Merseyside Bridges: 6. Paradise Street Bridge, Liverpool

Wilkinson Eyre built their reputation as specialist bridge design architects with a series of spans where the art of structural engineering was allowed to be the star. The architect's skill lay in pushing the engineering outside its normal comfort zone, in establishing a sense of sublime poise, and in ensuring quality of detailing. Paradise Street Bridge, in Liverpool, represents a major departure from that approach, although not the only such example in their portfolio.

Designed in collaboration with Arup, this £2.4m covered footbridge links a multi-storey car park to a John Lewis department store. The span, approximately 60m, is unusually large for such a structure, although certainly not the longest (the Ney & Partners bridge at Esch-sur-Alzette spans further).

Images of the bridge that I had seen before visiting it were oddly disturbing. The bridge's lack of lateral symmetry appeared forced, with little in the way of obvious logic. From above, a better sense can be obtained of how it works. The bridge kinks to either side of a central axis, but is rotationally symmetrical, with glazing offering views in and out in the areas furthest from the main axis.

A similar sense can be obtained from below. It's more ordered than the crumpled-paper architecture of Frank Gehry, it has more in common with the crystalline geometry of Daniel Libeskind, but it's still more than a little uncomfortable in its disdain for rationalism. While you begin to get a sense of how it works structurally (it's a varying section steel box girder supporting a set of clad and glazed frames), it refuses straightfoward comprehension.

It becomes clear that it's a skewed, distorted cousin of Wilkinson Eyre's earlier Bridge of Aspiration, which introduced the basic idea of a disguised box girder supporting a series of continuously varying frames. It's only when you go inside the bridge that it really starts to make any sense, as it's immediately clear that the outlandish geometry is there simply to obfuscate the possibility of a simple linear crossing, where you can see from one end to the other where you are going, and consequently focus on your destination more than on the journey.

At Paradise Street, there is no clear view from end to end, and instead your attention is drawn to the geometry of the enclosed space, and its relationship to the world beyond. The varying angles of the bridge relative to the sunlight allow the already peculiar geometry to project new patterns against itself, varying with time, season, location and orientation.

As a piece of structural engineering, I hate it - if the relationship between engineer and architect was truly collaborative, that's nowhere made visible. As a way to walk between a multi-storey car park and a department store, it's an interesting and unusual experience.

Further information:

• Google maps / Bing maps (current views pre-date bridge construction)
• Wilkinson Eyre

Merseyside Bridges: 5. Stanley Dock Bascule Bridge, Liverpool

My Merseyside journey continued south from Bootle into the centre of Liverpool. Travelling along Regent Road, I crossed the entrance to Stanley Dock via this bridge. It's of the Scherzer Rolling Lift type, a patented design where the bridge deck rocks back onto a roller girder in order to raise it to allow vessels to pass through. It's a little like a rocking-chair, pulled back by mechanical arms.

I've previously reported on a twin-leaf example of the genre, Queensferry Bridge, although that is no longer able to open. The bridge at Stanley Dock has only recently been refurbished, at the cost of £600,000. It was originally built in 1932, and allowed to run into disrepair by the owners, Peel Ports, leading eventually to its closure in May 2008. In 2010, repairs were carried out, the machine house re-roofed, and everything given a lick of new paint. The work won a Historic Bridge and Infrastructure Award earlier this year.

The rolling girder can be seen in the photo, complete with copious riveted stiffening - the entire bridge sits directly on this when it opens. One advantage of the arrangement is that the centre of gravity changes position with respect to the point of support - the counterbalance can be adjusted to make sure that when closed, the bridge tends to stay open, and when fully open, it tends to stay that way. The photo also illustrates one of the things I like most about bridges of this vintage - you can't escape the visual evidence of its making and assembly. Modern bridge technology tends to erase rather than emphasise this aspect, and such bridges often appear as if wished-into-place without having experienced any birth pains.

The bridge's machine room spans the roadway, and is something of a blot on the landscape, although not without character. I've included a couple of links at the end to websites with photos of the interior.

The bridge isn't unique, even locally, as there's a very similar span, Egerton Bridge, on the other side of the Mersey at Birkenhead, although I didn't get to visit it on this trip. Examples elsewhere in the UK include those at Barrow-in-Furness, Inchinnan, Keadby and Poole.

The bridge sits amidst some spectacular disused dockside structures, most notably the absolutely enormous Stanley Dock Tobacco Warehouse building visible in the final picture. There is still a lot of industry nearby, but much of the area is derelict. It's clearly ripe for some kind of Docklands-style redevelopment, but presumably the money simply isn't there.

