Winner announced for Hamburg Southern Elbe crossing

A winner has been announced for the bridge design competition to design a new highway bridge across the Elbe near Hamburg. The bridge will connect the A1 and A7 highways, and is approximately 535m long, with a main span of 350m. The winning entry was selected from 12 competition entrants.

Winner: Schlaich Bergermann und Partner / Dissing + Weitling / WTM Engineers

Centrally located mono-tower cable-stay bridges seem to in fashion. The winning design in Hamburg is on a much smaller scale but bears a certain family resemblance to Hong Kong's Stonecutters Bridge, which is probably no surprise given the involvement of architects Dissing + Weitling in both designs.

Both bridges have twin planes of cables supported from two main towers (140m tall in Hamburg). These carry the inner edge of twin decks, which are connected ladder-like by a series of cross-girders. Both bridges have towers which flare below deck level and which are essentially prismatic for most of their above-deck height. This is a decision which is driven by the geometric requirements of the cable anchorages, to avoid unsightly cable attachments outside the tower envelope.

Below the lowest cable, the tower splits in two, with a similar twin-leg arrangement below deck, echoing the Millau Viaduct, another bridge which follows the mono-tower fashion. The same fashion has taken over in the UK, with Mersey Gateway and the Forth Replacement Crossing both taking the same approach. The reason, I believe, is visual legibility, with the single row of pylons and single plane of cables creating a far clearer silhouette than is achieved with more traditional twin-pylon and portal-frame pylon designs (UK examples include the Kessock Bridge, Second Severn Crossing and Dartford Crossing).

I don't know enough about these designs to comment on the economics - it seems to me that the greater torsional stiffness required in the deck for the mono-tower design, plus the much greater cross-section of the tower itself, will make it more expensive overall, even if the number of foundations and towers is reduced. The Southern Elbe crossing design is certainly reasonably elegant overall, although the second image shows how perspective can lead to a certain awkwardness when horizontal and vertical curvature is combined.

2nd place: Kinkel + Partner / Ges Consulting Engineers

The second placed design strikes me as quintessentially German, although the simple harp-type cable arrays here are those better known from Düsseldorf than from Hamburg. It always seems the most visually elegant arrangement, although rarely if ever the most economic, as the forces in both the deck and tower are greater than for the fan-type arrangement chosen by the winning entry. In the second-placed design, this is doubly true, given the wide spacing of the cables.

Indeed, it's hard to see how this bridge could be built economically. With a large number of cables, individual deck units can be relatively short, and hence straightforward to assemble in place as the bridge deck is progressively cantilevered out from the towers. Assuming the second-placed design has the same span as the winner, each deck segment is up to 40m long between cables, requiring both larger plant for erection and also potentially considerable temporary works to stabilise the main towers against out-of-balance bending.

3rd place: Ponting

Slovenian designers Ponting depart from the symmetrical two-span cable-stay solution with this asymmetric arrangement. Similar to the winning design, the main span is 355m, but with only one main tower, the masts have to be 200m tall to support the deck. It's not clear to me why such an arrangement would be preferred, and building inclined masts of such height requires some justification. I am not sure that the response of the cables to the deck curvature, or the desire to add transverse stability to what is already quite a wide deck, are sufficient.

There seems to be me an element of trying too hard to stand out, which is a frequent problem in bridge design competitions, and one which was also very much true in the Stonecutters Bridge contest some years ago. Ponting's website has several more images not shown here, plus a video.

Foryd Harbour Bridge - an update

It's often the case that I report on interesting bridge projects but then never follow up on their progress. One such case is the Foryd Harbour Bridge, being built in Rhyl, in north Wales.

In June 2009 I reported the announcement of a winner in the Foryd Harbour bridge design competition, an unusual twin-bascule "drawbridge" type structure, designed by Gifford (now part of Ramboll) and to be built by Dawnus Construction. I also provided a few details of how the £4m design was proposed to work, including its low-maintenance GRP decks, and showed some of the unsuccessful design competition entries.

It took until March 2011 for the design to secure planning consent, and at the time it was stated that off-site fabrication would take place during 2011, with a site start in 2012.

