ABSTRACT
There has been considerable research and interest in the topic of fracture-critical members (FCMs) during the past decade. As a result, the entire concept of what constitutes a nonredundant steel tension member has been completely revised and many long-standing ideas and opinions related to this classification of members have been shown to be overly conservative. After years of research, two new stand-alone AASHTO Guide Specifications that give codified direction on how to perform 3D system analysis to verify system redundancy, as well as AASHTO Guide Specifications to evaluate internal member-level redundancy of mechanically-fastened built-up members, have now been developed and adopted by AASHTO. This paper will summarize the background to the current views of FCMs and suggestions about how this new integrated approach to redundancy, in particular as related to the fatigue and fracture limits states is being implemented in the US.
