The Stone Skeleton: A Reappraisal

Jacques Heyman’s 1966 article “The Stone Skeleton” has been influential in the assessment of masonry arches in general, including masonry bridges and gothic architecture. Heyman’s article relies on limiting assumptions about arch behavior, and concludes that an arch can be declared stable based on the location of a statically admissible thrust line within the arch. In the following commentary, we assess the validity of the assumptions made by Heyman and the uses that have been made of his application of the lower bound theorem of plasticity. We conclude that Heyman’s methods have enduring value, but that the user needs to recognize the limitations of the assumptions made and the limits on the validity of conclusions imposed by these assumptions.