ABSTRACT
A funicular masonry dome experiences no hoop stresses, whether tensile or compressive, so it is always on the verge of bursting. Shallow spheric domes maintain compressive stresses in each course and are therefore more stable than the “ideal” funicular form. Viable non-funicular domes also include Herrero’s flat vault at the Escorial, and Mackenzie’s 1840 concept of an inverted vault fan. The author and a team of students studied these forms through active structural models. They also built other forms in un-mortared, un-reinforced, and frictionless masonry, including an “anti-dome” that descends from its abutments to a low center, and an “ambi-dome” that rises from a peripheral ring to a circular crown and then descends to a central, circular oculus. These counter-intuitive forms demonstrate compressive hoop actions and orthogonal shear resistances that are seldom discussed in structures texts. Exploring these capacities is instructive, exploiting them expands the formal limits of masonry construction.
