Maribor footbridge competition winner announced

I've got a real backlog of posts building up here: lots of things I want to write about, and a couple more posts still to come to finish off my Manchester series. So bear with me, I'm going to have to pick and choose what to cover and when, and some bridge-related news may come pretty late as a result.

Back in November, I mentioned a footbridge design competition being held in the town of Maribor, Slovenia. This is part of a trio of contests seeking enhancements to the townscape in advance of Maribor becoming European Capital of Culture in 2012. I complained at the time that the competition was open only to registered architects, although I believe they did reverse that ruling before entries had to be submitted in February.

Anyway, results have now been announced. It was a popular competition, with 124 entries (even more for their contest for a new art gallery, which garnered 217). Three entrants have been given a share of the prize fund, with two others singled out for honourable mentions. Click on any image for a larger version.

Winner
Burgos & Garrido Arquitectos / Idom (Spain)

This design is a three-span girder bridge, with timber-clad steel edge girders, and arrays of inclined stainless steel tubular piles forming the piers. The spans seem to be sympathetic to the existing three-span arch bridge a short distance away, and it seems a modest but well-detailed proposal.

2nd prize
Viktor Markelj and others (Slovenia)

This is a single span steel box girder arch bridge, with semi-glazed balustrades. Again, it's attractive and almost utopian in its simplicity, although I wonder whether the ground conditions are suitable for an arch of this span, with the foundations illustrated looking somewhat unconvincing.

3rd prize
José María Sánchez García and others (Spain)

I find it hard to believe there weren't more convincing entries than this, a tall, presumably steel, truss structure with walkways on three levels (including high-level links further into town away from the river banks). The illustrations are unconvincing, structurally, and it's hard not to think it spoils the views of the existing bridge.

Honorable mention
Gentiane Desveaux and others (France)

This is a two-span steel space truss supporting an interestingly shaped promenade. I like the organic, flowing form, but the choice of span arrangement seems as arbitrary as the deck geometry.

Honorable mention
Gašper Premože / Andraž Tarman (Slovenia)

So far as I can tell, this is actually a boat platform connected to a control rope, essentially a variant on the traditional idea of a rope ferry. It's always good to see a brief being challenged: is a bridge really the right answer? But it's also hard to see this as the sort of permanent addition to the town that best exploits the opportunity for European funding.

Waiwhakaiho Update

Roughly a year ago, I discussed Novare Design's proposed footbridge in New Zealand. It's a 69m span bridge, part of an extension to New Plymouth's coastal walkway. The steel bowstring arch spans diagonally across the span, resulting in a rather unusual appearance for the structure.

Now, the bridge is getting closer to completion, with the main structure having been installed in mid-February in an operation that must have given a few locals cause to wonder exactly what they were seeing (all photos are courtesy of Novare Design).

The 83m long superstructure was ferried for 1.5km, with the final stage seeing one end sitting on two excavator bases coupled together, and winched across the river.

I think it looks pretty good, and it will be nice to see the finished structure.

Olympic Central Park Footbridge installed

I reported over a year ago on the outcome of a competition for the design of a footbridge for the London 2012 Olympic Park. That was won by Adams Kara Taylor with Heneghan Peng.

Now, the first parts of their unusual bridge design have been installed on site by contractor Lagan Construction.

The design is for three permanent link bridges spanning 36m above Carpenter's Lock. What makes them unusual is that during the Olympics, the spaces between these structures are also filled in, creating a single bridge some 54m wide. Once the circus leaves town, the temporary infill structures are to be removed.

The geometry is such that the two edge bridges have a curved, twisting form. These two structures (each weighing between 40 and 50 tonnes) were erected in early March (see video). Structurally, they are tubular space trusses, sufficiently unbalanced in shape that they need to be temporarily propped until the third link bridge is installed between them (due to take place in April).


They are also clad in mirror-polished 4mm thick stainless steel, the fabrication of which will have been quite a challenge. I guess from below they will give the impression of some kind of giant Anish Kapoor sculptures (see picture). Building magazine has much more information on the difficulties of fabrication and construction.

Manchester Bridges: 12. Mariners Canal

Having got the two more interesting bridges at Salford Quays out of the way, I made the big mistake of venturing further, along a channel called "Mariners Canal".

