Field monitoring and numerical analysis of two Illinois integral abutment bridges

As compared to conventional jointed bridges, integral abutment bridges (IABs) require lower construction and maintenance costs and have a longer service life, leading to their increased use by Departments of Transportation in the U.S. However, due to their unique design, their structural behavior is not as fully understood as that of typical jointed bridges. Previous research on IABs has been heavily focused on substructure performance, leaving a need for better understanding of IAB superstructure behavior and interdependent effects. The aims of this project were to further investigate IAB structural behavior, particularly of the superstructure, under thermal loading and validate employed modeling assumptions through implementation of a field monitoring program. Two Illinois IABs were instrumented to monitor: i) global bridge movements, ii) pile, deck, girder, and approach slab strains, and iii) rotations at different abutment interfaces. Field monitoring results corroborate that IAB longitudinal expansion and contraction is somewhat less than theoretical free expansion and contraction, and is influenced by bridge skew. Pile strain values were below the yield limit and indicate there is likely some reserve pile deformation capacity typically available. Significant girder stresses due to thermal loading were observed, particularly at the girder bottom flange, which can be considered in design. Results indicate the abutment cold joint behaves as a rigid connection, while the girder-abutment connection displays a slight amount of differential rotation. Overall field results and corresponding bridge numerical models provide valuable insight into different aspects of IAB behavior and validate key modeling assumptions, indicating the potential for further application of the field monitoring and prior parametric study results in future IAB design