30 November 2009

How not to run a bridge design competition

Here are a couple of bridge design contests I've not previously mentioned, both in their quite different ways offering examples of how, perhaps, such competitions should not be run.

The first is the Four Mile Run contest, for a new pedestrian / cycle bridge across a flood control channel (pictured below) in Arlington, Virginia, USA. This forms part of a wider scheme to revitalise the flood ditch's ecology and turn it into a park. They're currently inviting prequalification submissions (deadline December 7), with the intention to shortlist three teams to come up with concept designs and present them in a public forum.

So far, so good. It's a flat site offering plenty of scope for creativity (a couple of overhead cables in the way being the only significant problem), although equally the landscape is somewhat uninspiring.

It's more of a competitive interview than a design competition as such: they're looking for a team who they can work with in future as much as they are looking for a bridge concept. To that end, the prequalification criteria emphasise previous experience of similar span footbridges, ability to work with multiple stakeholders, and professional standing measured by number of awards and past innovation. That's all likely to result in a safe, conservative selection.

What's really wrong with the competition is that there's no way for entrants to judge risk against reward, and hence decide whether they have any real chance of winning.

There's no suggestion that anyone has carried out the sort of preliminary feasibility study that might confirm they've chosen the right location for the bridge, or provide engineering data to inform the design. There's very little guidance on how ambitious a bridge they're looking for, whether a landmark or something more subtle. The lack of anonymity also leaves the process open to favouritism or political sway (this is inherent to the competitive interview format).

Worst of all, there's no serious prize money for the winner (the three shortlisted entrants each get a US$5,000 honorarium); no indication of what funding, if any, is in place to take the bridge design contract forward; and indeed no commitment whatsoever to actually appoint the winner to a further contract.

The other competition I spotted recently is an open contest for a new footbridge in Maribor, Slovenia. This one is clearly aimed at choosing a design, not a designer, and it's part of a three-part contest, the other two sections relating to an art gallery, and river embankment improvements. Contestants can enter any one part of the contest, or more than one if they wish. It's all part of Maribor's status as European Capital Culture in 2012. A site plan is shown below.

Registration closes on 4 January 2010, and is open only to registered architects. What's that? You think an engineer can design a perfectly good bridge on their own? Well, the town of Maribor doesn't agree, largely because they've adopted wholesale the guidance on architectural design competitions promoted through UNESCO by the International Union of Architects, and as with all such trade bodies, the guidelines are there to protect their members' interests as much as anything else. All the judges will be architects too, they may seek technical advice on the designs submitted, but there's no strong voice for engineering, or for the people who will have to pay for the bridge or maintain it once built.

You might expect they'd at least insist that architects partner up with an engineer, but no, they've succumbed to the same malaise that afflicted the Krakow contest. Nobody should be surprised if the result is the same: a design that looks impressive, but couldn't actually stand up.

Like the Four Mile Run competition, there's no information on whether the organisers have a budget to build a bridge, but at least they make a firm commitment to appoint the winner to a design contract, and the prize money is relatively attractive, with 30,000 euros for the winner, and further prizes for 2nd and 3rd place.

Related links

27 November 2009

Bridges news roundup

V&A Ceramics Gallery Bridge
Is it a bridge? Is it a staircase? Wilkinson Eyre's latest design (pictured right)

Lost in the name of sustainability
Jonathan Glancey attacks the decision to demolish Leicester's historic Bowstring Bridge

We all have a bridge to bear
Should the loss of Cumbrian bridges to floods provide a spur to imaginative reconstruction along the lines of Christopher Wren's blueprint for London after the Great Fire?

Bridge could gain £2.7m in time for its centenary
Middlesborough Transporter Bridge considers viewing platform as part of 2011 commemorative programme

19 November 2009

Calgary's bridges a-go-go

Phew, no news on Calgary's "iconic" footbridge proposals for a while, then it all comes at once.

First, there's the news that construction tenders for Calatrava's Peace Bridge (pictured above) have come in over budget. The lowest bid, Graham Construction's CAN$20.5m, is $2.5m above the available $18m budget, while the highest came in at $31m. Negotiations are underway with Calatrava's design team to "value engineer" the project (i.e. cut costs), including ditching an expensive granite flooring and using concrete instead.

I predicted back in June that the prospect of staying within budget was low. The original budget already made this design one of the most expensive footbridges in history (its £17k per square metre of deck budget is above London's Millennium Bridge, and up there with the super-expensive Kurilpa Bridge in Brisbane). But it's inevitable when structural common sense is thrown out the window that there will be difficulties keeping costs down (the ill-fated Neptune's Way footbridge in Glasgow is another classic case).