This channel is a recent construction, opened in July 1989, and links Erie Basin (where the Detroit Bridge sits) with Ontario Basin to its south. To either side of the channel are low-rise residential developments. Both canal basins are used for watersports, so presumably Mariners Canal provides a useful functional link as well as increasing the amount of higher-valued waterside property.

The Canal is crossed by four bridges, three for pedestrians and one carrying the highway. Starting from the north end, the first bridge is a ghastly faux cable-stayed bridge, with masts grossly out of proportion to the bridge and its span. Indeed, the mast and stays are essentially useless, considering that the bridge spans no more than 15m, and probably less than that.

Clearly, they wanted a landmark at the end of the channel, but surely it would have been better to erect a more straightforward structure, and just add a tall sculpture beside it? Or perhaps, a large pike with the head of the designer on top?

As if its general conception were not sufficiently ridiculous, the bridge is further diminished by an ultra-cheap cable anchorage via a joist below the deck, and by bizarre circular plates at the head of each mast.

Heading south, and still in something of a state of shock, I came to the Grain Wharf footbridge. My stomach still felt slightly nauseous, but this bridge began to calm me down. The bridge is "dressed" with non-functional steel plates to look like an arch, although in fact it is a Howe truss design.

I can almost forgive the fake arches because of the effort put in to make the parapets interesting, with parapet infill bars parallel to the truss diagonals rather than in the more normal vertical arrangement. Indeed, it's actually quite an attractive idea.

The next bridge along is a highway bridge, and although rather ugly it is not without its redeeming features. Semi-circular belvederes jut out from the sides of the bridge (not because there is literally any "fair view", of course).

The underside, with its series of fanned ribs, might be thought reminiscent of the great Italian engineer, Pier Luigi Nervi. If you were very, very drunk.

The undercroft to the main bridge deck has a rather startling allure. The circular reinforced concrete support columns should by rights be highly unattractive. However, there's a mysterious, grotto-like quality to this space. I'm sure it is unintentional, but I really enjoyed it (honest, no sarcasm now).

The final of the four bridges along Mariners Canal is simply a repeat of the first, so I skipped past it quickly and took a photo of this nearby bascule bridge (across the entrance to the Ontario Basin) instead. You can see the Lowry Millennium Bridge in the background.

Further information:

• Google maps
• Salford Quays heritage trail (PDF)

Manchester Bridges: 11. Detroit Bridge

From the Lowry Millennium Bridge, it's only a short walk to Detroit Bridge, which spans Erie Basin just off the Manchester Ship Canal.

In its former life, this was a twin-track railway bridge, one of a number of swing bridges spanning across the Manchester Ship Canal. A single-track rail swing bridge at its original site was first built in 1895, but replaced in 1942 by a twin-track version weighing some 300 tonnes, built by Dorman Long.

With the decline of dock industry in Salford, the bridge became redundant in 1981, and was refurbished seven years later and floated to its current location. The refurbishment design was by Arup, and included installation of a hardwood timber deck for use by pedestrians, and the loss of all the mechanical equipment. It's no longer a swing bridge, but is permanently fixed in position.

The bridge is 80m long, 9m wide and over 10m tall above deck level. It's in the form of a balanced cantilever modified Warren truss. I would have thought a Pratt truss would be slightly more efficient for this arrangement, as it would eliminate compression in the diagonals, but this may depend on the balance between dead and live load. In its original swing configuration, the bridge acts as twin cantilevers under dead load, while under live load, the bridge behaves as a two-span continuous beam. The balance between each load determines the most efficient truss arrangement.

The timber decking and paintwork lasted 17 years before £0.5m was spent on refurbishment in 2005. The decking has been replaced with non-slip GRP planks, the bridge repainted, and flush-faced panels added to all the truss web members. These are there to prevent people climbing up onto the top of the truss and diving off, which was reported as a regular problem (although they didn't entirely solve it). The panels have also been treated with anti-climb paint. While the practicalities are unavoidable, they definitely detract from the appearance of the bridge.

It's marvellous to see an old bridge reused and treated so well. The bridge was well-used when I visited and is likely to become more so when the nearby Media City development is complete.

The most interesting feature of the bridge is the installation of an observation deck below its redundant pivot in the middle of the canal basin. This is accessed on curved staircases, and while it hardly offers a useful viewing platform, it does make the bridge experience more interesting.

