25 January 2009

Bridge criticism 5: Criticism as a learning tool

In a recent post, I noted that structural engineering degree courses make little or no attempt to help students develop a critical attitude to design quality. They're given little if any tuition on aesthetic issues, and it's doubtful how much they really learn from design projects.

Design projects are usually artificially simplified to match them to the abilities of the students. I know from experience that these projects are difficult for academics to mark, as designs that would never see the light of day in real life may still need to be marked well if students at least show they understand key issues such as buildability. The end result is that while students often enjoy their design projects, I doubt that they actually learn much of long-term value about the design process, whether that's the interpersonal dynamics of design teams, or techniques for jump-starting creative thought.

While few in the field would see this as an opportunity to introduce a confrontational "crit" such as architects undergo, it could be an opportunity for student peers to challenge each other’s work. This would encourage them to analyse the merits of their own designs more thoroughly, and also open them to alternative ideas and options that they may not have considered. Such a process clearly needs to be facilitated in such a manner that criticism is constructive.

One question is whether they could learn more about design without actually having to do it. In professional life, there's little doubt that we learn as much from considering other people's designs as from the process of developing our own.

This approach is being included as part of a bridge engineering course at the University of Bath directed by Professor Tim Ibell. In this course students are asked to collect data on an existing bridge, critically analyse its aesthetics, carry out a simple structural assessment, and comment on how it was built and whether better alternatives were available. The aesthetic analysis is based on a set of formal considerations set out by Fritz Leonhardt in his book Brücken. The resulting papers offer a comprehensive critical review of each structure, combining both objective and quantifiable issues with matters which can only be treated subjectively.

I personally believe the focus on existing structures may give students a greater understanding of the challenges of bridge design than does the conventional student design exercise. They have to consider how design choices have been made, without being asked to make choices for which they lack sufficient knowledge and experience.

As well as improving their understanding of bridge engineering and of the design process, the course must encourage them to be more confident in forming and expressing opinions on structural engineering.

The student papers from 2007 and 2008 are available online, and cover bridges as wide-ranging as Brooklyn Bridge, the Millau Viaduct, Sunniberg Bridge, the Clyde Arc and the Menai Suspension Bridge. They generally make interesting reading - you get a real sense of the students beginning to understand structural engineering beyond the confines of the calculator, although inevitably many of the judgements presented are either mistaken or in some cases plain daft.

The value of the "case study" approach is its realism - it forces students to confront real problems of buildability, aesthetics of real structures, in a way that never works as well with the creations of their own imagination. I think it would be great if more universities would take up this idea!

Memories of Swiss Construction Online

In a recent post I linked to a paper by Bill Addis that is freely available at the Memory of Swiss Construction Online website. I think the website is an excellent historical resource for serious students of bridge engineering, and hence worth a short post of its own.

For monolingual English speakers such as myself, the most useful part of the site is the extensive digitised collections of IABSE publications, including conference reports, journals etc, dating back to 1932 (see cover image, right). These include material on all sorts of specialist subjects, such as ship collision with bridges, cable-stayed bridges, and numerous individual structures such as the Ganter Bridge. The most recent IABSE publications remain available only to members, but making so much material available freely still represents exceptional generosity.

Of particular interest to me, for example, is IABSE's 15th Congress report which includes amongst many other things an extensive set of papers on aesthetics in structural engineering. But the real benefit is for historians - there are IABSE papers dating back several decades, many by key figures in bridge engineering history.

For those whose language skills are wider, there's more excellent material to be found in the archived Swiss journals such as Schweizer Ingenieur und Architekt and Schweizerische Bauzeitung (cover image shown right for the very first issue), some of which date back to the 19th century. These include original papers by engineers ranging from Robert Maillart to Jürg Conzett - all relatively easy to locate through the search system provided.

If only others with similar resources would follow suit: access to the equivalent records of the Institution of Civil Engineers can cost as much as £1,776!

23 January 2009

Bridges news roundup

Forth Bridge design warmly welcomed

Monotower cable-stay looks good (but might be difficult to widen in future?), crossed cables offer unusual solution to multi-span stiffness requirements

The man behind Calgary's troubled bridge
Interesting profile of Santiago Calatrava and overview of the Calgary footbridge controversy, with further information here and here

Supplier of "squinty bridge" steel faces £1.8m legal case
Clyde Arc bridge contractors in dispute, more technical details here

£1.2m needed for Transporter Bridge refurb
Newport City Council still struggling to find cash for important historic bridge

22 January 2009

Bridge competition debris part 7: Carpenters Lock

One of the most recent footbridge design competitions in the UK was launched by the Olympic Delivery Authority in May 2007, seeking a 54m wide, 26m long bridge as part of the proposed 2012 Olympic Park in East London. The unusual aspect of the bridge was that it only needed to be so wide during the actual Olympics, and will be partially dismantled to leave two 6.5m wide legacy bridges, passing above Carpenter's Lock, once the Olympics leave town.

