Reliability Index for Serviceability Limit State of Drilled Shafts under Undrained Compression

In recent years, reliability-based design (RBD) has gradually gained popularity in geotechnical engineering. Several RBD codes have been developed and implemented around the world that calibrate ultimate limit state (ULS) designs for a target ULS reliability index (βuls). However, the serviceability limit state (SLS) design still is considered using conventional deterministic approaches with an unknown SLS reliability index (βsls). This paper makes use of a relationship between βsls and βuls to infer the βsls of drilled shafts under undrained compression from the βuls that is specified already in the design codes. The values of βsls are estimated for drilled shafts designed in accordance with three different design methods (i.e., semi-empirical analysis using in situ and laboratory test data, analysis using static loading test results, and analysis using dynamic monitoring results) of the National Building Code of Canada (NBCC). The results indicate that, for the undrained compression capacity of drilled shafts designed in accordance with the NBCC, the designs automatically fulfill the corresponding SLS design requirements.