Mechanical behavior of tensegrity structures with High-mode imperfections

The potential applications of tensegrity structures are widely accepted in fields, such as civil engineering and soft robotics. However, the curved shapes of struts in tensegrity inspired applications and the corresponding nonlinear mechanical behavior make it necessary to introduce initial imperfections, especially high-mode imperfections. This paper works out a method to analyze the initial imperfection analytically with the basic assumption that the strut length would not change with the deformation. Then a simple three-member tensegrity structure is harnessed here to investigate the mechanical behavior of tensegrity structures with the first three modes of initial imperfections. Our analytical results demonstrated that the stiffness of the tensegrity structure will be reduced significantly with even small initial imperfections. The analytical result of load-displacement curve shows that the deformation shows an upward trend with the rise of initial imperfection mode. Further, a strong nonlinearity arises with increased initial imperfection both in terms of the maximum deformation of the strut as well as the stiffness behavior of the tensegrity. Finite element simulations of tensegrity structures with 6 struts show great consistency with the analytical computation. The initial imperfection method provides an intuitive way to introduce nonlinearity to mechanical behavior. It has major implications in understanding load bearing capacity and force distribution in applications of tensegrity structures.