This report focuses on post-test finite element analysis (FEA) of and design recommendations for in-span hinges (ISHs) of reinforced concre te (RC) box-girder bridges when subjected to vertical loads through the bearings. ISHs are disturbed regions due to a complex three- dimensional (3D) stress state caused by the concentrated bearing loads and the possible existence of utility and maintenance openings. The common modeling practice for ISHs is the use of simplified two-dimensional (2D) modeling as short cantilevers, following standard procedures, e.g., those in ACI318. Such simplified analytical and design procedures lead to inefficient detailing because they do not take into account the expected failure modes of ISHs, where punching shear is one of these critical modes. For the post-test analysis, a 3D finite element analysis (FEA) is developed and validated against the results of five tested ISH specimens. This computational model considers the cracking behavior of concrete and the elastic-plastic behavior of the reinforcement. The reinforcing steel is modeled using an embedded reinforcement formulation assuming perfect bond between the concrete and the reinforcement. The concrete material is modeled using the total strain rotating crack method. The reduction of compressive strength due to perpendicular cracking is incorporated in the constitutive model. With the validated FEA, a parametric study is conducted to predict the behavior and the strength of ISHs with different detailing and geometrical characteristics. As a result of this study, detailed design recommendations and guidelines are presented for ISHs in RC box-girder bridges. These recommendations are aimed to obtain optimal designs with less congestion and improved structural behavior. The findings from this study revealed that the strength of the ISH should be estimated from five critical design criteria: (1) sliding shear friction, (2) bending moment, (3) 2D SAT, (4) one-dimensional shear, and (5) punching shear. Additionally, it is concluded that the strength of ISHs is improved most by increasing the amount of diagonal reinforcement of the seat.
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