18 January 2015

Irish Bridges: 1. Ha'penny Bridge, Dublin

I had a flying visit to Dublin late last year, and have three bridges to cover here on the blog, all of them spanning the River Liffey.

The first, variously known as Liffey Bridge, the Metal Bridge, or the Halfpenny / Ha'penny Bridge, was built in 1816, Ireland's first iron bridge. It was imported from the Coalbrookdale foundry in Shropshire, England, and comprises a cast iron arch spanning 43m. When first built, a half-penny toll was charged to bridge users.

The bridge was extensively refurbished in 2001, but so far as I could tell on my visit, the bridge appears to have been very little altered.

I think this is a bridge which has aged well. The shallowness of the arch is bold and attractive, as is its shaping, with the slender crown and stout abutments. The pattern of the arch ribs seems more open and appealing than the criss-cross arch webs used on many other bridges of the time, and closely echoes Cantlop Bridge, built in England three years previously, and which was possibly designed by Thomas Telford.

I like the "two-layered" parapets, but the overhead ornamental lighting brackets are not to my taste.

Further information:

17 January 2015

London's Garden Bridge: to build, or not to build?

There's an excellent post about the London Garden Bridge on the Being Brunel blog, titled "Why do we hate the Garden Bridge?". I don't think the author has covered all the bases, and he seems far too well disposed to the possibility that this unspoiled spot on the Thames could reasonably be home to a private garden. However, it's well worth reading.

I've discussed the scheme here before a few times - I think its failings are primarily political rather than in the detail of its design.

I'm interested in what others think: should the Garden Bridge be built? Will it get built? Please feel free to post in the comments.

If the Garden Bridge is not built, what else could usefully be done with the money?

For a start Wandsworth Council are planning a far more practical bridge between Pimlico and Nine Elms which is not yet fully funded. Various ideas for bridges over the Thames in East London also remain overwhelmingly popular with the public.

My reader (and author of an excellent encyclopaedia) David McFetrich posted in the comments to my last post with the following suggestion:
"If there is money available for a new 'fun' bridge in London, instead of the Garden Bridge (with its problems of high cost, impact on Thames views and questionable infrastructural benefit) why not build a replica of the medieval London Bridge? Since this could be built on dry land across a site that later became an artificial lake, it would be far cheaper to build, and it would generate its own income by letting out the shop space either side of the roadway and from entrance fees paid by visitors. The lake could even be surrounded by gardens. The main problem would be to find a sufficiently large space in a readily accessible part of London. Is there room at the new park where the Olympics were held?"
Now there's a question, which chimes well with Being Brunel's view that the proposal has merits as a garden, just not with public money or necessarily at its proposed site. Again, I'd be interested in comments - what do you think would make a sensible bridge-related alternative to the Garden Bridge?

I quite like the idea of a replica Old London Bridge, although I'm pretty sure there's no space at the former Olympic Park and there's an element of kitsch to it. It could be built for far less than the Garden Bridge, and raise rather than waste money by providing lettable space.

02 January 2015

"Trutg dil Flem: Seven Bridges by Jürg Conzett" by Wilfried Dechau

There can be few contemporary bridge engineers who have been as well-celebrated in photographic coffee table tomes as the Swiss designer Jürg Conzett. Indeed, the only competitor in this arena is Santiago Calatrava, who is as inappropriate a comparator as could be found.

I think Trutg dil Flem: Seven Bridges by Jürg Conzett (Scheidegger and Spiess, 2014, 192pp) [amazon.co.uk] is the third book by photographer Wilfried Dechau to depict Conzett's bridges and the landscape in which they are set. I've previously reviewed Traversinersteg and Dorfbrücke Vals, both of which are excellent.

The Trutg dil Flem is a riverside pathway, along the River Flem north of Flims in south-eastern Switzerland. The pathway is a recent project, connecting up isolated and barely-walkable sections of path. This is only possible thanks to the construction of seven new pedestrian bridges, all designed by Jürg Conzett.

These are not especially spectacular structures, ranging in length from two to eighteen metres. They are only for use by visitors on foot, with the narrowest bridge being a mere 0.7m in width. Nor do they all exhibit the innovation for which Conzett is best known. Most are simple timber beam bridges, highly economic and suitable for the context, and in no way of particular architectural or engineering interest. They enable visitors to cross the stream, and also provide vantage points from which the surroundings can be better seen.

There are three bridges of greater interest. One is a tiny oval slab, with a bare handrail on one side only, originally conceived as a stone slab but built in concrete. It's so short as to barely be a bridge at all.

A second is a simple reinforced concrete beam, spanning 3.8m. The balustrades have cranked posts, projecting horizontally from the sides of the beam, then cranking vertically. This makes the concrete appear little more than a plank, and it looks great. It's also interesting how the balustrades continue off the bridge onto the approach staircases, which rise up the side slopes away from the bridge.