The ODA received 46 expressions of interest, and the shortlist was announced two months later, and was notable for largely featuring teams who had relatively little experience of bridge design: a number of the usual suspects in the field were certainly quite surprised to be left out. I think it was really quiet commendable, however, as if the Olympics isn't an opportunity to give new talent a chance, what is?

The winning design by Adams Kara Taylor and Henneghan Peng was chosen by the competition jury and announced in October 2007. A construction contract was due to be awarded late in 2008.

The thing that strikes me most on looking at the images from this competition is how little it had to do with bridge design - this was really a competition for landscape architecture, with the sheer width of bridge required leading inexorably to a "land bridge" solution where anything structural is hidden below deck.

The AKT / Future Systems entry was for a stressed-ribbon design, which seems somewhat unnecessary where there's no vantage point to admire its slenderness, and which is less than ideal for mobility-impaired access or drainage.

The design from Jane Wernick and McDowell / Bennedetti is one of only two with a landmark structural element - a somewhat convoluted twisted "arch" used to suspend parts of the bridge, and very much out of scale with the deck. The Softroom and Eckersley O'Callaghan design is the other one, with slender arches in the temporary situation.

I think the winning design was definitely the best, with a more interesting legacy structure providing viewpoints down to the lock below, and with the most visually striking integration of the pre-games and post-games landscaping. Its central area, embedded with lights which can be programmed to display Olympic rings, colours, or flags, sets its apart, although its not clear to me if there's anywhere that anyone could actually see its display clearly.

As always, click on any image for a full-size version. Links are only provided where there is additional information available on each design.

Most of the images below were shamelessly "borrowed" from Building Design's website, where there is further information on each of the designs.



Buro Happold / Ron Arad Associates

Eckersley O'Callaghan / Softroom

Adams Kara Taylor / Future Systems

Atelier One / Tonkin Liu

21 January 2009

Bridge criticism 4: Teaching engineers to criticise

In the last post on this topic, I covered Alan Holgate's ideas for a practice of structural engineering criticism. Holgate's book The Art in Structural Design was aimed largely at engineering students, to give them a better idea of the "softer" aspects of engineering which are often largely absent from an undergraduate education.

Architecture students are often given a very harsh introduction to the idea that their designs are subject to criticism, with the institution of the architectural "crit" whereby their designs are reviewed by their tutors in front of the class. In theory, this is to provide constructive criticism of flaws in design, and to prepare them for the real world where clients will often have very strong views on the merits of designs they are paying for. In practice, it's seen by many students as nothing but an ordeal, a trial by fire (see cartoon).

Engineering students generally experience nothing of this sort. In a future post, I intend to discuss an excellent example where structural engineering students are being explicitly introduced to the value of criticism. For now, however, I'd like to cover some proposals that Bill Addis made back in 1996.

In his paper "Structural criticism and the aesthetics of structures" (IABSE 15th Congress, available online), Addis (pictured, right) noted the absence of critical evaluation of design from undergraduate education:

"In the light of ... the recent fashion for clients to appoint architects to lead bridge design teams, it is perhap time to consider what engineers might do to establish their territory more firmly".
Addis notes that students of the humanities are immersed in criticism of the works that they study, and that this helps them develop:
  • a critical vocabulary

  • the ability to discriminate aesthetically

  • willingness to express their self
Addis's view of how limited most structural engineering students are with these facilities is as true now as it was in 1996:

"The engineer's weakness in these areas should scarcely be surprising, given the content of most engineering courses, the typical educational background of many engineering students, their poor ability to communicate effectively and with confidence, and the very few opportunities they are given to develop such skills by talking eloquently about structures and design. The activity of structural criticism can provide such opportunities."
Addis doesn't suggest that student engineers should be subjected to anything like the crit. Instead, he suggests they could be asked to take two existing structures, describing them visually, structurally, environmentally; discuss their feelings about the structures; and write a comparative evaluation.

