Bridge competition debris part 14: Thames Water Habitable Bridge

Back in February I featured the various entries to the Peabody Trust Habitable Bridge competition, held in 1995 and involving design of a crossing of the Thames between St Pauls Cathedral and Bankside in London. The idea of "Living Bridges" was very much in the air at the time, with an exhibition at the Centre Pompidou.

Indeed, it's an idea that (despite its many problems) still hasn't gone away, with schemes in Hamburg (pictured, right) and Duisburg, for example, not to mention Zaha Hadid's bridge pavilion in Zaragoza.

The problems of "living bridges" are well illustrated in Amsterdam's Entrepotbrug, built in 1993, a monolithic blot on the landscape that would be far better hidden amongst other buildings than allowed to dominate river views.

In 1996, the Royal Academy held its own exhibition on the subject, documented in the excellent book Living Bridges. In conjunction with the exhibition, they held an invited competition to design a habitable bridge at a different point on the Thames, running between Temple Gardens on the north bank and the LWT building on the south bank.

This competition was essentially speculative: there was no funding to actually build such a bridge. It was an attempt to promote the concept itself, in the hope that publicity might get developers to take forward a scheme. The competition was sponsored by Thames Water. Seven designers were invited to submit ideas.

People attending the exhibition were asked to vote for their favourite designs: I recall voting for the Daniel Libeskind proposal, with its interlinking network of walkways likely to make for a more interesting experience than some of the others. The Zaha Hadid design was somewhat unfathomable in its perspex blockiness, but seemed to offer a compromise between keeping the habitation on the banks (to preserve views) and siting it on the bridge (to provide the over-water experience).

Antoine Grumbach's design sought to preserve views by keeping most of the building off the bridge entirely, essentially just riverside apartments joined to a nice pier. Like Ian Ritchie's minimalist slab, it was a sober effort. By contrast, Branson Coates' phallic alien mothership was amusing but impossible to imagine being built at this site.

Much the same was true of Future Systems' dayglo pod, or Krier Kohl's dark tribute to Crystal-Palace era London. What were they thinking?

Now in 2009, London Mayor Boris Johnson has revived the Grumbach proposal, with an estimated cost of £80m attached. This isn't the first time it has been resurrected - it had the dust briefly shaken off in 2000 as well. It remains extremely unlikely ever to be built.

Essentially, the problem of the habitable bridge is still the impossibility of resolving the visual impact on the riverscape against the need for sufficient accommodation to achieve economic viability. In 2000, English Heritage were scathing about the Grumbach design's impact on river views, describing it as "walling off" the river.

With that in mind, the feasible options are reduced. One is to minimise the accommodation and its height, which limits viability to narrow rivers or locations with cheap land (in which case, why build on the river at all?) The other is to find locations where the views simply don't matter, which means leaving the river behind and building above streets and railways - and who would want to live there?

As a concept, the habitable bridge isn't quite dead, but it's difficult to see many being built in future.

(For those interested, there's more on the "living bridge" subject at A Daily Dose of Architecture, covering designs by Steven Holl and Dan Hisel).

The entries

Ove Arup / Zaha Hadid





Marc Mimram / Antoine Grumbach





Buro Happold / Branson Coates




Techniker / Future Systems




Arup / Krier Kohl





Daniel Libeskind





Ove Arup / Ian Ritchie Architects

Request for bridge competition information

I'm preparing a number of future posts in my ongoing "bridge competition debris" series, but having difficulty finding details of some entrants and their designs.

I'm particularly looking for information on the unsuccessful entries for:

- Gateshead Millennium Bridge
- Stockton-on-Tees North Shore footbridge
- Basildon bridge competition
- St Helier footbridge competition
- London Millennium Bridge

If you can assist, please get in touch via happypontist at googlemail dot com.

Infinity Bridge opens

Today marks the start of a three day "Infinity Festival" in Stockton-on-Tees, with its centrepiece being the official opening of the Infinity Bridge, a spectacular £15m double arch footbridge (pictured right, image copyright Expedition Engineering). Expect fireworks.

