Development of a New-Generation High-Strength Post-Tensioned Anchor Bar
The new signature, steel arch bridge for I-74 over the Mississippi River is connected to the abutments by high-strength, post-tensioned anchorage bars. To achieve a design 100-yr service life for the anchorage bars in an exposed condition, a literature review and experimental study was performed to develop a robust, high-strength, post-tensioned bar system that provides improved corrosion resistance. Five candidate materials, including three stainless steels, a carbon steel, and a galvanized carbon steel, were tested. Full-scale specimens were specially fabricated for the test program to replicate actual conditions.
The physical, material, and corrosion testing program included tensile, coupling and end nut, stress relaxation, hardness, toughness, galling, critical pitting temperature, stress corrosion cracking, hydrogen embrittlement, and inelastic behavior testing. A duplex stainless steel demonstrated superior corrosion resistance while the other precipitation hardened stainless steels performed poorly in corrosion testing. The study concluded that the duplex stainless steel is the preferred material, with the conventional plain high-strength, carbon steel bar with a robust corrosion protection system as an alternate. The project team selected the duplex stainless steel for the project with slight design modifications.