Curvature Limitations of Non-Composite Girder Bridges at Construction Stage

In bridges with light curvature, the curvature effects on bending, shear and torsional shear stresses may be ignored if they are within acceptable range. Treating horizontally curved bridges as straight ones with certain limitations is one of the methods to simplify the analysis and design procedure. Recently the Canadian Highway Bridge Design Code, CHBDC, the AASHTO Guide Specifications for Horizontally Curved Bridges, and AASHTO-LRFD Bridge Design Specifications have specified certain limitations to treat horizontally curved bridges as straight ones, but still more investigations are needed to examine these limitations for different bridges configurations (i.e. open I girders versus closed box girders). In this study, a series of noncomposite horizontally curved braced steel I-girder bridges at construction stage were analyzed under dead load condition using the finite-element program, ABAQUS. Major internal forces developed in the members were determined, namely: flexural stresses, vertical deflections and vertical support reactions for different degrees of curvature. These values were then compared with those for straight bridges of similar span and cross-section configuration. Both single and two-span horizontally curved non-composite steel I-girder bridges were considered in this study. The design parameters considered in this study were degree of curvature, span length, number of lanes, number of girders, and span-to-depth ratio. The stipulations made in bridge codes for treating a curved bridge as straight one were then examined. Based on the data generated from the parametric study, sets of empirical expressions were developed to evaluate girder flexural stress, deflection and support reaction magnification factors in a curved bridge system as related to a straight bridge system. Then, these expressions were extended to establish more reliable expressions for curvature limitations to treat a curved bridge as straight one as opposed to the available curvature limitation equation available in CHDBC and AASHTO Specifications. It should be noted that the current study proved that the available CHBDC and AASHTO curvature limitations underestimates the structural response of few curved bridge configurations.

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