Infinity Bridge is 237m long in total, with the two arches being 120m and 60m. It was designed by Expedition Engineering and Spence Associates (not without controversy), and has been built by Balfour Beatty. It was the winning design in a RIBA competition held in 2003, and more recently it won the ICE Robert Stephenson Award. Quite right too - although I've got a few quibbles with it below, it's a distinctive and impressive structure.

It's not difficult to see why this design was a winner. Working on the assumption that what regeneration bodies are really after is a gigantic logo, not a bridge as such, the twin arches lend themselves to this purpose (see also Spence's River Wear design for the same principle). If you go to the Infinity Festival website, you can see the logo that has resulted.

What makes it work as a logo is the sag-curve connecting the two arches, giving the bridge an attractive sinuous quality, looking as if it would rather dance across the river than plunge into it. I've had a problem with that sag ever since I first saw it, as structurally it appears to be doing very little, and actively misleads the viewer as to how the bridge really works. However, in some of the more recent construction photos, the legs of the arch are more prominent visually, and I think you can see it either way, it's a more pleasing detail than I had thought. It also connects the arches such that they stiffen each other, reducing the bending moments in both arches.

I'm less convinced by the river pier, which looks like a set of four paper fans folded and propped against each other. The legs are angled to contain the worst-case arch thrusts, and are also designed to resist ship collision forces. The stepped edges in the pier legs (pictured right, courtesy John Yeadon on Wikipedia) seem fussy and inconsistent with the main arches, although the same detail has been used on the bottom section of the arch to visually separate it from the sag element.

The only other criticism I would offer is the tripodal nature of the split arches, whereby their extreme ends sit on a single point of support, with the river-pier legs offering two supports. From most viewpoints I think it's very elegant (see image on the left, copyright Expedition Engineering), which may owe something to the way the arches have been shaped by form-finding procedures to carry little or no bending under dead loads.

However, it leads to an awkward structural detail, as the arch ties and arch support don't coincide in plan, resulting in a hammerhead detail hidden below the deck to carry the thrust forces. I don't imagine anyone other than an engineer would ever notice, let alone find it unsatisfying. It's not clear what the alternative would have been, as bringing the arch tie directly to the arch springing would be geometrically very difficult.

Noting that the bridge deck is 4m wide between handrails, it has cost about £15,000 per square metre, which is very definitely at the upper end for landmark footbridges (compare Forthside Footbridge, which was similar). This figure seems particularly high when noting that the approach spans are relatively straightforward in structural form i.e. if you looked at the river spans alone, their cost per square metre is actually higher.

In this context, it's perhaps worth noting that back in 2003, Tees Valley Regeneration were seeking a bridge costing a mere £4m to £5m. By any yardstick, a 200% cost over-run is a shocking performance, but there's little doubt that Stockton-on-Tees would have got a considerably less special bridge for the original budget.

Why did the Infinity Bridge cost so much more than anticipated? For one thing, the original budget was clearly out-of-step with the client's aspirations for a major river crossing such as this. Nonetheless, I wonder whether the form of bridge chosen plays a big part.

The bridge is designed as a twin tied-arch, where the arch thrusts are resisted not by the foundations, but by tie cables running at deck level. These are visible in the photo on the right (courtesy John Yeadon), just outside the deck edges (there are "bars" running below the deck, but I assume these are service ducts e.g. for lighting cables). As with any tied arch, the structure as a whole is not stable until both the arch and tie member are complete, and any structure which is not stable until complete normally requires extensive temporary support and/or a more complex construction sequence.

From the construction photo on the left, it's apparent that the ties were installed only after the arches were lifted in, implying that the foundations must be designed to resist thrust from the arches' self-weight in the temporary state. This should not be a huge force, and the erection sequence has at least minimised the need for temporary propping. I am also told that it doesn't govern the river pier design (as this has to cope with ship impact, which is larger).

