GUIDE SPECIFICATIONS FOR Analysis and Identification of Fracture Critical Members and System Redundant Members
|Publication Date:||1 January 2018|
The provisions contained herein shall be used to evaluate system-level redundancy of a bridge after the failure of a member traditionally designated as an FCM. The results of the evaluation shall place such members into one of two categories:
• Fracture Critical Member (FCM)
• System Redundant Member (SRM)
An FCM may be re-designated as a SRM depending on the outcome of the evaluation using the performance criteria specified in Article 8.1. The primary tension members undergoing evaluation shall be identified on the contract plans as either SRMs or FCMs on new bridges, or as such in the bridge record file for existing bridges.
In the case of newly designed yet to be constructed bridges, both FCMs and SRMs shall be fabricated to satisfy the provisions of Clause 12 of the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code. The provisions of Article 9.1 shall also apply. For members which are entirely built-up from components attached using mechanical fasteners, the load-carrying components shall satisfy the Fracture-Critical Tension Component Impact Test Requirements specified in AASHTO M 270M/M 270 (ASTM A709/A709M).
Unless otherwise specified by the Owner, the assessment procedures included herein shall only be considered applicable to straddle beams and integral cap beams, and to the following steel-bridge structure types:
• Simple-span and continuous-span I-girder (rolled or fabricated plate sections) and tub-girder bridges (including curved and/or skewed bridges);
• Through-girder bridges;
• Truss bridges; and
• Tied-arch bridges.