Effects of riverbed scour on seismic performance of high-rise pile cap foundation

To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity (or supply) of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.