Reliability-Based Serviceability Limit State Design of Spread Footings on Aggregate Pier Reinforced Clay

Despite the availability of numerous methods to predict the load-displacement response of aggregate pier reinforced clay, accurately modeling the nonlinear displacement response remains challenging. Moreover, the uncertainty in the bearing pressure-displacement prediction has not been satisfactorily estimated, preventing the generation of reliability-based design (RBD) procedures. This study proposes a simple RBD procedure for assessing the allowable bearing pressure for aggregate pier reinforced clay in consideration of the desired serviceability limit state. A recently established bearing-capacity model for aggregate pier reinforced clay and its uncertainty is incorporated into a bivariate bearing pressure-displacement model appropriate for a wide range in displacement and calibrated using a high-quality full-scale load-test database. Several copulas were then evaluated for goodness of fit to the measured dependence structure between the coefficients of the selected two-parameter bearing pressure-displacement model. Following the generation of an appropriate performance function, a combined load and resistance factor is calibrated in consideration of the uncertainty in the bearing pressure-displacement model, bearing capacity, applied bearing pressure, allowable displacement, and footing width using Monte Carlo simulations of the respective source distributions. An example is provided to illustrate the application of the proposed procedure to estimate the bearing pressure for an allowable displacement at the desired serviceability limit probability.