Damages on complex structural systems: Effects on load paths

In the event of damage to a structural system, ensuring the redistribution of loads becomes crucial to mitigate the risk of progressive collapse. By providing alternative load paths, structures can accommodate load redistribution, adapting to progressive changes in structural conditions over time, reducing the probability of failure and demonstrating increased robustness. In conventional redundant structures, say frames, the main behavior is expected to be parallel-like, with individual load paths within the structure capable of interacting and redistributing loads in response to localized changes. The alteration of the stiffness of one element due to damage may cause a change of the overall behavior. In this paper it is shown that the evolution of a random damage on the structure, in particular when the arrangement of the element is non-trivial, highlights a transition between the overall behavior of the system. Specifically, as damage progresses, the system may shift from parallel-like to series-like, typical in non-redundant structures, with consequent dramatic and potentially non-robust situations. Examples on simple structures are provided to highlight the difference in the behaviors.