Serviceability Limit State in Reliability-Based Design of Foundations

Over the last two decades, reliability-based design (RBD) methodologies gradually have gained popularity in geotechnical engineering. Several RBD codes have been developed and implemented in the United States, Canada, Europe, and Japan. Although most of these RBD codes apply reliability principles for ultimate limit state (ULS) designs and calibrate the designs for a target ULS reliability index (Beta_uls), the serviceability limit state (SLS) designs still are evaluated using conventional deterministic approaches with an unknown SLS reliability index (Beta_sls). This proposed research aims to develop a simplified approach to assess the SLS requirement in reliability-based design of foundations. A general relationship between Beta_uls and Beta_sls will be developed, and hence, the Beta_sls can be directly inferred from the Beta_uls that is specified already in the design codes. Using the Beta_uls and Beta_sls relationship, the values of Beta_sls will be assessed for various types of foundations, such as spread foundations, drilled shafts, and pressureinjected footing. In addition, the effect of foundation limiting tolerable settlement on Beta_sls will be explored.