Tubular flange girders (TFG) are an innovative I-shaped steel bridge girder, which have tube-shaped flanges rather than the flat plate flanges of a conventional I-girder. The tubes significantly increase the torsional stiffness of the TFG compared to the torsional stiffness of a conventional I-girder. For single horizontally curved TFGs, the increased torsional stiffness of the TFG significantly reduces the warping stresses, vertical displacements, and cross section rotations relative to those of a conventional I-girder. The goals of this research are to develop better understanding of the behavior of single curved TFGs under vertical load, and to experimentally validate finite element (FE) models for single curved TFGs.
First, a ½-scale TFG test specimen is developed and studied experimentally. The test specimen is developed at full-scale initially. The effects of scaling the dimensions from full-scale to ½-scale are examined. For the experiments, a test setup, loading plan, and instrumentation plan are developed. Experimental results include vertical displacements, cross section rotations, normal strains, and shear strains.
Then, FE models were developed and validated. FE results for vertical displacements, cross section rotations, normal strains, and shear strains within the span are compared to the experimental results. A parametric study using FE models was conducted to study the effects of the end conditions of the TFG on shear strains near the ends of the TFG. Experimental results and FE results are compared qualitatively and quantitatively to determine the accuracy of the results, and make observations on the behavior of a single curved TFG under vertical load.
Finally, the behavior of the ½-scale TFG test specimen is analyzed further using theoretical analysis methods from Fan (2007) and FE analyses. The FE analyses are conducted using one model with constraints which prevent cross section distortion, and another model which permits cross section distortion. The theoretical and FE analysis results are compared to assess the effects of cross section distortion on curved TFG behavior.
The results of this research show that FE models can accurately predict vertical displacements, cross section rotations, normal strains, and shear strains measured in the experiments away from the ends of the TFG. The results of the parametric study show that different end conditions have a significant effect on the shear strains near the ends of the TFG. The experimental results and the further FE analysis results show that cross section distortion has a noteworthy effect on curved TFG behavior in terms of warping strains, although the total normal strains are dominated by primary bending and the total shear strains are dominated by St. Venant torsion.