You may watch and listen to this major event on the web (on-demand starting October 15)

With its vast scale and corresponding immense cost, extraordinary speed of erection (532-537 AD), and stunning interior space, the Hagi Sophia is unparalleled in premodern  Western architecture. As such, its achievement begs answers to three intriguing and interrelated questions. The first falls mainly in the realm of architectural/technological history and concerns the nature of the theoretical and material resources used by Hagia Sophia's designers, Anthemius of Tralles and Isidorus of Miletus, for the creation of this great building. Historians of architecture usually explain the miracle of the Hagia Sophia's construction in terms of technological-design revolution. On the other hand, the development of engineering mechanics to a point where it could begin to treat structural problems as complex as that of a vault is of relatively recent origin.

The second question concerns the behavior, under the action of environmental loadings, of Hagia Sophia's much-modified structure over the centuries and worthiness of the present-day structure in a major earthquake, an event that is most likely to occur within the next-half century. It is known that exceedingly large deformations of the main piers supporting the central dome disquieted Hagia Sophia's builders even before the original campaign of construction was completed. And in 558, the great central dome fell after being subjected to two earthquakes, first in August 553, and again in December 557. A nephew of Isidorus then erected the current dome. The form of the second dome remains basically unchanged despite its partial collapses, first after an earthquake in the 10th century and again after another in the 14th.

In this talk we address the third question, which is directly related to the first two questions and concerns the shape of the original dome built by the two great architects, through two approaches. The first is through tests performed on the structural model. By means of this computer model we can study the structural integrity of the various shapes suggested for the first dome and compare their predicted behaviors. Second, we look at literary descriptions of the Hagia Sophia's vaulting by Procopius, Agathias, Paul the Silentiary, and Malalas, paying particular attention to the evidence of what collapsed, what was taken down, and finally what was rebuilt. Based on both the technical studies and a careful reinterpretation of the available sources, we propose a new reconstruction of the first dome of Hagia Sophia which is compatible both with the results of our scientific studies and with the original sources