A Class of Tensegrity Domes

Abstract

The paper investigates the structural behaviour of a class of cable-and-strut prestressed tensegrity domes which have been proposed by D.H. Geiger. The largest existing dome of this type, completed in September 1989, has circular plan and diameter of 210 m. The investigation concentrates on a cut-down version of this dome, consisting of only twentyfour cable segments and eight struts, with one statical indeterminacy (as in the bigger domes) and thirteen independent inextensional modes of deformation. It is shown that the state of self-stress associated with the statical redundancy stiffens all of the inextensional modes. The response of the domes to a general load condition is discussed: the inextensional loads, which can induce large displacements from the initial configuration, are identified and contrasted to the extensional loads, which induce mainly tension changes and comparatively small displacements. For a particular extensional load, a simple stability analysis shows that overall buckling of the dome and slackening of some cables occur at approximately the same value of the load but, if the same loads are applied in the opposite direction, overall buckling precedes cable slackening. An experiment on a 1.7m prestressed dome is described. The measured response is compared to analytical predictions based on the nominal shape of the dome, as well as on its actual shape — which was carefully measured.