Design of tension structures and shells using the Airy stress function

Discontinuities in the Airy stress function for in-plane stress analysis represent forces and moments in connected one-dimensional elements. We expand this representation to curved membrane-action structures, such as shells and cable nets, and graphically visualise the internal stresses and section forces at the boundary necessary for equilibrium. The approach enhances understanding of the interplay between form and forces and can support design decisions related to form-finding and force efficiency. As illustrative examples, the prestressing needed for three existing cable nets is determined, and its influence on the edge-beam bending moment is explored.

From finding of tensile structures in Faculty of Civil Engineering classes

In Structural Analysis 2, the third year’s course of undergraduate studies at the Faculty of Civil Engineering, University of Zagreb, students acquire theoretical knowledge on the design of tensile structures (with emphasis on prestressed cable nets). Prior to calculation, to better understand the problem of form finding, students are assigned to build a physical model of tensile structure from elastic mesh fabric. Following, they apply the force density method to numerically determine the equilibrium position. To establish numerical model, Rhinoceros and Grasshopper (visual programming language within Rhinoceros) are used, while calculations are made in SageMath, an open-source mathematical software.

Hemp Cables, a Sustainable Alternative to Harmonic Steel for Cable Nets

Recent developments in the field of materials engineering have allowed for the use of natural materials for common structural elements, instead of traditional materials, such as steel or concrete. In this context, hemp is a very interesting material for structural building design. This paper proposes the use of hemp cables for roofs with hyperbolic paraboloid cable nets, which sees the use of a sustainable material for structure, thus having a very low environmental impact, in terms of structural thickness and amount of material. The paper discusses five different plan sizes and two different hyperbolic paraboloid surface radius of curvatures. The cable traction, which gives the cable net stiffness, was varied in order to give a parametric database of structural response. Three dimensional geometrically nonlinear analyses were carried out on different geometries (i.e., 10), cable net stiffnesses (i.e., 8), and materials (i.e., 2). Traditional harmonic steel and hemp cables are compared, in terms of vertical displacements and natural periods under dead and permanent loads.