Seismic Performance of Shallow Founded Structures on Liquefiable Ground: Validation of Numerical Simulations Using Centrifuge Experiments

Abstract

The results of fully coupled, three-dimensional (3D), nonlinear finite-element analyses of structures founded on liquefiable soils are compared with centrifuge experiments. The goal is to provide insight into the numerical model’s capabilities in predicting the key engineering demand parameters that control building performance on softened ground for a range of structures, soil profiles, and ground motions. Experimental and numerical observations will also guide future analyses and mitigation decisions. The numerical model captured excess pore pressures and accelerations, the dominant displacement mechanisms under the foundation, and therefore building’s settlement, tilt, and interstory drift. Both experimental and numerical results showed that increasing the structure’s contact pressure and height/width (H/B) ratio generally reduces net excess pore pressure ratios in soil but amplifies the structure’s tilting tendencies and total drift. The settlement response of a structure with a greater pressure and H/B ratio was also more sensitive to soil-structure-interaction induced forces, which could at times amplify on a denser soil with less softening. A denser soil profile also increased building’s flexural drift in all cases by reducing excess pore pressures and rocking drift, while amplifying foundation accelerations and total drift. Numerical simulations captured these trends well. These experimental and numerical results point to the importance of taking into account a building’s dynamic properties and overall performance in mitigation design.