The third bridge is a very slender stone arch, almost a mirror image of Conzett's famous Punt da Suransuns. This was originally proposed as an 11m span, and drawn up as an arch of varying depth, thicker at the ends. The version eventually built spans 18m, and is equally slender over its entire length. This is made possible by using the lower rail of the stainless steel balustrade as a prestressing ribbon, pre-compressing the arch and enhancing its resistance to buckling failure. It's a marvellously ingenious solution, tremendously clever engineering in the service of minimalist beauty.

The book features a number of useful, if short, essays, in both German and English, including one by Conzett on the design of the arch bridge. His beautiful original drawings for each bridge are also included.

The bulk of the volume is taken up by Dechau's photographs, in two sections. The first documents the Trutg dil Flem and the completed bridges, giving priority to the landscape itself. It would clearly be a very attractive place to visit, and it's also clear that the bridges enhance the landscape, and are appropriate rather than showy.

The second section documents the construction of the bridges, and focuses as much on the builders as what was built. I found these a real pleasure to examine.

As with previous Dechau / Conzett books, Trutg dil Flem has been produced to a very high standard, it's a gorgeous book which well befits its subject.

See also:

28 December 2014

"Footbridges: Small is Beautiful" (ed. Gorazd Humar)

There are a surprising number of books devoted just to the subject of pedestrian bridges. I've previously reviewed Footbridges and The World of Footbridges, as well as the design guide Pedestrian Bridges.

"Footbridges: Small is Beautiful" (ECCE, 414pp, 2014) is a valuable addition to this particular bookshelf. It has been produced by the European Council of Civil Engineers, an umbrella body for various national groups such as the UK's Institution of Civil Engineers. It surveys nearly 200 pedestrian bridges, with over 600 photographs, covering most of Europe as well as a bonus selection from Japan.

The bridges are both ancient and modern and have been chosen for their technical, architectural or historic interest. The book is selective rather than comprehensive: for example, the eleven footbridges from the UK represent only a fraction of this country's excellent bridge heritage. Some countries are under-represented (such as Ireland, with only a single bridge included), while others are conspicuous by their absence, such as Belgium, the Netherlands, and all of Scandinavia. None of that matters given how much other interesting material the book includes.

Each chapter has a different author, and the book has been compiled rather than edited in the proper sense. Either the various writers were given different briefs, or they have disregarded them. The result is a book which is uneven in terms of depth of detail, reasons for selection of bridges, and also stylistically. Examples include the Czech Republic's chapter, which might lead the unsuspecting reader to believe that the only designer working in the country is Jiří Stráský, and article lengths which vary from the epic to the abbreviated.

Nonetheless, I found it a hugely impressive and enjoyable book. There are numerous high quality photographs, some reproduced over single and double-page spreads, and colour on every page. To get a book of this size and quality for only €29.90 (plus shipping costs) is quite amazing (order direct from ECCE).

The book opens with a lengthy chapter on the history of bridge structures, by the editor Gorazd Humar. This is useful, informative and well-illustrated. It's also idiosyncratic, with a quantity of material on Venetian bridges that goes well beyond their actual historical significance, and not one but several sections on the development of hinges in bridge structures.

The body of the book covers some 24 countries, and some truly fantastic bridges. There are some duds, but they are distinctly in the minority. Many of the photos are of exceptional quality, and really made me want to add a few new destinations to my future travel plans. Any pontist will find dozens of bridges which are new to them. The accompanying texts are for the most part aimed at the general reader, rather than at engineers or other specialists, although to be honest the book is well worth getting just for the photographs even if you don't have time to read the text.

26 December 2014

Nine Elms Bridge Design Competition

A new bridge design competition has recently been launched, for a £40m pedestrian and cycle bridge across the River Thames at Nine Elms in London. The new bridge would link Pimlico on the north bank of the river with Nine Elms on the south bank, soon to be home to the new US Embassy, as well as various other developments.

The competition website describes a three-stage process. Design teams are first requested to jump through a pre-qualification hoop, via the local authority's procurement website, presumably to weed out the chancers, no-hopers and ne'er-do-wells. There's no limit to the number of teams which then proceed to the second stage, submission of preliminary designs.

Competitors are asked to respond to five specific challenges, all of which are well chosen and show that the promoting authority, Wandsworth Council, has given serious thought to the project. The challenges include how to accommodate pedestrian and cycle traffic while providing a happy experience for both, how to achieve sufficient navigational clearance over the river while avoiding lengthy approach ramps, and how to tie the bridge in effectively to the public realm at either end.

