The text presented here is not precisely as published by OUP, but modifications are minor. Illustrations are another matter. Where images used in the original book were not my copyright, I have in most cases been able to substitute links to coloured images on the web.

When this text was submitted as part of a PhD thesis in 1996, the Notes were greatly extended. Most readers may prefer to ignore them. They have been collected at the end of each chapter, with internal links leading to them and back to the text. They are a mixture of: simple page references; additional examples or quotations to justify generalisations; and some afterthoughts.

On criticism.

Much has already been made of the complexity of structural engineering and the context within which the engineer must operate. The question to be considered in this section is: 'In view of this enormous complexity, is it at all possible to evolve a theoretical basis on which to judge the merit of a particular structure?'

It is generally accepted in the engineering profession that adverse criticism of another's design should not be made publicly. When Billington (1977b) made some criticism of Amman's design for the George Washington Bridge ex-colleagues sprang energetically to the defence of the designer (discussion, June 1978).

The nearest thing to criticism in the world of structural engineering at present is the annual awards for excellence given by professional organizations and manufacturers of materials. However, these are usually intended to promote the profession or the relevant industry and only the merits of the entries are publicized.

There is obviously no need for the type of journalistic criticism which is mainly a vehicle for displaying the satirical wit of the critic. However, an honest and informed appraisal of the merits and weaknesses of a structure could be of great benefit to both the designer and the rest of the profession, particularly if it took account of all the problems faced during the design phase. The type of criticism found in the better architectural journals indicates that something along these lines should be possible.

There are a number of common objection to any form of criticism. The first is that criticism is necessarily destructive, dissecting what the creator has laboured so painfully to synthesize. This is expressed in Archibald Macleish's famous statement that "a poem should not mean, but be". However, as Howard says (1966, p.3):

"there is a meaning in the very existence of any work of art. Criticism seeks out those meanings; good criticism reveals them in such a way as to increase the pleasure of those who look at a work of art and participate in it by their experience. A good critic may clarify aspects of which the artist himself is unaware."

Engineers are certainly eager to learn from the experience of others and informed criticism would provide for this need.

The second major objection is that the typical critic is not as competent as the practitioner whose work he is evaluating and cannot have had personal experience of the difficulties which the latter must face in working at an advanced level of performance. This cannot be denied and must always make criticism less than perfect. On the other hand it does not wholly negate the value of criticism since most critics are able to develop a useful second-hand knowledge of the technique and difficulties of an art-form. That this sort of knowledge can be of value is demonstrated by the fact that musicians of international concert standard regularly return to their teachers for constructive criticism of their technique, even though the teachers would in most cases be unable to reach the same heights of achievement. A good critic may therefore make a positive contribution without being an accomplished practitioner.

A more serious objection to criticism in structural design is that each individual design situation is so complex, that only those personally involved could possibly have enough relevant information to make an intelligent appraisal. Nervi seemed to subscribe to these views when he wrote (1956a, Preface):

"a structure unveils its nature and the most interesting aspects of its behaviour to its creator, designer and builder. It tells very little to the man who watches it from outside or examines it through photographs."

Of course the knowledge of the outsider can never equal that of those directly involved. It is also true that only a critic with some training in engineering and economics could begin to comprehend and evaluate the solution of the load-bearing problem, and that a knowledge of architecture and aesthetics is necessary to appreciate the role of the structure within the entire design problem.

However, the insider is disadvantaged just as much by his very closeness to the problem. To draw again on Boyd, the designer must, if he wishes to progress, evolve a "guide-vision" as he wrestles with the complexities of the problem, and then pursue this with conviction. When it is all over and there is time to relax and reflect, the designer will often realize. as we have seen, "that his guide vision was not the only possible one after all, and was not even the best possible one". The critic, partly because of his lack of involvement, thus has much to contribute. The only problem is to maximize the quality of his contribution.

