Seismic response of underground reservoir structures in sand: Evaluation of Class-C and C1 numerical simulations using centrifuge experiments

Centrifuge experiments were conducted to investigate the seismic response of stiff-unyielding buried reservoir structures with varying stiffness in medium-dense, dry sand. The results of these tests were used to evaluate the predictive capabilities of Class-C and C1, nonlinear, finite element analyses of the seismic response of these relatively stiff buried structures. All simulations were performed in two dimensions using the pressure-dependent, multi-yield-surface, plasticity-based soil constitutive model (PDMY02) implemented in OpenSees. For Class-C simulations, model parameters were calibrated based on the available cyclic simple shear tests on the test soil. For Class-C1 simulations, the same soil model was used along with user-defined modulus reduction curves that were corrected for soil's implied shear strength. The use of shear modulus reduction curves, which modeled a softer soil response compared to PDMY02, generally improved the prediction of site response in the far-field as well as seismic racking deformations, earth pressures, and bending strains on the structures. Experimentally, the dynamic thrust, racking, and bending strains on or of the model structures were shown to primarily peak near the strain-dependent fundamental frequency of the site, regardless of the fundamental frequency of the structure itself. This influence in addition to other important response parameters were captured reasonably well by Class-C1 simulations, with residuals ranging from −0.25 to 0.2.