Univ. Prof. S. J. Britvec’s research while affiliated with University of the Bundeswehr Munich and other places

Elastic space structures, composed of pin-jointed slender members with symmetrical flexural properties, loaded centrally at the joints by conservative loads represent a class of symmetrical elastic systems discussed before.1 The behavior of such structures in the critical and post-critical statical equilibrium states is similar to that of plane pin-jointed frameworks, discussed in Chapter 1 and at length in Ref. 15. Also, the statements made in regard to the onset of unstable motion for plane isostatic frameworks, apply equally to space frameworks or lattices. In hyperstatic lattices the onset of unstable motion may take place only in certain restrained mechanisms. Hyperstatic systems are discussed later.

In this chapter we consider hyperstatic lattices composed of three-dimensional space elements such as tetrahedrons, octahedrons, combinations of cubes and tetrahedrons etc., in which each element is made of light flexible members jointed together by hinged or quasi-hinged (hinge-like) connectors at the nodes. By giving these members appropriate lengths, the lattice may be shaped into any curved three dimensional array of space elements, as demonstrated in Fig. 3.1.1. Curved three-dimensional arrays of space elements constitute shell-type geometrical configurations. Lattices and, in general, structures of this type are called reticulated shells.

Many types of structural elastic systems are composed of pin-ended or hinged bars or members. The most common types are plane and three-dimensional space trusses commonly used in structural engineering applications. More recently new types of structural trusses composed of light, slender and very flexible but axially very stiff members have been increasingly used especially in the aerospace applications and in applications in outer-space as masts, or as supporting structures for space stations, large telescopes and radiometers and in other similar light structures of large dimensions. It turns out that such structural systems are very stiff, if connected by precise member fasteners and loaded or supported by concentrated loads centrally at the nodes which connect the members. Such structures can be formed into arbitrary global geometrical shapes, if the members are given different lengths. First, space elements such as tetrahedrons, octahedrons, cubes combined with tetrahedrons etc. are formed from such flexible members and connected. Then the space elements are assembled into a three-dimensional array forming such a space structure in which any two adjacent nodes are connected by a simple bar. As, in general, global geometry of such a structure may be curved as a shell, we speak of shelltype lattices or of reticulated shells1. Such structures may be enveloped by a membrane or cover-shell if necessary and they may be used effectively for the coverage of large areas, on the earth, for example.