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. The sources are listed under Image Acknowledgements.

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.

Design theories and practice.

The previous sections have presented two themes; the design method as it is normally practised; and techniques which have been suggested to improve its effectiveness. Such theorizing is of little value unless it is tested against accounts of actual designs, particularly where there has been significant innovation.

As we saw earlier there is a sparsity of first-hand accounts of design in structural engineering, but there are many news reports of innovative structures in the engineering journals. It is possible from these to build up an impression of the major characteristics of innovative design. There is not space in this book to do more than mention some salient points, but copious references to individual examples are given in the source material for the questions on this chapter.

The question of 'Attack' (the manner of approaching the task, and the choice of starting point) is well illustrated in the accounts available. The appropriate starting point is determined to a large extent by the function of the structure. In only a few types, such as transmission towers, dolphins and railway signal gantries, is the task of resisting given loads in given locations the principal factor in design. Bridges, liquid-retaining structures, crane runway gantries and suspended floors are a separate case. Although at first sight their job is simply to support loads, the variable position of the loads requires that they incorporate a surface or line of support rather than a number of points of support.

In structures such as multi-storey buildings and power stations the load-bearing function is still important but the objective of enclosing space is almost equally so. In low-rise habitable buildings the enclosure of space, involving thermal and sound insulation and weatherproofing tends to dominate the load-bearing function.

Fig. 17.1. Gateway Arch, St. Louis, Mo., 1966. A structure whose main purpose is symbolic, with tourist access. (Archt: Eero Saarinen. Engr: Severud.) Photo: [US National Park Service.]

For a small group of structures, such as the Gateway Arch at St. Louis and the Statue of Liberty, the function is almost entirely symbolic (apart from tourist access) and the main purpose of the structure is to support the self-weight and resist wind and earthquake forces.

These categories may be summarized as follows:

1. Support only (to loads of fixed location);
2. Support only (to loads of variable location);
3. Support and shelter;
4. Mainly shelter;
5. Visual effect (self weight, wind, etc.)

For the early categories it is natural in design to choose the load-bearing function as the starting point for choice of structural form, while for the later ones the space-enclosing or symbolic function is the more appropriate.

Examples of the latter course are provided by Torroja in his Structures of Eduardo Torroja (1958, pp.3-18). Figure 17.2 shows how he developed the structural form of the Zarzuela grandstand from the functional arrangement shown in the larger sketch. His method was to identify possible load-paths within a complex functional arrangement.

Fig. 17.2.  See sketches and explanation prepared for the internet version. For a photograph showing the final effect see e.g. ALOSS, Fukui University.). Look for 'Stand. Hippodromo de Zarzuela'.

In contrast Nervi (1965) tended to envisage fairly simple enclosures to satisfy the basic functional needs, and with these in mind to go straight to the load-bearing problem to find a form which appeared economical and showed promise from an aesthetic point of view. [Note 1.]

"When I approach a project, my first instinctive thought is to reject the solutions which, even at first glance, do not seem to be economically valid. To search for an economic solution in the structural field means to find the most natural and spontaneous solution or, in other words, to find the method of bringing dead and live loads down to the foundations in the most direct way and with the minimum use of materials" (1965, p.24).

Later, with reference to the Florence Stadium, he writes "Soon it became evident that a notable aesthetic expression could be achieved ..." (p.24).

Fig. 17.3. Cross-section of Nervi's stadium at Florence (1932) showing how form is related to functional requirements and efficient structural action. Photo: [Columbia University, GSAPP.]

For structures in categories 1 and 2, the 'prescriptions' discussed above provide guidance in the determination of an initial form. The theories of optimization considered in Chapter 16 may then assist in its subsequent refinement. The form may be further modified to take account of construction costs and possibilities, maintenance considerations and aesthetics. As has already been noted, such an approach cannot guarantee the efficacy of the initial choice. Hence it would be appropriate to try out a number of different basic forms and compare cost estimates. The best and most experienced designers will make an initial choice in which the other factors are, perhaps subconsciously, foreseen and provided for, so that a minimum of modification and compromize is necessary and the structure maintains its initial conceptual unity. If it proves impossible to envisage a form which satisfies all the requirements to a reasonable degree, it may be necessary to try the formal design methods or techniques for improving creativity which have been discussed earlier in this Chapter.

The major lesson to be learned from a survey of reported designs is that there is much more to innovation than enthusiasm and a 'bright idea'. Enthusiasm for innovation must be tempered by an awareness that new techniques often introduce unexpected problems and, conversely, existing methods often contain an unconscious rationale arrived at by years of trial and error. [Note 2.]

Two writers who have made a close study of the history of structural forms emphasize the gradual nature of their development. Mainstone wrote

Fig. 17.4. Church of Hagia Sophia, Istanbul (537), now converted to a museum. A great leap forward in technique, its construction was nevertheless firmly founded on prior experience. Photo: [Structurae.]