Some of the stated aspirations for the bridge are at odds with each other. Take, for example, the first two:
  • Be innovative and memorable and challenging previous interpretations of bridge design
  • Be of an appropriate design
Is it right that an appropriate design is one which "challenges previous interpretations" of bridge design? Not only must the cake be had, it must also be eaten, apparently. An interpretation-challenging cake, innovatively made from snake's eggs and hyperflour, perhaps. That would certainly be memorable.

Entries will be judged by a jury panel featuring, amongst others, engineer Henry Bardsley, who has been involved in a few innovative bridges in his time, and architect Graham Stirk, whose practice was responsible for the Neptune's Way bridge debacle in Glasgow.

The contest does not seem to be anonymous, raising the prospect that the jury or promoter may be influenced by the names attached to entries: the desire to be associated with the Fosters and Hadids of the world rather than the Bloggs or Joneses. The promoters are open about the fact that they are not just looking for a design, but for a design team who are creative, can communicate, and have the capacity to deliver a complex and challenging project.

Following evaluation of the second stage entries, three or four teams will be selected to proceed to the final stage, developing their proposals in closer consultation with stakeholder and community groups, and each receiving a £12,000 honorarium, which is better than a slap in the face with the proverbial wet kipper, but hardly sufficient recompense for the hard work likely to be involved.

This will be an interesting competition to watch: it should attract many enthusiastic entrants, some prominent designers, and the very real difficulties of the site should lead to a number of interesting responses.

22 December 2014

London's Garden Bridge: grumbling rumbles on, but here's a wrinkle

With the utterly unsurprising announcement that London's Mayor, Boris Johnson, has given the go-ahead to the Garden Bridge project, it's perhaps worth taking stock.

I commented on this fiasco-in-the-making last month, noting that its progress now seemed unstoppable, short of the unlikely scenario of the bridge's designers suddenly realising their own folly in an "Oh my goodness, what have I done?" moment, and deciding to quit.

This is a bridge, let's recall, which at £175m has a price tag grossly in excess of what even Donald Trump could consider reasonable (indeed, it's perhaps a surprise that Trump isn't involved, offering copious sponsorship in return for adding a couple of par-3 golf holes to the bridge). This puts it well beyond the realm of the most expensive pedestrian bridges ever built, by a considerable multiple. Having initially promised that no public funding would ever be provided, Johnson and partner-in-crime George Osborne then each offered £30m of taxpayers cash to underwrite the job.

The rest of the funding has to come from private sponsors, and so much is required that this supposedly public oasis will be converted twelve times a year into a private garden party for the use of its wealthy benefactors. Perhaps the capital city's poor and hungry can swim beneath the bridge on such occasions in the hope that some crumbs may spill from the lavishly decorated table. For the rest of the year, the bridge will be closed at night, forbidden to cyclists, and large groups (of 8 or more people) will be obliged to sneak across hoping they can dodge the inevitable CCTV hidden behind cherry blossom. For a bridge supposed to offer a great experience for the public, it won't even be a public right of way.

The bridge will ruin views along and across the Thames, including of St Paul's Cathedral, who have joined an ever-lengthening list of people who have woken up to the bridge's adverse impacts. It's neither a very good garden (central London being already well-provided with large public parkland), nor a very useful bridge, serving no genuinely worthwhile transport need. As the Guardian has recently noted, it turns the Thames into a playground for private fantasies, not public benefit.

Even bridge engineers, never an outspoken lot, are lining up to critique the proposals. Bridge expert Simon Bourne (not a fan of extravagance) was cited in the New Civil Engineer magazine stating that a decent bridge could be built for just £50m, a snip compared to the bill for the Garden Bridge. That certainly sounds reasonable, given that the structurally challenging Millennium Bridge cost about £23m just over a decade ago, and that between £26m and £40m is anticipated for the new pedestrian bridge planned at Nine Elms (of which, more another time).

In the latest New Civil Engineer, the Garden Bridge Trust's Paul Morrell responds to Bourne's criticism. Morrell is a Big Cheese, formerly the government's Chief Construction Adviser. However, his defence of the Garden Bridge illustrates everything which is wrong with this scheme.

Morrell says: "I could ask for the breakdown of [Bourne's] estimate of £50m so we can learn from it", which would seem a complete waste of time given that we already have well-established benchmark costs for pedestrian bridges over the Thames. However, a failure to benchmark costs against comparable projects is entirely normal for those whose infatuation with grandiosity triumphs over common sense.

Morrell goes on to note that £50m wouldn't even cover the Garden Bridge's non-construction costs (fees, fund-raising, land, compensation and "a long list of issues that you really do need to be working on the project to understand"). This patronising contempt for transparency is startling, but not as startling as learning that well in excess of £50m is required before you even start building the bridge - this is really quite disgraceful, but typical of a Grand Projet culture where there is little or no meaningful challenge regarding value for money.

