RELIABILITY INDEX FOR SERVICEABILITY LIMIT STATE OF DRILLED SHAFTS UNDER UNDRAINED COMPRESSION

Abstract

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 (β(subscript uls)). However, the serviceability limit state (SLS) design still is considered using conventional deterministic approaches with an unknown SLS reliability index (β(subscript sls)). This paper makes use of a relationship between β(subscript sls) and β(subscript uls) to infer the β(subscript sls) of drilled shafts under undrained compression from the β(subscript uls) that is specified already in the design codes. The values of β(subscript sls) 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.