"the pattern has been an evolutionary one throughout. Every innovation has had firm roots in prior experience, even such apparently unprecedented achievements as Justinian's Church of St. Sophia in Istanbul, the dome of Florence Cathedral, and the Britannia Bridge over the Menai Strait. There is strong prima facie evidence for the continuing importance of such experience." (1970, pp.107-8.)

Fig. 17.5. Another apparent leap of technique: the dome of Florence Cathedral by Brunelleschi, 1434. Photo: [Essential-Architecture.]

Fig. 17.6. A great advance of the nineteenth century, based on experience and laboratory tests: the Britannia Tubular Bridge, Menai Straits, Wales. (Engr: Robert Stephenson, 1850.) Photo: Godden Collection. See under "beam structures" then "Box girders - constant depth".
Godden's photo shows the original box-girders. These contained combustible material and were rendered unserviceable by a fire in 1970. They were replaced by a new structure incorporating arches for the main spans.
See also the historic painting at the Library of the Institution of Civil Engineers.

Maillart's characteristic three-hinge arch bridge form (Fig. 17.7) of the 1920s and 1930s is often quoted as an example of brilliant innovation. However Billington (1970, pp.122-3) has traced its pedigree back as far as 1886. In this year tests were carried out in Berlin on arches of similar form and details were published in a handbook on reinforced concrete construction in 1908. Just before 1900 Professor Mörsch of the Technische Hochschule, Zurich, from which Maillart graduated in 1894, designed a bridge over the Iser of a form similar to that which Maillart was to perfect.

Fig. 17.7. A fourth apparent leap in fact based on precedent. Maillart's characteristic three-hinge arch bridge type. See Isono. Look for Salginotobel bridge. See also the Godden Collection - look under 'arch structures' then 'three-hinge arches: bridges' for Salginatobel.

Thus, while there is no need to underestimate the real contribution of the individuals concerned, many apparently brilliant ideas were not quite as revolutionary as they now seem. This is because history concentrates on the flowering of a concept and forgets the more mundane developments which led up to it. Mainstone sees successful innovation

"stemming, first, from close familiarity with and experience of previous achievements and, secondly and very importantly, from a generalized understanding of structural actions which gives the necessary depth of meaning to the experience and makes it possible to move beyond it with some sense of direction and some assurance of success" (1970, p.105).

Nevertheless, any innovation must involve a certain degree of risk and a willingness to bear the responsibility for such risk is a common theme in the literature.

Amongst the other personality factors listed by researchers, 'dominance' and social skills are very evident in Komendant's accounts (1975) of how he manipulated contractors into accepting new forms of construction for Louis Kahn's structures. (The natural unwillingness of contractors to take financial risks in bidding for unconventional projects is a major brake on innovation.)

In some cases the driving force necessary for innovative effort appear to come from an innate desire to create, and here the factors of curiosity and fascination with complex problems are evident. In other cases the motive comes from a desire to solve a larger, pressing problem in which the individual problem is seen as a stumbling block to progress. The 'fanciful' demands of architects are often a stimulus to developments in structural engineering (Fig. 17.8). In some cases the motive is the designer's need to extricate himself from a tricky situation. As Dunican wrote

"Progress often results from overenthusiastic and underthought commitment to projects which cannot be changed for political, commercial or some other non-technical reason. The structural engineer has to retrieve some error of judgement or technical mistake which cannot be made public for reasons of professional pride, among others" (1980, p.29).

Fig. 17.8. National pavilions at trade fairs and exhibitions allow architects and engineers to play with complex and unconventional forms. Model of the structure of the Australian Pavilion, Expo '70. Osaka, Japan. (Archt: J. C. Mac Cormick. Engr: N. Sneath, Commonwealth Department of Works.)

Persistence in overcoming the inertia of individuals and bureaucratic organizations and the subsidiary technical problems involved in bringing any 'good idea' to fruition is also very marked.

A related factor is a willingness to enlist wide-ranging expert help in the search for a solution. Many reported cases indicate the importance of a wide net of contacts with individuals and firms. Coupled with this however must go a knowledge on the part of the designer of the likely potentialities of any such expert referral. This ties in with findings that wide reading is one of the major characteristics of successful technological innovators.

Playfulness is a quality stressed by many researchers into creativity. The only solid evidence for this in the literature are those cases in which useful ideas have stemmed from 'follies' erected for international exhibitions such as 'Expo'. Although the budget for these may be limited, the idea is to invent a form for a nation's pavilion which will attract attention by its unusual character, and many sober engineers must have questioned the value of such exercises. Perhaps the same can be said of the sometimes exacting demands which architects make of engineers. 2100.

