A weightless wire coat hanger bent out of its plane is one of the simplest possible structures. All it does is transfer a force and moment around a closed space curve. Assembling a family of coat hangers enables us to build up trusses and frames and if we allow an infinite number of coat hangers which overlap we can assemble plates, shells and fully three dimensional structures. We can apply loads to these structures via a loading frame and wires, also made from coat hangers. A wire carrying an electric current produces a magnetic field in the space surrounding the wire. For the bent coat hanger we can imagine that there vector field surrounding the wire as a result of the force and moment in the wire. We can use this vector field to obtain expressions for the forces and moments in a shell in equilibrium with applied loads.
The best known isotropic membrane stress state is a soap film. However, if we allow the value of the isotropic stress to vary from point to point then the surface can carry gravity loads, either as a hanging form in tension, or as a masonry shell in compression. The paper describes the theory of isotropic membrane stress under gravity load and introduces a particle method for its numerical simulation for the form finding of shell structures.
Guest Editors Samar Malek and Chris Williams provide an overview of the aesthetic properties of shell and tension structures, drawing on classical arguments about the relationship between nature, mathematics and architecture. The letter concludes with an introduction to the papers in NNJ 19(3).
Corrugations are used to stiffen sheet materials and in so doing they increase the bending and torsional stiffness in one direction and reduce the in plane membrane stiffness in the other. In this paper we examine the implications of this for the equilibrium of corrugated plate and shell structures. In particular we show that if the derivation is kept in terms of membrane strain energy then such a structure is statically determinate. As a result, a closed-form solution is obtained for a corrugated shell which is simple to solve numerically and could allow a designer to explore a range of different corrugation patterns and support conditions in the initial stage of design
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