Trapezoidal Steel Box Girder Design for Spur 366 Extension Project

Trapezoidal steel box girders, commonly known as tub girders, have become more and more popular on the application of urban highway bridges due to their high torsional stiffness and the aesthetic appeal of their clean lines. Although much research has been done recently for better understanding the behavior of trapezoidal steel box girders, the findings are yet to be incorporated into design criterion. In addition, few publications were found in explaining the overall design process. Hence, with limited resources, designing a trapezoidal steel box girder for the first time can be challenging for a bridge engineer. The objective of this paper is to share with other engineers the authors' experience in the design of a simple span trapezoidal steel box girder bridge for the Spur 366 Extension Project located in Dallas, Texas. A project description and a design approach will be given first. A discussion of the framing considerations will follow and then the framing plan and typical section of the project will be introduced. Finally, the MDX software model and the designs of top lateral bracing, end support diaphragms and the elastomeric bearing will be briefly discussed.