Axial tensile test and design method of special-shaped rigid flange

Abstract

Unlike the conventional flange with 90°-connecting angle, the new type of special-shaped rigid flange adopting non-90°-connecting angle can effectively reduce the joint region dimensions of steel tube connection in some conditions. Three special-shaped rigid flanges that adopt 45°, 60° and 75°-connecting angles were designed and tested under axial tensile load to investigate the mechanical characteristics and design method. The slip and open deformations occurred between two flange plates under axial tensile load, and the connecting bolts bore non-uniform tensile and shear forces along the bolt elliptical circle, which increase from the short axis to the long axis of elliptical flange plate. In addition, the nonlinear finite element model, whose accuracy was validated by the test results, were built to further inspect the bearing capacity and force-transfer mechanism. The results reveal that the bolt tensile forces are larger than the design values, and the corresponding modified factor was proposed. The stress developments of different fan-shaped sectors were analyzed, and the sectors located on the short axis are suggested to be selected for strength design of flange plate. The stiffener of these sectors has larger load allocation factor, and should be chosen for the strength design of stiffener weld lines. Lastly, the design method of special-shaped rigid flange under axial tensile load was provided, in which the combined tensile and shear forces should be considered for the connecting bolts and weld lines.