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Spanning professions

The great bridge builders have much to offer architects willing to understand the value of engineering design

The Art of Structural Design: A Swiss Legacy By David P Billington. Yale University Press, 2003. 264pp

This is a beautiful book. Produced in association with a major retrospective exhibition at Princeton University Art Museum, it covers the lives and work of six Swiss structural engineers and academics: Wilhelm Ritter, Robert Maillart, Othmar Ammann, Pierre Lardy, Heinz Isler and Christian Menn.

Displaying the same clarity and production values as a modern exhibition catalogue, the book's series of essays by David Billington distils a lifetime of study and teaching into a substantial contribution to the possibilities of structural engineering.

The subject group has the Federal Institute of Technology (ETH) in Zurich in common - Ritter and Lardy as staff, teaching and researching;

Maillart, Ammann, Isler and Menn their pupils and close followers.

Billington explains clearly the circumstances that set this school apart, from its inception and its subsequent influence. Oddly, he fails to make any mention of ETH's more recent postgraduates, such as Santiago Calatrava, or situate its establishment within a larger Swiss legacy, stretching back to the Enlightenment timber bridges of the Grubenmann brothers and forward to the most recent bridge works of Graubünden engineers, such as Jorg Conzett.

His topic is interesting enough, but the true value of Billington's writing lies, as in previous work, in the critical framework he sets up within which the work of these engineers and others can be assessed. Recognising that engineering is embedded in a total environment (physical and intellectual), he seeks to understand the widest range of influences.

Taught structures The emphasis on the importance of teachers is only natural from an academic at a certain stage in his career, and Billington's earlier book of 20 years ago, Robert Maillart's Bridges, probably balances technical and conceptual milieux more successfully.

Nevertheless, the way information was transmitted by each master and the response of each student is understood and brilliantly explained.

Ritter's championing of graphical statics in the face of the increasingly complicated successes of the mathematical theory of elasticity led directly to Maillart's bridge forms.

Lardy earns the epithet of 'educational artist'. Ideas on composition are integrated directly into his lecture notes on structure; recurrent references to aesthetics occur with no mention of architects; and different forms are treated simultaneously rather than as independent topics.

Billington makes a telling comparison of Lardy's work with Hardy Cross, the exemplar of a teacher transcending the sedimentation of knowledge to produce a method and exposition of timeless simplicity. Pertinently, he asks the question: 'Why do we use only the latest textbooks?'

The research base of the book and its neat production values veil a strong polemical argument that the structural engineer can attain the status of artist. The debates that attended some of Maillart's work, the counter-currents of thought from other teachers at ETH such as Arthur Rohn and Max Ritter, who emphasised the role of architects, and others who sought form only through ever more complex analysis, are mentioned but not expanded on. A glance at John Chilton's book on Isler shows how selectively presented that engineer's work is to assist the argument.

The general condition of engineering through the century under debate is only implicit in the discussion.

The personalities of the individuals come across strongly. Sincere design, all of a piece, ringing true, is a recurrent theme in the commentaries of Maillart, Ammann and Menn.

After a long life beset by personal tragedy and having completed the Salginotobel bridge, now designated an International Engineering Landmark, Maillart is seen still striving for something better. 'Even [Salginotobel bridge] cannot lay claim to complete sincerity of form it is only in the bridge at Felsegg built as recently as 1933 I had the chance of realising a truly logical form.'

In his last two bridges, Maillart subtly modified the intrados of his arches from a continuous line to the celebrated broken-arch profile. This nuance is demonstrated clearly across two pages of images juxtaposed without words, where the graphic design succeeds (here and elsewhere) in achieving clear visual explanations.

Cover pages from the academic's textbooks, set alongside built projects, illustrate through their old Gothic script just how modern their ideas were. Many photographs of outstanding monuments, used over double pages and with full-colour bleeds, add real worth and a sense of the structural space and sweep involved in the projects.

In his description of the life and times of Ammann, written in collaboration with James Doig, Billington expands on political contexts. They place Ammann squarely in the 'right man, right time' category and his career does indeed reflect larger trends. An émigré, Ammann went on to build six of the greatest bridges of New York, produce several worldrecord spans, and invent a civil engineering mantra - the 'slightlylonger-than-its-predecessor' bridge.

Building bridges Isler's work on lightweight shell structures stretches the book's method the furthest. His work is usefully compared with that of Felix Candela. Isler worked from models with clamped edges and Candela was delighted with the beauty of differential equations and the way their solutions coruscate when boundary conditions are varied. The resulting differences in their approach to edge treatments are fascinating. Despite Isler's applications of shell forms to Swiss garden centres, it is Candela's pavilions that better reflect the morphologies of tropical botany.

The essay on Menn is excellent, benefiting from personal acquaintance. The Ganter bridge is described in detail, from the influence of foundation conditions on siting to its layering of technical and formal ideas. But the significance of the curving fin walls, one of the best idiosyncrasies of recent engineering design, seems to be missed. The author skates over this engineer's unseemly habit of subverting competitions (submitting alternative designs despite being on the jury? ), to return to moral precepts.

Menn is quoted: 'From an engineer's point of view, it is inconceivable to accept flaws in the structural system and details or disproportionately high cost in return for architectural embellishment.' He set 7 per cent as the maximum extra cost allowable on a bridge design for aesthetics - an odd figure, but 'Menn's law' will stay in mind on future projects.

Billington coins a term 'overwrought design'. And it is on this point that these engineers still have a great deal to contribute. At a time when every competition brief calls for a landmark structure, when it is acceptable to conceal counterweights, add props, employ mechanical compensation for ill-conditioning, and when profligacy with resources is rife, the views of these men remain trenchant. This book rewards close study.

Matthew Wells is director of Techniker and author of 30 Bridges, Laurence King, 2002

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