This study proposes a reliability-based design (RBD) procedure to evaluate the allowable load for augered cast-in-place (ACIP) piles installed in predominately granular soils based on a prescribed level of reliability at the serviceability limit state (SLS). The ultimate limit state (ULS) ACIP pile-specific design model proposed in the companion paper is incorporated into a bivariate hyperbolic load-displacement model capable of describing the variability in the loaddisplacement relationship for a wide range of pile displacements. Following the approach outlined in the companion paper, distributions with truncated lower-bound capacities were incorporated into the reliability analyses. A lumped load-and resistance factor is calibrated using a suitable performance function and Monte Carlo simulations. The average and conservative 95 percent lower-bound prediction intervals for the calibrated load-and resistance factor resulting from the simulations are provided. Although unaccounted for in past studies, the slenderness ratio was shown to have significant influence on foundation reliability. Because of the low uncertainty in the proposed ULS pile capacity prediction model, the use of a truncated distribution had moderate influence on foundation reliability.Author Keywords: ACIP piles; Reliability; Serviceability limit state; Statistics; Design
INTRODUCTIONA suitable foundation design will satisfy the strength limit or ultimate limit state (ULS) as well as the serviceability limit state (SLS), which is often associated with the allowable displacement or angular distortion of a structure. At present, the ULS has received considerably more attention in reliability-based design (RBD); however, the SLS is often the governing criterion for many foundation alternatives (Becker 1996;Wang and Kulhawy 2008; Zhang et al. 2008;Uzielli and Mayne 2011). Phoon and Kulhawy (2008) incorporated the accuracy and uncertainty of the Meyerhof (1976) method for estimating shaft resistance of drilled shafts to make assessments of reliability at the SLS for augered cast-in-place (ACIP) piles. However, the Meyerhof method was originally developed to predict the capacity of driven displacement piles and then modified for use with drilled shafts, which are constructed differently than ACIP piles.Additionally, Phoon and Kulhawy (2008) neglected toe bearing resistance when estimating ACIP pile capacity, resulting in a biased and considerably variable model (Phoon et al. 2006). Phoon et al. (2006) noted that models specific to ACIP piles needed to be developed (Phoon et al. 2006).The goal of this study is to use the ACIP pile-specific ULS design models presented in the companion paper (Reddy and Stuedlein 2016) to investigate reliability-based SLS design of ACIP piles installed in predominately granular soils. Those case histories described in the companion paper characterized with high quality load-displacement (Q-δ) curves were used to investigate foundation reliability at the SLS. First, an approach to link the ULS capacity models ...