Adjacent box girders without internal diaphragms or post- tensioned joints

摘要

Precast, prestressed concrete adjacent box-girder bridges are widely used in short- and medium-span bridges. Rapid construction and low cost are the main advantages of this system. Although the use of transverse post-ten-sioning to connect adjacent box girders can be effective and practical, end and intermediate diaphragms are necessary for continuity. Construction of diaphragms in skewed bridges is difficult and may significantly increase in the construction cost and schedule. Moreover, post-tensioned transverse diaphragms result in continuity at discrete locations, making the system more susceptible to cracking and leakage. This paper presents the development of two non-post-tensioned transverse connections for possible simplification of this already efficient bridge system. The proposed continuous connections transfer shear and moment between adjacent boxes without the need for diaphragms. The connections are based on monolithic emulation of a multicell cast-in-place box-girder superstructure, similar to a system commonly used in California. The wide-joint connection consists of a wide full-depth shear key filled with flowable concrete and top and bottom reinforcement. The narrow-joint connection consists of top and bottom couplers and full-depth grouted shear keys. Finite element models were used to develop design charts for different bridge configurations. Fatigue and static load testing were performed on the proposed connections and one commonly used connection to evaluate their fatigue capacity, ultimate capacity, and joint leakage. Test results indicate that the proposed connections outperform the current connection in addition to being more economical. Innovative concepts for the production of precast concrete box girders for highway bridges are also presented.