Of course, Morrell is a quantity surveyor, a man who knows the price of everything and the value of nothing. Notably, declarations of the value of the Green Bridge have been largely poetic rather than economic in nature: hello trees, hello flowers, hello sky. The government's own guidance for public investment, the Treasury's Green Book, is routinely ignored by political promoters of the extravagant, as it requires benefits, however nebulous, to be properly evaluated and judged against the investment required. With the Garden Bridge, the net benefit may in fact be negative, and it's no surprise that no assessment of the bridge's actual value has been undertaken or published. Morrell ought to know this, so his mis-direction in justifying his project's exorbitant cost is particularly depressing.

Morrell claims: "There is always something cheaper if that is your main aim in life, but it would not get consent, nor would it be fundable, and nor would it deliver what this bridge is designed to be: a unique celebration of British talent and creativity, of design and horticulture, of this great city - and of engineering".

Again, this is just rhetorical sleight-of-hand. We are not obliged to celebrate any of these, and certainly not to divert public money in order to do so at a time when increasing numbers of our population are unable to afford to feed their families properly. Given the other pedestrian bridges which have been built over the Thames or which are planned, it's perfectly clear that a bridge can be built which offers genuine value, at a lower price, which can get consent, and for which funding can readily be obtained, if only the political will permits. Morrell, dazzled by his association with celebrity, seems unable to see that every penny spent on the Garden Bridge folly diverts resources from transport links which would serve genuine need elsewhere in the city.

The sense of defensiveness and the deaf ear to criticism and challenge is deeply reminiscent of two other architecturally extravagant bridge follies from recent times. Sunderland's ill-fated River Wear Bridge was also widely criticised, and as with the Garden Bridge, its backers misrepresented public opinion and ploughed on regardless, wasting millions of pounds of public money in the process. Simon Bourne was one of the critics on that occasion, as well. Glasgow's Neptune's Way farrago was a similar example: an absurd and rightly-criticised design which could not, in the end, be afforded, and was ditched in favour of an economic design serving the same purpose without the pointless showing off.

There is some hope that the bridge may yet be put to the sword before too much money is wasted. There's a suggestion that lawyers may seek a judicial review of the planning decisions. In addition, one of the planning conditions imposed by Westminster is that Transport for London must underwrite the future maintenance costs of the bridge (several million pounds every year). Opponents of the project are hoping that this may yet scupper the plans, Mayor Boris Johnson has confirmed that TfL have no intention of underwriting the maintenance.

03 December 2014

Bristol Bridges: 4. Meads Reach Bridge

This bridge was another early morning visit, to an award-winning span which is probably unique in Britain.

Built in 2009 for £2.4m, the 55m long bridge is a rare all-stainless steel structure. It was designed by Price & Myers with Níall McLaughlin Architects, and built by M-Tec. You'll see it described on the internet as a "stressed skin" bridge, to make it sound like it's using aircraft technology, but to bridge engineers it's simply a twin half-through box girder bridge, conventional enough except for the geometry and material.

The two edge girders hold up the bridge and also double as parapets. They consist of continuously welded, perforated Duplex 2250 stainless steel plate (supplied by Outokumpu), wrapped around triangular diaphragms. A series of cross-beams and bracing frames are hidden within the deck, which is surfaces with perforated stainless steel planks (of which, more later). The entire bridge weighs about 75 tonnes, and sits on four hidden stub "legs", one at each corner.

The extensive use of stainless steel is a bold, and presumably expensive, choice. The bridge's skin is punctured with thousands of small holes, arranged in size according to the calculated level of stress at each point of the girder surface. The process of analysing the bridge, determining acceptable levels of perforation, and translating that back into a fabrication model, will have been complex and demanding, and is an impressive achievement.

Luminaires are located within the girders and below the bridge's floor, and the perforations allow the structure to glow from within at night.

The bridge won the IStructE Structural Award for pedestrian bridges in 2010, and I think justifiably so, as it is highly innovative and geometrically challenging. I haven't seen it illuminated at night, but in daylight, sunlight reflects off the skin in a very attractive manner. However, the bridge is not without its critics.

The main complaint appears to relate to the deck panels, which are clearly very slippery, to the extent that the bridge is disfigured by prominent warning signs at each end advising users to cross with care. Reportedly, bridge users who do slip and fall have frequently been injured by the "cheesegrater" quality of the decking. In one month, over 600 people signed a petition asking for the bridge decking to be replaced.

However, as with the nearby Valentine Bridge, this is a public amenity which is privately owned. Although the decking is clearly not fit for purpose, the public may find it hard to force change.

Further information: