Some Performance Trends in Hierarchical Truss Structures

Abstract

It has been previously demonstrated that increasing structural complexity can lead to lighter weight structures.However, it is not clear that structural complexity or hierarchy enables lighter weight structures for all architectures and load cases.In this paper, the performance trends in linear truss structures are investigated as a function of self-similar hierarchy order and of loading conditions.The investigations show the order of structural hierarchy resulting in a lightest weight self-similar four longeron solid element truss-column is 2 nd (a truss made from trusses) for requirements representative of space structures.The resulting truss-column is typically an order of magnitude lighter than the corresponding 1 st order truss-column and two to four times larger in diameter.Long and lightly loaded columns are shown to have the greatest potential for mass reduction with increasing hierarchy.Optimization results for 1 st and 2 nd order self-similar triangular single-laced double-bay trusses subject to bending strength and stiffness requirements are also presented.A comparison of 1 st and 2 nd order results show a factor of 30 reduction in truss mass and a simultaneous factor of nine increase in truss diameter.