Experimental Evaluation of Load Transfer Mechanisms in Steel Truss Bridges under Varied Damage Scenarios

This paper investigates the structural robustness of a steel Pratt-type truss bridge through a series of experimental analyses focusing on various damage scenarios. Twelve distinct damage scenarios were examined under two typical loading conditions: mid-span and quarter-span positions. The study highlights the critical impact of localized damage on the stiffness and overall stability of the truss bridge structure. Key findings suggest that the failure of upper and lower chord members, especially near mid-span, poses significant risks. Additionally, damage to vertical and diagonal members at quarter-span locations also undermines structural integrity. The robustness of the bridge was quantitatively assessed using the bridge’s global load–deflection response and stiffness reduction in its damaged state. The research emphasizes the importance of understanding the alternate load paths (ALPs) activated during localized failures, which allow the structure to maintain stability despite local damage. These ALPs are identified either through the heightened strain values in connected members or through changes between tension and compression. Understanding the available ALPs is crucial for design considerations, as identifying ALPs in scenarios of critical member damage, along with additional ALPs, can enhance robustness and ensure safety.