The Partial Collapse of the South Road Axis Viaduct in Brasilia—A Forensic Investigation

The partial collapse of the South Road Axis Viaduct in 2018 generated widespread concern about the safety of similar critical bridges and viaducts built during the same historical period in Brasilia. Since many of these structures were designed with analogous structural systems, a thorough post-incident investigation was conducted to understand the failure mechanisms involved. The viaduct collapse remains insufficiently examined in the available technical literature. The present work offers a detailed forensic investigation of the partial collapse of the asset, clarifying the key structural elements and governing mechanics that triggered the sudden failure. This study combined the collection of historical documentation, in situ debris investigation, geometrical and mechanical characterization, manual and numerical calculations, and the determination of structural performance. The results revealed that the viaduct had hidden vulnerabilities (such as a lack of structural redundancy and insufficient reinforcing steel) and significant material degradation and that it was operating under unpredicted high cyclic shear demands. Lastly, the repairs and strengthening techniques employed in the viaduct’s recovery are also presented.