PennDOT constructs first curved steel tubular flange girder bridge in the U.S.

​On Interstate 95 in southeastern Pennsylvania, we are constructing the first curved steel tubular flange girder bridge in the United States. The use of a tubular flange in place of a standard plate increases structural performance while reducing fabrication and erection material, as well as erection time compared to standard plate flange curved girders.

The use of steel plate flanges has been the standard for straight and most curved girder bridge applications. Lehigh University performed research supporting the design of curved steel girder bridges with tubular flanges. PennDOT developed a design and is constructing this innovation as part of an interchange project on Interstate 95 in District 6. The site constraints for erection are very challenging with overhead utility lines and rail lines below the bridge. Therefore, this type of design is a good fit.

This design was submitted to the American Association of State Highway and Transportation Officials (AASHTO) for consideration as a 2021 focused technologies candidate and for the additionally selected technologies. There were 41 candidates submitted to AASHTO overall. At the AASHTO Innovation Initiative (AII) annual meeting on October 26, 2021, the group evaluated the 41 candidates. The curved steel tubular flange girder bridge did make the list of 12 finalists out of the 41 but was not selected for the focused technologies or additionally selected technologies.

The tubular top flange concept was developed by Dr. Richard Sause of Lehigh University. In 2010, PennDOT funded research ang built a state girder bridge with tubular top flange - also the first in the nation. Dr. Sause continued research (not funded by PennDOT) to extend the concept to a curved girder, as we see in this project.