Determination of Partial Factors for a Vertically Loaded Pile Based on Reliability Analysis

The aim of this study is to establish a procedure to rationally determine the partial factors for a vertically loaded pile in the limit state design format based on a sound reliability theory. The frequency of the usage of pile types and dimensions are investigated first. Several design examples are selected, and load ranges and combinations on typical piles are studied. Based on these results, typical load intensities, load combinations and soil profiles are set for the code calibration. Also, uncertainties involved in seismic loading are investigated based on the historical seismic data using an extreme statistical analysis, so called POT (peaks over threshold) analysis. Uncertainties concerning resistances of piles are taken from two well known studies: Okahara et al. (1991) and AIJ (2000). FORM (first order reliability method) analysis is carried out to find out the current level of reliability index. Finally, the design value method is employed to determine the partial factors.