Interim Revisions for Steel Member Guide
The American Association of State Highway & Transportation Officials (AASHTO) has released the 2025 Interim Revisions to its "Guide Specifications for Internal Redundancy of Mechanically-Fastened Built-Up Steel Members", originally published back in 2018.
The 2018 Guide Specifications are intended to provide an analytical framework to evaluate the internal redundancy of typical steel bridge members, and designates primary steel members as either Fracture Critical Members (FCMs) or Internally Redundant Members (IRMs). They describe a procedure for evaluating the internal redundancy of the built-up tension members of the tension components of flexural members and axially loaded tension members.
The Guide also includes a methodology to establish the interval for inspections specifically intended to identify whether any of the tension components have failed. This inspection is referred to as a special inspection for IRMs and is a major departure from the current calendar-based approach to setting inspection intervals.
AASHTO's 2025 Interim Revisions include new rules finalized by FHWA in 2022 that pertain to the National Bridge Inspection Standards, including replacing FCM with the term “non-redundant steel tension member” or “NSTM”. A combined Guide that includes the original 2018 specs and FHWA's 2022 and 2025 interim rules is also now available.
About AASHTO
AASHTO is a nonprofit, nonpartisan association representing highway and transportation departments with the goal to foster the development, operation, and maintenance of an integrated national transportation system.
AASHTO works to educate the public and key decision-makers about the critical role that transportation plays in securing a good quality of life and sound economy for our nation.
