New Holistic Structural Robustness Index for Truss Bridges

This paper proposes a new structural robustness index for truss bridges along with a user-friendly framework of analysis. Bounded between 0 and 1, the index accounts for the structural response holistically by incorporating the system response including before the first element failure, the redundancy of the damaged state with respect to the intact version, and system ductility. The concepts of redundancy and robustness are distinguished in the formulation, where redundancy is the ability of a system to carry additional load after member failure, while robustness is the structure’s ability to absorb a local damage and not collapse. The framework of analysis using the developed robustness index is demonstrated on a simple two-dimensional truss structure subjected to lateral load with both brittle and ductile hinges, where brittle, ductile, and hybrid systems are considered. The proposed index is used to identify critical elements for two different damaged states, and the results are compared with those from five robustness measures published elsewhere. Ultimately, the new structural robustness index can provide valuable insight when evaluating existing bridges and rehabilitating those deemed deficient, presenting a step forward in the safety assessment of structures.