At the 1993 International Bridge Conference (IBC), University of Nebraska Professor Maher K. Tadros proposed a new generation of I-girder shapes for highway bridges. The presentation was based on K. Lynn Geren's master's thesis, with research partially supported by the Precast/Prestressed Concrete Institute (PCI). The proposed girders have varying depths, but the top and bottom flanges don't change from section to section. The section dimensions have been selected in hard metric form. Nebraska has adopted the new shapes, and several other states are considering them. The PCI Bridge Committee is currently considering the new shapes for endorsement.
For producers, there are several implications of these shapes, or others like them. Like AASHTO Type V and Type VI sections, the top and bottom flanges of the new sections have the same size, shape and web width. Each section could be produced with the same basic set of forms. By using the new shapes in conjunction with field splices and full-length post-tensioning, clear spans up to about 250 feet appear feasible.
Geren and Tadros reviewed existing standard sections and decided to study new ways to optimize girder cross sections. The optimization of the girder shape was based on three precast/prestressed concrete girder segments produced with current materials and post-tensioned to make a continuous two-span highway bridge designed for HS-25 truck loading.