Now the project seems to be making much better progress. According to the offical project website, the first of the two decks was delivered to site on 20th March 2013, with the second arriving just a few days ago, on 8th May. Delivery of the bridge mast is scheduled for 29th May, with the bridge decks craned into place at the beginning of June. I haven't seen any date announced for completing the bridge and opening to the public.

Isle of Wight based AM Structures, who fabricated the complex fibre-reinforced plastic decks, have a few images from the fabrication phase on their website. They make it immediately apparent that this is an exceptionally bold project, a real step forward in FRP bridge design and manufacture.

There are also some photos to be found on Facebook of the construction site, showing the bridge pier, abutment, and the first of the decks. However, for the best visual update on works, here's a YouTube video taken from a remote-controlled aerial camera, after the first deck unit had arrived on site.

Katehaki Bridge, Athens

Late in 2012, I visited Athens, not a city generally noted for its bridges. However, I did get time to visit perhaps its most striking contemporary design, Santiago Calatrava's pedestrian bridge at Katehaki. This 94m long, 50m tall bridge was built in 2004 as an offshoot of Calatrava's other activities in Greece, designing the Athens Olympic stadium.

I had seen photos of the bridge beforehand, and like many of Calatrava's recent bridge designs, felt it was an example of a tendency to take things to extremes, unnecessarily so.

What makes this bridge seem so preposterous is the treatment of the cable-stay back span. In an asymmetric cable-stay bridge, where the main span is longer than the back-span, the back-span cables are generally anchored to the ground to provide the necessary stability. In most such bridges, the back-span cables are angled so that they provide a horizontal force, helping the bridge's mast to resist the horizontal pull from the main-span cables.

On the Katehaki Bridge, the back-span cables are instead vertical, resisting none of the sideways pull from the main span. Instead, that pull is resisted through the curvature of the pylon, as a compressive thrust. The curvature is a rational choice rather than simply a sculptural affectation - the pylon can be thought of as a uniformly loaded arch turned on its side, with the thrust at either end of the arch restrained either by the ground support or by the vertical back-span ties. The pylon is therefore essentially funicular in its form - its geometry responds directly to the forces applied to it.

As with many of Calatrava's bridges, the pylon form is well-sculpted, and the recessed cable anchorages are, in my view, visually a very successful detail. At its base, the pylon comes to a perfect point, with the weight of the entire bridge carried onto a support pedestal through a simple steel plate pivot, which cannot be more than an inch or two thick. The photo (right) shows this detail, and also shows the challenge to the bridge's fabricators of achieving Calatrava's continuous, curved forms - it's essentially impossible without fabrication tolerances making the welded plate joints more visible than would be desirable. The bridge was built by the Greek contractor Metka.

Katehaki Bridge was to be something of a prototype for Calatrava's much larger Puente de l'Assut de l'Or, in Valencia, a 180m long, 125m tall cable-stayed bridge of the same overall form. In both bridges, the pylon is offset to one side of the deck, an arrangement that Calatrava is inordinately fond of and which allows the sculptural nature of his structures to be expressed with great visual clarity. The penalty is that both pylon and deck are subject to significant lateral and torsional forces, adding considerably to the overall cost.

At Katehaki, the tendency of the deck to twist is addressed by building a steel box girder along one edge, incorporated into the parapet height so as to reduce its overall visual impact. The cable stay anchors are on the inside face of this box, which helps to counteract the tendency to twist.

The opposite edge of the deck supports an open post-and-rail parapet, an arrangement which can be used to strong visual effect where there is a desire to orient bridge users towards certain viewpoints. That doesn't seem to be the case here - it's simply an artefact of the prior design decisions.

The decking is formed in short timber planks, all lined up neatly rather than staggered. These are supported on steel ribs, and the whole deck is cross-braced to provide in-plane stiffness. The underside of the deck is given a somewhat scabby appearance by the deteriorating finish of the wood planks, although the top-side still looks very good.

There is some nice detailing at the end of the bridge away from the mast, where a triangular frame supports the bridge deck (I confess, I didn't take any note as to how the bridge may cope with thermal movement). The adjacent lift shaft and staircase structure has an attractive white terrazzo finish.

On the whole, the bridge does not feel out-of-scale to the task which it accomplishes, spanning a highway tunnel and two adjacent two-lane carriageways. It certainly makes crossing a busy traffic junction easier, as I found when having to cross other parts of the junction to take some of these photos.

