Sponsor: Texas Department of Transportation

PI: Todd Helwig
Co-PI's: Michael Engelhardt, Eric Williamson, Patricia Clayton

Steel trapezoidal box girders, generally referred to as tub girders, have been widely used on a number of bridges throughout the State of Texas. The smooth profile of the girder systems provides an aesthetically appealing bridge that also possesses several structural advantages compared to other girder types. Due to the significant torsional stiffness of the closed box section, the girders are a popular choice in horizontally curved systems where the bridge geometry leads to large torsional moments. The girders have also been used on a number of straight girder systems throughout the state leading to improved bridge aesthetics. While tub girders have primarily been used on bridges with longer spans where concrete girders are not viable, an application of relatively shallow steel tub girders was recently used in the TxDOT Waco District on a bridge with span lengths normally reserved for concrete girder systems. The resulting bridge provided an aesthetically appealing structure that satisfied a demanding vertical clearance requirement and was cost-comparable with precast concrete girders. This shallow tub girder application demonstrates that steel trapezoidal box girders offer a viable alternative that should be considered for a wider variety of bridge applications. However, to augment the viability of tub girders, improved details need to be considered to further enhance their economic and structural advantages. Modifications in the girder geometry can provide more efficient systems.  The objective of this research is to develop improved details for tub girders as well as design methodologies for the girders and bracing components.