01 September 2008

Secret bridge unveiled ... and you can see why they kept it secret!

Today is a great day for followers of the wild and wacky world of the bridge design competition.

At last, the public can see Techniker and Spence Associates' design for the River Wear Crossing competition. Since they won in September 2005, their design has been kept strangely secret. Architect Stephen Spence has complained loudly about this supposed injustice, stating that "his plans had been checked by engineers and no problems had been found". The Happy Pontist commented on the kerfuffle in July.

The bridge, along with a watered-down version and more conventional option, is to go to public consultation in the next few weeks. However, images of the design have been revealed early in the Sunderland Echo and The Journal.



The iconic bridge design is simply amazing. Amazingly beautiful. And amazingly daft. You can instantly see how it would appeal to the marketing types at Sunderland Arc, the development body who promoted the original design competition. It's tall, it's curvy, it's spectacular: in particular, it would make an exciting logo for the city of Sunderland. Thrusting upwards. Dynamic. That sort of thing.

Matthew Wells, the structural designer, says that "the bridge was not a technically difficult or radically new structure". He certainly knows his stuff, as evidenced by his very readable book 30 Bridges. The local press claims it's a bit like the Erasmus Bridge in Holland, to back up the view that it's a proven design. But here's where the problems really begin. It's nothing like the Erasmus Bridge, or any other cable-stayed bridge I've ever seen. And it undoubtedly is both technically difficult and radically new.

For one thing, the twisty masts tilt towards the deck they are supposedly supporting. At Erasmus (and other expensive designs such as Calatrava's Alamillo Bridge and Sundial Bridge), they slope away from the deck, which helps to counterbalance the dead weight and traffic loads.

At Erasmus, there are cables which hold back the masts, restraining them against the enormous horizontal forces introduced by the main deck cables. In Sunderland, there are no such cables, and the tops of the masts aren't even tied together. The whole bridge is therefore held up by tall, pointly cantilevers. Which tilt towards the deck. Calling that amazing doesn't begin to capture the audacity of the concept! It's a bit like hanging the Brooklyn Bridge off the side of the Empire State Building.

The Sundial Bridge just about gets away with this sort of ambition by virtue of being a relatively lightly loaded footbridge. But the River Wear crossing will carry a multi-lane highway. To avoid vibration problems, or just the deck sagging into the river, those masts would have to be enormously strong, with huge quantities of steel and concrete pressed into service. As a bridge engineer, I personally find it very difficult to imagine.

Go back to the original competition and you'll find that the budget for the bridge was £43m, which worked out at about £4,000 per square metre of deck. In my view, there's absolutely no way a bridge of this scale and type could be built for that sum.

I look forward to reading other views. It's good that at last this design has been made public, opening an opportunity for debate, not just about the merits of this particular structure, but about the process by which it was developed (a design competition, judged in secret, and without an experienced large-span bridge engineer on the jury). I also wonder about the process going forward: judging from the Sunderland press, there are strong voices in favour of the design, not least from the leader of local government opposition, who we might assume to be relatively ignorant of structural engineering (or at least to have commented prior to actually seeing the design). It looks like local people will be asked to tell their elected leaders whether they prefer bread or circuses: low-cost versus spectacle.

No doubt the designers will continue to defend their proposal robustly. But amongst all the consideration of cost versus quality that will probably dominate discussions, I think it's important not to forget about risk. Whether it will stand up or not, for a given budget or otherwise, it's undoubtedly a very high-risk proposal. And Sunderland might be wise to look at recent examples from Glasgow and Stratford-upon-Avon for cases where high-risk competition-winning designs were dropped only after first wasting considerable sums of public money.

5 comments:

The Happy Pontist said...

And the initial vox pop is in:

"It's a beautiful design, much better than the one in Newcastle"

"It's good, it's unusual"

"It's about time we had something to compete with Newcastle. Newcastle has got all those fantastic bridges, and that (design) would be fantastic"

"That design looks like something really impressive"

All courtesy of the Sunderland Echo. It's hard to escape the thought that Sunderland are really shooting themselves in the foot with this public consultation, offering it up to dozens of people who can tell (rightly) when something looks nice, but have no idea what makes a bridge stand up.

Knit MN said...

Why are they so bothered about competing with Newcastle, I wonder?

The Happy Pontist said...

If Wikipedia is to be believed, rivalry with Newcastle dates back to the 1640s and Charles I awarding coal-trading rights to Sunderland's rival.

But lots of places envy Gateshead's "blinking eye" - it was a very obvious theme in Glasgow's "glasgowbridge" competition, where they even chose the winner based on seeming homage to the Gateshead Millennium Bridge. I think Sunderland's envy is similar, and may even end up the same way - a structurally radical proposal that goes way over budget before being dropped ignominiously.

Anonymous said...

Two points:

The competition was not judged in secret. A record of events was produced and would be available from SCC if requested.

All of the competition bridges were reviewed by a technical panel prior to judging. The judging panel included two bridge building experts. Once the preferred design was chosen it was subject to an extensive peer review with a long span expert from Mott Macdonald. All of the above gave the 'thumbs up' for the design prior to SCC announcing the result of the competition in September 2005.

The Happy Pontist said...

From the tone of your post I suspect you have some inside knowledge :-)

All competitions are essentially judged "in secret" to avoid outside influence on the jury panel. However, there are a number of disadvantages to this. One is the possibility of jury nobbling - there's certainly anecdotal evidence from elsewhere that a strong participant in the jury can drive their opinions through e.g. if they are the senior political representative. There's also the concern that because the designs are not subject to public scrutiny, inexperienced jury members may choose a design which has serious feasibility problems. This happened in Krakow and probably also in Glasgow.

It would be interesting to know who the "bridge building experts" were on the judging panel. The competition brief mentioned but didn't identify an ICE representative. I believe there have been concerns with other RIBA competitions that the ICE representative has not always been an appropriately knowledgeable person. The brief also said that the technical panel included the council's head of structures, who is unlikely to be an expert in this type of bridge.

It's interesting you state that SCC would release the record of the jury's deliberations: if so, this would be quite unusual, but I will certainly ask them for a copy. Do you know who is the best person to ask?