The first requirement is that the critic should have educated himself to a reasonable degree in the major relevant areas. The second is that he should have an educated audience. This means that he must address himself to professionally-trained people in the industry and, since traditional training is heavily biased, he will have to educate his audience in certain aspects. The third major requirement is that he should have the fullest information possible concerning the individual design problem and the manner in which the solution developed.

This third pre-requisite is the major stumbling-block to criticism of structural design. Obviously it would be part of the professional critic's job to discover such information for himself. However, his task would be made unnecessarily difficult by the convention that engineering design should be reported as though it were a logical process and the final solution more-or-less self-evident. There is a need for more papers, like Arup's on the Sydney Opera House, in which the designers take the time to explain what false leads they followed, why they abandoned them, what they saw as the major imperatives and constraints defining the design-space, and how the interaction of the various participants influenced the final result.

Naturally there are many reactionary pressures which oppose this. These include a simple desire to avoid public responsibility for real or perceived defects, the need to maintain a competitive image in the market place and preserve industrial secrecy, and the embarrassment that might arise through the revelation of politically sensitive actions and motivations.

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.

The limits of rational criticism in structural engineering.

One of the major aims of this book has been to show that it is futile to consider the load-bearing function alone in discussing the merits of a structural form. Questions of primary function, economics, aesthetics and even politics must be taken into account.

However opinions on these matters are so varied and so greatly influenced by social conditioning and personality, that any criticism which includes them can hardly be described as rational. In many cases it may be no fault of the structural engineer that he has been unable to influence the broad definition of the problem and has been obliged to work totally within the constraints set for him by others. If these are taken as read it should then be possible to develop a reasonably objective criticism of the structural engineer's contribution.

It is not necessarily an evasion of social responsibility to concentrate for our purposes on the field of structural art alone. In fact, it can be argued that to advocate a single universal guide-vision is psychologically unhealthy. Different styles of buildings are suited to different personalities. Some prefer spaciousness in buildings and others prefer cosiness. Some desire materials and styles which make them feel close to nature (Wright) and others enjoy the machine aesthetic (Mies) and monuments to the triumph of technology. Even the individual needs different types of architecture to suit his different moods; workplaces for weekdays; stadia for Saturdays; cathedrals for Sundays. [Note 1.]

It is therefore constructive to define a technological criticism which is a sub-set of general criticism and, being the more rational part, is more widely acceptable.

If the principal function of the structure is to transmit load we can ask whether this has been achieved with economy and elegance, within the constraints imposed by functional requirements. If the designer believed that good aesthetics is the result of 'truth' or of refined efficiency we would not ask how beautiful the structure was, but how truthful or efficient. If the engineer were working with an architect we should have to accept the latter's aims with regard to functional layout and architectural expression and ask how well the engineer had provided for these. Yet even within these limits the task of criticism remains complex.

As Billington points out, 'structural art' is neither architecture nor sculpture (1977, p.44). Even for the purer forms of structure such as the bridge, criticism must be much more complex than for a sculpture. While the Sculptor may have had to wrestle with technical problems in order to dispose his material in the desired form and keep it there, his work is entirely complete in itself. The layman can appreciate it for its immediate emotional impact, the craftsman for the skill with which the artist has handled his materials and the connoisseur for its symbolism and its relation to art history.

However, no structure is in this way an end in itself. Its main function is usually to provide surfaces on which loads may be supported, or to provide sheltering surfaces which will inevitably collect loads. It is therefore necessary to envisage the possible types and combinations of load in order to make any sense of the structural action.

Thus a person who has no understanding of engineering is able to criticize an engineering structure only in a very limited sense. His immediate emotional response, assuming the structure to be a sculpture supporting only its own weight, is directed at something considerably less than the actual work, and the only valid complaint he can make is that the designer has neglected to allow for the layman's point of view.

Even a qualified structural engineer may be reduced to this form of criticism unless he is able to view the design drawings for a structure. Foundations are always concealed from view. A barrel vault may depend on concealed abutments or on a buried tie-rod to resist the outward thrust, (Fig. 20.1). It is usually impossible to discern the true thickness of a shell. Concealed steel lintels and reinforcement in brickwork may give the appearance of tensile capacity in masonry. It may be difficult to guess whether the reinforcement of a concrete member is prestressed or not. [Note 2.]

