Structural Appraisal of a Roman Concrete Vaulted Monument: The Basilica of Maxentius.

The Basilica of Maxentius, the largest vaulted space built by the Romans, comprised three naves, the outer ones covered by barrel vaults and the central, the highest one by cross vaults. It was built on a sloping site, resulting in a possible structural vulnerability at its taller, western end. Two naves collapsed in the Middle Ages, leaving only the barrel vaults of the north nave. We describe surveys and analyses aimed at creating an accurate record of the current state of the structure, and reconstructing and analyzing the original structure. Key features include distortions of the barrel vaults around windows and rotation of the west wall due to the thrust from the adjacent vault. Thrust line analysis results in a very low safety factor for the west façade. The geometry of the collapsed cross vaults was reconstructed from the remains using solid modeling and digital photogrammetry, and thrust line analysis confirmed that it was stable under gravity loads. A survey of the foundations and earlier structures under the collapsed south-west corner revealed horizontal slip and diagonal cracking in columns and walls; this is strong evidence that the site has been subject to seismic loading which may have caused the partial collapse. [ABSTRACT FROM PUBLISHER]