Reliability Index for Serviceability Limit State of Building Foundations

Abstract

Extensive research has been conducted on reliability-based design (RBD) for the ultimate limit state (ULS). Several RBD codes have been developed and implemented around the world that calibrate the ULS design 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 presents a relationship between βsls and the βuls that is specified already in the RBD codes. This relationship is linear, and a key variable in it is the ratio (R) of the SLS capacity ( Qsls ) to the ULS capacity ( Quls ) . Both closed-form approximations and Monte Carlo simulations are used to characterize R probabilistically. For illustration, the relationship then is used to estimate βsls for augered cast-in-place piles designed in accordance with the RBD methodologies in the National Building Code of Canada. The results are highly dependent on the statistics of the limiting to...