A New Semi-Active Tensairity Structure Equipped With Shape Memory Cables: Experiments And Computations.

The concept of tensairity structure is interesting for numerous applications in several application fields according to the low ratio between self-weight and its loading capacity. The basic components of a tensairity are represented by a cylindrical pneumatic/inflatable element, a couple of cables wrapped around and attached to a slender beam positioned along the generatrix of the cylinder. When the tensairity is loaded, the beam is compressed while the cables are subject to tension thus realizing a very efficient structure. However, one of the main limitations for dynamic applications is due to the low damping ratio which makes the structure susceptible of continuous vibrations. This study explores a new concept of semi-active tensairity that provides a solution to this loss of performance. A reduced-scale prototype has been manufactured according to the tensairity concept in U.S. Patent No. 10,407,939. The main innovations are represented by the employment of NiTiNOL wires wrapped around the pneumatic element, the introduction of manual and automatic tensioning systems at the ends of the slender beams and the adoption of a design that provides the capability of sustaining loads in any direction. The load-displacement curves have been acquired with a MTS testing machine for the tensairity equipped with NiTiNOL and steel wires, respectively, and for different pretension levels. Dynamic experiments have been performed to measure the resonance frequencies of the lowest few modes as a function of the pretension levels. The results demonstrate the higher dissipation capacity of the tensairity equipped with shape memory wires whose tensions are semi-actively controlled. Finally, a nonlinear FEM model has been implemented in ABAQUS and parametrized in Python to simulate the static and dynamic tests.