Nonlinear time-domain soil–structure interaction analysis of embedded reactor structures subjected to earthquake loads

• Derived modified version of Bielak’s SSI method for nonlinear time-domain analysis.
• Utilized a Ramberg–Osgood material with parameters that can be fit to EPRI data.
• Matched vertically propagating shear wave results from CARES.
• Applied this technique to a representative SMR, compared well with SASSI.
• The technique is extensible to other material models and nonlinear effects.

A generalized time-domain method for soil–structure interaction analysis is developed, based upon an extension of the work of the domain reduction method of Bielak et al. The methodology is combined with the use of a simple hysteretic soil model based upon the Ramberg–Osgood formulation and applied to a notional Small Modular Reactor. These benchmark results compare well (with some caveats) with those obtained by using the industry-standard frequency-domain code SASSI. The methodology provides a path forward for investigation of other sources of nonlinearity, including those associated with the use of more physically-realistic material models incorporating pore-pressure effects, gap opening/closing, the effect of nonlinear structural elements, and 3D seismic inputs.