Advanced Modeling and Evaluation of the Response of Base-Isolated Nuclear Facility St

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Advanced Modeling and Evaluation of the Response of Base-Isolated Nuclear Facility Structures to Vertical Earthquake Excitation

Author: Eric Scott Keldrauk | Size: 12.9 MB | Format: PDF | Quality: Unspecified | Publisher: University of California, Berkeley | Year: 2012

The commissioning and construction of new nuclear power plants in the United States has dwindled over the past 30 years despite signi cant innovation in reactor technology. This
is partially due to the ever-increasing seismic hazard estimates, which increases the demand on and risk to nuclear power plant structures. Seismic base isolation is a mature technology which introduces a laterally- exible and vertically-sti layer between the foundation and superstructure to signi cantly reduce the
seismic response of the structure, systems, and components therein. Such devices have also been noted to concentrate the displacement response in one plane, reduce higher-mode
participation, and provide damping to protect against excessive displacements, all of which aid in increasing safety margins for seismically-isolated nuclear structures. Despite numerous
studies analyzing the applicability of seismic base isolation to nuclear power plant structures, some of which are discussed herein, no seismically-isolated nuclear plant has been constructed in the United States. This study presents a time-domain procedure for analyzing the performance of seismicallyisolatednuclear structures in response to design-basis earthquake events using ALE3D. The simulations serve as a parametric study to assess the e ects of soil column type, seismic isolation model, superstructure mesh, and ground motion selection on global displacements, rotations, and accelerations, as well as internal oor accelerations. Explicit modeling of the soil columns and superstructures enables detailed analysis of soil-structure interaction. The
soil columns analyzed have constant properties over the height of the nite element soil mesh
and include rock, soft rock, and sti soil sites, as well as a \no soil" case for comparison.
Four separate 3-dimensional seismic isolation bearing models were coded into ALE3D and validated. These include models for friction pendulum, triple friction pendulum, simpli ed lead rubber, and robust lead rubber bearings. Lastly, two superstructure nite element meshes were considered: a cylindrical plant design meant to represent a typical conceptual
design for advanced reactors, and a rectangular plant design meant to represent an advanced
boiling water reactor. The ground motions considered include 30 three-component time his

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