Interim Conclusions, Recommendations, and Design Guidelines for Durability of Post-Tensioned Bridge Substructures

The use of post-tensioning in bridges can provide durability and structural benefits to the system while expediting the construction process. When post-tensioning is combined with precast elements, traffic interference can be greatly reduced through rapid construction. Corrosion protection of the post-tensioning system is vital to the integrity of the structure because loss of posttensioning can result in catastrophic failure.

The research program involves exposure testing of twenty-seven large-scale beam specimens and ten large-scale column specimens to investigate numerous combinations of variables for durable post-tensioned substructure design. Beam variables include prestress level, loading, grout type, duct splices, concrete type, strand type, duct type, and end anchorage protection. Column variables include foundation connection, post-tensioning protection, concrete type, and loading. In addition, a testing program with small-scale macrocell corrosion specimens was used to investigate corrosion protection for internal tendons in precast segmental construction. A comprehensive study concerning grouts for bonded post-tensioning included fluidity testing, accelerated corrosion testing, and field testing in a large-scale clear parabolic duct. Preliminary durability design guidelines were developed for durability design of post-tensioned bridge substructures. Many of the experimental programs are ongoing, and final design guidelines will be developed at the completion of the project.