| 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 reinforce concrete (RC) box-girder bridges have not been studied adequately ISH's are classified as disturbed regions due to the concentrated bearing loads and the possible existence of utility and maintenance openings, which induce complicated three- dimensional (3D) stress states. Nevertheless, ISH's are commonly designed as two-dimensional (2D) short cantilevers, following standard procedures in ACI318. Such simplified analytical and design procedures lead to inefficient detailing because they do not take into account the expected failure modes of ISH's, where punching shear is one of these critical modes;In this dissertation, the BFI's are assessed using combined computational and experimental approaches. This evaluation focuses on ISH's of prestressed concrete box- girder bridges when subjected to vertical loads through the bearings. For the experimental approach, five 1/3-scale specimens are tested at the University of California, Berkeley. For the computational approach, a 3D finite element analysis (FEA) is developed and validated against the results of the tested ISH specimens. This computational model considers cracking behavior of concrete and plastic behavior of the reinforcement. The reinforcing steel is modeled using 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 strength of ISH's with different detailing and geometrical characteristics.;As a result of this dissertation, detailed design recommendations and guidelines are presented for 1SH's in RC box-girder bridges. These recommendations are aimed to obtain optimal designs with less congestion and improved structural behavior. Findings from this study revealed that strength of the ISH should be estimated from the critical of five design criteria: (1) sliding shear friction, (2) bending moment, (3) 2D strut-and-tie, (4) one-dimensional shear, and (5) punching shear. Additionally, it is concluded that the strength of ISH' s is mostly improved by increasing the amount of diagonal reinforcement of the seat. |
