The metal roof truss of the Pantheon’s portico in Rome – 152 tonnes of bronze

• Published in: Construction history : journal of the Construction History Group Vol. 33; no. 2; pp. 1 - 22
• Main Authors: Heinzelmann, Dorothee, Heinzelmann, Michael, Lorenz, Werner
• Format: Journal Article
• Language: English
• Published: Ascot Construction History Society 01.01.2018
• Subjects: 1st century; 2nd century; Architectural history; Architecture; Bronze; Bronzes; Building construction; Castings; Cultural heritage; Energy management; Historic preservation; Historical structures; History of engineering; Interdisciplinary aspects; Interdisciplinary studies; Roman civilization; Roofing; Roofs; Shear tests; Urban VIII (Pope) (1568-1644); Rome Italy; Italy
• ISSN: 0267-7768

By order of Pope Urban VIII in 1625 the ancient bronze roof structure over the portico of the Pantheon in Rome was demolished and melted down for canons. So, after 1,500 years, this remarkable witness to Roman engineering, and the only known example of a completely metal structure built prior to the modern age, therefore disappeared. An interdisciplinary research team is now reconstructing this extraordinary roof structure and how it fits into the history of the Pantheon’s construction. They have collected all the relevant sources and findings: drawings and writings of earlier architects, archival documents describing the weight and form of the bronze removed from the roof, the only remaining rivet in the Antikensammlung Berlin and, very importantly, the survey of the Pantheon itself, which reveals traces of the original roof structure. Structural calculations, copies of original castings and tensile/shear tests verify the archaeological reconstruction. Furthermore, the rebuilding of one joint at full size enabled important conclusions to be drawn regarding the jointing method. Owing to this project, it can be presumed that Roman engineers built a 152 tonne roof structure entirely in bronze long before the first iron structures of the industrial age.