The 2013 Interim Revisions of the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (LRFD) Bridge Design Specifications allow reinforced concrete bridges to be designed using high-strength reinforcing steels up to a 100 ksi yield, such as MMFX2 (AASHTO MP18/ASTM A1035 Grade 100 [690 MPa]).
“The updated specification will benefit state and federal efforts to rebuild the nation’s infrastructure with lower costs while using higher-strength reinforcing steel,” affirms MMFX CEO Tom Russo. “The expanded use of MMFX2 at its full strength will result in bridges that are not only constructed better but also offer the lowest life-cycle cost.”
High-strength rebar allows DOTs to design structures to be built with 20 to 50 percent less steel that can result in up to 60 percent lower labor costs for rebar placing. By specifying high-strength steels, designers can solve costly rebar congestion problems and developers can complete structures more quickly, resulting in substantial cost savings.
“Prior to the LRFD Bridge Specification revisions, engineers were limited in their designs to only include reinforcing steel up to 75 ksi for bridge structures,” notes Russo. “Now that the revisions are published, engineers and contractors have access to the new 100 ksi rebar specification and can solve difficult infrastructure design and construction issues with the best available tools and techniques.”
Made up of the chief transportation officers from every U.S. state, the District of Columbia and Puerto Rico, AASHTO is an international leader in setting technical standards for highway systems. Its approval of the 100 ksi higher-strength steel was based on the finding and recommendations of the National Cooperative Highway Research Program Report 679 released in 2011, which states “…using steel with this higher capacity could provide various benefits to the concrete construction industry by reducing member cross sections and reinforcement quantities, leading to savings in material, shipping, and placement costs. Reducing reinforcement quantities also would reduce congestion problems leading to better quality of construction.” — MMFX Steel Corp. of America, Irvine, Calif., 949/476-7600, www.mmfx.com