Examples of innovation in the literature are rarely sufficiently detailed to allow recognition of factors such as 'tolerance of ambiguity' or 'lack of set', but it is often possible to see how a designer has been able to define a problem in a radically new way. It is also interesting to check for the removal of mental blocks against a list such as Simberg's (1964).

It is possible to form a general impression of the personality of such innovators as Candela, Finsterwalder, Freyssinet, Leonhardt, Maillart, Morandi, Nervi and Torroja from books and articles about their work, but these are mostly of an adulatory nature. [Note 3.] There has been little analytical study of their personalities and certainly nothing of the type done by MacKinnon on architects.

Billington (1970) pointed out that to study past achievements properly we need three new types of study; first of the work itself, then of the man, and then of an abstract theory of efficiency against which we can measure his achievement. [Note 4.] He has since moved to correct this deficiency, particularly with his books Robert Maillart's Bridges (1979) and The Tower and the Bridge (1983).

In conclusion it is perhaps advisable to place the need for innovation in perspective. Many authors warn against innovation 'for its own sake'. There is little to be gained from introducing new ideas if they cannot be justified on economic grounds at least in the long term, or as research and development projects in which the risks of financial loss or inconvenience are known to the client and designer and are not imposed on an unsuspecting user. An exception is where the client consciously wishes to project an image of progressiveness or modernity, or is genuinely interested in development in architecture or engineering.

Notes.

Note 1. An example of Nervi's approach is contained in his account of the design of the UNESCO Building in Paris. He commenced with an arbitrary decision that the number of columns at ground level should be a minimum. (Nervi 1965, p.19.) [Return.]

Note 2. An example was the first aluminium bascule bridge in the UK which was scrapped in 1976 after only 20 years' service because of excessive corrosion. (New Civil Engineer 15 Jan. 1976, 26-7.) One of the engineers concerned with the bridge throughout its life recalled "there was a great deal of optimism about aluminium in those days and we were being pressed by the Aluminium Development Corporation and the Government to exploit it". The failure of the bridge was attributed to an unfortunate choice of alloy. When the bridge was built in 1947, experience with this alloy had been limited to military aircraft whose life was not long enough to reveal the dangers of corrosion. A similar bridge in Aberdeen which happened to have a weaker mix lasted well, until demolished for other reasons. Dunican (1966, pp. 98, 100) cites the case of a tower block in which the outer skin was non-loadbearing so that the floors cantilevered out from the core. The designers decided to invert the conventional coffer slab so that the continuous membrane was on the bottom and in the best position to resist the compressive stresses due to the cantilever action. At first sight this seems like a sound idea. Unfortunately, it meant that the membrane could no longer serve a dual purpose as a walking surface, and additional slabs had to be provided to sit on top of the ribs, adding to the cost and complexity of the floor system. Furthermore, although the perimeter was stiffened by edge-beams the differential deflections were quite large and led to problems in the detailing of the infilling. Dunican writes: "Whether this sort of ingenuity is justified can be argued. Perhaps it would be better to ask the designers whether in similar circumstances today they would repeat their design. Probably the answer would be 'No'." See also Goldstein (1963, p.219) and Scott (1976). [Return.]

Note 3. For Candela: Faber (1963) and Billington (1985). For Finsterwalder: Böhme,G. et. al. (1973). For Freyssinet: Fernández Ordóñez (1978) and Travaux No.50 April-May 1966. For Leonhardt: New Civil Engineer International January 1983. (For his own memoirs see Leonhardt, F., 1984.) For Maillart: Bill (1969), Billington (1970), (1977a1), (1979), and (1990) and Giedion (1967). For Morandi: Boaga and Boni (1965). For Nervi: Desideri (1982) and Malave (1984). For Torroja: Billington (1983b). (Some impression may also be gained from his own works, Torroja 1958a and 1958b.) [Return.]

Note 4. Billington (1970), p.121. On p.129 he writes that, of the biographies of noted engineers, "only Trachtenberg's brief sketch in Brooklyn Bridge attempts to get beyond mere narrative and into the cultural context and personal thoughts of a civil engineer". [Return.]

Image Acknowledgements. Linked images, Chapter 17.

Grateful thanks to the following organisations and people who have made it possible to provide links to full colour photographs and descriptions of buildings for this chapter.
William G. Godden Collection, University of California, Berkeley. Link.
Columbia University, NY, Graduate School of Architecture, Planning and Preservation Link.
Institution of Civil Engineers. Link.
Yoshito Isono, Dept of Architecture and Civil Engineering, Fukui University. Link.
Structurae. Link.
Tome Fletcher's Essential-Architecture. Link.
USA, Dept of Interior, National Park Service. Link.

[Top.]

The art in structural design navigation:
[Chapter 16.] [Chapter 18.] [Contents] [References]

Site navigation:
[Aesthetics of built form.] [Papers.] [Work of Jörg Schlaich.]
[John Monash's early engineering.]