Bridges news roundup

I'll return to posting more commentary on Footbridge 2011 shortly, but I'll just break things up with a quick round-up of bridges news which has sneaked past in recent weeks.

In a Sublime Setting, a Bridge is Born
Brilliant photographs by Jamey Stillings of the Hoover Dam Bypass bridge under construction.

Alternatives called for on railway footbridge design
Council backtracks on plans for an "iconic" bridge at Sleaford.

A trio of pedestrian bridges proposed by Boston architect Miguel Rosales could change the face of Cleveland
The good, the bad, and the derivative. Personally, I like the good one.

The world's 18 strangest bridges
Some are strange, some are fine, all I know is everyone sure seems to love a list.

Footbridge 2011: papers roundup pt 2

I've had time to jot down a few more comments on the papers presented at Footbridge 2011. Again, this is a highly selective bunch, there were many others which were interesting but which I simply won't have time to cover.

The Arganzuela helicoidal bridge over the Manzanares River, designed by MC2 Engineering Cosultants with Dominique Perrault Architecture, belongs to the increasingly popular genre of helical truss bridges, a genre I have surveyed previously. There are plenty of images online, but I've just chosen one from the conference paper.

It's actually two separate bridges, with a total length of 278m. Each is in the form of a cone, varying in diameter from 6m to 12m, and structurally they are helical trusses, with straight upper and lower chords intersected with spiral diagonals, taking the general form of a through Warren truss. This is pretty much as rational as this helical form ever gets, but as the authors noted, it still imposes significant secondary stresses on the steelwork, requiring substantially more material than would the more conventional solution.

I've included it here because while I have my doubts about the conic geometry (attractive in the widening direction, but visually constricting in the other direction), this is one of the best of its genre. This is largely, I think, because of the cladding treatment, which with its varying densities of mesh, distracts from the structural frame and uses its apparent solidity to create an object with a greater sculptural weight.

I enjoyed Andreas Keil's presentation, Passerelle sur Nanterre - spatial play of forces, on the La Defense footbridge designed jointly by Schlaich Bergermann und Partner and Deitmar Feichtinger Architectes. This is a remarkable 88m long bridge which passes around the perimeter of a curved building, without touching it, and with supports only towards the ends. This is a challenge in itself, but the choice was made to support it on only one edge using the "inverted Fink truss" typology (a system which has only limited resemblance to a genuine Fink truss).

The result is a truly superlative example of high-tech structural engineering. The main vertical support comes from the truss, which is essentially a series of successively cantilevering cable-stays. The number of cables in each bay of the truss are varied according to their order in the cantilever i.e. the number of cables used is proportional to the force to be carried. This system is assisted by a set of ring-cables offset below the deck level, which are cranked back up to deck level at the ends and hence carry a share of the vertical load in a manner similar to an external prestressing tendon. This also reduces the possibility of uplift forces on the bridge's end bearings.

The deck is a hollow steel box, providing some of the much needed torsional stiffness. However, this is far from sufficient on its own, and the lower ring-cables provide the remaining torsional restraint. The vector sum of their forces at each mast position imparts a net inwards force, which, because of its level, acts to counterbalance the torsion resulting from the deck dead and live loads only being supported on one edge. For some reason, the bridge as a whole reminds me of a set of gimbals, as in a gyroscope, possibly because of the way the whole ensemble appears to teeter on only a few pin-point supports.

It's a remarkable bridge.

Another bridge which impressed me was Link 27 - a new footbridge in the west of Vienna, Austria, presented by Rudolf Branstötter. This 38m span bridge was completed on site in September 2010, and was the end result of a student design contest which Branstötter had won. I thought this was an exceptional structure, where the structural form, although unusual, was a carefully thought-through response to the site's very specific constraints.

It spans over both a railway line and the River Wien. The different permissible clearances led to a structural form which has a low level springing on the river bank, and which is supported over the railway from above. One end resembles a concrete arch, while the other is a concrete cantilever, with fixity provided by steel tie-down bars. However, both aspects appear fully integrated. The method of construction was also unusual, with both edge girders precast on site, lying on their side, before being rotated and lifted into place.

Footbridge 2011: papers roundup pt 1

Okay, I thought I would attempt a quick round-up of some of the papers and presentations from Footbridge 2011 which particularly caught my eye. Apologies to anyone whose presentation I saw and found interesting, but have missed out, I only have so much time so will have to be quite selective!

