Numerical and experimental characterisation of tensegrity for structural applications
Tensegrity structures are made up of bars in compression within a set of tensioned cables. All kinds of structures can be built using this concept: footbridges, towers, roofs or domes. In addition to their impressive architectural appearance, these structures are lightweight, offer variable rigidity and can be built and deployed quickly. However, the geometry of these structures depends on the external loads applied to them. This is due to their large number of cables, which means that we have to make non-linear calculations. In addition, to increase the rigidity of these structures, they have to be prestressed by tensioning cables or extending bars.
This geometric non-linearity and prestressing create a lack of confidence in these structures on the part of engineers. Very few commercial software packages address these two issues. The project I'm working on involves perfecting and validating the numerical tool designed during previous work at UCLouvain (in particular Jonas Feron's thesis). This is a plug-in for the Rhino-Grasshopper software developed in Python and C# denoted as MUSCLE.
What further steps are required to achieve a comprehensive tool?
During our previous tests, we noticed a curve in the bars under high loads. This is the first sign of buckling, which we have called second-order controlled bending. This bending disturbs the internal distribution of the prestressing. And this bending is not taken into account in our numerical tool. The so-called dynamic relaxation method, designed for the non-linear calculation of tensioned structures, is based on lattice elements and therefore does not take into account either shear forces or bending. We therefore need to modify this method to be able to predict the behaviour of tensegrity structures as accurately as possible.
In addition to this, a large part of the dynamic behaviour of tensegrity structures remains to be explored. Once these phenomena have been described numerically, I will validate them using large prototypes, which will also present a challenge in terms of the construction and design of these structures and the implementation of prestressing in an efficient and precise manner. This research topic aims to assist the construction company in the conception of tensegrity structures.