Engineering Fail-Safes in Greek Architecture: An Evaluation of the Double Cantilever and Flat-Arch Relieving Devices

Abstract

Greek architecture is known for its post-and-lintel construction, but recent scholarship has uncovered evidence of significant structural experimentation beneath the surface of several Greek buildings. Two structural relieving devices – the double cantilever and the flat arch – were integrated into the Doric colonnades of the Square Peristyle (ca. 300 BCE) in the Agora of Athens and the Stoa (ca. 270-250 BCE) in the sanctuary of the Great Gods on Samothrace. Both systems divided the frieze into a series of blocks with keystones that effectively redistributed their own weight and any superimposed loads to the adjacent frieze blocks and columns rather than onto the middle of the architrave below. This project examines the structural behavior of the flat arch and double cantilever in these two structures to bolster our understanding of their load-bearing capacity. To evaluate each relieving device, this paper calculates their internal stresses under static loads compared to hypothetical cases without reinforcement. In addition to analytical methods, contact-based, block-based solid finite element models are employed to consider each system as a composition of discrete elements with deformable geometries. The results of this study indicate that the double cantilever and flat arch achieved the same reduced tensile stress in the architrave, though differences and limitations arise in the structural behavior of the frieze. Additional reductions in tensile stress were offered by the inclusion of the cornice in the simulated models, and it is shown that the friezes of both buildings function as cantilevers before the addition of relieving devices. More broadly, this paper enriches our understanding of the double cantilever and flat arch as methods of ensuring structural robustness in ancient Greek construction.