Determining the Bilateral and Unilateral Mechanisms of Tensegrity Systems

Tensegrity systems as kinematically and statically indeterminate pin-jointed systems are characterized by mechanisms and self-stress states. Taking into account the unilateral rigidity of cables may cause other mechanisms (unilateral) rather than bilateral infinitesimal mechanisms to be produced. Two numerical methods are presented for determining of bilateral mechanisms in tensegrity structures which are based on the geometrical characteristics and positive-definiteness of the tangent stiffness matrix, respectively. These methods allows distinction between first-order and higher order mechanisms. A numerical method is submitted for determining the unilateral mechanisms of these systems which uses the basis of the self-stress states for identifying prestressed and non-prestressed cable elements.