Calibrating resistance factor for LRFD of deep foundation under lateral loading condition with serviceability limit state

Deep foundations are often used to support bridges and buildings when the surface soils are not sufficiently strong. In this study, the resistance factor (RF) in the load and resistance factor design (LRFD) for laterally loaded drilled shafts as deep foundation was calibrated and proposed. The serviceability limit state (SLS) associated with allowable displacement was targeted as it frequently governs the design of deep foundation. For this purpose, a database was established for rigid piles, such as drilled shafts, by collecting various load test results from full-scale field tests, centrifuge tests, and 1-g model tests. The normalized load–displacement curves were introduced, and uncertainties were captured and characterized based on the normalized hyperbolic relationship. The statistical properties of load and resistance were evaluated and introduced into the Monte Carlo simulation, which was performed for calibrating RF according to the allowable displacement and target reliability index. The relationship between the SLS RF and the allowable displacement was proposed and compared with the factor of safety for the conventional design method for laterally loaded drilled shafts.