Parametric study of curved steel I-girder bridges at construction phase.

The desire to conform to the existing terrain has largely increased the use of curved bridges for complex interchanges. Bridge curvature produces warping moments (lateral bending moments) in girder flanges under truck loading conditions and even during the construction phase. These warping moments increase girder flexural stresses at construction phase in case of un-shored construction. An extensive parametric study was conducted, using the finite-element analysis software "SAP2000", to examine the key parameters affecting warping stresses in curved girder bridges under construction loads. A strengthening technique "torsion box" at the girder supports was proposed and examined with respect to girder warping, flexural stresses and support reactions. The key parameters considered in this study included number of girders, girder spacing, number of cross bracing intervals, degree of curvature and girder span length. Based on this study empirical expressions for moment and shear distribution factors for the curved girder were developed.