Stability of Curved Steel I-Girder Bridges During Construction

Structural stability is one of the essential aspects of the construction of curved steel I-girder bridges. The AASHTO load and resistance factor design (LRFD) bridge design specifications require the consideration of stability-critical conditions during the construction of curved I-girder bridges through checking (a) nominal initial yielding due to combined major-axis bending and flange lateral bending, (b) strength under combined major-axis and flange lateral bending, and (c) web-bend buckling. These specifications limit the flange lateral bending stress to 0.6F(y). In some cases, these rules may not be sufficient unless global second-order amplification of the lateral-torsional response is considered. In particular, structures with narrow widths and long spans may be susceptible to large second-order amplification that could compromise the overall system constructability. This paper presents analytical studies of a slender curved and skewed I-girder bridge unit that exhibited difficulties during the placement of the concrete deck. The results of approximate one- and two-dimensional analyses of the construction phase are compared with refined three-dimensional finite element solutions to highlight their differences. Guidelines are provided for handling cases in which the slender geometry of the structure may be an important constructability consideration.