Further information:

• Google maps / Bing maps
• moveablebridges.org.uk
• 28dayslater (photos before and during refurbishment, and inside the machinery room)
• Northwest Exploration (photos inside the machinery room after refurbishment)
• MC Construction

Merseyside Bridges: 4. Pennington Road Footbridge, Bootle

Ok, heading south along the coast from Southport, we come to Bootle, at the northern end of Liverpool.

In 2006, RIBA organised a bridge design competition for a replacement of a rather grim pedestrian bridge spanning the Leeds to Liverpool Canal in Bootle. They received 88 entries (some of which I've shown here before), and in early 2007 announced the winning design, from Softroom and Eckersley O'Callaghan.

Out of seven RIBA bridge design competitions that I considered in July 2009, this is the only one which has resulted in a bridge actually being built. Such a rare specimen clearly merits close attention. Several of the RIBA bridges foundered over funding, either because there never was any, or because of unacceptable cost increases. The Pennington Road bridge suffered from the same issue, costing £750k to build against an original budget of £400k. That's a very large sum for what is basically a very short span pedestrian bridge, so someone must have thought it was worth it.

The bridge spans east-west across the canal. At its east end, it ramps straight down to ground level. On the west side, the deck spills you out onto the top of a large mound, which can be descended to the west and south by staircases. Between the staircases, there are a series of switch-back ramps, some of which you can see on the right of the photo (click on any image for a larger version). This is a fairly horrid solution to providing mobility-impaired access, and it's far from clear that there wasn't enough space for a more direct ramp arrangement.

When it was built, the ramps had slopes with planting on them, currently being rebuilt in block-paving, presumably a response to vandalism, although not one that improves the bridge's aesthetic.

The staircases are bordered by timber walls, which give the impression of flowing seamlessly into the timber beams which carry the main bridge deck. The trough-type deck is bounded by two glulam timber beams, but the timber continuing down the ramps and stairs is essentially cosmetic.

These timber parapets support a handrail and also a post-and-wire fence. I'm not sure whether this is to provide a required balustrade height, or just to stop people skateboarding along the top of the parapet beams. I do like the jagged relationship between the handrail and parapet on the staircases.

The floor of the bridge is in timber as well, and I have to say it's great to see timber being used on such an "architectural" bridge. I can imagine there were a few questions asked about durability, resistance to vandalism, and fire risk, but the wood has worn well so far, with very little visible damage (although a number of recessed light fittings have been broken, unsurprisingly).

From underneath, the structural form is perhaps clearer. It's also possible to get an idea of the original, unweathered colour of the wood, which is much warmer in tone. I think this is one aspect of the bridge which is a little unfortunate: wood is often commended for its organic approachability, but as it silvers with age it does lose a lot of what initially makes it attractive. A darker timber may have worked better, as from above, the bridge does now look cold and washed-out.

You can't really tell from the soffit photo, but if you squint at the first photo you can just about see that the main span is simply supported at either end on very small lugs, which project out from the concrete abutments (this is made clearer on some of the images at the Eckersley O'Callaghan website linked below). Initially, this offended my structural engineer's sensibility, that the structural form and the geometric form should be closely partnered - the deck supports break up the sense of visual flow. However, it's a reasonable compromise in achieving the architect's concept, so nothing to worry about.

I was left with a sense of appreciation for the bridge's modesty. It has been built in a slightly run-down area where functionality and robustness are laudable aims, and it rightly avoids a level of flash that would never have suited the site.

Further information:

• Google maps / Bing maps (both sites currently show images pre-dating the construction of the bridge)
• Softroom
• Eckersley O'Callaghan (includes images from design development and construction)
• Wrenco
• RIBA competitions

Prince's Dock Footbridge, Liverpool

I was in Liverpool recently, and visited the Prince's Dock Footbridge (pictured below).


Built in 2001, this was the winning design in a competition run jointly by the Prince's Dock Development Company and the Liverpool Architectural Society. The contest was won by architectural student Eduard Ross, aged 23 at the time, who teamed up with his tutor Ian Wroot and structural engineers Arup to bring the design to fruition.

It's a very unusual, assymetrical design, comprising a steel wishbone arch spanning 30m, supported at one end on curved rib members, T-shaped in cross-section, with a bowstring tie hidden behind perforated cladding panels. The ribs also support the bridge deck. It seems almost impossible to understand how it works just by looking at it, but perhaps the various design details I've included will help (all taken from a 2001 Architects Journal feature).

