<p>Real-time hybrid simulation (RTHS) has demonstrated certain advantages over conventional large-scale testing. In an RTHS, the system that is under study is partitioned into a numerical and a physical substructure, where the numerical part is comprised of those elements that are easier to model mathematically, while the physical part consists of those that present a complex behavior difficult to capture in a numerical model. The most complex part of this study is the isolation system, a technology used to protect structures against earthquakes by modifying how they respond to ground motions. Unbonded Fiber Reinforced Elastomeric Isolators (UFREIs) are devices that can accomplish this task and have gained attention in recent years because of their modest but valuable features that make them suitable for implementation in low-rise buildings and in developing countries because of their low cost. Our end goal for this work is to enable the testing of scaled versions of these elastomeric isolators to understand their behavior under shear tests and realistic loading. </p> <p>A testing instrument was designed and constructed to apply a uniaxial compressive force up to 22kN and a shear force of 8kN simultaneously to the specimens. A testing program was conducted where four primary sources of signal distortion were identified as caused by the servo-hydraulic system. From these results, a mechanics-based model was developed to understand better the dynamics that the sliding table can introduce to the measured signals accounting for inertial and dissipative forces. Two Bouc-Wen models were implemented to simulate the behavior of the UFREIs. The first only accounts for the hysteretic behavior of the isolator, and the second accounts for the additional nonlinearities found in the isolator’s behavior. These models were assembled in a virtual RTHS which is available to users interested in learning the applications of RTHS of a base-isolated structure with a nonlinear component.</p> <p>An RTHS experiment was conducted in the IISL where the control system comprised a delay compensator and a proportional-integral controller, which exhibited a good tracking performance with minimal delay and low RMSE. However, it can increase the distortion of the oil-column resonance in the measured signals. The simulation captures the behavior of the isolated structure for small displacements. However, it underestimates the displacement of the full-scale specimen for large displacements. The RTHS showed a better approximation of the displacement of the full-scale structure than the theoretical behavior approximated by the Bouc-Wen models.</p>

<p>The research presented in this dissertation investigates the influence of soil-structure<br> interaction on seismic isolation of nuclear reactor vessels using numerical simulations. This<br> research is motivated by the nuclear industry searching for viable solutions to standardize<br> the design of reactor vessels. Seismic isolation of reactor vessels is a potential solution as it<br> enables deployment of standardized reactor vessels irrespective of site seismic hazard<br> thereby saving time and cost by allowing large-scale factory fabrication of standard<br> modules and by eliminating the need for repeated approval of reactor vessel design. Seismic<br> isolation is also a technology that has matured from successful implementation in buildings<br> and bridges allowing easier transition to nuclear applications. Currently, the<br> implementation of component-level seismic isolation in nuclear industry is challenging due<br> to gaps in research and lack of specific guidelines.</p> <p><br></p> <p><br> In this research, the effectiveness and potential limitations of using conventional friction<br> pendulum bearings for component-level isolation are investigated based on conceptual<br> numerical models of seismically isolated reactor vessels at different nuclear power plant<br> sites subject to a variety of ground motions. The numerical modeling and analysis<br> approach presented in this research are checked using experimental data and results from<br> multiple numerical codes to ensure reliability of the obtained analysis results.</p> <p><br></p> <p><br> Within the scope of this study, it is found that slender vessels are particularly vulnerable<br> to rotational acceleration at the isolation interface. Rotational acceleration at the isolation<br> interface is caused by rotation at the foundation level of the containment building housing<br> the isolated reactor vessel and by excitation of higher horizontal translational modes of the<br> seismically isolated system. Rotation of the building foundation increases with decrease in<br> shear wave velocity of the soil surrounding the building foundation. When the containment<br> building is embedded below the soil surface, the effect of embedment on peak horizontal<br> acceleration of the isolated vessel depends on the amount of increase in shear wave velocity<br> at the foundation level of the building. When embedment does not result in any change in<br> shear wave velocity, it is found to have negligible impact on the acceleration response of the<br> isolated vessel.</p> <p><br></p> <p>  The optimum location to support a vessel for seismic isolation is found to be on a plane<br> passing through its center of mass. It minimizes horizontal acceleration in the isolated<br> vessel as well as the tendency of isolator to uplift. Isolator uplift and exceedence of<br> displacement capacity of the isolator during extreme events are possible drawbacks in using<br> seismic isolation technology since they produce impact forces due to uplift and<br> re-engagement of the isolator or due to collision between the isolated system and the moat<br> wall. If such cases are avoided, seismic isolation of reactor vessel could provide more than<br> 50% reduction in peak acceleration of vessel except for low-intensity motions that do not<br> engage the isolator.<br>  <br>  </p>