Behavior of horizontally curved steel tubular-flange bridge girders

A new type of curved steel bridge girder, called a curved tubular-flange girder, with rectangular tubes as flanges, is proposed and studied in this dissertation. A curved steel tubular-flange girder has much larger torsional stiffness than a curved I-girder and less potential for cross section distortion than a curved box-girder. Therefore, it has potential advantages compared to curved I-girders and box-girders.; A theoretical analysis method for systems of curved tubular-flange girders braced by cross frames is presented. A stress analysis method for tubular-flange girders is also provided. The behavior of curved tubular-flange girder systems is studied using the theoretical analysis method and compared to the behavior of the corresponding curved I-girder systems. A parametric study is performed using the theoretical analysis method to investigate the effects of geometric parameters on the behavior of curved tubular-flange girder systems. The studied parameters include tubular-flange width, tubular-flange depth, cross section depth, girder curvature, and the number of cross frames. Finite element analyses are conducted to verify the theoretical analysis method, to study the behavior of a curved tubular-flange girder system under dead load, and to study the behavior of a curved tubular-flange girder system with a composite concrete deck under dead and live load.; The study shows that a curved tubular-flange girder system develops much less warping normal stress and cross section rotation than a corresponding curved I-girder system. The difference is especially significant for a single curved girder under its own weight, suggesting that curved tubular-flange girders would be much easier to transport and erect than curved I-girders. As girder curvature increases, the rate of increase in the stresses and displacements for a single I-girder is much greater than for a single curved tubular-flange girder. Smaller cross frame forces develop in a tubular-flange girder system than in an I-girder system, which results in smaller cross frame members. The study also indicates that a curved tubular-flange girder system may need fewer cross frames than a curved I-girder system. Finally, for curved girder systems with a composite deck, the behavior of tubular-flange girder systems is dominated by bending stresses, while the behavior of I-girder systems includes significant warping stresses, again suggesting that the tubular-flange girder system may be more efficient.