Structural behavior of tall haunches in concrete composite girders



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Composite bridges constructed using prestressed concrete (PSC) girders with cast-in-place (CIP) or precast panel (PCP) decks commonly incorporate haunches. A haunch refers to the concrete region located between the top of a bridge girder and the bottom of the deck. The purpose of a haunch is to ensure a consistent deck thickness, taking into account factors like camber, cross-slope, construction errors, and other relevant considerations. TxDOT (2022) permits a maximum haunch height of 3.5 in. without special detailing for PSC girders, but construction errors or unique design requirements can result in haunches as deep as 12 in. In such cases, the effective composite action may be compromised as shear connectors may not penetrate the deck, and local concrete failures in the haunch can occur before other anticipated failure modes. This study aimed to investigate the behavior of PSC girder bridges that incorporate tall concrete haunches. Push-out tests were conducted to assess the capacity and limit states in the composite connection between PSC girders and the concrete slab with haunches. In addition to experimental testing, three-dimensional finite element (FE) models were developed and validated using the obtained experimental results. These FE models allowed for parametric studies beyond the scope of the physical experiments, enabling a more comprehensive understanding of the behavior for a wide range of design details. The results of the study demonstrated that the behavior of PSC girders with tall haunches is influenced by factors such as the type of deck (CIP or PCP), haunch depth, loading conditions, and other parameters outlined in the study. Based on the research findings, design and detailing guidelines for tall haunches in PSC girder bridges are recommended. Overall, this research contributes to enhancing our understanding of the behavior of PSC girder bridges with tall haunches and provides guidance for their design and construction.


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