In addition to the three keynotes previously mentioned, I enjoyed Henryk Zobel's Contemporary structural solutions of timber pedestrian bridges, which offered a nice survey of the range of timber designs currently in use. One that struck me as especially attractive was the treetop walkwway in Tharandt, Germany, pictured right (click any image for a larger version). This 118m long curved, stress-laminated timber structure was explained further in its own paper, although I missed the presentation.

There were relatively few other presentations to suggest any acceleration of the use of timber footbridges, although the Margaretengürtel design in Vienna was presented (see my previous post for details), and another presentation addressed some of the reasons why timber bridges remain unpopular in the UK. Client inertia appeared to be the deciding factor, although I know from my own experience as a designer that client concerns over vandalism, fire damage and general durability are often hard to refute. Having said that, at one time, the UK was claimed as home to the longest timber arch footbridge in Europe (the Middlewood Way Bridge near Macclesfield, a 50m span built in 1992), although that claim has certainly now been overtaken by bridges over the River Lora, near Florence (72m span) and in Rimini, Italy (92m span).

One aspect of the conference which I thought was quite unfortunate was the separation of most of the footbridge dynamics papers into a separate strand, which meant that those of us interested in more general design case studies or topics probably saw very little about dynamics at all. The ghettoisation of the dynamics specialists did mean that the entirely non-technical could avoid the subject, but runs the risk of re-opening a gulf between academia and practising engineers which had been temporarily narrowed in the post-Millennium Bridge years.

Nonetheless, some of the dynamics presentations which I did see were quite staggeringly esoteric, and it was tempting to wonder to what extent they were researching areas which were likely to have real practical relevance.

One dynamics paper which clearly was highly relevant, was Aleksandar Pavic's keynote Vertical crowd dynamic action on footbridges: Review of design guidelines and their application. Pavic's paper reviews five current published methods of dealing with this problem (see table, left), provides worked example calculations for a simple structure (itself very useful, given the ambiguities present in some of these documents), and observes that they can lead to very different results, with serious implications both for economy of design and the potential for error.

Two of the guidelines, HIVOSS and SETRA, are available online. It's notable that when Eurocodes 0 and 1 were published, a methodology for dynamic analysis of footbridges was conspicuous by its absence, including the load models which had been expected to appear (and which are given in the 2005 fib document Guidelines for the design of footbridges). Some of this is because the state-of-the-art in this area has been a constantly moving target, but I think it's a shame that Eurocratic deadlines for publication of the Eurocodes were allowed to take precedence over the presentation of standards which would assist rather than confuse designers. For anyone who doesn't follow the footbridge dynamics literature, it must be a real struggle working out how to proceed.

I saw two presentations where weathering steel was treated in very different ways. Martin Knight and Simon Fryer presented Combining engineering and aesthetics: The Town Centre Link, London, which must be one of the largest scale footbridges shown, at some 135m long and 12m wide. It's enormous weathering steel Vierendeel trusses (pictured, right) are detailed to avoid water traps, and are protected against the risk of graffiti by their height above the rail station platforms below, and by the use of full-height glazing on their inner face.

In contrast, Xavier Font discussed the lovely Can Gili Footbridge (pictured left), which I have covered on this blog before. Here, the pedestrians are kept away from direct contact with the rusty weathering steel by an internal guardrail. However, the potential for graffiti clearly exists, and I understand graffiti is now present. The absorbent surface patina on weathering steel makes graffiti hard to clean off, and only a fresh blast cleaning can reliably remove it (in the UK, this is covered by Highways Agency standard BD 7/01). In addition to the cost, I guess that will affect the uniformity of colour of the weathering steel patina, which may be undesirable. I greatly admire the appearance of weathering steel bridges, but as with the timber designs already mentioned, clients may have to adopt a more flexible attitude to the issues of durability and vandalism.

I was also impressed by a couple of weathering steel footbridges presented by Mario Guisasola, but would like to prepare a full post on them some day, as they were easily amongst the best designs presented at the conference.

Okay, that's all I have time for now, I will say more on the conference presentations later.

Footbridge 2011

I spent most of last week in Wrocław, Poland, for the Footbridge 2011 conference. It was a wonderful opportunity to meet old friends and make new ones, and made particularly enjoyable by the generous hospitality of our Polish hosts. The 2011 Footbridge Awards were presented at Wrocław's Town Hall, parts of which dating back to the 13th or 14th century. The gala dinner at the Centennial Hall was also hugely enjoyable, although sadly this didn't take place within the Hall's main building, a spectacular reinforced concrete dome spanning 65m (pictured, courtesy m.by).

The conference featured 162 papers from 38 countries, and I was pleasantly surprised at the generally high quality both of the papers and accompanying presentations. There were seven keynote lectures, of which the first three set the agenda for many of the informal discussions that took place throughout the week.

