Prediction of worst combination of variable soil properties in seismic pile response

Robustness analysis of seismic pile response of a structure-pile-soil system with uncertain soil properties is presented in this paper. The uncertainties of soil properties are extremely large compared to superstructures and inherent. The upper and lower bounds of the bending moment of a pile are investigated by means of the previously proposed uncertainty analysis method (Updated Reference-Point method). Soil stiffnesses and damping ratios as uncertain parameters are treated as interval parameters. The earthquake ground motion defined in the engineering bedrock in the form of a response spectrum is used as the input. An efficient finite-element model of an overall structure-pile-soil system is adopted and a response spectrum method is applied in the evaluation of the seismic pile responses of the system. It is shown that the worst combination of uncertain soil parameters can be determined and this information certainly upgrades the robustness of the structure-pile-soil system.