The arch members are 406mm tubes, with the deck spanning transversely between 168mm tubes. The 2.55m wide deck consists of aluminium planks, and the cladding is powder-coated aluminium. It all looked in good condition when I was there, perhaps it was refurbished when it was recently altered to ensure that boats could pass underneath as part of the Liverpool Canal Link scheme.

There are aspects to the design that I definitely enjoy. The overall structural form, the wishbone arch both hung from and hanging curved ribs is clearly reminiscent of some great cetacean skeleton, although I don't think Prince's Dock was historically home to Liverpool's whalers. I like the opportunities that the assymetrical geometry gives to vary the ribs, it makes the bridge a more dynamic experience, and with a directionality not always found in bridge design.

The bridge only really makes sense as a portal onto the Mersey estuary (shown left). Is the inspiration a whale's rib cage? A mediaeval ogival arch? Or perhaps something more sexual? Whatever, the bridge seems to prefer one-way traffic, with the raised wishbone also providing a clear pointer as to which way to go.

The reverse view is closed down, narrowing, darker (shown below right). It's more a tunnel than a gateway, an effect clearly accentuated by all the cladding panels, perforated or not. I find these odd - they are in no sense functional (neither sheltering against rain nor protecting against wind), but it's hard to imagine that the bridge would look better without them. I think they look pretty good, although as a structural engineer I also think it's a shame that they help to hide how the bridge actually works (by obscuring the arch's bowstring tie).

I'd love to know more about how the design came to be. I'm fairly certain that both structurally and visually, it's unique, and I guess that may have been something to do with the naivety of an architectural student unconstrained by having a structural engineer looking over his shoulder. While that approach quite often leads to poor designs, in this instance I think it has proven a success.

The initial concept has also clearly benefitted from careful detailing, and close attention to the geometrical logic of the structure. The only real oddity is the absence of some of the ribs below deck level at one end. I believe these have been cut off when the bridge was recently modified to allow boats to pass below as part of the Liverpool Canal Link. That's a shame, but the alternative of raising the entire bridge would have required more extensive and hence expensive modifications of the dock banks.

The bridge was clearly built to help facilitate development of the dockside, but from what I could see on my visit, development stalled, with a number of office and hotel buildings completed, and a couple of apartment buildings looking very isolated. One side of the dock is occupied by waste ground in the guise of a surface car park. All this despite being only a few hundred metres from the Royal Liver Building. A bridge like this needs to be the centre of the action, and there was very little of that when I visited.

Further information:

• location on Google Maps
• Architects Journal buildings library
• case study on bridge lighting
• 'A Prince Among Bridges', Liverpool Echo

RIBA bridge design competitions - any better?

Last August, I asked the question: do RIBA bridge design competitions work? At the time, my conclusion was that they offered a mixed bag: out of six competitions I considered, two ended going nowhere; one appeared to be going well; and three were impossible to tell. None of them had actually resulted in a bridge being built, which you might have thought was the aim of the promoters in each case.

One reason for asking the question was that at the time, RIBA-run bridge competitions were proving controversial in the engineering press. This was largely because of RIBA's insistence that entrants to their competitions must include an architect on the team, a ridiculous requirement in the bridge design field (to be clear: architects can help design great bridges; they're just not essential). However, behind the scenes, there was greater discontent, with a number of prominent designers concerned that RIBA (and other) design competitions were producing designs that were structurally bonkers, and expensive to both build and maintain.

Since then, RIBA has agreed with the ICE and IStructE to allow engineers to enter such competitions without an architect (the recent architects-only ideas contest for an inhabited London Bridge notwithstanding), and to include knowledgeable bridge engineers on all bridge design competition juries. So, the question is, have things improved?

I'll cover the same six schemes as last time, to see how they've moved on, plus the one other RIBA bridge competition held since then.

River Wear Crossing

An invitation-only competition was held in 2005, with the winner announced in September of that year as Techniker and Spence Associates (pictured right). Last August, there were moves to secure government funding, but the bridge design itself hadn't been made public. Things moved on rapidly, though. Wraps were taken off the design in September, it was subject to public consultation, and then confirmed as the preferred option, subject to further feasibility study and cost review. Sunderland Council has never made public the losing entries, but I showed two of them here in March.