The first of these was Benchmarking cost and value of landmark footbridges, by Brian Duguid. This took the conference's official theme ("Attractive structures at reasonable costs"), and tackled the question of reasonableness in two ways. First, by presenting a survey of about forty recent landmark bridges which suggested an average cost of about €8k per square metre, or €38k per linear metre. More intriguingly, it asked us to consider what value a landmark pedestrian bridge provides to its local community, and whether we could actually calculate it. I suspect that's a tall order, although perhaps worth pursuing in the current climate (which, at least in the UK, has seen landmark footbridge construction hugely diminished). The presentation nearly managed to make cost estimating sound interesting, which is a tough challenge.

This was followed by Cezary Bednarski's The 'Chained' Bridge: Attractive structures at reasonable cost?, which pursued the theme of "reasonableness" from a very different angle. This talk's contention was that designers have an obligation to avoid waste, and that bridge architects tend to produce designs which are both wasteful and irrational when not restrained by chains, particularly the chains imposed by the requirements of sound structural engineering. A number of examples were given, including a footbridge proposed for Krakow which I have covered here previously (pictured below).

Bednarski's outrage both at its structural impudence and its visual impact on a nearby castle was a rare and welcome case of a head being raised above the parapet, although it proved controversial, with one Polish engineer boldly stating his view that the engineer's job was to help realise the architect's vision, a suggestion which didn't even meet with the approval of many of the architects present. The Poles are clearly treating the Krakow bridge as a serious proposal, with the magazine Mosty ("Bridges") devoting six pages of a recent issue to an explanation of the engineering plans, including various technical and construction sequence diagrams (these make clear, incidentally, that it is a twin-cantilever bridge, not an arch).

Jan Biliszczuk and Wojciech Barcik's keynote presented Footbridges in Poland - the history and present state. This made for interesting viewing following on from open criticism of the Krakow bridge (as well as another landmark footbridge Krakow, already completed). Large parts of the presentation suggested that Poland has yet to catch up with the aesthetic sensibilities that most contemporary footbridge designers aspire to.

The Luk Erosa footbridge, pictured, is one of a number of Polish bridges where bold colour seems to be used to divert attention from an unnecessarily gimmicky structural form and, in many cases, an over-reliance on circular steel tubes. Those tubes are everywhere, the styleless stock-in-trade of dozens of footbridges. The colour at Luk Erosa is pretty inoffensive compared to some of the other examples which were presented. I heard one attendee asking whether it was all an exuberant over-reaction to freedom from communism, but there are other countries in Eastern Europe which don't seem to share this affliction.

In fairness, I heard a lot of criticism of Polish designs, but I saw several footbridges which were sensitive and attractive in appearance. In Wrocław itself, there is a simple glulam timber bridge over the town's old moat (pictured above), which sadly I didn't get a chance to visit, and at Sromowce Nizne, there is a 90m span glulam timber cable-stayed design which is both technically adept and charming (pictured below). [Incidentally, following that last link leads to a collection of the papers from Footbridge 2008, and many other conference proceedings in rather blatant breach of copyright].

There were several other papers that I would like to discuss here, although I am currently snowed under with work, so don't expect anything very quickly. I also visited quite a few bridges in Wrocław, and will post photos and commentary on those, again when time permits.

The next Footbridge conference will be in 2014, and it will have a tough job living up to the hospitality, organisation, and delightful setting which Wrocław provided.

Footbridge Awards 2011: Winners

The winners of the Footbridge Awards 2011 were announced at the Footbridge 2011 conference in Wrocław, Poland, on 6th July. The venue was Wrocław Town Hall, and the awards results were dominated by Belgium's Ney and Partners, and Germany's Schlaich Bergermann und Partner (SBP). I will have more to report from the Footbridge conference when I get time.

I've included links if I have previously posted anything substantial on the individual bridge.

Aesthetics short-span

Winner: Castleford Footbridge, England (McDowell & Benedetti / Alan Baxter Associates).
Highly commended: Bracklinn Footbridge, Scotland (Strong Bridges / David Narro Associates); Glass Footbridge, Portugal (SBP / Charles Correa Associates).

Aesthetics medium-span

Winner: Te Rewa Rewa Footbridge, New Zealand (Novare Design).
Highly commended: Lyon Confluence Footbridge, France (RFR); Knokke-Heist Footbridge, Belgium (Ney).

Aesthetics long-span

Winner: Rhein-Herne Canal Footbridge, Germany (SBP).
Highly commended: Collegebrug, Belgium (Ney / Sumproject); Esch-sur-Alzette, Luxembourg (Ney / Metaform Atelier d'Architecture).

Technical short-span

Winner: Stalhillebrug, Belgium (Ney).
Highly commended: Marinic Footbridge, Slovenia (Ponting); Glass Footbridge, Portugal (SBP / Charles Correa Associates).

Technical medium-span

Joint winners: Knokke-Heist Footbridge, Belgium (Ney); Riverside Footbridge, England (Ramboll).
Highly commended: Paloma Footbridge, Spain (Cesma Ingenerios); Tradeston Footbridge, Scotland (Halcrow / Dissing + Weitling).

Technical long-span
Winner: Rhein-Herne Canal Footbridge, Germany (SBP).
Highly commended: Forthside Footbridge, Scotland (Gifford / Wilkinson Eyre); Collegebrug, Belgium (Ney / Sumproject); La Defense Footbridge, France (Dietmar Feichtinger Architectes / SBP).

Where are they now? Part 2

Okay, I've previously provided a catch-up on bridges which I mentioned in 2008 but never really followed up afterwards. This time, I'm moving on to 2009, and there are enough bridges from that year that I will probably split things across more than one post.

River Soar Footbridge

Another RIBA bridge design competition, with a cute little suspension footbridge as the winner in February 2009. As with so many schemes, it was part of a regeneration project. Ownership of the project passed from Leicester Regeneration to Leicester City Council, which I'm told then killed the regeneration scheme the bridge was part of, as a result of budget cuts. The regeneration body was absorbed into Prospect Leicestershire, which I believe is also now being closed. There's no "prospect" of this bridge being resurrected any time soon.

Parrot rating: 'E's not pinin'! 'E's passed on!

Metro West Liffey Bridge

The winners for both River Soar and for the design competition for the Metro West bridge, a light rail structure near Dublin, were announced in February 2009, and were superficially very similar designs, by the same design team, although on very different scales. Metro West is a 25km long rail scheme, one of several projects promoted in the Dublin area by Ireland's Rail Procurement Agency.

The companion Metro North scheme was granted approval to proceed in October 2010, and enabling works were due to commence earlier this year, with a contractor appointed in early 2012.

Metro West is behind that schedule, with its application for permission only submitted in October 2010, and no decision yet made, so far as I can see. The winning bridge is an expensive concept, and in the current climate it's hard not to see that it could fall victim to "value engineering" i.e. cost-cutting.

Parrot rating: He's probably pining for the fjords.

Williamette River Bridge, Portland

I first featured this bridge right at the very end of 2008, and then again in January 2009 in its guise as an innovative "wave" bridge proposed by architect Miguel Rosales. This proposal didn't last long: by March 2009, its excessive cost had seen it ditched, and a hybrid cable-stayed and suspension bridge design come to the fore. That was probably the last time I mentioned the project.

The hybrid option also didn't last long, with the transport authority opting for a conventional cable-stayed bridge in June 2009 (pictured above right). This was always the obvious choice, despite sniping from the sidelines from aesthetes possessed of at best a superficial understanding of bridge design. Construction of the cable-stayed design started on site on 1 July this year, due to complete by 2014.

Parrot rating: Remarkable bird, the Norwegian Blue! Beautiful plumage!

Rijnhavenbrug

The search began for a new opening bridge design in Rotterdam in 2007, with a competition winner announced in December 2008 (I only picked up on it two months later). This was a broadly conventional but not unattractive bascule bridge design, and at the time, they predicted a construction start in 2009, with the bridge open by 2011. So far as I can tell, it's behind schedule, but is actually going ahead, with construction work now commenced in February 2011.

Parrot rating: It nuzzled up to those bars, bent 'em apart with its beak, and VOOM!

Middle Rhine Valley

In April 2009, a winner was announced in the contest for a highway bridge near the Lorelei Rock between Mainz and Koblenz in Germany. The winning design was a pretty unusual venture, with trusses on only one side of the bridge deck, not something I've seen attempted anywhere else on a bridge of this scale or type. The location of the bridge is highly sensitive, being a UNESCO World Heritage Site, and it was unclear how far the scheme would be allowed to proceed. In July 2010, UNESCO finally came to a decision - in favour of the bridge. Campaigners still hope that the bridge will not proceed, but that instead a ferry may be adopted as the preferred option.

Parrot rating: He's not dead, he's, he's restin'!

Foryd Harbour Bridge

A couple of months later, June 2009, another bridge design competition, another winner. This time it was an opening cycle/pedestrian bridge at Rhyl in north Wales, won by a unique drawbridge design with twin fibreglass bridge decks. Planning consent was eventually secured in March this year. The project website states that offsite fabrication is expected to take place during 2011, with a site start next year.

