The trihedral system is the principle of the space frame structure used for the Ville Spatiale and for the ‘span-over’ conceptions of e.g. Span-over Blocks and Bridge Towns. This flexible building method was proposed by Friedman during the congress of CIAM in Dubrovnic (Yugoslavia) in 1956.
His idea to use the trihedal system stemmed from meeting with Konrad Wachsmann at Technion, Haifa (Israel) in 1953. Wachsmann visited there while campaigning worldwide for the use of space-frame structures. Friedman thought his ideas convincing and deemed this system the best his Ville Spatiale’s structure as it was feasible to use with the existing technology at the time. (Note: see Orazi, Manuel, ‘A Conversation with Yona Friedman’, Log, nr 26, New York, USA).
–Trihedral system, 1955