The construction cost isn't the only source of controversy relating to the Peace Bridge. The direct appointment of Calatrava in the absence of any competition caused something of a furore last year. That one hasn't gone away, with local columnist Rick Bell reporting that an investigation is ongoing into the legality and prudence of the appointment decision, one that gifted Calatrava an incredible $3m fee.

Next up, the Calgary Municipal Land Corporation (CMLC) have announced the shortlisted designers for the final stage of the St Patrick's Island bridge design competition. They are:

Back in September, I predicted six designs who I thought would make a shortlist, none of which did. Oops. I also gave the six designs I'd personally like to see on the shortlist, and two of those (Arup / Schmitt, and RFR) did indeed get through. So perhaps that's a lesson not to be too cynical about these things: common sense and refinement has for once been allowed to triumph over nonsense and extravagance.

CMLC's boss Chris Ollenberger was quoted:
"The three finalists were chosen because they’re respectful, elegant and functional, and offer different attributes for consideration ... The advisory committee agreed that the bridge should be simple and elegant, and that the scale of the structure, in relation to the site and its surroundings, be complimentary and not be overwhelming. Public commentary also supported this direction and we believe that we have three strong, feasible concepts to move forward with."
I previously posted a five-parter on the competition entrants: 1, 2, 3, 4 and 5, which you can check out if you want to see what kind of marvels weren't good enough for the shortlist. Personally, I hope the Arup design now wins: if they're going to go for minimal impact rather than structural gymnastics, that one certainly has it.

The Accelerated Bridge Construction blog speculates that the cost overrun on the Peace Bridge has scared the St Patrick's Island contest organisers away from designs that were daring or innovative. Maybe, but I think the fact that the project promoter, CMLC's Chris Ollenberger, has an engineering background possibly also had something to do with it: a report in the Calgary Herald makes clear that CMLC thought several designs were too ambitious, technically challenging, or just plain expensive.

They've gone for elegance, subtlety and economy, and I guess it's just a shame for the unsuccessful competitors that they didn't state in advance that those would be the criteria (essentially, this unwillingness to say what they were looking for turned the contest into a hugely expensive lottery where the odds of winning could not be predicted).

The promoters also make it clear that public opinion played a large part, which is interesting, because much of the commentary that appeared on the web was from people seduced by architectural flamboyance and largely ignorant of the engineering issues. I think CMLC may have been too conservative though, the final bridge is unlikely to be the kind of landmark which will have potential developers itching to get into the area, which is the ostensible purpose of the whole scheme.

Good news is that each finalist gets a CAN$50,000 stipend to develop their design before a final choice is made, a welcome recognition both for the effort they've put in so far and the work still to come.

17 November 2009

"Masterpieces: Bridge Architecture + Design"

Chris van Uffelen's "Masterpieces: Bridge Architecture + Design" (ISBN 978-3-03768-025-4, Braun Publishing, 2009, 304pp) [Amazon UK] is a trilingual (English, German, French) visual encyclopaedia of (mostly) recent signature bridges, a cornucopia of structural extravagance.

However, before I tell you what's good about this book, let's get some of the negatives out of the way.

This is a very middle-of-the-road coffee-table architecture book. So don't expect very much information on the engineering or technology behind each bridge, don't expect comprehensive information on bridge materials or dimensions (such as spans, in many cases), don't expect a critical point of view or even very much on what makes certain bridge designs notable.

This is also a book with a highly idiosyncratic choice of bridges, so excellent recent footbridges such as Kurilpa in Brisbane, Forthside in Stirling, Knokke, or Lake Austin, aren't in here. In the UK, for example, the unbuilt Lochnagar Street and River Hull bridges are included, but the Sackler Crossing at Kew and the Infinity Bridge at Stockton are out.

For those bridges that are included, the text (in English, French and German) is fairly brief (and in one or two cases, appears to have been written by the designer or adapted from their publicity material). This is a book to buy for the images, not for the contextual material.

Pretty high amongst my quibbles is its practice of listing most structures by the name of the architect, regardless of whether they were the lead designer or not, with the structural engineer's name generally buried in the small print. In several instances (e.g. Millau Viaduct), there's no design engineer mentioned at all, and the builders are entirely invisible. It's not the first architectural book to take this thoroughly inappropriate approach (Jobson and Pearce's "Bridge Builders" was a similar offender), but it's a shame.