Further information:

• Google maps (present location)
• Google maps (original location)
• Report on 2005 bridge refurbishment (DOC)
• Salford Quays heritage trail
• Bridges of the Manchester Ship Canal (includes photo in original location)

Knight & Helbig win at Margaretengürtel

A competition to design a 380m long footbridge at Margaretengürtel in Vienna has been won by Knight Architects and Knippers Helbig. The bridge will link recreational parkland to Bruno-Kreitsky Park, carrying pedestrians over a busy highway. The designers beat 36 other entrants [PDF, German], and win a share of a 70,000 euro prize fund.

The design proposes a startling intrusion into the historic Vienna cityscape, with its organic folds and curves oddly reminiscent of a crinkly pringle. It also makes me think of the Termite Pavilion at London Zoo, a sculptural environment built from contoured timber strata.

I’m not entirely sure that I understand the bridge’s structural concept. The larger spans are supported from concrete plinths (resisting highway vehicle impact loads), from which the timber deck appears to grow upwards like a dust cloud. Away from the highway, the supports are extremely slender steel stilts. The deck has a core of layered glulam timber (spruce), which appears to be clad with the contoured outer layer (larch). The timber is reinforced with steel rods inserted between the various layers.

It is intended to be built as a series of pre-assembled sections up to 20m long, stitched together on site. In total, there’s an estimated 960 cubic metres of timber involved. The designers state that the choice of material is far more environmentally friendly than any steel or concrete alternative, and it’s undoubtedly the case that timber is under-exploited as a material for modern bridges. In large part this is due to nervousness on the part of public bodies regarding its long-term durability, and its resistance to vandalism.

The bridge’s S-shaped curvature in plan is complemented by the creation of high, curved edge upstands. These provide a convenient space for bench seating, but have the unfortunate effect of increasing the bridge’s visual mass. They also obscure views off the structure (although they are above the highway so it’s unclear whether the view is of much interest). They also seem to offer a fantastic inclined surface for skateboarders and cyclists to try and negotiate, not unlike the banked surface of a velodrome track.

The parapets appear to be illustrated as simple stainless steel frames with an infill mesh, with a relatively transparent quality allowing the visual focus to remain on the laminated timber. The visualisations suggest a highly unusual structure with the potential to be quite gorgeous if the simple, smooth detailing can be successfully carried through into construction. Timber lends itself to the forming of such irregular surfaces, which would be far less economic in steel or concrete. As a result, the engineering, while clearly unconventional, is probably less forced in service of the architectural concept than is the case for much other modern blobitechture.

2nd prize in the contest was awarded to Luggin with Martin Kohlbauer (see Luggin website for images). 3rd place was taken by PCD ZT with Zeininger Architects (see Competitionline for images).

Updated 29 March: details of prize money corrected.

RFR/Halsall win St Patrick's Island contest

A winner has been announced in Calgary's St Patrick's Island footbridge design competition. The Calgary Municipal Land Corporation have chosen an elegant design by RFR and Halsall Associates Limited for this CAN$25m footbridge, which replaces an ageing suspension bridge link across the Bow River.

The contest was in marked contrast to the direct appointment of Santiago Calatrava for Calgary's other new iconic footbridge. It was open to any interested participants, there was plenty of public involvement, and the process for selection of a winner was relatively transparent. Given the criticism that Calatrava's appointment drew, no doubt CMLC are happy that Halsall, a Canadian firm with an office in Calgary, were part of the winning team (I predicted at the outset of this contest that two of the three shortlisted firms would feature locals, pretty much correctly).

The RFR design was the one I tilted towards out of the three finalists, and it's gratifying to see an honest, engineering-led but architecturally-refined design turn out the winner. The design has seen considerable modification since the initial entries, but it has retained its simplicity and delicacy throughout.

Related posts:

• St Patrick's Bridge - the final designs
• Calgary's bridges a-go-go
• St Patrick's Island Bridge Competition entries: Part 1
• St Patrick's Island Bridge Competition entries: Part 2
• St Patrick's Island Bridge Competition entries: Part 3
• St Patrick's Island Bridge Competition entries: Part 4
• St Patrick's Island Bridge Competition entries: Part 5
• How to win a bridge design competition
• St Patrick's Bridge design competition announced