It must therefore be the task of the professional critic to ascertain such facts where they are of importance and to inform his public so that they can make an intelligent assessment of the merit of the structure. It is equally important that he ascertain and pass on to his public the constraints within which the designer was working and the goals set for him by his client or colleagues. This must be done with great care. Certain words mean so many different things to different people ('design' is an example) that they are almost useless for precise communication. It is easy to assume that the reader shares the critic's basic premises and that certain things may be left unsaid.

These difficulties are illustrated by the contrast between the views of Nervi and Gordon (1978) on the merits of ancient Greek architecture. Both speak from an apparently straight-forward engineering viewpoint but arrive at totally different conclusions. Nervi claims that the aesthetic effect is determined by structural imperatives within the limits of existing technology. Gordon points out that the ancient Greeks, like the Egyptians, purposely eliminated the arch and vault from public architecture. [Note 3.]

Fig. 20.1. Structural action cannot always be expressed, especially when it is dependent on the nature of concealed foundations.

The construction of a Greek temple roof is shown in Fig. 20.2. The mound of earth would have provided some insulation but this does not seem sufficient justification for a structural system so incongruous in relation to the masonry, particularly when the scarcity of timber in Greece is taken into account.

Fig. 20.2. The clumsiness of ancient [archaic] Greek roof construction [after Gordon, 1977] contrasts strangely with the quality of the masonry and again demonstrates the over-riding importance of aesthetic and symbolic purpose.

The reason must be that the low profile achieved by this form of construction did not detract from the rectilinear nature of the lower parts of the structure. Certainly if vaults had been used the character of the lower structure would have been entirely different. Therefore, for functional or aesthetic reasons, the Greeks did not want the type of structure that would have resulted from exploiting the technically efficient arch or vault.

A careful specification of the religious, functional and aesthetic objectives of the builders is therefore necessary if Nervi's viewpoint is to make sense, and this must apply to all similar criticism.

General criticism of structures.

To criticize the overall design of structures is at once more interesting and more foolhardy than to concentrate solely on the engineering. However, if it is done well it is certainly more meaningful.

It is still possible to avoid complete subjectivity by adopting an intermediate position in which the interplay of the engineering with the other factors is recognized and yet the broad aims of the other members of the design team are accepted. Attention may then be directed at the 'degree of fit' achieved on all fronts. To what extent has the team succeeded in balancing the conflicts between the various objectives? In particular, how far has the structural engineer compromized the aims of the others? To what extent has he distorted the structure to accommodate the other requirements, and how far was this unavoidable? [Note 4.] Has the engineer (or any other member of the team), 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? To what extent has he been encumbered by political and social pressures both within and outside the team, and in what measure has he coped with these? What problems of organization and communication did he experience?

When architect and engineer have set out jointly to create a perfect harmony of structure, function and aesthetics, the critic may ask whether, for example, sacrifices made in structural logic are worth the resulting improvements in aesthetics. (In providing his own answer to this question he must make subjective value judgements and accept that others may not share them.)

The problem in this sort of criticism is that while everyone wants as much from a building as he can get, each individual does his sums in a different way. The best answer is that in addition to putting forward his own conclusions the critic should make sufficient facts available for the reader to develop an informed alternative opinion.

The final alternative is to judge a design entirely on the basis of subjective personal preferences. To adopt this approach intelligently requires a solid grounding in all the applicable fields described or mentioned in this book. It is obviously beyond the scope of the present discussion.

In this type of criticism, the way is wide open to the inclusion of all sorts of moral, political and aesthetic criteria: what Scott called "the literary fancy, the historical imagination, the casuistry of conscience" (1924, p.210). It has practical value only in so far as it clarifies issues and defines concepts, enabling participants in design to at least communicate with one another even if they cannot agree, and observers to appreciate the rich complexity of any particular design.

