Analysis of structures composed of cables and skins

Abstract

An iterative method for the static analysis of structures which include cables and fabrics is presented here, although fabrics must be substituted by equialent sets of cables. The structure is supposed to be composed of straight members which accept tension and/or compression, which may have an elastic no-ñonear behaviour, and are joined in articulated nodes. Sequences of consecutive connected members, slipping on the intermediate nodes (polygonal cables) and all of them withstanding the same tension, may also be considered. Nodes are supposed to have large displacements so that their equiilbrium is established in their displaced position. External concentrated loads acting on the nodes, initial strains in the members and displacements of the rigid supports may simultaneously act on the structure. The method consists in finding the set of node displacements that produce in the members tensions and compressions that equilibrate the external loads and that accomplish both rigid and elastic support conditions. An initial solution, which may be suppoied by the designer is successively corrected in the direction of the solution of an auxiliary linearly elastic articulated structure, whose nodes are in the present position, whose members have the corresponding tangent Young module, and on which the node unbalanced forces act. This solution is scaled so that, if axial load effects would linearly vary with node displacements, the total energy of the structure becomes minimum in every step. Structures composed of rods cables and fabrics can be analysed using this method, which is fully described and a set of examples is included.