Analysis of a Collapsed Long-Span Reinforced Concrete Roof in South Italy: Design Mistakes and Material Degradation

In 2004, during ordinary maintenance work, consisting of waterproofing a building located in the south of Italy, the long-span (14.5 m) in situ RC roof partially collapsed. The building, constructed in 1950, was in service as a cinema until 1967 and then utilized as a school until 1985. Lastly, it was a hotel until 2000. In 2004, when the building was not in service and was undergoing maintenance work, it partially collapsed under dead load. After the collapse, which involved a large portion of the roof, several beams, and two columns, the Italian court nominated an official technical consultant to investigate the direct and related causes of the failure. After the main causes were identified, the building was repaired and the roof was reconstructed with a light steel structure. This article is focused on the behavior of the collapsed structure considering the original design choices, the construction details adopted, and the material properties, including the effect of concrete and steel degradation. The influences of these aspects on the collapse are examined, with particular emphasis on concrete carbonation, steel bar corrosion, and design mistakes. The lessons learned from the case study could help professional engineers to be aware of the main peculiarities and structural deficiencies of structural systems affected by material degradation and the importance of in situ periodic checks and monitoring during the life of the structures.