There are also problems with attribution: Alan Baxter is credited as structural engineer for the Castleford Bridge, but not Tony Gee who actually did the detailed design; while Rosales + Partners claims architectural credit for three bridges (Leonard P Zakim Bunker Hill Bridge in Boston; Liberty Bridge in Greenville; and Woodrow Wilson Memorial Bridge in Washinton DC), although for the first of these, Rosales was employed by Wallace Floyd Associates (who have suggested his involvement was not significant), and the other two should surely share credit to Frederick Gottemoeller, given that Rosales was part of Rosales Gottemoeller and Associates when they were designed. Gottemoeller certainly claims a key involvement in these bridges on his website.

My final complaint is that the book is far from rigorous in stating which images are photographs and which are renderings, with some finished bridges represented by both (e.g. Gateshead, Swansea's Fabian Way). Several bridges are included which are unbuilt, and some which will never be built (e.g. SLA's Rijnhavenbrug design, and a design for the Bering Strait crossing), although no distinctions are ever made. In the Rijnhavenbrug case, it's actively misleading, since the actual competition winner by Quist Wintermans is neither shown nor even mentioned.

So, I'll put the problems to one side, and tell you where the book is a success.

Of the 69 bridges featured, some have had plenty of exposure elsewhere (Gateshead, Sundial, Millau). But most of the structures were unknown to me, and the coverage of European bridges in particular is very good: this is where an idiosyncratic selection is a good thing. Several structures are well known to pontists but have not yet appeared much in print: Calatrava's Quarto Ponte sul Canal Grande (looking resplendent here), the amazing Grand Canyon skywalk, the Liberty Bridge in Greenville.

But amongst the lesser-known bridges, there are several which are intriguing (such as Craigieburn Bypass, Melbourne) and a few which are particularly excellent (Brick Pit Ring in Sydney, the Passerelle Valmy in Paris, and Next Architects' Melkwebrug proposal).

The photos are of high quality and in several instances quite stunning. It's a great book to leaf through, and there are several bridges I'll undoubtedly return to look at again and again. The flaws certainly didn't stop me from enjoying the book.

16 November 2009

Bridges news roundup

A proper post is in preparation, but until then, just some quick mentions:

Humble design projects win architectural awards
Includes a Kansas City utility conduit bridge which glows from within (pictured right).

Cleveland City Planning Commission praises Miguel Rosales bridge design for North Coast Harbor
Planners also approve Plan B in case highly innovative design hits a snag (see previous post for more on this).

Transporter Bridge seeks world fame
Newport and other transporter bridge authorities mull bid for UNESCO world heritage status .

Iconic bridge wins award with a little help from Imperial students
Infinity Footbridge relied on students to work out how to build it. Apparently.

Swing bridge in Odense to be longest in Northern Europe
118m span designed by ISC Consulting Engineers.

Top 5 Most Innovative Green Bridges on the Planet
Well, not really, but I guess it makes a good strapline.

'Gateway to Auckland'
Shrinkwrapped truss design unveiled for NZ$5m footbridge.

10 November 2009

Knokke Footbridge

Someone recently emailed me a link to an Archdaily feature on the Knokke Footbridge, in Flanders in Belgium. Although it was completed a couple of years ago, I wasn't previously aware of it, and it's such a gorgeous design I just had to include some pictures here.

It was designed by Ney & Partners, whose website is well worth a look, as this is far from the only marvellous bridge they've designed.

It's a three-span hybrid cable-stay/suspension bridge (28m, 46m, 28m), albeit one which is both technologically audacious and aesthetically exceptional. It carries cyclists and pedestrians via a curved route above the Queen Elizabeth Avenue, a dual carriageway on the way into Knokke.

The concept sketches show the basic idea: the bending moment diagram for a three-span structure is used as the basis of the overall structural shape (see left, click on any image for the full-size version: all sketches are by Ney and photographs by Daylight). This gives the standard form for a suspension bridge or a haunched girder bridge, with a deeper section above the supports. They then proceeded via a series of design optimisation steps to remove as much material from the "web" as possible, resulting in the elegantly curved cut-outs of the final bridge.

The photo on the right shows the result, and you could interpret it as either a cable-stay bridge or a suspension bridge according to preference. The webs are formed from 12mm steel plate, as is the main deck girder, allowing the "cables" and deck to be formed from a continuous joint-free material.

In profile, it reminds me very much of the Tavanasa Bridge (see left, photographer unknown), where Robert Maillart started with a closed-spandrel arch design, creating cut-outs where he knew the concrete to be providing little real benefit. The Knokke bridge is just the Tavanasa structure turned upside down, with concrete replaced by steel.

In cross-section, the Knokke designer's sketches (see right) show the bridge webs continued and curved below the deck, acting as a cradling suspension system transversely (i.e. the steel plate is all in tension, never subject to significant bending).

As can be seen from the photographs (see left), that's exactly what they achieved. The deck part is partially infilled with concrete to form a box girder which is stiff in bending and torsion, and also stiff enough axially and horizontally to sustain the effects of deck curvature (arching in plan).

Essentially, it's a bit like a membrane structure, where everything is form-found to carry only tension forces, except for the stiff box girder deck (see image on the right for a better view of how the deck is put together).

One of the disadvantages of doing this in steel is clearly the cost of bending all the steel to the desired profile. Another is that unlike a fabric structure, the steel doesn't alter its shape in response to varying loads, so in many situations it will be in a far from perfect stress state. The final difficulty is simply that of welding large thin sheets together (see left), but I think the resulting evidence of the bridge's making (weld lines) is a positive thing in what would otherwise be an ultra-smooth bridge.

The deck is hung from two Y-shaped piers (see right), and considerable effort has gone into making these as minimal as possible, just some stiffened steel plate rather than the box sections that would be a more conventional solution. This is presumably possible because of the bridge's curvature, which allows the lateral forces in the deck to be reacted elsewhere. The piers wouldn't satisfy UK requirements for strength against accidental vehicular impact, so let's hope they never get hit!

The whole thing is finished off with some simple chain-link balustrades with LED lighting recessed into the handrail, and a couple of tiny deflectors above the highway (see left), which I presume are there to prevent people urinating too easily on the electric overhead tramway wires.

Overall, it's an absolutely gorgeous design, an exemplary piece of engineering, and one of the finest bridges I've seen this year.

There are dozens more great pictures at the ArchDaily and Ney and Partners websites, so go and take a look!

See also:
Knokke Footbridge at Structurae

08 November 2009

The Battle of Johnson Street Bridge rages on

Last month, I wrote about the Johnson Street bridge in Victoria, British Columbia. This is a historic Strauss heel trunnion bascule bridge, with parallel opening spans carrying both road and rail traffic (pictured below, image courtesy of City of Victoria).

Plans were afoot to replace it with a CAN$63m MMM / Wilkinson Eyre design, itself an unusual bascule bridge featuring a striking ring-girder support (again, pictured below).

The project was fraught with controversy, with a highly articulate online campaign opposing the scheme on the grounds that the existing bridge could be refurbished rather than replaced. This view ran counter to the advice received by the city authority.

The whole debate seemed to become moot when it was announced that the City of Victoria would not receive the federal funding it had been counting on to pay for the bridge replacement.

Since then, the pendulum has swung back the other way, with the announcement that some federal money is available after all: CAN$21m, to be precise. That "only" leaves $42m for the City to find, with the provincial government of British Columbia keeping its hands in its pockets.

The opponents of the bridge replacement option are undeterred, and have redoubled their attempts to win support for a refurbishment approach. Parsons Brinckerhoff engineer Frank Nelson has been invited to Victoria to present the case, arguing in the Victoria News that it's "a one-of-a kind bridge, the e-mail chain [between historians] has been going mad for the past month and they can’t find another one". The opponents are pressing for a referendum.

A cynic might argue that Nelson is unlikely to make any other argument: he's a specialist in bridge conservation, not in design of new signature bridges (for more detail on his views, there's a 125MB Powerpoint presentation at johnsonstreetbridge.org).

But for me, it's difficult to come down on one side. It's undoubtedly a spectacular structure (although a struggle to find it beautiful) - see some great photos at Yule Heibel's blog, for example. Opponents of replacement are arguing that it's unique worldwide (because of the parallel road and rail spans, not because it's a Strauss heel trunnion design), and the heritage value is therefore substantial. But refurbishment will be expensive, and replacement of the mechanical and electrical systems won't mean a bridge of this age becomes maintenance-free.

It's not yet clear whether we're seeing the opening skirmishes in a lengthy battle - certainly there's no sign that either side has mounted a decisive offensive just yet. There's no obvious compromise solution available. For me, it's great to see an informed public taking such a great interest in the bridge, and I'm sure I'll follow this story further in the future.