The tie cables are independent of the deck itself (this is shown in the construction photo on the right, again courtesy John Yeadon, where the cables are temporarily lifted out of the way while deck segments are installed). This will have complicated the erection sequence, but substantially reduces temporary propping requirements, as the foundations don't have to resist temporary arch thrusts relating to the weight of the concrete deck.

Essentially, the tied arch is not the most economic option at this site. A cable-stayed design (which can be built segmentally and is normally stable throughout construction without significant temporary works) would have been cheaper. Buildability should come first in any bridge engineer's thought process, but on the Infinity Bridge it has been more of a case of choosing the bridge's structural and sculptural form, and then working through the challenge of construction in an intelligent manner. That's not necessarily the wrong decision, but it certainly reduces economy, and many of the cleverest bridge designs are those that arise naturally from the imperatives of construction, rather than hinder it.

Having said all that, one thing that most impresses me about the design is the extent to which the designer's original vision has been translated into the final construction. Having seen the tender drawings back in 2006, it's clear that the contractor has made very few changes to Expedition's design. That must be a tribute to the thought given to the buildability of the bridge, some of which is illustrated in the assembly images Expedition produced (see example on the left).

Overall, it's easy to nit-pick, but I think this is a very successful design, with an original aesthetic vision which has been followed through with minimal compromise. Unlike several recent bridge competition winners, the design is led by a clear structural concept, rather than distorted for exaggerated effect.

Photo credits: construction photos from North Shore Footbridge website; visualisations copyright Expedition Engineering; all other photos are credited as appropriate.

Bridges news roundup

Garden link bridge proposed across the Thames
From Kew to Syon in one easy step

Lake Hodges ribbon bridge opens
It's a ribbon bridge, and it's opening. 'Nuff said.

Calatrava arrives in Dublin
Samuel Beckett bridge arrives from Holland

World's first major tensegrity footbridge nears completion
Decking completed on Brisbane's Kurilpa Bridge. Is this the world's most expensive footbridge? A question for another time, I think!

Bridge over troubled waters
SF Examiner discusses the San Francisco Oakland Bay Bridge

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

"Bridge" by Peter Bishop

"Bridge" (ISBN 978 1 86189 346 8, Reaktion Books, 2008) is one of several books in the Objekt series which takes a cultural studies perspective on key products of modern life. The author, Peter Bishop, graduated in 1967 and worked in civil engineering for five years, but is now an associate professor in communication and cultural studies. As such, he offers a perspective unlikely to be familiar to most bridge enthusiasts or designers. (For more on Bishop, there's a short interview at Who Walk in Brooklyn).

This book is not structured in the way that many books about bridges are – by technology, by history, or by geography. Instead it offers more of a meander through the manner in which bridges are represented, encountered or influential upon society. Although occasional attention is given to the designers of bridges, they are largely absent from Bishop’s perspective, which comes instead from the point of view of those who use or are affected by bridges.

Some indication of how much the book meanders might be gained from knowing that the 55-page introduction is longer than any of the four chapters of the book. Bishop wants to consider the idea of the bridge from as many angles as possible, so in the introduction he offers sections on “the bridge as stage and target”, “psycho-philosophical bridges”, “invisible bridges”, and many other sometimes oblique ways in which the topic could be approached. Central to the book is the concept of bridges as stories rather than objects – as Bishop puts it, “telling the bridge”.

Occasionally, this leads him to consider how people from within the bridge design community tell the bridge story. Writing about David Billington’s seminal book The Tower and the Bridge, Bishop describes Billington’s idea of bridge design as “structural art”, but concentrates on Billington’s somewhat dubious contention that:

“lightness, fragility perhaps – closely parallels the essence of free and open society … [the Menai suspension bridge was] the first major work of structural art visually to symbolize, in its thinness, the lightness of the new engineering and the demands of the new politics”.

These multiple perspectives are aimed at the non-specialist reader, but are a particularly valuable antidote to the narratives which dominate writing on bridge design and bridge history. Most non-technical writing on bridge design concentrates on visual aesthetics, often promoting recipes for supposedly objective ideals about the “beauty” of bridges, flogging the dead horse of function begetting form, or poeticising the shaping of a bridge’s structural elements. A surprisingly small proportion of bridge design literature places the end-user or neighbouring community as central.

