Probabilistic evaluation of economical factor of safety for the geotechnical design of pile axial load capacity

Abstract

The inability to evaluate the effects of the various uncertainties due to spatial and material variability of the soil and pile properties in the axial load capacity of a pile foundation had led some designers to adopt higher global factors of safety in design, which may be conservative and uneconomical if it were not properly evaluated. In addition, the use of lower factors of safety in pile design is often traditionally justified only by the performance of specific pile load tests. This study presents the application of probabilistic analysis based on Stochastic Finite Element Method (SFEM) and Monte Carlo Simulation (MCS) in the selection of economical factors of safety for the geotechnical design of pile axial load capacity. The SFEM is implemented by a coupling between the reliability algorithm with the MCS technique in MATLAB® and the OpenSees finite element program. A probabilistic method of pile analysis evaluates the risk, reliability, or probability of failure associated with the selection of lower factors of safety in design. The results of a probabilistic method of pile capacity evaluation then provide guidance in the selection of a more reliable, unconservative, and economical factor of safety at an acceptable level of risk by making cost comparisons with available options for design.