Composition and Shape of Hadrianic Domes

Luca Cipriani,Filippo Fantini,Silvia Bertacchi

doi:10.1007/s00004-020-00514-z

Abstract

In-depth studies on the design of the domes of the Octagonal Hall of the Small Baths and the Vestibule of the Golden Court at Hadrian’s Villa in Tivoli have been conducted starting from 3D surveys carried out with active and passive sensors. Through the comparison of the ichnographia and orthographia of these emblematic examples of architectural experimentation, common elements and features have emerged which, thanks to the integrated use of new measurement technologies, have allowed us to hypothesise dimensioning systems of the vertical structures together with possible criteria for defining the intrados–extrados relationship. Hadrian’s architects’ use of precise grid-based designs to facilitate the achievement of target quantities (required areas and volumes) as well as modules aimed at defining alignments of horizontal and vertical structures emerge clearly, providing useful elements for an integrated reading of the individual buildings to support the archaeological investigation.

Highlights

In the first construction phase there is no case of structural lightness akin to that of the Octagonal Hall at the Domus Aurea, whose thickness is around a Roman foot (1 Roman foot = 29.56 cm), or even of extrados domes: internal and external profiles do not match in any of the examples of the initial building development
For further analysis of these terms see (Adembri et al 2015). Their key to reading the architecture supposed that ancient builders used a square made of 7 × 7 modules for the internal dimensioning of this hall, while the bending radius of the curved sides was of 15 Roman feet
The comparison between the two domes has allowed us to find a series of common elements that, compared to previous studies, sheds new light on the more complex of the two cases, the Octagonal Hall of the Small Baths: how did ancient architects determine the wall thickness?

Summary

Introduction

In the first construction phase there is no case of structural lightness akin to that of the Octagonal Hall at the Domus Aurea, whose thickness is around a Roman foot (1 Roman foot = 29.56 cm), or even of extrados domes: internal and external profiles do not match in any of the examples of the initial building development. To repeat the steps of the design process carried out by the original architect, a specific workflow had to be developed, based on the use of reverse modelling applications in combination with the hints from the limited amount of surviving technical literature regarding vaults and domes of the Roman world.

Results

Conclusion