Frequency- and deformation-dependent macroelement model for dynamic axial soil-buried structure interaction in time domain

The spatial distribution of horizontally buried structures makes them more susceptible to seismic hazards. This naturally requires a reliable and effective method to analyze soil-buried structure interaction (SbSI) problems, in which the reduced-order model is widely-used thanks to its robustness and computational efficiency. However, for buried structures, no reduced-order model was capable of simultaneously capturing the frequency-dependent characteristics and the true nonlinear nature of the interaction forces. Accordingly, we proposed a dual frequency- and deformation-dependent macroelement model to investigate dynamic axial SbSI problems in the time domain. Novel uniaxial material models, such as Modified Bouc-Wen and Gyromass, were also implemented in OpenSees for the macroelement model development. Results of the proposed approach show good agreement with those of published experiments and finite element analyses. Finally, we present an illustrative example of a buried pipe subjected to spatially varying seismic ground motions. To highlight the importance of frequency- and deformation-dependent characteristics, we compared the results obtained from the proposed approach with those from a frequency-independent Kelvin-Voigt model. It is noticed that ignoring the frequency-dependency can lead to an underestimate of the axial strain envelope, e.g. up to 30% in the case of seismic excitation with a central frequency of 6 Hz.