Lateral–torsional buckling study of a continuous,skewed,steel bridge during deck placement

Abstract

A recently constructed four-span composite steel I-girder bridge with skewed supports located in Delaware was used to study torsional buckling behavior during deck placement. Numerical models of the bridge were developed and buckling analyses were performed. Based on the analyses, it was determined that the originally designed bracing system was not adequate to satisfy the stability requirements during the concrete deck pour. Subsequent studies identified three possible ways to correct the problem without changing the original design – a solution that was ultimately implemented. The first solution would be to utilize the beneficial effects of the formation of composite action during the pour sequence. The second solution would be to modify the pour sequence to minimize instability effects. The third solution would be to adjust the orientation of the deck pour (which originally was specified to be parallel to the skew). The study results show that adjusting the pour sequence and increasing the time between pour intervals to increase the effects of composite action would be potential solutions, while changing the orientation of the deck pour relative to the skew would lead to only slight increases in safety.