Abstract: Steel plate girder bridges with concrete slab decks are prevalent in the U.S. highway system, with many nearing or exceeding 45 years of service. Currently, around 26% of these bridges are structurally deficient due to concrete slab delamination, excessive cracking, and steel girder corrosion, which leads to costly rehabilitations and reduced load ratings. This study focuses on predicting the effects of corrosion on steel girders and proposing a novel solution to extend bridge service life without full replacement or load rating reduction. Experimental investigations assessed corrosion morphology and its impact on mechanical performance under varying chloride concentrations, temperature conditions, and the presence of mill scale. Results showed that mill scale can initiate corrosion even in chloride-free environments and that corrosion morphology significantly affects ductility, rendering simplified design approaches based on average area loss inaccurate. To mitigate load reductions caused by corrosion, the study proposes replacing conventional reinforced concrete slabs with lighter Ultra-High Performance Concrete (UHPC) slabs, reducing dead load by over 20%. A case study on a 43-year-old bridge in Pennsylvania demonstrated that this method allows the bridge to maintain full live load capacity without rehabilitating the steel girders. Additionally, a new method for casting UHPC slabs with preferential fiber orientation was developed to enhance structural strength. Finally, the interaction between steel fiber volume fraction and reinforcing rebars was studied in UHPC beams with prismatic cross-sections.

Bio: Shady Gomaa holds a Ph.D. in Civil Engineering (2020) from Rensselaer Polytechnic Institute, along with an M.S. in Structural Engineering and a B.Sc. in Civil Engineering from Zagazig University in Egypt. He is currently a postdoctoral scholar in the Department of Civil and Environmental Engineering at Northwestern University. His research focuses on additive manufacturing of Ultra-High Performance Concrete (UHPC), with broader interests in steel corrosion, sustainability, concrete mechanics, and deterioration mechanisms in materials and structures. Shady is an active member of ACI Committees, including Committee 564 on 3D Printing with Cementitious Materials and Committee 239 on Ultra-HighPerformance Concrete.