Tensile structure form-finding on the basis of properties of frame-grid template

Abstract

The design of a tensile structure differs from the one used in conventional structural design in that it is impossible to predict the tensile structure form. This paper describes a special 3D Frame-Grid template for efficient form-finding of the tensile structure. The basis for the template is a Frame object consisting of a set of spatial edges, connected with each other in vertices. The Frame edges and nodes correspond to fabric structure singularities and to boundary constraints. The grid is hung on the Frame object and is subject to optimal form-finding by the Stretched Grid Method (SGM) as close to the minimum surface as possible. Moreover, the problem may occur when designing awnings with a “narrow neck.” Taking into account this singularity, we provide a special adaptation tool based on a non-linear function for each weight ratio of the Grid edge separately. The final structure surface inherits geometric properties from the Frame object. Therefore, the Frame-Grid template makes it possible to redefine the surface form automatically, modifying only the Frame structure. However, the numerical problem solution leads to the fact that the final surface is represented by an arbitrary polyhedron. This may cause the appearance of surface wrinkles or folders at some narrow surface regions. To avoid this, we developed a special corrective criterion. In many cases, a structure’s integrity, stability and safety may be based on a “pre-stressing” process. The paper describes the way to orthotropic non-dimensional pre-stressing taking into consideration the twofold difference of rigidity between warp and weft directions.