George Gamanis, Engineer, Inventor Skytech® Space Frames , Thessaloniki, Greece

Space frame systems comprising spherical nodes, tubularstructural members and connectors have been well known for over sixty years. The first commercially available system of this type was developed by Dr.-Ing. Max Mengeringhausen and a small team of

close collaborators in Berlin. In this system the connector disclosed in Patent Nos DE 874 657 (date of filing: March 12, 1943) [1] and DE 901 955 (date of filing: July 23, 1950) [1]—both Patents issued to Dr.-Ing. Max Mengeringhausen in 1953—is used. Figure 1 shows the Patent drawings of this connector.

Connectors of this type gained in popularity after the Second World War—particularly after the expiry of the above mentioned patents in the late 1960s—and were originally used for temporary exhibition buildings. However, during the 1970s they were used in large-span permanent buildings.
In connectors of this type, a relatively large opening is made on the pipe portion of the tubular structural member for the insertion of the bolts, which reduces both the ultimate tension and the ultimate
compression resistance of the pipe.

In the case of compression, it is possible to have failure of the pipe due to asymmetrical local elastic-plastic buckling of the walls of the pipe (“asymmetrical” because of the fact that only one opening is provided, although claim 2 of document DE 901 955 recommends symmetrical—with respect to the longitudinal axis of the tubular framework member—openings).

Figure 2 shows the modes of failure of the tubular structural members of a steel space frame canopy covering the excavations of a 3,700-year-old archeological site on Santorini, one of the Cycladic
Islands. The canopy partially collapsed in September 2005. The collapse killed Richard Bennion, 45, of Wales, and seriously injured a tourist from Slovakia and another from the United States.

Five other people suffered lesser injuries. The canopy was designed to carry a 150 mm layer of earth to make it blend in with the surrounding environment. Furthermore, the longitudinal slotted holes through the walls of the sleeve, as in Figures 1 and 2 of document DE 901 955, reduce the ultimate compression resistance of the sleeve. In this case, it is possible to have premature failure of the sleeve due to plastic buckling.

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