Although the shape and height of the mast announces clearly the very conscious creation of a landmark (the bridge is unmissable on a car journey into the city centre from Athens airport), the more intimate features of the bridge have generally been detailed with care, and it's pleasant to walk across.

Perhaps the only thing that I find odd, and this is as a northern European visiting a southern European country, are the open-air escalators which provide access at both ends of the bridge. It's impossible to imagine such exposed machinery lasting long in a northern climate, although here they are simply an extension of the adjacent subway station, which is also entered via exposed escalators.

Overall, I very much enjoyed visiting this bridge, it strikes me as a very successful design (at least visually - it cannot have been particularly cost-effective).

Further information:

• Google maps / Bing maps
• Structurae
• Athens Today
• 360 Cities
• Masterpieces: Bridge Architecture + Design (van Uffelen, 2009)

Bridges news roundup

Wow, has it really been over a month since I last posted? Life remains very busy, so even putting together a simple blog post on a bridge I visited six months ago is proving difficult. Until that happens, here are a few news items:

A Wavy, LEGO-Inspired Concept For A Public Footbridge
"Those who use the Footstep Bridge, experience a new way of crossing over a road, river, etc." Yes, a really tedious, annoying way.

The tabikappa blog has, as always, several rather excellent Japanese footbridges to showcase, of which my favourites are one, two, and three.

IABSE Workshop: Guidelines for Design Competitions for Bridges
The international guidelines receive a UK launch at the IStructE on 21st June. The Happy Pontist plans to be there and will report here afterwards.

New Bridge in Gothenburg, Sweden
Only just over a week to go for anyone wanting to prequalify for this highway bridge design competition. You can download information from the official competition web page.

Sneak peek at new footbridge proposals
Images of a proposed swing footbridge at Deptford Creek, London.

Sculptural London lift bridge secures planning permission
Very unusual bascule footbridge at Paddington, London (pictured), takes a step closer to becoming reality.

Boston bridge will benefit whole of Lincolnshire
A somewhat bold claim for a little footbridge, due to be built this summer.

YouTube has three short films about Copenhagen's Inderhavnsbroen, the "kissing bridge" currently under construction, interviewing designers Ian Firth and Cezary Bednarski. One, two and three.

London Bridges: 30. Olympic Park Footbridge

London’s Olympic Park is home to a number of interesting bridges. Several were not easily accessible to the general public when the Olympics were in progress, but hopefully will become so once the Park’s redevelopment is complete.

I’ve previously covered one which was very accessible, the Stratford Town Centre link bridge. I’ve also discussed the results of the design competition which was held for the Park’s centrepiece bridge, a super-wide structure which had to accommodate massive crowds during the games. It was a difficult challenge, as the same bridge had to be easily modified to suit the smaller number of users of the park after the games had ended. The contest attracted several high-profile designers, and the visualisations of the winning design (like the one shown here on the right) made it look like an excellent choice.

I visited this bridge during the Paralympics in 2012, and found it hugely disappointing. From above, you would barely know that a bridge existed at all, it is so wide (55m), something that readily illustrates how misleading the birds-eye views used in visualisations can be (see image, left). That’s not necessarily a bad thing in its own right, but it made me wonder how necessary the design competition really was.

From below, the bridge was a mess. In its post-games configuration, a large area of central temporary decking will be removed, leaving two separate 26m long walkways. Each of these will be a sleek form in stainless steel, slightly amorphous in a Terminator 2 style. In practice, the stainless steel cladding is not quite as regular as it needs to be to deliver this vision, nor as clean. It looks like what it is – a conventional bridge wrapped in cladding, and it’s a let-down.

The temporary decking provided welcome shelter from the rain to several visitors while I was there, but is ugly and oppressive. It’s a shame that a little more money wasn’t found to cover over the underside.

In combination with the evident cheapness of the gabion-basket walls at either end of the bridge, the overall impression is dismal. The design competition delivered a bridge which fulfils its carrying function well, but is visually unprepossessing. It will be interesting to see, if and when the temporary infill deck is ever removed, whether the twin-walkway arrangement is more successful.

There seems some doubt as to when the temporary deck will actually be removed. The original intention was for it to be taken out this year, as part of the general Olympic Park transformation following completion of the games. However, a report in the Architects Journal suggests it will stay in place at least until the World Athletics Championships in 2017.

