Guide Specifications for Internal Redundancy of Mechanically-Fastened Built-Up Steel Members, First Edition
Handbook / Manual / Guide by American Association of State and Highway Transportation Officials, 2018



These Guide Specifications are intended to provide an analytical framework to evaluate the internal redundancy of typical steel bridge members, and designate primary steel members as 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 Specifications are based on research Transportation Pooled Fund Project TPF-5(253) “Evaluation of Member Level Redundancy in Built-Up Steel Members,” which addresses the important issues related to performing a “credible” analysis to identify built-up members that have adequate internal redundancy to resist complete failure of the cross section should one component suddenly fail.

The Guide Specifications also include 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 must be of sufficient depth to reliably detect a severed component. This is a major departure from the current calendar-based approach to setting inspection intervals.Some of the major updates in this new edition include a title change from the 2009 first edition, AASHTO LRFD Bridge Design Guide Specification for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings, to acknowledge the inclusion of information beyond bridge decks and traffic railings; greater consistency with the AASHTO LRFD Bridge Design Specifications, 8th Edition; consideration of flexural members, such as girders and bent caps, not included in first edition; consideration of substructure and foundation elements along with compression members; differentiation between the fatigue and creep limit states; and revised shear design methodology.

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