New Static Analysis Methods and LRFD Recommendations for Steel H-Piles in Rock-Based Intermediate Geomaterials

Existing static analysis methods and their resistance factors recommended in the AASHTO LRFD Bridge Design Specifications (2020) were developed for pile resistance predictions in soils. The performance of existing α- and β-methods on the LRFD design of steel H-piles in rock-based Intermediate GeoMaterials (IGMs) were evaluated in terms of both resistance and efficiency factors. Compared to AASHTO (AASHTO LRFD bridge design specifications, 9th ed, U.S. Customary Units, Washington, DC, 2020) recommendations, lower resistance factors calibrated for IGM-rocks confirmed that the prescribed reliability level cannot be attained using the existing α- and β-methods. Furthermore, lower efficiency factors were determined for the α- and β-methods on the shaft resistance and end bearing predictions. To improve the efficiency of pile designs in rock-based IGMs, calibrated α- and β-methods consisting of new equations for design coefficients were developed based on an electronic database (WyoPile) of pile load test data in IGM-rocks of Wyoming. The proposed LRFD procedure consists of probability based resistance factors determined using the First Order Reliability Model and Monte Carlo Simulation for target reliability indices of 2.33 and 3.00. Higher resistance and efficiency factors were achieved for the calibrated α- and β-methods. The uncertainties of the calibrated resistance factors described by the mean, standard deviation, and 95% confidence interval are also presented to address the effect of sample sizes used in this study.