Further information:

• Google maps / Bing maps
• Heneghan Peng
• Heneghan Peng Architects to design Olympic Park Footbridge for 2012
• Detail Online

Bridges news roundup

Deptford Creek - a tale of two footbridges
Two footbridge proposals in London. The tilt-and-twist one seems unlikely ever to be built.

Two fine blog entries from my favourite Japanese bridge blog:
Parapets? Who needs 'em?
Some lovely stepping stones

Three accolades awarded for Wilkinson Eyre-designed Peace Bridge in one week
And they won't be the last, surely.

Making peace with the bridge: Calgary's most controversial span is winning over its critics
A year after opening, Calgarians are better reconciled to that other Peace Bridge, the Calatrava one.

The Mystery of the Missing Suspension Bridges of Paris

It's not really a mystery of course, but this blog features some great images of historic suspension bridges in Paris, and tells a good story. Suspension bridge construction took a nose-dive throughout France following the 1850 collapse of Chaley and Bordillon's Basse-Chaîne Bridge, attributed to corrosion in the main cable anchorages, and a tale with resonance for modern engineers (e.g. the 1990s moratorium on post-tensioned bridges in Britain).

Flood-hit iconic bridge is restored to its full glory
The ancient Tarr Steps rebuilt for less than £10,000. A bargain by any measure.

'A bridge too low': Chinese town planners build flyover that pedestrians have to duck to walk beneath
Built with a headroom of only 1.3m, there are some great pictures here. The Daily Mail is fast becoming the go-to destination for lovers of exotic bridge news.

Inca jewellery and Peruvian minery-inspired bridge in development by OOIIO Architecture
New bridge in Lima is to be a cross between a starfish and a piñata. Hopefully it will survive a good poke with a sharp stick, although the images don't fill me with confidence.

Twin Sails bridge shortlisted for architectural award
"A bridge that is called a Twin Sales Bridge and when it blows a gale of wind has problems because the sails cannot cope with the wind force. How on earth they can recommend that for an architectural award is beyond me", says grumpy old man.

£30m footbridge design competition, Chelsea / Nine Elms, London

There hasn't been a major bridge design competition in the UK for a good while now, so last week's announcement of a contest to design a £30m pedestrian crossing of London's River Thames will likely have seen a mass stampede of the country's bridge design teams rushing to line up partnerships in readiness.

 

The bridge is a proposal by the Nine Elms Partnership, to connect the Nine Elms area south of the river with Pimlico on the north bank. The Nine Elms area is scheduled for major redevelopment, and a new footbridge would cut nearly a mile off the route via the nearest existing foot crossing, Vauxhall Bridge, which lies to the east. To the west, the nearest crossing is Chelsea Bridge. In addition to the bridge's other benefits, it will allow the occupants of the new American embassy at Nine Elms to minimise the amount of time they actually have to spend south of the river, a miserable happenstance notoriously bemoaned by London's cab drivers.

At this stage, little is known of the scheme other than the headline budget (one presumably set simply by taking the cost of London's £23m Millennium Bridge and adding on a few bob for inflation), the likely bridge alignment, and that the contest will be properly launched in late 2013. The scheme is being promoted by Wandsworth Council and presumably their fellow members of the Nine Elms Partnership. There are a few initial images available in a planning document, which I've pilfered for this post (click any image to see it full size).

The naysayers have already planted a stake in the ground. Last August, London's Evening Standard newspaper managed to dredge up at least two locals who would offer a quote opposing the plans.

This isn't the only current scheme for a new footbridge in this corner of London. Roughly two miles further west, there is a proposal for a £22m span, connecting Chelsea Harbour on the north bank to Lombard Road on the south bank, close to Cremorne Railway Bridge. Images of this proposal were made available in November last year (see video below), and it has been submitted for planning consent by designers One-World Design (Expedition Engineering helped develop the proposals). The planning committee is due to consider it in April.

This one has no funding in place and has been dreamed up by the designer rather than the local authority. They hope to find a private sponsor to pay for it. A bridge had been considered at the same site in 2003/4 to offer a good ratio of benefit to cost, but had failed to progress then due to lack of funding. I predict a similar fate this time around.