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Key to the success or failure of any seismic isolation system is whether or not it can deliver stable, predictable performance over its lifetime. Seismic isolation is an established technology that will only gain in prevalence as engineers shift focus towards performance-based design rather than merely satisfying code requirements. This thesis focuses on improving the reliability and predictability of the Axon seismic isolation system. The system proved to be an effective means of reducing seismic response in shake table testing performed by Wolff and Constantinou (2001). These tests also however, identified various concerns with the sliding interface and restoring force element that could potentially lead to variable or inconsistent behavior. This thesis first presents the experimental work done to identify low friction materials for the sliding interface that offer stable properties under high loads and a wide range of sliding velocities. Subsequently, experimental work on urethane and natural rubber restoring force elements is presented. After the experimental work, both complex and simplified analysis of the restoring force element is shown with comparisons made to experimental results. The more sophisticated approach involved large displacement finite element analysis. Simplified analysis was based on a simple, physical model of the restoring force element. This is later used for design work. After experimental and analytical work performed at the component level was complete, experimental testing of a small-scale prototype bearing was performed. With this, sufficient information was generated to draw conclusions regarding the isolation system's effectiveness and applicability for use and to make recommendations for design.