Evaluation of model uncertainties in reliability-based design of steel H-piles in axial compression

To account for uncertainties of load and resistance in a more rational way, reliability-based design (RBD) concepts have been increasingly applied to design bridge foundations. One of critical elements in the geotechnical RBD process is the characterization of model uncertainties. This paper compiles 126 and 23 reliable static load tests for steel H-piles in axial compression from two databases: Pile-Load Tests (PILOT) and Deep Foundation Load Test Database (DFLTD), respectively. The Davisson offset limit is adopted to define the measured resistance in clay, sand, and layered soil, which is verified with the L-1-L-2 method developed for drilled shafts. A hyperbolic model with two parameters is chosen to fit the measured load-settlement curves. The uncertainties in resistance calculations and the load-settlement curves are captured by a ratio (or model factor) of measured to calculated resistance and the hyperbolic parameters. The mean values, coefficients of variation, and the probability distributions of the model factors are established from 149 load tests. The statistics of the resistance model factor are applied to calibrate the resistance factors (for the ultimate limit state) in load and resistance factor design of steel H-piles in axial compression. In future, the statistics of the hyperbolic parameters can be incorporated into the development of RBD of steel H-piles at the serviceability limit state.