05 February 2009

Bridge criticism 6: Too little, too late

In a series of recent posts, I've wondered why there's so little public criticism of poor bridge design. Perhaps engineers feel restrained by institutional ethics, perhaps there are too few models for engineering criticism, perhaps it's a matter of education.

But although there's very little public criticism, there is some. In this and the next post, I'll discuss two examples of the various critiques that do take place, one on the theme of When Bridge Design Competitions Go Bad, and the other taken from the more rarefied realms of a technical paper. Both suggest that while criticism is alive, it isn't necessary very well.

In 2003, a competition was held to design a new footbridge across the River Clyde in Glasgow. Ive previously posted in more detail about the competition and the various designs entered.

The winning design, by Atkins and Richard Rogers, featured a deck elliptically curved in plan, supported from a steel arch inclined above and towards the deck (see image). In turn, the arch is supported by tie-back cables. It was, by any standard, a very unusual structural form, probably unique.

The arch sloped at an angle of 26° (it had been 22° in the competition submission, but was increased during detailed design to try and get it to work), far shallower than most inclined arch bridges, which in any event generally have the arch sloping away from the deck to counterbalance its weight, and so that both elements stiffen each other.

The finished design also introduced props to the arch (shown right), again suggesting that the basic concept was flawed.

There's an excellent published account of the design process ("The Evolution of the Structure for Glasgowbridge”, Footbridge 2005 conference, December 2005), unfortunately not available online, which makes it clear that several decisions on the structural form were driven by the architects, and that the competition period allowed insufficient time for the analyses the engineer would like to have carried out. This is nothing unusual for design competitions, indeed, it's the norm!

For example, the paper says:
"The architects began looking at other masted structures"
"on further consideration, the architects felt that the angular form of the twin masts did not sit comfortably with the curvature of the deck"
"If we had had more time in the closing days of the competition we would have liked to have carried out some analyses on the arch angle, however there was no time to change the model or the architectural drawings so the angle remained at 22 degrees"
The image on the right shows one of the many variants the design went through as it was developed.

Published criticism of the design when the winner was first announced was very limited and largely limited to architectural critics and losing competitors. In the former camp, Penny Lewis of Prospect magazine said in the Scotsman (21 November 2003):
"I thought it was the scheme that had the highest number of clichés."
Representing the losers, architect Alan Dunlop was quoted in the same newspaper:
"It was most disappointing of all to have lost to that bridge. I wish the city well and I hope it comes off, but we went through every possible permutation about who was going to win this competition and we never even considered Neptune’s Way. That’s how flabbergasted we are by this."
The public were even less impressed, at least judging from the letters pages of Glasgow's papers:

"WHAT a ridiculous bridge! It has been described as a "long way for a short cut". Imagine trying to cross it in our horizontal Scottish rain. This is not London. Being in such an exposed location it should have been enclosed." (Niall Barker, Glasgow Herald, 24/11/03)

"Whatever the architectural merits (and I personally think the elliptical design is impractical and frankly stupid), this bridge will be completely useless as an economic stimulus to the city, and will turn out to be a massive £40m white elephant." (Iain Mann, Glasgow Herald, 1/12/03)

"True to form, Foster [sic] can't just span a river – he has to take a long sweeping way round. For what reason? Not function; seemingly he thinks it will look good. Well, it won't. All it will look like is an architect who doesn't understand engineering trying a poor imitation of Calatrava." (John McNeil, Glasgow Herald, 3/12/03)

The design was put out to tender, but the only two tenders received were both in excess of budget, and the design was quickly dropped by the client, Glasgow City Council.

At this stage, the design’s engineering principles received greater public criticism, although still relatively limited in extent.

Writing in a letter to New Civil Engineer (30 March 2006), Cezary Bednarski was “astonished by the winning design as it was clearly unworkable and hugely expensive”, while in the same issue of NCE David Collings suggested “that the Glasgow footbridge is over budget is not surprising – structurally it is an appalling design”. Neither criticism offered more detail.

So was this another case of sour grapes (like Alan Dunlop, Bednarski was one of the unsuccessful competitors), or even just the benefit of hindsight? I think neither - they are fair viewpoints, just far too late to be of any help to anybody.

Generating innovative concepts without the time to properly test their feasibility is always a risky business, and developing the Glasgowbridge concept was clearly always going to be difficult. I reckon that was apparent to most bridge engineering specialists throughout.

Clearly, in this case, the project outcome might be traced back to the robustness of the competition jury’s decision-making process. However, I wonder whether the promoter might have been greatly assisted, if anyone had stuck their head above the parapet at a much earlier stage. This could have been facilitated in several ways: the client could have sought a peer review of the unusual design from another firm; they could even have sought comments on each design from the other competitors.

But ultimately, what is needed is a bridge engineering community where people have the courage to speak their mind publicly. This will always be difficult where commercial interests encourage silence, but the institutions could assist by revising their ethical instructions, which don't help. Academics, slightly less restrained by commercial issues, should also seek a louder voice on design issues (as is the case elsewhere in the world).

Having said all that, in the case of Glasgowbridge, I suspect that whatever criticism was voiced, the client would not have listened, as they seemed fixated on their Gateshead-rivalling dream, and defensive about its merits.


Anonymous said...

How could the Glasgow bridge ever rival Gateshead? It was both contrived and derivative whereas Gateshead, for all its expense, was shaped by its context and opening function. There is another aspect which is often overlooked when competitions go wrong - that of the client who generates the brief and administers the process. Frequently the client has never procured a bridge before, and even less likely a bespoke 'landmark' structure. Expert guidance at the jury stage may already be too late.

The Happy Pontist said...

I think Glasgow's dream was to rival Gateshead - I certainly didn't mean to imply that the design they chose actually did!