23 December 2008

When bridge design competitions go bad (and good, sometimes)

I recently went to a very interesting talk in Preston by architect Cezary Bednarski, billed as "River Douglas Bridge - architects and engineers in competition", but which turned out to be a far wider journey through the murky waters of bridge design competitions past and present.

In the process, many interesting points emerged, not least the astonishing statistic that despite Bednarski's exceptional success rate in winning bridge design competitions, only about 1 in 10 of his competition-winning structures have ever been built. The reasons are many - some competitions have little real support to begin with (e.g. Liverpool Cathedral's Glass Bridge); others are the pet projects of politicians and hence quickly dumped when a new regime is voted in (Carlisle's Hadrian's Bridge); others underestimate the funding required to complete an ambitious landmark structure (e.g. Helsinki, Glasgow). It seems that bridge design competitions are great both for getting some publicity and free optioneering for a promoter, and also to allow designers to flex their creative muscles. But they're perhaps not the best way to get a real bridge built.

Bednarski did discuss the River Douglas footbridge competition, for which he had acted as a juror. This was run by RIBA on behalf of REMADE, a local development agency, and sought to restore a river crossing on the line of a long-disused railway. The contest was initially controversial because of RIBA's absurd insistence that teams could only enter if led by an architect. There were 110 entries altogether, whittled down to a shortlist of seven by the jury. The competition was won by Arup and JDA architects, with a combined stress ribbon and arch design.

It was interesting seeing various examples of Studio Bednarski designs, such as the Kelvin Link competition entry, a stressed ribbon supported by an arch (top). Compare this with the winning entry for River Douglas, another stressed ribbon supported by an arch (bottom):

Spot the difference!

We were told that many of the entries to the competition were very poor, and even the shortlisted ones far from perfect. An open competition such as this avoids the predictability of an invitation-only competition, giving newcomers their fair chance to shine. However, it's also far more likely to bring forward designers who lack the knowledge or resources to actually take a bridge through to being built, and the number of entries (and hence low chance of success) puts off experienced designers who do have those resources.

Bednarski showed several entries to the River Douglas competition which brought smiles to our faces: but these were entries to a childrens' competition, colorful, ambitious, and naive. You can find these online at Remade's website.

Another theme which came up repeatedly in Bednarski's competition examples were the many cases where competitions are won by structures which are either stretching the boundaries of feasibility, or simply not feasible at all. Understandably, losing competitors feel somewhat disgruntled when beaten by something like this (I've been in this position myself). But that's a subject to return to another time ...

19 December 2008

Bridges news roundup

Derby, swing footbridge, delayed, over budget
£3.8m design now £4.3m, 11 months late, not yet open (pictured below, click image for larger version)

Calatrava knock-off at Achill Sound now open
€5m swing highway bridge opens 7 months late, and looks a little odd too (best photo I can find online is on flickr, showing what looks like a steel arch bridge with curved hangers) Update 6th January 2009: better photo now available

Genuine Calatrava opens in Valencia
€35m Serreria Bridge opens, 11% over budget, designers everywhere murmur in surprise at the sight of an iconic cable-stayed bridge which actually uses back-stays, lots of photos here

Bridge opens on time, on budget
No link for that one, couldn't find an appropriate story!

16 December 2008

River Soar shortlist announced

RIBA have announced the shortlist for the £1.5m River Soar footbridge competition in Leicester. Six entrants have been selected from over 150 expressions of interest:
  • Allies and Morrison with Price and Myers
  • Explorations Architecture, Paris with Buro Happold
  • Knight Architects with Gifford Bridge Designers
  • McDowell & Benedetti with Arup
  • Moxon Architects with Arup
  • Ramboll Whitbybird

Some interesting choices there, with a number of firms who are not the better known architects and consultants. I think that's a good thing, as one of the problems with a closed competition such as this one is the risk that it may just feature "the usual suspects".

The entrants have to submit their designs in February, and a winner should be announced in March 2009. A preliminary briefing paper for the project is available online [PDF].

15 December 2008

More Calgary shenanigans

Ah, Calgary, oh Calgary. As Happy Pontist readers may recall, this Canadian city is looking to build two new "iconic" footbridges, at a staggering combined cost of US$50m. And they want both of them to be designed by Santiago Calatrava, probably the most famous bridge designer in the world.

Back in September, there was controversy as to why Calgary City Council wanted to directly appoint Calatrava, rather than selecting a designer for the bridges by means of a juried competition. The bridge proposal had been rejected by a local committee, and moves to appoint Calatrava only approved by the full council because two members of the opposition had been away that day.

