Investigation of LRFD Resistance Factors with Consideration to Soil Variability along the Pile Length

The main goal of this study is to examine the Load and Resistance Factors Design (LRFD) approach for pile design in a wide range of soil types considering the use of a combination of static analysis methods. First, the reliability-based regionally calibrated LRFD resistance factors for the design of bridge pile foundations were developed for clay, sand, and mixed soils in Iowa. The framework used for this calibration included a more efficient in-house static design method developed by the Iowa Department of Transportation. Then, the benefits of conducting the calibration using the combination of static methods giving due consideration to the soil variability along the pile length is presented. Finally, it is shown that: a) using a combination of methods improves the efficiency in mixed soils, and b) utilizing a more refined soil categorization based on the actual soil profile on a site-by-site basis provides significantly more efficient LRFD approach for the piles.