Against Gravity

Alexander von Kienlin

Forgotten Constructions: Wide Spanning Trusses in Imperial Rome
The bronze roof truss of the Pantheon entry hall was without doubt one of the great feats of Imperial Roman engineering. But during all times it stood in the shadow of the cupola, which remained unreached in width and beauty until the Renaissance Time. Destroyed by a pope in the 17th Century, it is still surviving on numerous Renaissance drawings, which give us at least an idea of its shape and construction.

After centuries, Lothar Haselberger dared a closer look on this construction – not on the truss itself, but on its supporting structures. Further scholars gave attention to this extraordinary construction, but still there are basic open questions: How did the construction work, and even more exciting: how did its engineer expect it to work? Lothar likes this kind of questions, since (ancient) design drawings seem to interest him even at least as much as buildings, so I am hopeful that he will appreciate my approach: The Pantheon roof will deliver the discussion points of my paper, but I will focus on another roof, one century later, wooden, and built not in Rome, but in Western Anatolia. Significant demolition material of the Odeion of Kibyra firstly gives us opportunity to reconstruct all elements of an ancient wide spanning roof construction. It was one of the greatest trusses in the Roman world, and it might give us insights into completely forgotten engineering theories: The characteristics of the Kibyra roof point to the idea of latticed truss (Fachwerk-Binder) - which is considered as invention of the 19th Century.

The paper will discuss these high capacity constructions and their importance for the Roman architecture. I will try to explain, why they were fully lost and forgotten in Late Antiquity.