Bridge criticism 3: What would structural engineering criticism look like?

In recent posts I've wondered why poor bridge designs receive so little public criticism.

If you go back into the times of the Stephensons, Telfords and Brunels it seems engineers were considerably more willing to critique each other's ideas openly*. Perhaps the ethical constraints were less formal then, but I'd guess one main change is readier recourse to the libel law in modern times.

However, I wonder not only why there is so little public criticism, but what would it actually be like if there were more? Architectural criticism is a well-trodden field, but engineering criticism is a barely-explored jungle.

One of the few writers to have explored the possibilities for a practice of structural engineering criticism is Alan Holgate. Another is Bill Addis, and I may well return to him in a later post.

In his 1992 book The Aesthetics of Built Form, Holgate quotes Le Corbusier's somewhat ridiculous view on engineers:

"Shall we see engineers trying to turn themselves into men of aesthetic sensibility? That would be a real danger ... An engineer should stay fixed, and remain a calculator, for his particular justification is to remain within the confines of pure reason."

Many engineers even today would like to ignore aesthetics, unless it can be codified into series of rules and principles. But engineers should really be best placed to judge the merits of bridge designs, and that should include efficiency, economy and also aesthetic value.

In his earlier 1986 book, The Art in Structural Design, Holgate had considered how to develop and promote engineering criticism that could be distinct from architectural criticism. The entire book is available online, and it's well worth a read. He suggested three typical objections to the whole idea of criticism in the structural engineering field (most quotes below are from the same chapter - just follow that link):

• Criticism is necessarily destructive


• Critics are not as competent as the practitioner


• Any unique design is too complex for anyone other than those directly involved to properly appraise

Each of these points can however be addressed: engineers are usually keen to learn from their own and others’ experience, for example, and often someone remote from the details of design can provide a view untarnished by tunnel vision.

Holgate proposed three means by which the quality of structural criticism could be maximised.

• The critic should be educated to a reasonable degree in the relevant areas


• They should have an educated audience


• They should have as much information as possible about the design problem and solution

Frequently, the third of these is the hardest to achieve, as full details of only a few designs are published. Even where a design is documented in a technical paper, it rarely discusses the choices made in the design process in great depth.

There are examples of published engineering criticism (e.g. David Billington & Shawn Woodruff's review of Calatrava's Sundial Bridge) which try to deal with this by carrying out their own analysis of selected structures. I'll cover some of these in a later post. However, it's hard to see how their judgement of the balance between aesthetic integrity and cost is intrinsically superior to the designer’s judgements on the same matters.

Holgate suggested that better-informed criticism would be possible if designers could be encouraged to be more open about the process by which they identify a solution. However, this could be hindered by embarrassment, commercial sensitivity, and fear of litigation. He concluded:

“Hence a considerable amount of courage may be required on the part of the designers in providing the critic with the information necessary to make a fair appraisal of their skill in solving the structural problem. On the other hand designers can hardly blame the critic if he makes an unfair assessment because information is unavailable due to the disinterest or secrecy of those concerned.”

Holgate offered several ways a critic could evaluate a structure:

• Does it transmit its loads with economy and elegance?


• Is the structure efficient or ‘truthful’ (as opposed to deceptive)?


• How well does it address functional requirements e.g. those determined by an architect?

He suggested further questions that allow a balance to be struck between subjective and objective judgement:

"To what extent has the team succeeded in balancing the conflicts between the various objectives? In particular, how far has the structural engineer compromised the aims of the others? To what extent has he distorted the structure to accommodate the other requirements, and how far was this unavoidable?

"Has the engineer … by a brilliant stroke of creativity, devised an original form which improves the degree of fit on all fronts simultaneously over that achieved in conventional solutions to the problem? Has he suggested a complete redefinition of the problem which is satisfactory to all parties and permits a simple, elegant solution?"

Discussing the tension between a critic’s preconceptions and their inevitably subjective reaction to any structure, Holgate concluded that:

"in a field as complex as structural design there can be no single, simple prescription for design or criticism … The wisest commentators on the philosophy of design might be those who will take the discussion to a certain point, and beyond that realize that they have to leave the individual to react in accordance with his own instinct."

I think The Art in Structural Design remains extremely valuable. The book was aimed at engineering students to counteract the impression they often receive that engineering design is all about calculation and rational analysis. In addition to his attempt to single-handedly inspire a new field of structural engineering criticism, he includes interesting chapters on the process of creative design and the philosophy of structural design.

But more than two decades on, little has happened to make criticism of this sort a reality. Technical papers routinely receive little or no published discussion, even where the bridge presented is ripe for some pithy comment. There's no shortage of criticism that goes on in private, so I think there must be some way to bring it out into the open and see whether feedback on design quality can improve the general quality of product provided to clients.

One option is to create more spaces for views to be expressed: blogs like this one, or online forums like skyscrapercity.com, and to encourage knowledgeable engineers to participate.

Clients often take the lead in changing the culture of the engineering community, and should be less afraid to expose designs to public and expert comment.

Another way forward is to start at square one, and encourage future engineers to have a more holistic education, to hold opinions, and to gain confidence in expressing them. There are very few publicly visible, articulate structural engineers (certainly compared to the architects we collaborate with), and we need to cultivate more of them, so that structural engineering considerations can begin to be heard amidst the wider cultural chitter-chatter on architectural matters.

In future posts, I'll cover in more detail some examples of where useful published criticism of bridge designs has actually been made; how it is actually being cultivated today in engineering education; and also perhaps look at some of the prescriptions for aesthetic evaluation of bridges that have been made in the past by engineers such as Fritz Leonhardt.

[*The image relating to Brunel and Telford is from Eugene Byrne and Simon Gurr's Isambard Kingdom Brunel: A Graphic Biography]