Force Finding Analysis of Hybrid Space Structures

Abstract

Some aspects of the application of the equilibrium matrix theory in hybrid space structures are discussed in this paper. In hybrid space structures that are composed of cables and bars only, the flexibility distribution of each bar element should be considered at the same time. Otherwise the structure would probably not be tensioned and constructed successfully. A method to obtain the flexibility distribution of cable-bar hybrid structures is presented by using compatibility equations and equilibrium equations at the same time. This is verified by two numerical examples (Example 1 and 2). In hybrid space structures composed of beams, cables and bars another problem exists, namely constructing the equilibrium matrix of two-node beam element. There are 6 or 3 columns for each two-node beam element in the whole equilibrium matrix. In the case of a suspen-dome there are lots of independent self-equilibrated stress modes. However, in a beam-string structure there is only one self-equilibrated stress mode. In order to avoid the combination of many independent self-stress modes a method named local analysis method is proposed in this paper to obtain the initial pre-stress distribution of the beams. A small beam-string structure is to verify this method.