DESIGN OF HORIZONTALLY CURVED COMPOSITE BOX-GIRDER BRIDGES - A SIMPLIFIED APPROACH

Because of their excellent torsional capacity, box girders are used ex tensively in modern bridge construction having curved alignments. Appl ications of most design codes have been limited to bridges where the r adius of curvature is much greater than the span length and cross-sect ional dimensions. To meet the practical requirements arising during th e design process, simple design methods are needed for curved bridges. This paper presents the results of a parametric study on the relative behaviour of curved and straight box-girder bridges and on the develo pment of a simplified design method for the combined longitudinal mome nt of curved bridges. The combined moment includes the effects of flex ure, torsion, and distortion. Three simply supported concrete-steel co mposite bridge models, including single-cell, twin-cell, and three-cel l box girders and subjected to loadings as specified in the Ontario Hi ghway Bridge Design Code, were analyzed using the finite strip method. The parameters considered in the study include types of cross section ; types, locations, and magnitudes of loads; span lengths; and radius of curvature. Preliminary analysis of the results suggests that the be haviour of horizontally curved box-girder bridges is dependent on a va riety of parameters, but most importantly on the span-to-radius ratio. Empirical relationships for combined longitudinal moment between curv ed and straight box-girder bridges are also proposed.