Inconsistent Detailing of Cross-frame Members in Horizontally Curved Steel I-Girder Bridges

For horizontally curved steel I-girder bridges, not only must a suitable erection sequence be selected to minimize construction difficulties, but it is also imperative that the cross-frames and girders be detailed in a consistent manner that preserves the original design intent; especially in larger bridges. Nonetheless, inconsistent detailing of cross-frame members and girders is sometimes employed in order to force bridge components into some desirable geometric configuration: girder webs vertically plumb at the steel dead load condition, for instance. The bridge components are typically inconsistently detailed because the rotation of the girders and the subsequent lateral displacement of the top flange due to applied or dead loads are predicted to be "excessive." It is then hoped that by intentionally detailing the diagonal cross-frame members to be either too short or too long, the girders will be forced to be vertically plumb at the given loading condition. However, this is not the case, and will instead result in connection misalignments during the erection of the steel superstructure; or worse yet misfits of such a magnitude as to render the bridge un-constructible. The current paper is intended to quantity, qualify, and promote awareness of the issue of inconsistent detailing in horizontally curved steel I-girder bridges by studying two recently constructed horizontally curved steel I-girder bridges that were inconsistently detailed. The discussion highlights the fact that practice of inconsistent detailing can lead to very formidable and costly fit-up problems in the field; especially when girder sizes are large.