Pier Luigi Nervi vs Fazlur Khan: the developing of the outrigger system for skyscrapers

The structural development of tall buildings has been a continuously evolving process. There is a distinct structural history of tall buildings similar to the history of their architectural styles. In this structural history it might be interesting to investigate how one of the most popular system used nowadays to build super tall skyscrapers, the outrigger structure, was designed for the first time. A very early example of outrigger structure is the Place Victoria Office Tower of 1965 in Montreal designed by Pier Luigi Nervi and Luigi Moretti (Fig.1). It was also used by Fazlur Khan in BHP House in Melbourne, completed in the 1972 and in the First Wisconsin Center of 1973 in Milwaukee.

The paper focuses on how this particular structural system was first developed, trying to link the experience of two outstanding engineers who worked after the Second World War, the Italian Pierluigi Nervi (1891–1979) and the Bangledeshi-American Fazlur Rahman Khan (1929–1982).