SEI - Illinois Chapter September Dinner Meeting - RESCHEDULED for September 27th

Development of a New Generation, High-Strength Post-Tensioned Anchorage Bar

Presented by: Jared E. Brewe, PhD & Neal Anderson, P.E., S.E.

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.

Dr. Brewe specializes in the design, construction, evaluation, and repair of structures.  His experience includes: condition assessment and structural evaluation of existing structures; repair, rehabilitation, and strengthening of deficient and deteriorated structures; forensic investigation of structural distress and failures and design and construction defects; advanced structural evaluation and finite element analyses of existing structures; and evaluation of building components for code acceptance.  He has applied analytical knowledge to investigate existing structures, design repairs for concrete structures, evaluate the effect of design and construction errors on the expected performance of structures, and determine cause of structural failures.

Neal Anderson has over thirty years of experience in the construction and engineering field working on a variety of structural and materials evaluations, bridge superstructure and deck repair projects, and assignments including structural building frames, building facades, plazas, slabs-on-grade, historic steel construction, and parking decks.  He has served on the investigation team for several structural collapses.  He has experience in the evaluation and repair of steel structures, with particular emphasis on riveted steel repair and weathering steel rehabilitation.  He also has experience in the condition assessment and rehabilitation of historic concrete and steel bridges, and major stadium structures.