14 December 2012

"Kurilpa Bridge" by H Beck & J Cooper: Part 4

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).


Imre said...

Dear Happy Pontist!

There are some interesting points in your book review, as to how architects look at bridges.

The question whether bridges - and especially the Kurilpa Bridge - are art or not, is in my opinion no question at all. Bridges, like buildings and architecture generally, can be positioned to the applied arts. Their possible shapes, decoration, etc. is strongly influenced by utilitarian aspects. For buildings it may be less so, and they may allow more room for creativity and free choice of shapes, structural systems. Bridges are, however, at the "lower end" of this line, with structural considerations dominating in decision making. Other engineering structures, like pipelines or ship docks fall on the other side, with aesthetics playing almost no role at all.
Here, the money-consciousness of a client plays a major role. If someone looks at a financial plan of e.g. a pipeline or some similar "engineering" structure, it contains elements with lower uncertainties, and they are generally less elusive (like the prices of transported oil or gas throughout the years of operation, to stick to the example of the pipeline). On the other hand, financial aspects of urban or transoprtation infrastructure development schemes are very often more elusive. (E.g. additional investitions attracted to the area or region - good examples are the afterlives of olympic facilities throughout the world.)

Architects are very often "entangled" in the role of architecture as creating spaces for people (living, working, social life, etc.). Their success is primarily measured by the public's appeal, as how they meet people's demands. In this context, visually unappealing buildings are often criticized as "they should have spent somewhat more on it, then it would at least look good".
On the other hand, civil engineers are expected to work "on the border", since their facilities are still built for people, but not to suit their "primary" needs. (Here I mean places to live, sleep, work, meet other people, etc.) But due to stricter technical constraints, the idea that "spending somewhat more money on something would make it look much better" doesn't hold anymore. I think this lies at the heart of the blog entry's sentence "The bridge, however, is not like the mobile phone, which must provide good value at low cost or fail in the marketplace - with major infrastructure like this, a clearer understanding of whether the cost is reasonable is harder to obtain."

Imre said...

To the thoughts about the "fear of hybrid srtuctures":
It is true that most civil engineers are "safety players", and yes, it comes from a wider cultural context. Today bridges and buildings are expected to provide a very high level of security at reasonable (but still very high) costs. For example, in the Eurocodes the failure probability of a building should be less than 0.0001 (10^-4) during its lifetime, mostly 50 years. Accidents get strong publicity, and the procurement costs are very high even on community level. Compare this to a mobile phone or even a car, and add that for civil engineering structures there's no "second chance", you cannot do crash tests as with cars.
This also hinders the lust for experimenting, which would be possible - at least in the designer office - given todays simulation and analysis possibilites. Here, the paper of Stefan Holzer: The Polonceau Roof and its Analysis (http://www.ingentaconnect.com/content/maney/het/2010/00000080/00000001/art00002) may be a good reading, since it provides a nice summary on how engineers in the past looked at structures we consider nowadays simple. They calculated with mathematical tools they had at hand (truss theory, continuous beam theory), no matter if the model followed the real structure well or not. This way of thinking can also be followed on cable-stayed bridges: the number of stays increased with increasing computational capabilites. Here, one Hungarian proverb comes to my mind: "If someone only has a hammer, then everything looks like a nail." Or in a "safety player"-fashion: If I only have a hammer, I won't touch anything else than nails.

Best regards:

The Happy Pontist said...

Thanks for the comments!