Since the end of 2008, things have gone quiet, although I understand preparatory work on the Sunderland Strategic Transport Corridor, the grandly named road scheme that the bridge forms part of, is continuing. However, as it stands, Sunderland Council's support for the Techniker design is subject to further assessment of its affordability, and central government have not yet given unconditional agreement to fund the scheme. My own view is that the present cost estimates for the iconic bridge are too low (given its profoundly unusual structural behaviour) and that it will never be built.

Is that the fault of the RIBA competition process?

I think so. The design was chosen on aesthetic merit before it was subject to a technical review by engineers with appropriate expertise, and has been allowed to gather public support before any serious attempt to review its cost or feasibility has been completed. The risks inherent in the design should have been challenged robustly before a winner was chosen.

River Avon Footbridge

No change here: the competition winner (pictured left) was announced in January 2007, and the scheme cancelled in July 2008 due to rising costs. It won't be resurrected. I've covered the losing entries for this one as well.

I don't think the competition process is especially to blame - the winning design (by Schlaich Bergermann and Ian Ritchie) is attractive and the engineering risks should have been low. Lack of strong local commitment to the scheme seems to have been the main problem, although I have to say the increased scheme costs are a puzzle - they don't seem to be merited by such a simple bridge.

Leeds-Liverpool Canal Footbridge

This one was looking good last time around. The competition for a bridge in Bootle was won in February 2007 by Eckersley O'Callaghan and Softroom (pictured right), who went on to secure planning permission by May 2008, despite a near doubling of the project budget. An August 2008 start date was reported, but as far as I can find out, construction has still not started. Competition entries here.

The cost rise here seems largely attributable to the low initial budget of £400k, which is very low for a landmark structure, however short the span. It's not clear at all why this scheme has stopped. I think the competition organisers must take some of the blame - if funding is the issue, as seems most likely, they should be telling promoters upfront when their budgets and aspirations don't match. There's also a need to discourage competitions from being run when funding isn't secure, as the cost to unsuccessful competitors is an unfair burden - people compete in the expectation that the winning bridge will be built. Where that's not the case, prize money should be greater to reflect the greater fee risk.

New Islington Footbridge

Last year, it was too early to tell if this Manchester footbridge would go ahead. A winner, by Michael Hadi Associates and Gollifer Langston (pictured left) had been announced in July 2007. Since then, it became apparent that funding was no longer available to build the winning design (if it ever was). The local regeneration company has had staff budgets slashed, which means they will have little money for the bridge. However, the very latest news is that the design has been submitted for planning consent, and that efforts to secure funding are still ongoing.

As for RIBA's role, I think it's the same as at Bootle - the competition simply shouldn't have gone ahead if there was a high risk that entrants would go unrewarded. Competition entries here.

Sheffield Parkway Footbridge

In January 2008, Norlund Architects and Ramboll Whitbybird won this footbridge contest. Since then, there's been complete silence, although on the Norlund Architects website it says the bridge is due to be built in 2010. I don't really believe that, but let's be kind, give it the benefit of the doubt, and assume this bridge is still undergoing design development. Competition entries here.

River Douglas Footbridge

The proposal to span the River Douglas, near Preston, was always on the optimistic side. It was clear even at the time of the competition that there was no funding in place to actually build the bridge, and that the organisers intended to use the winning design (by Arup and JDA Architects, pictured left) to try and drum up some cash. Quite how many entrants actually realised that is a different matter, as the contest had a ridiculous 110 submissions.

So far as I can tell, the project has yet to secure funding, and once again designers have been very poorly rewarded for a scheme which seems to be going nowhere. I've previously discussed both the shortlisted designs, and shown some of the other unsuccessful entries.

River Soar Footbridge

Here's a case where it really is too soon to judge - the winner (Buro Happold with Explorations Architecture, pictured right) was only announced at the end of February. Other entries here. I don't know whether design is progressing yet, and it would be rather unfair to speculate how well it will go just yet. Compared to other recent RIBA competitions, this one seems to have been run well, with only six firms invited to submit entries, and each of them paid £6,000, which will cover a reasonable proportion of their costs.

So, what are the scores on the doors? I make it: one bridge cancelled for definite (Stratford); three stranded without funds (Bootle, New Islington, River Douglas); one still trying to prove its feasibility (River Wear); and two don't knows / too early to tell (Sheffield, River Soar).