Further information:

06 November 2009

Bridges news roundup

The World’s 18 Strangest Bridges
Popular Mechanics presents the weird, the wonderful, and the wobbly. Actually, no wobbly, I just couldn't think of another "w".

Carrick-a-Rede is a bridge for all seasons
Crossing so popular it will no longer be stowed away in winter

Italians, not Texans, building signature Dallas bridge
Calatrava's Margaret Hunt Hill being assembled by visitors on allegedly dodgy visas. Texan welders not happy.

Bridgewater Bridge, Stoke-on-Trent by NORD Architecture
New Buro Happold footbridge has pretty diagrid ribbed soffit (shown right), welders kept well-employed stitching short stubby beams together. Built by Birse, but I don't know who the poor fabricator was.

New Earthquake-Proof Alloy Allows Bridges to Bend but Not Break
Nickel-titanium alloy used as ultra-expensive concrete reinforcement. The Popular Mechanics article is a little short on the technical detail, but essentially the alloy is a superelastic metal with an elastic strain limit many times that of steel, perhaps best know for its use in spectacles.

Spanning Time: Rare Images of the Brooklyn Bridge
The Tribeca Trib reviews John Manbeck's book "Historic photos of the Brooklyn Bridge" (see also The Villager for another interesting review).

Central Park development with Darlington town centre
Super-dull headline hides news of progress on the innovative new FRP Haughton Road footbridge, perhaps one of the more aesthetically-conscious composite bridges I've seen (shown left).

Support for bridge blades
Bonkers Tasmanians suggest hanging wind turbines off the Tasman Bridge.

Suppose design office: heiwa-ohashi pedestrian bridge proposal
Twin stressed-ribbon designs for peace memorial park in Hiroshima (story spotted via ABC).

03 November 2009

Kraków footbridge undergoes metamorphosis

I've touched in the past on a pretty bizarre competition-winning bridge design at Kraków in Poland. This design was featured in New Civil Engineer magazine a few years ago, as an example of the sort of result that can happen when a contest has no judge with suitable structural engineering expertise.

The competition was held in 2006, and the winning entry was by Biuro Projektów Lewicki Łatak. It was seen as a partner to a new replacement for the Podgórski Bridge, a 150m span steel arch footbridge which is currently under construction. Łatak's design, however, has yet to secure definite funding, and no firm decision has even been made on its precise location.

The competition-winning image (shown above) is for an exceptionally slender structure. At first sight, it looks like an underslung suspension span on the left, and an arch-suspended span on the right, until you look at the junction between the two and realise that this point is unsupported. In technical terms, it's a "hinge" - a point of negligible bending stiffness at a position on the span where the bending moment would be considerable. In lay terms, it simply could never stand up.

The fact that this design ever won a bridge competition highlighted the often incomprehensible way in which such contests are organised. I believe this one was part of an architectural biennale, and the image represented the apex of a tendency where it seemed architects could design something that superficially resembled a bridge structure, without it having to have any structural rationale at all. Without an informed public, or a competent jury, the image was everything, and patent nonsense such as this could be declared a winning idea.

Although I believe the project has been officially shelved, the winning design has been developed further since 2006, and it's interesting to see the latest image, shown below. What do you do, if you win a competition with an unbuildable bridge, but people show interest in actually building it?

There are answers to the same question to be found elsewhere (Neptune's Way in Glasgow, where props were added to try and hold up an inefficiently-angled arch, or River Wear in Sunderland, where a decidely sub-optimum structural form was made to work simply by throwing more and more concrete and steel at it). In both cases, the result was a bridge costing considerably more than the promoters had budgeted for when they declared a competition winner.

It's unclear if the Kraków footbridge ever had a serious budget (29 million złoty has been mentioned recently, which is £6m or US$10m, while £5m was mentioned when the design was first publicly criticised), but as at River Wear, the most obvious change to the design has been to thicken everything up, turning the main deck into a stiff shallow arch (or possibly cantilever girders, it's hard to tell from the rendering). It's still somewhat unconvincing, but again, throw enough material at it, add beefy foundations, and it can be made to work. The upper and lower arches are essentially non-structural in this revised design, just glorified staircases to provide interesting viewpoints (so long as you're not mobility-impaired). I hope the lower one has been set above maximum flood level ...

I've located a couple more images of the revised design, which perhaps help clarify how it works (also see the image here). Whatever, the moral of the story is (as ever) that bridge design competitions need an informed and competent jury; that designs likely to require substantial structural and hence financial amendment need to be weeded out; and that architect-led bridge design only works with an architect who has a sympathy for structural behaviour.