Superelement Stiffness Matrix for Space Trusses

Abstract

The techniques of discrete field analysis are used to analyze a class of longitudinally oriented space trusses. These trusses consist of three planar trusses which make up the faces of the space truss and are combined to form a triangular cross section with common chords. Three types of configurations are considered: (1) X‐braced; (2) Warren (with verticals); and (3) Vierendeel. The approach used here is to treat a truss segment having regular repetitive properties over an arbitrary number of panels as a superelement. Difference equations for each of the three truss configurations are derived and deflections found using finite fourier series. Based on these solution forms, stiffness coefficients are derived. The results are exact in the classical sense and enables a space truss with a large number of joints to be accurately reduced to a single member defined by beam type stiffness coefficients. This superelement can be used in conjunction with other elements to analyze complex truss systems such as guyed towers and space truss roof systems.