Statistics of model factors in reliability-based design of axially loaded driven piles in sand

Abstract

This paper compiles 162 reliable field load tests for axially loaded driven piles in sand from previous studies. The L1–L2 method is adopted to interpret the measured resistance from the load–settlement data. The accuracy of resistance calculations with the ICP-05 and UWA-05 methods based on cone penetration test profile is evaluated by the ratio (bias or model factor) of the measured resistance to the calculated resistance. A hyperbolic model with two parameters, where the load component is normalized by the measured resistance, is utilized to fit the measured load–settlement curves. The means, coefficients of variation, and probability distributions for the resistance model factor and the hyperbolic parameters are established from the database. Copula theory is employed to characterize the correlation structure within the hyperbolic parameters. The statistical properties of the model factors are applied to calibrate the resistance factors in simplified reliability-based designs of closed-end piles driven into sand at the ultimate and serviceability limit state by Monte-Carlo simulations. A simple example is provided to illustrate the application of the proposed resistance factors to estimate the allowable load for an allowable settlement at the desired serviceability limit probability.