This is the final part of a 4-part review of the book Kurilpa Bridge. For some of the context, see Part 1.
The book's final main chapter offers a history of bridges, attempting to place Brisbane's Kurilpa span in a wider context. This is pretty well informed for a text aimed at the general reader.
The book notes that considering the long-term, design of vehicular bridges is a relatively recent phenomenon. Indeed, the history of bridge engineering is to a great extent a history of footbridges, with most new technologies and structural types pioneered in such structures. It's proposed that bigger spans and the commercial requirements of private funding led to an obsession among engineers with economy as their key yardstick during the industrial revolution. In time, economy became synonymous with engineering elegance, and the paring down and exposure of material became the engineer's aesthetic.
The authors contrast the 19th century development of bridge design in the UK and the USA to note that stylistic preferences are to some extent culturally determined - the Brits were "rhetorical", with gestures such as Telford's castellated towers, while the Americans were "utilitarian". Different preferences for craftsmanship as against mass production resulted mainly from differing availability of labour and material resources.
The Tacoma Narrows bridge is identified as both the epitome and failure of "Functionalist Modernism", the implication being that engineers who still adhere to this philosophy are following a failed tradition. Some of the book's comments are somewhat unfair. For example, Leon Moisseiff's Deflection Theory is depicted as "hunches and hypotheses dressed up as theory", which is absurd. For one thing, Deflection Theory had been devised decades before Tacoma's designer Moisseiff came along (he simple extended Josef Melan's theory and gave it a name), and for another, it was a well-developed analytical method, significantly more accurate than its precursors.
The book notes that the modern reintroduction of cable-stayed form has liberated engineers from the purely functionalist aesthetic - "a poetic genie was let out the bottle". This is clearly true - the form's inherent adaptability has triggered an explosion of creative design, especially for footbridges.
Kurilpa Bridge also includes texts from the bridge's designers, contractor and client, and a wide variety of generally excellent photographs of the bridge. Some of these reveal how the bridge's aesthetic vision has been compromised. There are balconies or belvederes at intervals, which to me don't visually cohere with the bridge's main identity, and the way the overhead canopy changes in its method of support at odd locations is visually disconcerting.
There are woven steel mesh side panels above a riverside highway which stop very abruptly, in an area where the canopy looks like it could have been hung from the bridge's tensegrity masts, but has not been.
Although the bridge is not entirely visually successful, it is undoubtedly a considerable engineering achievement. Beck and Cooper's book is also an unusual attempt amongst bridge architecture monographs to consider more widely the philosophies that can be applied by both designer and critic to evaluating the aesthetics of an engineered structure. For students of architecture, it may help shed some light on how engineers generally think. For students of engineering, it might perhaps prompt them to re-evaluate some dearly held principles and understand how to consider their work from a different perspective. I enjoyed reading it.
(Images of Kurilpa Bridge courtesy of Sankarshan Mukhopadhyay).