Reliability-Based Calibration for the Design and Load Rating of Segmental Bridges

Abstract

This dissertation addresses the need for rational provisions in the design and load rating of segmental bridges, emphasizing clearer distinctions between the inventory level, which demands higher reliability, and the operating level, which requires a lower level of reliability. Bridge engineers have advocated for less stringent evaluations at the operating level, prompting a request to refine the AASHTO Manual for Bridge Evaluation (MBE) provisions to better reflect operational conditions. The reliability analysis was conducted for both service and strength limit states. The primary objective of this study was to determine and validate the load and resistance factors required for the design and load rating for the Service III limit state, which governs post-tensioned segmental bridge superstructure components. This involved the statistical analysis of segmental bridges, the selection of representative bridges, the formulation of limit state functions, the selection of a reliability analysis procedure, and the determination of the target reliability index. Statistical models of load and resistance were developed, including parameters for thermal gradient, fabrication factor for flexural strength, and yield stress of reinforcing bars for shear strength. Reliability analysis was conducted for the selected representative bridges across the considered limit states, and target reliability indices were determined. The load and resistance factors for the service limit state were then calibrated and verified, and the effect of the proposed changes on the rating factors was determined. The main results include recommendations for updating provisions for the operating rating of segmental bridges. These findings are expected to be valuable for designers and load-rating engineers of post-tensioned segmental bridges.