Behavior of Tubular Flange Girder System in Curved Overpasses

Curved overpasses with steel girders are now widely used in Iraq because they add significant flexibility in the determination of highway alignments, especially at congested interchanges inside major cities. The horizontal curvature produces significant torsional effects in the bridge girder system. In this study new types of curved steel girders are proposed to make the system stable against this torsional effect where their behavior in curved bridge systems is investigated and compared with the typical I-section girder under the same geometry and loading conditions. These new types of girders have a tube in place of the bottom flange of the I-section girder. Four models are proposed herein. The finite element program SAP2000 version 14 is used for the linear analysis of the horizontally curved simply supported composite bridge decks with the proposed girder models and the reference I-section girder. The factors considered in the parametric study are span length, curvature, number of mid diaphragms and girder type. The results include the longitudinal stresses and the vertical displacements in the mid span of the bridge. These results have been compared with those of the reference I-section girder. The results showed that the proposed models give less stresses and deflections than the typical I-section and the most effective model in curved deck bridge is girder model D (the bottom plate is made of steel channel with plates inclined with 45 welded together instead of the bottom steel plate and filled with concrete).