Bending Parabolas: Formwork for Compression-only Structures
al Asali, Wesam
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The “elastic” curves formed by a uniform buckled strut are not optimal shapes as guidework and formwork for compression-only structures. In this paper, we adapt the family of elastic curves to vaults and arches, by changing the stiffness of the strut to force it to buckle as a parabola. The approximation of elastica to parabola in a bent strip makes it useful to form-find, support, and guide the construction of vaults. Consequently, an average variation of the stiffness will form a strip that always generates parabolic arches as it moves, opens, or closes. Hence, the strip becomes a tool that always finds and describes multiple vaulted geometries that otherwise require complicated, one-use, and bulky formwork systems. The system was tested with thin-tile vaulting through building three thin-tile vaults using the bending system for simple in-situ construction. Finding simple in-situ solutions for compression-only structures advocates local grassroots construction that seeks alternatives, not only to the way we build now, but also to the way we think about design. The production of the built environment is not always in the hands of architects and engineers; a dialogue between high-knowledge analysis and low-tech everyday construction is much needed. In this particular context, the paper proposes optimizing on- site technology through design analysis that focuses on the dialogue between material behavior and craftsmanship.