Experimental and Computational Evaluation of Current and Innovative In-Span Hinge Details in Reinforced Concrete Box-Girder Bridges

During the last three decades, considerable research efforts have sought to improve the seismic design of California highway bridges. However, the in-span hinge regions of concrete box­ girders have not been studied adequately. In-span hinges are classified as disturbed regions due to the concentrated bearing loads and the possible existence of utility and maintenance openings, which induce a three-dimensional (3D) behavior. Nevertheless, in-span hinges are commonly designed as two-dimensional (2D) short cantilevers, following standard procedures in ACI318. These designs typically lead to congested reinforcement, causing constructability concerns from practical and economic aspects. In this study, the strength of in-span hinges is assessed using a combined computational and experimental approach. For the experimental approach, five 1/3scale specimens were tested at the University of California, Berkeley. The computational approach adopts nonlinear 3D finite elements that consider embedded reinforcement and cracking behavior for the concrete. As a result of this study, the failure modes are identified and realistic idealizations of the behavior and strength of the in-span hinges are developed aiming toward an improved design for better constructability of these disturbed regions. The findings from the experimental results revealed that in-span hinges fail with a combination of three failure modes: (1) one-dimensional shear, (2) 2D strut-and-tie, and (3) punching shear.

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