Nominal bending and shear strength of horizontally curved steel-I-girder bridges

The use of horizontally curved girders in the design of highway bridges and interchanges in large urban areas has increased dramatically in recent years. The I-shape plate girder is one type of section commonly used in the superstructure. Unlike straight I-girders used in straight bridge design, the horizontally curved I-girder is subjected to significant torsional stresses, even under pure gravitational loading. In addition, deflection, cross-section distortion, and deflection amplification effects are much more critical in the curved girder system and the inherent rotation characteristics of horizontally curved girders require that the diaphragms and bracing that are used in straight girder systems simply to prevent premature lateral buckling become very important (primary) load-carrying components in curved systems.; The currently used AASHTO Guide Specifications for Horizontally Curved Highway Bridges is primarily based upon research performed as part of the CURT project during the early 1970's. Since that time, numerous problems with the Guide Specifications have been revealed. The Guide Specifications in its original form is disjointed and difficult to use. There is significant discontinuity in the compressive strength formulation between compact and non-compact sections and the strength predicted by the formulations does not approach that predicted by the formulations for straight girders as the radius of the curved girder approaches infinity. For these reasons, among others, it has never been adopted as an integral part of the AASHTO Standard Specifications for Highway Bridges.; The present research addresses many of the strength related issues in the design of horizontally curved I-girder bridges including: (1) the overall lateral-torsional buckling and large displacement behavior including the design spacing of cross-frames and diaphragms; (2) the local buckling behavior of the curved compression flanges; (3) the buckling and finite displacement behavior of the curved web panels under bending, shear, and combined bending and shear; and (4) construction issues involving the large displacement behavior of single long slender I-girders during lifting and transporting. Theoretical and analytical results are presented on the behavior of such systems along with design recommendations. Also, in all applicable areas, an in-depth review and comparison of existing Japanese research results is presented.