Curvature Limitations for Slab-on-I-Girder Bridges

Abstract

In recent years, horizontally curved bridges have been widely used in congested urban areas, where multilevel interchange structures are necessary for modern highways. In bridges with light curvature, the curvature effects on bending, shear, and torsional stresses may be ignored if they are within an acceptable range. Treating horizontally curved bridges as straight bridges with certain limitations is one of the methods to simplify the design procedure. Bridge design specifications and codes have specified certain limitations to treat horizontally curved bridges as straight bridges. However, these limitations do not differentiate between bridge cross section configurations, in addition to being inaccurate in estimating the structural response. Moreover, these specifications were developed primarily for the calculation of girder bending moments. To investigate the accuracy of these limitations, a series of horizontally curved, braced concrete slab-over steel I-girder and slab-on-concrete I-girder bridges were analyzed, using three-dimensional finite-element modeling, to investigate their behavior under dead loading. The major internal forces developed in the members were determined, namely, girder longitudinal bending stresses, vertical deflections, vertical support reactions, and bridge fundamental flexural frequencies for different degrees of curvature, span length, bridge width, and span continuity. Empirical equations for these straining actions were developed as a function of those for straight bridges. The stipulations made in bridge codes for treating a curved bridge as a straight bridge were then correlated with the obtained values from the finite-element modeling. Results proved that such code limitations were unsafe. Based on the data generated from this parametric study, sets of empirical expressions were developed to determine such limitations more accurately and reliably.