Experimental and Numerical Evaluation of the Postfracture Redundancy of a Simple Span Truss Bridge

The fracture critical (FC) classification was developed and implemented for bridges in which the failure of a single member could lead to failure or collapse of the structure. The FC classification can increase the fabrication cost of the bridge, but far more expensive are the required arms-length biennial in-service inspections. To reduce costs for state highway agencies, it would be beneficial to reconsider the FC designation or, at least, the frequency of the arms-length in-service inspections for bridges, where appropriate. This research evaluated (1) the redundancy of a full-scale 45.72-m (150-ft) truss bridge structure by conducting controlled fracture tests in the field and (2) the use of numerical analysis techniques for quantifying the postfracture behavior and redundancy of the full-scale truss bridge. The experimental results indicate that the truss bridge structure had significant member-level and system-level redundancies, which prevented failure or collapse of the structure caused by failure of the FC member. The numerical models can predict the postbehavior and redundancy of the full-scale truss bridge reasonably well, but with some limitations. The experimental and numerical approaches presented in this paper are recommended for conducting additional investigations, expanding the knowledge database, and eventually for reconsidering the FC classification or the frequency of arms-length inspections.