Parrot rating: Oh yes, the, uh, the Norwegian Blue ... What's wrong with it?

Cityplace Footbridge, Toronto

I wrote about this not particularly out of interest in the bridge, but because of a design charrette which was run to try and raise interest in more "architectural" proposals for what was always a difficult structure spanning a number of railway tracks, connecting to the Cityplace residential development. The charrette's website no longer exists, but I featured a number of the designs here, as well as the original warren truss design which inspired the charrette into existence.

The final design (pictured) was made public in April 2010, and is a variation on the original Warren truss design with the trusses curved inwards towards each other - this significantly increases the size required for the truss web members, and hence the overal expense. Construction has commenced, with foundations installed earlier this year, and the bridge due to open by October.

Parrot rating (for the charrette proposals): 'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisible!

Where are they now? Part 1

It occurred to me, as the number of posts on this blog recently passed the 400 mark, that I mention quite a few bridge schemes while they are in the news, and not thereafter. What happened to them? Have they expired and gone to meet their maker, or are they merely pining for the fjords?

So here they are, some of the bridges which blogging forgot. These were all covered here in 2008 - I will try and do a similar exercise for more recent bridges when I get time.

River Douglas Footbridge
This was one of the earliest schemes I covered, a RIBA bridge design contest. A shortlist was announced in August 2008, and a winner in October 2008. Two years ago, in July 2009, I noted that there seemed to be no further progress, which was no surprise as the competition had been run before any funding for a bridge was in place anyway.

The project's website has never been updated, but with the government's decision to abolish the North West Regional Development Agency in September 2010, Lancashire County Council's REMADE programme was also closed. This was the body ultimately promoting the bridge. I believe the replacement organisation is now the Lancashire Economic Partnership, who don't mention the River Douglas scheme on their website. I can't see it being revived in the current economic climate.

Parrot rating: Look, matey, I know a dead parrot when I see one, and I'm looking at one right now.

River Wear Crossing
This was a long time Pontist favourite. My last update was when the design was submitted for Planning Consent in January 2010. Consent was granted in April 2010, although I don't think I ever actually reported the fact. The bridge forms part of the £133m Sunderland Strategic Transport Corridor, and along with other major transport schemes was subject to a government moratorium in late 2010 as part of the comprehensive spending review.

Since then, Sunderland Council have reiterated their interest in proceeding with the scheme, most recently inviting people to an industry "market sounding" day in March this year. The Council has to submit a revised proposal to central government in September 2011, who are then due to decide in December whether the scheme will be funded or not.

Their funding package previously relied on £6m input from the regional development agency, One North East, who are being abolished. Central government were being asked for £98m, with Sunderland contributing £29m. They do say on the new project website that detailed design is complete and "significant cost savings have been identified". However, I can only speculate that if this proceeds, it will be by Sunderland agreeing to dig even deeper into their own pockets, leaving them highly vulnerable to the full impact of any cost over-runs.

Parrot rating: The only reason that it had been sitting on its perch in the first place was that it had been nailed there.

Ballsbridge - Dodder Footbridge

Another bridge design competition, this time run by Ireland's RIAI, and won in September 2008 by a slender girder span designed by Alan Dempsey, of NEX Architecture. The bridge was part of Mountbrook Group's Jurys Berkeley Court Redevelopment. This was refused planning consent in early 2009, with Mountbrook appealing in September 2010, and being turned down again in February this year. I'm amazed the developer persisted that long given the state of the Irish economy.

Parrot rating: This parrot is no more! He has ceased to be!

Dubai Smile

In November 2008, I featured this almost self-consciously wacky proposal to replace Dubai's temporary Floating Bridge built in 2007. Even by Dubai's megalomaniac standards it was an absurd design, and with the bursting of Dubai's economic balloon, the scheme has stalled. In late 2009, it was announced that the Floating Bridge would remain in use until 2014. I can't see this monstrosity getting built any time soon, if ever.

Parrot rating: He's not dead, he's, he's restin'!

New Islington Footbridge

The RIBA design contest here pre-dates this blog, with its winner decided in July 2007. It wasn't an especially expensive component of the wider regeneration scheme at New Islington, Manchester, but four years on there appears to be no movement. One of the funding agencies, New East Manchester, forecast an Autumn 2010 opening date, which came and went. The New Islington website says they are "just waiting for the funding to fall into place."

Parrot rating: No, 'e's stunned! Yeah! You stunned him, just as he was wakin' up!