Looked at another way, only three out of the seven have made it as far as planning consent stage (Bootle, New Islington, Stratford). None have made it as far as putting a spade in the ground. By those measures, the RIBA design competition seems a pretty good way to get lots of publicity, but not a great way to actually get a bridge built. To be fair to RIBA, past competitions prior to these seven have not always been so unlucky - they have led to bridges being built (e.g. the Infinity Bridge, although in that case only at a cost three times what was allowed for in the competition). It's also important to understand that the process of getting any bridge built can be subject to lengthy hiatuses and false starts, so some of these bridges may yet get there in the end.

The cost to the bridge design sector of these seven competitions is substantial, and certainly well in excess of £1m. The customers don't seem to worry about that: if you could get dozens of concept designs and still pay peanuts, why wouldn't you? However, the cost to the taxpayer will also be considerable, particularly on schemes like River Wear and Stratford where substantial investment has been made in the designs.

The real question is whether there's a better way to procure a landmark bridge design. Bridges at Stirling, Brisbane and Glasgow have recently been built through the Design-and-Build route, with no evident loss of design quality, and although a risky design was chosen, the Rhyl opening footbridge may well prove to be similarly successful. Other fine bridges have resulted from the promoter going it alone and organising their own competition.

Keys to success? A clear political will, with public support. Funding in place. Inviting a small number of designers and rewarding them sufficiently to spend time optioneering rather than just being obliged to draw up their first idea in order to meet the contest's deadline. Giving engineers a strong role (design-and-build normally forces this to happen, because no sensible contractor will put forward a design they aren't confident they can build for a known sum of money).

There's no reason why all of these can't be in place for a RIBA competition, but the evidence suggests that when any one of them isn't there, the scheme will fail.

Update 15 July 2009: I'm told by Prospect Leicestershire that the next stage of design of River Soar Footbridge is about to start, progressing towards a planning application.

Bridge competition debris part 13: Liverpool Glass Bridge

In January 2004, at the start of Liverpool's Year of Faith, a competition was launched to design a "glass bridge".

The site was the city's Anglican Cathedral, Sir Giles Gilbert Scott's great edifice towering above the edge of St James' Cemetery, a former quarry which had been converted to a burial ground in 1829, and then into a public garden in 1972. In its present form, this artificial canyon acts as a 50-foot deep barrier, preventing access to the Cathedral's south face from nearby Hope Street.

Scott had himself proposed a bridge across the sunken quarry (pictured, right), but this traditionally styled arch viaduct was never started. Construction of the Cathedral had begun in 1904, but it was only formally declared complete in 1978, and the bridge was dropped from the plans as work progressed.

Proposals were again made for a bridge by students at Liverpool University in 1948, and published in the Architectural Review. Their scheme was for a far more modern reinforced concrete arch (pictured, left), but this was somewhat speculative and again, never realised.

The 2004 competition was organised by Dr Robert MacDonald, an architectural lecturer at Liverpool John Moores University. This again was somewhat speculative - there was no funding, and I gather that the Cathedral's support for the proposal was somewhat ambiguous. The hope was that a good idea might attract sufficient funding to become reality, particularly with Liverpool's status as European City of Culture on the horizon in 2008.

The open competition was announced in Building Design magazine, and 23 entries were received. A shortlist was drawn up, and the winner eventually announced in June 2005 as Buro Happold with Hakes Associates. However, the project never did secure funding, and the bridge remains unbuilt.

There are many bridge design competitions which stand on similarly shaky foundations - in recent years, RIBA's River Douglas contest comes to mind as another case where considerable creativity was devoted to a scheme which had no committed funding behind it. Like the RIBA contest, the Liverpool competition attracted a wide variety of entrants, from the seasoned professionals to students, many from people with little understanding of basic structural engineering. Nonetheless, the "glass theme" and the challenging site led to several very interesting designs.

As ever, links are only provided to a competitor if they have a website with more information. Click on the thumbnail images for full-size versions. All images have been provided courtesy of Rob MacDonald but are the copyright of the original competitors. Contestants are invited to get in touch if they want an image removed or can identify the one or two images where I couldn't identify the entrant.

Winner

Buro Happold / Hakes Associates

Shortlisted

Julian Penni


Carl Thompson Associates


WhitbyBird


Ken Martin


DJR Architects

Others

Alison Coleman


"Angel Rising" (designer not known)


Ann Hollingsworth


Architecturem


Studio Bednarski / Jiri Strasky


Ben Batrak


"Bridge of Faith" (designer unknown)


Gang Wu


Dewhurst Macfarlane / Aire Design


Clive Gray


Kieran Hughes


Christian Camcain


Studio BAAD


Simon Hinton


Paul Carr

McChesney Associates / Atelier One

Jamie McShane