For decades, the System for Analysis of Soil Structure Interaction (SASSI) program and its derivatives has been an accepted and favoured analysis tool for treatment of seismic soil-structure interaction (SSI) effects on nuclear facilities. With continued advances in the fields of structural and geotechnical engineering, and increasing detail and refinement of analysis models, SASSI has become a computational bottleneck in the design and evaluation of nuclear plant structures, and may not provide the fidelity and detail expected in modern engineering. Gross model simplifications are commonplace to ensure reasonable analysis schedules, necessitating numerous assumptions, sensitivity studies, and qualitative evaluations to address specific nuances and details of SSI phenomena.

Enhanced solution algorithms have become available since the development and adoption of SASSI, and have been incorporated into the SASSI framework to efficiently take advantage of modern high-performance computing (HPC) to drastically reduce analysis run-time and increase permissible model sizes (i.e. larger number of interaction nodes). These expanded SASSI capabilities allow more accurate and streamlined treatment of considerations that have traditionally been treated indirectly or in limited detail, including:

  • Structure-soil-structure interaction (SSSI) analysis of multiple buildings
  • Probabilistic (versus deterministic) SSI analysis and in-structure response spectra
  • Deep embedment, especially with soft soils and high-frequency hazard
  • Ground motion incoherency
  • Variation of potential system configurations / boundary conditions
  • Multiple hazard levels for input to component fragility analysis

This paper provides a variety of recent project examples highlighting how enhanced solution algorithms coupled with HPC capabilities have allowed SASSI to be efficiently used for directly addressing such considerations, resulting in gains such as improved accuracy, reduced uncertainty, and accelerated schedules.

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