Jannasch, Emanuel1

1 Senior Instructor, Dalhousie University School of Architecture, 5410 Spring Garden Road, Halifax, NS, Canada, jannasch@dal.ca

The author and his students have built several counter-intuitive and in some cases unprecedented masonry domes. Forms include the anticlastic or bell-shaped pseudomes and antidomes that descend from their foundation ring to form a basin. An ambidome, which rises in the normal manner but descends to a pendant oculus, is shown in Figure 1. The domes are all unreinforced and un-mortared masonry, and un-bound except by a tensile foundation ring. The completely flat floordomes achieve span-to-depth ratios up to 27:1. Some are made of voussoirs that taper upward rather than down. Yet all the structures are built of loose blocks held in place by gravity alone. Our experiments to date are small in scale, but no matter how unbelievable they appear in cross section, physical demonstration of their inherent stability is incontrovertible. None of the domes are understandable as arches rotated about a vertical axis, but seen as vertical stacks of fully circular horizontal arches they begin to make sense. This conceptualization emphasizes the hoop compression that pre-stresses and stabilizes extant shallow domes, and reminds us of the horizontal and vertical shear forces that act throughout all “compression-only” domes and arches. Some of the forms look more useful than others, but all of them are instructive. They show that our funicular conception of domes is incomplete, and suggest ways of broadening our perspective. Whether unreinforced masonry is valued for social or environmental sustainability or to avoid rust-driven failures, any improvements to masonry theory should be of value.


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