Finite beam element with 26 DOFs for curved composite box girders considering constrained torsion, distortion, shear lag and biaxial slip

Curved steel-concrete composite girders have been widely used in curved bridges of overpasses in urban areas as they have a lower self-weight and require less construction time. These curved beams have been often numerically simulated with the use of a more elaborate three-dimensional (3D) finite element (FE) model to predict their mechanical behavior with high accuracy. However, a more elaborate FE model requires a more complex modeling process and higher computational cost, which significantly reduce its efficiency. In response to these problems, a one-dimensional model of curved composite box girders is proposed as a high-efficiency numerical simulation method, which therefore warrants further investigation. This one-dimensional theoretical model can account for constrained warping, distortion, and the shear lag in concrete slabs and steel bottom plates, biaxial slip at the slab-girder interface and curvature differences along the width of the beam. Although there are numerous studies on curved beam theories, an accurate and efficient one-dimensional theoretical model of curved composite box girders is still lacking. Additionally, experimental studies on curved composite box beams that are subjected to coupled bending and torsion are few compared to those on the mechanical behavior of straight composite girders, especially curved composite box beams with wide flanges. This study proposes a onedimensional model of curved composite box girders. Then, using an FE discretization method, a high-efficiency finite beam element with 26 degrees of freedom (DOFs) is developed for curved composite box girders which accounts for constrained torsion, distortion, shear lag, biaxial slip at the interface and curvature differences along the width of the beam. Subsequently, two large-scale tests of a curved composite box girder are conducted and the findings are reported. A comparison among the experimental test results, elaborate FE model with shell elements and developed beam element shows good agreement. The force transfer behavior of curved box beams is further analyzed based on the proposed beam element, and the influence of the key parameters on the mechanical performance is investigated. In summary, this study contributes to the current literature with the development of a one-dimensional theoretical model for curved composite box beams and tests on curved box beams with a large curvature.