Conclusion.

The conclusion to be reached from this argument is that in a field as complex as structural design there can be no single, simple prescription for design or criticism. This point was well made by Arup in a talk he gave on BBC radio, printed in The Listener of 7th July 1955. Such prescriptions as have been advanced in the past are all fairly easily faulted. Only by taking the non-engineering factors as fixed can some degree of rationality be achieved. The price that must be paid for this rationality is that the conclusions reached are of limited value.

If the results are to be of more general applicability, some account must be taken of subjective factors. There is room for a multiplicity of objectives, and a multitude of ways in which a satisfactory total may be achieved in the 'creative account'. A design which approaches simultaneous satisfaction of all considerations is praiseworthy; a tour-de-force of the designer's technique. However the occasional 'sculpture' which does not work quite as well as it should, or the occasional unprepossessing building which is a delight to live or work in, while perhaps being not entirely rational in the structural sense, may still contribute just as much to our environment.

In attempting to define a theory of criticism we must remember that fashions and social conditions change and that the user and the observer will find 'delight' or 'commodity' (or their opposites) where the designer and critic did not expect them. 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.

The critic would do well to remember that it is far easier to criticize than to practise, and to keep in mind the words of Gropius, Corbusier and Nervi about the misinterpretations of their motives and pronouncements.

Notes.

Note 1. In Arup's opinion, "there are almost as many approaches to architecture as there are architects, and … an almost infinite number of architectural jobs or situations". Arup (1966), p.354. [Return.]

Note 2. See also Torroja's statement (1958a, p.276) that to enable a full appreciation of structural action in concrete structures, it would be necessary to paint the location of the reinforcement on the side of the structure. [Return.]

Note 3. Nervi: "The buildings of the Greeks and Egyptians were determined and limited by the nature of the materials (marble and stone) available to their builders and by the elementary nature of the static scheme which their technicians could understand." (Nervi 1965, p.4.)
Gordon: "Vastly eminent Athenian architects … consciously rejected arches and vaults as a method of roofing their buildings, and yet they failed conspicuously to invent the roof truss or to devise any really adequate substitute for it. The brilliance of Hellenic architecture seems to come to a stop, rather suddenly, when one gets to the architrave. Greek roofs can only be described as intellectually squalid." (Gordon, 1977, pp. 216-7.) See also Hodge, A. T. The Woodwork of Greek Roofs. Cambridge University Press, London, 1960. [Return.]

Note 4. Dunican (NCE 1 June 1978, p.78) asks "How far should the engineer stand on his head in order to realise the architect's dream?" He does not supply the answer. It could also be asked, how far should the architect stand on his head to achieve structural honesty despite the conflicting demands of spatial organisation and aesthetic principles? Was Stubbins' vision of clear structural form in the Berlin Congress Hall worth the practical drawbacks in detailing and internal arrangement? One of the supporting arches of the Hall roof collapsed in 1980 due to fatigue in the awkward connection between the arch and the perimeter of the roof. Fortunately, this occurred while the Hall was unoccupied. The collapse could otherwise have resulted in great loss of life. An obvious question is whether the responsibility was the architect's, for presenting the engineers with an unnecessarily difficult (perhaps impossible) problem of detail, or the engineers' for either (a) not meeting this challenge, or (b) not realising the inherent dangers, or (c) not insisting that the architect adopt a more structurally rational system. (An expert inquiry decided that it would have required great prescience on the part of the engineers to foresee the dangers, given the current climate of knowledge at the time.) It is not considered appropriate to press the debate further in this thesis. Details of the original design were provided in Bauwelt 1958 49, 1, 7-16 and Baukunst und Werkform 1958, No.1, pp.13-24. The collapse was reported in NCE 16/10/80; 29/5/80, pp. 4 and 5; and 5/6/80 pp. 22 and 23 and in Beton und Stahlbetonbau 12/80 pp. 281-94. [Return.]

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