Mayor Dave Bronconnier appears to be keen to get a Calatrava-branded crossing, and has plenty of money available in the forms of a no-strings-attached grant from the provincial Government of Alberta. He's trying to finalise a contract with Calatrava in partnership with a single local firm.

The latest controversy is because a small group of councillors are trying every available route to get the Calatrava appointment rejected, and the scheme opened up to other bidders. They've failed in a direct proposal to get the council to reconsider, and their attempts to get Alberta to intervene have also been turned down. The rebels even tried to get Alberta to stall other funding as punishment for Calgary daring to single-source the Calatrava design. The rebels are still moving ahead with an attempt to review the council's legal policy on single sourcing.

Their efforts have been furiously rejected by the council's powers-that-be, accusing them of betraying Calgary's democratic decision. The Mayor argues that the council is following provincial funding guidelines carefully, and that even if the design is single-sourced, competitive bids will be sought for the construction.

From my perspective, over 4,000 miles away, all of this is pretty incomprehensible. I have no idea what the local legal aspects are (there are few if any public bodies in the UK who could appoint a design consultant for a project of this size in this way without putting the job out to competition). But it's fundamentally unfair to the design market, and the people of Calgary, not to seek out a designer who will offer the best bridge at the lowest price - a consideration of value that Calgary seems to entirely ignore.

Writing in the Calgary Herald, Paula Arab clearly agrees:

"River crossings should be beautiful, but there are better ways of getting it designed than to go to the best-known architect who charges the most money.

"The assertion that only Calatrava can give us 'extraordinary' bridges is utterly false.

"It's also typical of the nouveau-riche attitude that continues to believe style and class can be bought by paying the highest price. Not so."

Well said.

14 December 2008

Is there an engineer in the house?

The good people of Portland, Oregon have been busy discussing a new light rail bridge over the Williamette River. The new bridge would carry the proposed Portland - Milwaukie light rail line as well as foot traffic, and is promoted by local transit body TriMet.

There seems to be considerable interest in which bridge option will be chosen. The three initial options were an arch bridge, a cable-stayed bridge (shown top), and a structure described as a "wave frame" (shown bottom) but which is essentially a somewhat dubious cross between a Vierendeel truss and a suspension bridge. Of those, they seem to have whittled the choice down to several variations on the cable-stayed and "wave frame" options.

The somewhat unconventional "wave" option seems popular with the natives, if a poll at BlueOregon is to be believed. The Portland Spaces blog is sufficiently keen that they interview the designer, architect Miguel Rosales.

You might think that Rosales would know his stuff: he worked on the US$115m cable-stayed Leonard P. Zakim Bunker Hill Bridge in Boston, as well as the Liberty Bridge in Greenville, South Carolina, a curved suspension bridge. It may seem somewhat odd, however, that his website doesn't so much as mention the engineers who played key roles in these structures (Christian Menn in Boston - who returns the favour by making no mention of Rosales; and Schlaich Bergermann in Greenville).

Reading the interview with Rosales at Portland Spaces, there's still no mention of an engineer, and I came away with the distinct impression that this is a bridge promoted by an architect who doesn't really understand bridge design. In the comments at the foot of the interview, Rosales says:
"The flowing top chord follows the flow of forces and moment diagram resulting in a slender and elongated structure. The clean design avoids the visual confusion often found in steel trusses with their multiple layers of diagonal and vertical members."
But of course, it doesn't follow the moment diagram at all, which would be cusped above the piers (i.e. "pointy"), in the same manner as a conventional suspension bridge. And it avoids the truss diagonals only at the expense of requiring massive amounts of additional steelwork to provide equivalent stiffness (and it's stiffness that's normally critical on a light-rail bridge).

It's far from clear how the bridge (which spans about 200m) actually works - the very slender depth at midspan provides insufficient moment continuity for it to work as an efficient continous truss, while the weedy vertical members lack the stiffness required for suspension bridge towers. If, as it appears, it's a bizarre hybrid self-anchored suspension bridge relying on Vierendeel action, throughout, it's no surprise that TriMet's cost estimates show it as significantly more expensive than the cable-stayed alternative.

Rosales is keen to promote his design, and suggests that TriMet's engineers have been unreasonable with their cost estimates. From the TriMet website [PDF], it's apparent they have put considerable effort into trying to make the Rosales design work, but still estimate its cost at US$119m, against US$93m for the cable-stay option. That works out at about US$10.5k per square metre of deck for the "wave frame", or about £7,000. That seems about right for an unconventional design like this, but it's easy to suggest it could be more.