In the historical field, writing about bridges is frequently dominated by the history of technology – the story of bridge design told as a sequence of inventions, or by the heroic narrative – the tales of the valiant Great Men who designed bridges (almost never the people who built them, maintained them, or had their homes destroyed to make way for them).

Having set himself against these one-dimensional methodologies, Bishop’s polymorphous, diversely-voiced book generally succeeds in offering something fresh, stories about bridges which haven’t been heard too many times before.

The book’s chapters draw on the introductions wide-ranging ideas but distil these into four basic themes: “technologies of extension”, “technologies of assemblage”, “technologies of connection”, and “spanning technologies”. The last of these falls closest to conventional tales of bridge engineering, identifying key structures from the engineering chronology and discussing the tension between innovation and failure which has driven the quest for ever-longer spans. However, even this section moves beyond this to consider the impact of super-spans such as the proposed Straits of Messina and Hong Kong – Zhuhai – Macau crossings, noting their ability to shift the centres of gravity of existing cities and to enable the creation of new mega-conurbations (the Macau project potentially creating a “city” of nearly 50 million people).

A key focus in earlier chapters is on the bridge as a tool in economic and political expansion, as in the controversial Qinghai-Tibet railway project, incorporating over 600 bridges and helping to cement Chinese political and cultural dominance of Tibet. While opposed by many in the West, this project has clear echoes of the westward expansion of American railroads in the mid-nineteenth century – what is seen by pro-Tibetan westerners as authoritarian in China was seen by most as pioneering and adventurous in America, but the urge to cement control of territory and open up new economic opportunities may be the same in both cases.

A similar example is given in the Hindmarsh Island bridge in Australia, promoted by developers as the vital connection to enable new marina development, but opposed by the aboriginal Ngarrindjeri community due to its purported impact on a sacred fertility site. It was opened in 2001 after a long and bitter legal battle. Like the Tibetan railway, it’s a fascinating account of what is often disguised by bland terms like “stakeholder impact”, but bridges aren’t really central to these accounts, which would be little different whether the projects incorporated bridges or did not.

While this is a weakness, other stories in the book do maintain the focus on the issues specific to bridging. For example, the Skye Bridge is offered as a case where the power of a bridge to connect is not always welcomed by people for whom a sense of disconnection is part of their identity. Another interesting illustration is given in the use of bridges in Israel to facilitate social apartheid by carrying strips of Israeli territory above Palestinian land, a poignant reminder that the ability of a bridge to disrupt shared space and eliminate coexistence (normally, of two types of traffic such as road users and boat users) is not always a happy act.

In general, I thought this was an excellent book, consistently thought-provoking and for the most part free of the impenetrable obfuscation and obsessive quoting of post-structuralist masters (Barthes, Baudrillard et al) that mars much “cultural studies” writing. As a bridge designer, I found it a welcome reminder of the need to think beyond the narrow horizons inherent in a specialist’s interests. It emphasised to me that much of what goes unchallenged by bridge engineers is just the result of our immersion in one of many possible stories about bridges and their creation. This book offers some of those diverse narratives, while making clear that many more remain to be told.

Bridges news roundup

Boris living bridge plan savaged by Grauniad
"Most of us would surely prefer to cross a beautiful, open bridge offering fresh air and inspiring views of London" sez critic

Calgary's Calatrava icon to be unveiled soon
No news here yet, really, although nearby heliport may reduce chance for structural acrobatics

Arup, Benthem Crouwel win bridge competition
Rusty new footbridge for Den Bosch

Brunel's Saltash Bridge celebrates 150 years
Although rust and algae draw criticism

Portland's I-5 bridge to be a battle between aesthetics and jobs?
Oregon governor happy to sacrifice aesthetics in drive to create employment?

Samuel Beckett sets sail
New Calatrava bridge leaves Rotterdam on way to Dublin