He offers several criteria students can use to carry out their evaluation. Examples include:
  • skill and clarity with which structural actions are expressed

  • elegance or simplicity

  • expression of solidity or delicacy

  • expression in geometry of the imposed loads and internal forces

  • interaction between load-bearing and non-load-bearing aspects
My own experience in working with universities is that few have taken these ideas on board. There is so much technology and analysis in the curriculum that there is little time to cover the philosophy of design other than to hope that it somehow emerges magically from design exercises. Again in my experience, it doesn't - students are so preoccupied with the details of their projects that they have little opportunity to sit back and reflect on the wider lessons from the design process.

It's also clearly the case that few academics teaching structural engineering have substantial experience in a design office any more. Their backgrounds predispose them to teaching topics that can be simply measured and evaluated, mathematical topics, and to shy away from having to judge subjective views on aesthetics or design quality.

New graduates continue to arrive in the workplace with little or no knowledge of engineering history, of the great designers, of how to design (rather than analyse), and of how they might take responsibility for engineering in any way other than as a responsive technician (usually the architect's servant).

Addis concludes:

"to be a good structural engineer it is essential to be able to discriminate between good and bad examples of structural engineering. In the context of structural engineering, any concern with aesthetics should be addressing the question as to what constitutes good and bad design and what it is to be a good structural engineer."
Fortunately, the outlook isn't entirely bleak. In a later post, I'll cover examples of how structural engineering criticism is now being cultivated at university, something that many others would benefit from taking on board. And how does all this relate to bridges? Well, I'll get back to that too, although perhaps not immediately!

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]

20 January 2009

Bridge competition debris part 6: Glasgowbridge

The Glasgow footbridge competition of 2003 was something of a watershed for bridge design competitions in the UK. Glasgow City Council invited design teams to propose a new footbridge across the River Clyde between Broomielaw and Tradeston, along with other improvements to the riverside. Thirty one teams expressed an interest, and six were shortlisted. A £40m project budget was declared, of which £15m was to cover a 100m long bridge.

The competition was won by Atkins and Richard Rogers Partnership, whose detailed design went out to tender in 2005. Only two bids were submitted in early 2006, both well in excess of the original budget, the lower being £50m. Glasgow unceremoniously waved goodbye to the winning design, and organised a fresh contractor-led competition with a lower budget. This was won in turn by Nuttall, with Halcrow and DISSING+WEITLING acting as designers. At the time of writing, construction of the bridge is proceeding on site, although it has not been without some hitches.

While the original glasgowbridge competition is far from the only such contest in the UK to result in a bridge that bust the budget or suffered technical problems, it was a very prominent example of what can go wrong, and helped trigger considerable discussion on how such competitions could be run better, and who should run them.

The original competition website has long since disappeared, but some information on the scheme is archived at e-architect, and there was a lengthy discussion in the competition's aftermath at archiseek, including comments from at least two of the unsuccessful designers. The bridge's troubled gestation has also been covered at skyscrapercity more than once.

This was a competition where the client had a clear idea what they wanted: a big name to wave around, and their own attention-seeking rival to the Gateshead Millennium Bridge. It's good that they shortlisted some less well known competitors as well, although the inclusion of gm+ad may just have been a sop to local interest.

I remember thinking at the time how odd it was that both Clyde 9 and via involved a glazed arch bridge with pedestrian access to the top of the arch. Was something in the air? How many drunken Glaswegians late at night could have resisted the temptation to find out how breakable the glass was?

The Latis scheme was presented so obscurely it was hard to work out what type of bridge it was (or, on some of the hand-rendered visualisations, where it was). The Mirror Bridge was an admirable attempt to design something sensitive rather than pandering to Glasgow's aspirations, but it's no surprise the council opted for something tall and striking. The same will have also applied to People's Crossing, although it wins points for being the least conventional structure (impossible to tell from the images what type of structure it actually is!).

The winner, Neptune's Way, was well-criticised at the time, especially after the project failed, and I think its structural perversity was obvious from the start. In most inclined arch bridge designs the arch slopes away from the deck to counterbalance it, and in this case it was obvious that very high cable tensions would be required to hold it up at the very shallow angle depicted. The images show that additional props to hold the arch up were added to the design after it had won.

As always, click on any image for a larger version. Links are only provided where there is project-specific information relating to a design or designer.

Atkins / Richard Rogers Partnership: "Neptune's Way"

Arup / Foster and Partners: "Mirror Bridge"

Faber Maunsell / Studio Bednarski / Austin Smith Lord: "Clyde 9"

Gifford / Lifschutz Davidson: "via"

Mott MacDonald / Future Systems: "People's Crossing"

Whitbybird / gm+ad: "Latis"

Tradeston Bridge
Nuttall / Halcrow / DISSING+WEITLING