Quick! Is there an engineer in the house?

Seemingly not.

09 December 2008

"American Bridge Patents: The First Century (1790-1890)" by Emory L Kemp

The nineteenth century saw bridge design worldwide develop at a furious pace. While there was pioneering technical work taking place throughout the world, much of the development in the United States would leave a particularly lasting legacy for future bridge designers. This is because of the invention of a proliferating range of truss forms, some of which are still in use today.

The names of the inventors (Squire Whipple, Theodore Burr, Wendel Bollman, Albert Fink, William Howe) were immortalised by their truss designs. Activity certainly wasn't confined to the USA, with Alfred Henry Neville, Arthur Vierendeel and James Warren amongst the creators elsewhere. Warren's truss remains one of the most popular workhorse designs today, while others receive continued use only through radical reconfiguration (e.g. the use of Fink's truss in inverted form at Royal Victoria Dock Bridge and Forthside Footbridge).

A book covering the history of these designs should therefore make for a very interesting read. "American Bridge Patents: The First Century (1790-1890)" (ISBN 1-933202-06-8, West Virginia University Press, 2005) [Amazon UK] focuses mainly on designs which were recorded by the US patent office, and its main target is the American engineering history community.

Not all the important bridge designs were patented, and exclusion of overseas designs is quite understandable (while the US patent office makes copies of all old patents freely available online, its UK counterpart offers no equivalent access, for example).

The book is in four main sections. The first offers a potted history of American bridge development from 1790 to 1890, focussing on designs which were patented, including catalogue bridges. New bridge types are very rarely (if ever) patented today, but the introduction of new materials during the 19th century saw an explosion of new structural forms which exploited the properties of iron, steel and reinforced concrete. It remains to be seen whether more modern materials (such as fibre-reinforced plastic) hold the same potential to revolutionise not just buildability or durability but also the possibilities of form.

The history covers all the main American designers of the period, and includes copies of some patents, and many patent drawings. Before buying the book, I had expected more of an encyclopaedia of the patents themselves, but I guess this could be somewhat pointless - most of them were unsuccessful, and several heavily flawed. It certainly leaves scope for a far more thorough tome on the subject for an author so inclined.

The second part of the book covers the history of the patent office itself, which wasn't of great interest to me. The third gives a personal view on the joys of bridge patent research, and is accompanied by various reproductions of original watercolour patent drawings. These are rather gorgeous in a way that 21st century CAD renderings rarely are, but printed quite small and it would have been nice to see them at a larger scale.

The final section explains how to find the patents online, with an extensive list of over 600 relevant patents, which is tedious but essential since the patents database can only be searched if you already know the patent number. The list is structured both chronologically and by patent-holder.

There are several topics the book doesn't address, and as a result it's really only a taster for this vast subject. Despite the focus on patent records, it doesn't consider how the patent process affected development of new bridge technologies - whether it facilitated greater commercial competition, or held back the wider adoption of monopolised innovations. There's also little if any explanation in pure structural engineering terms - the reader familiar with bridge design is left to work out for themselves how each structure actually works.

There's nothing here on the fallout from this period: which designs are still used, and why, or which still offer untapped potential for the modern engineer. Essentially, this is a book aimed at the historian, and it doesn't really consider the engineering audience as such.

There's also no index, which is pretty much criminal in a history book!

Overall, I found "American Bridge Patents" a little disappointing, mainly for its lack of depth. The authors acknowledge that its main aim is to document the bridge patent research completed so far, and offer a starting point for future research. Nonetheless, the book's best feature is the large number of original patent illustrations included, featuring many well known bridge designs as well as several which are far more obscure. I'm glad I bought it.

For anyone interested in alternative views, ther are other reviews of the book at the IStructE by Tom Swailes and at the Journal of the Society of Industrial Archaeology by David A Simmons.

05 December 2008

Bridges news roundup

Squiggly Bridge gets its final link
Most of Glasgow footbridge now on site

Next step for River Wear crossing confirmed
Techniker to review costs and address technical issues with design

Interview with Tom Oslund
Architectural input to the replacement I-35W design (pictured)

Jerusalem mayor plans to demolish brand new Calatrava bridge
£40m light rail bridge could become redundant if light rail scheme cancelled

Portland could get USA's first ever extradosed bridge

04 December 2008

A bridge with a twist

It seems the fashion for post-modernism in bridge design is steadily departing further and further from "normal" structural constraints to the extent that it's no longer post-modernism at all, it's good old-fashioned surrealism.

The latest case in point is a proposed new foot and cycle bridge in Houston, named the "Tolerance Bridge" and planned to cost US$7m. Announcing the winner of a 54-entry "international artistic competition" (whatever that is), mayor Bill White declared that "great art is part of a real city".

Like everyone else in the entire world, they were evidently looking for something unique, a landmark, an icon (etc etc etc), and the design chosen is definitely that. It's not entirely clear from this image, but it's intended to look as if the bridge deck rises up into an arch, twisting around as it does so into something that nobody other than the most ambitious skateboarder could possibly cross. In reality, the bridge deck is at grade. Other images of the design show streetlights on the arch, enhancing the illusion that a giant toddler has vented their frustration on a more conventional bridge.

As a structural engineer, comment seems largely superfluous. The "arch" is purely sculptural, it's not there to hold up the deck below, essentially the entire bridge is a one-note joke. Depending on taste, it's either a welcome dose of humour in a genre normally known for serious structural acrobatics, or it's a case of all common sense thrown overboard. I'm finding it hard to decide which is my view: my sensible structural engineer's heart rebels against the fundamental irrationality of it, while my brain tells me we should all be more open to the eccentric and unpredictable (even if it does cost 7 million bucks). At least one Houstonian seems inclined firmly to the more sceptical view.

Bridges to nowhere

If you had to define a bridge, it would probably be something like "a structure spanning and providing passage over an obstacle" (slightly abrided from dictionary.com, that one). But what about a structure that provides passage above an obstacle ... but not actually over it?

Not sure what that means in practice? Well, Deputy Dog has the answer with a delightful set of six bridges-to-nowhere that take people out into mid-air, and no further. These include the astonishing Grand Canyon Skywalk; viewing platforms in the mountains of Italy, Switzerland and Austria; and Norway's design-conscious but frankly terrifying Aurland Lookout (pictured, photo courtesy of Lewis Martin).

Pontists may also be interested in another recent Deputy Dog post on the use of rockets to build a suspension bridge.

03 December 2008

Sunderland council decide way forward for River Wear crossing

Today, Sunderland City Council's cabinet are meeting to agree the way forward for their iconic bridge scheme (iconic is a much abused term in bridge design, but this is one bridge that if it is ever built, will undoubtedly merit the description).

The Sunderland Echo recently reported that the current Spence / Techniker concept design (pictured) "will have to go out to tender to engineering companies. Experts will then come up with a working design and accurate costings for the structure to see if it will work and be affordable." The Happy Pontist previously wondered whether the current designers might not be too happy to see their work passed on to another firm i.e. the un-named experts.

It seems the Echo's report was slightly misleading; the council's actual intention is to appoint Techniker to develop their own design further. In a report to the council cabinet (available online [PDF]), the council officers recommend appointing Techniker to "continue with the development of the concept design up to a stage where sufficient confidence on cost, risk and buildability can be provided to assess its affordability". No doubt Techniker will be pleased to take back the lead role on this bridge at long last.

The council are definitely taking the risks associated with this highly unconventional design seriously - their report acknowledges it to be "innovative and unique", stating that "a bridge of this type and scale has not been built anywhere else". They want to achieve a comparative level of cost certainty to a conventional bridge, which will require a very substantial amount of design work indeed.

The report discusses the extra £30m required for the iconic bridge (over and above the cost of a conventional bridge), but since it doesn't split out the cost of the bridge from the cost of the wider Sunderland Strategic Transport Corridor scheme (of which it forms part), it's difficult to comment on how reasonable their estimates are. By my estimate, £30m works out at about an extra £3,000 per square metre of deck.

Techniker's designer Matthew Wells has previously suggested that a bridge "of similar size and span and of exactly the same construction and arrangement has been constructed a decade ago without any difficult[y] or on-cost or excessive maintenance regime", so perhaps this will now be an opportunity to tell everyone what that bridge is and use it as a cost benchmark. Perhaps Calatrava's Alamillo Bridge is the best comparison: it cost US$38m when built in 1992, and allowing for inflation that would work out at roughly £5,000 per square metre of deck today. However, the River Wear design is substantially more exotic than even Alamillo, so any benchmark may be futile.

The council report also discusses the recent public consultation. Newspaper polls found over 90% in favour of the Techniker design. However, the council's own consultation finds that only 52% of people were in favour of "a striking design", against 49% wanting something "tried and tested". So with half of Sunderland opposed to the bridge, you must wonder exactly why their council is quite so keen to pursue it.

I sometimes feel as if the River Wear story has taken over this blog (notwithstanding exciting side trips to the Alps), but it undoubtedly has a long way to go yet!