Experimental and Computational Evaluation of In-Span Hinges 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 (ISH) regions of concrete box girders have not been studied adequately. ISHs are classified as disturbed regions because of the concentrated bearing loads and the possible existence of utility and maintenance openings, which induce a three-dimensional (3D) behavior. Nevertheless, ISHs are commonly designed as two-dimensional short cantilevers, following standard procedures in “Building Code Requirements for Structural Concrete and Commentary” of the American Concrete Institute. These designs typically lead to congested reinforcement, causing constructability concerns from practical and economical aspects. In this study, the strength of current ISHs is assessed by using a combined experimental and computational approach. For the experimental part, two $1/3$-scale specimens were tested at the University of California, Berkeley. The computational part adopted nonlinear 3D finite elements considering embedded reinforcement and concrete cracking. Failure modes were identified, and realistic idealizations of the behavior of the ISHs were developed. The findings from this study revealed that ISHs fail with a combination of two failure modes: (1) beam shear and (2) punching shear.