26 August 2014

Cumbria Bridges: 12. Devil's Bridge, Kirkby Lonsdale

This is one of several bridges I visited back in May, all around the border between Cumbria and Lancashire, and all of which span over the River Lune.

"It is by far the finest bridge in the north of England", wrote Edwyn Jervoise in 1931. Like the similarly ancient Twizel Bridge (in Northumberland), it is a ribbed arch, a type I always find visually attractive. It is a Scheduled Ancient Monument, and a very handsome structure.

The bridge dates to the 13th or 14th century, and as with many other structures around Europe, it was reputed to have been built by the Devil. An old woman made a deal with the Devil for him to build the bridge in return for the first soul to cross over. She then tricked him by throwing bread across the bridge so that her dog ran over it first. The story is recounted in more detail in George Bernard Wood's book, Bridges in Britain.

There are many variants on this tale for the many so-called Devil's Bridges, suggesting that the poor fellow struggled to learn any lessons from being repeatedly tricked.

Further information:

24 August 2014

Yorkshire Bridges: 5. Scammonden Bridge

This is the last, and largest, in a set of Yorkshire motorway bridges which I visited earlier this year.

Spanning 125m, it is the biggest concrete arch bridge in the UK. It carries a local highway across the motorway where it passes through a huge cutting. In some photographs, Scammonden Bridge can appear almost "small", as it is scaled appropriately to its setting.

Its sheer size becomes more apparent only when passing underneath. A construction photo from 1969 showing the scaffolding used to erect the arch also gives a much better idea of quite what an enormous structure it actually is.

The concrete arch comprises a twin-cell reinforced concrete box section, supporting slender spandrel columns. These are hinged at the top to allow thermal movement of the deck to take place. The deck is built from conventional precast, prestressed concrete "T" beams.

As with the other bridges I visited in the area, this structure was designed by the West Riding County Council. Sri Sriskandan was credited with a key role in an obituary published by the New Civil Engineer.

The bridge provides spectacular views along the motorway and onto the moorland that the road bisects. It's startling to try and imagine this setting before the motorway was built, as the huge "valley" that the road passes through is entirely artificial.

The bridge seems to be in generally good condition, with the notable exception of the parapets, which are in serious need of repainting.

Aesthetically, it is appropriate to the place, and generally well-proportioned. The only "wrong note" is the way that the profile of the arch at its crown cuts into the deck profile, but this is a minor matter.

It would be fascinating to see what kind of bridge would be built today if a new motorway were built in the UK requiring a similar span. However, it's hard to imagine such a road being allowed to be built, given the visual impact on the rural landscape.

Further information:

28 July 2014

Yorkshire Bridges: 4. Needle Eye Bridge

Okay, I'll continue this series of posts a little further north along the M1 Motorway. I'm bypassing the Cock Inn Bridge simply because it proved impossible to get a decent photograph, which means the next bridge of interest is the Needle Eye Bridge.

This is a three-pin concrete arch "accommodation bridge", built to carry farm traffic and pedestrians. The arch spans 88m between springings, and was cast entirely in-situ in reinforced concrete.

It seems to owe more than a little to Robert Maillart's 1933 Felsegg Bridge, the first of the Swiss designer's concrete arch bridges to adopt an angle at the upper hinge rather than a continuous curve. This is a departure from pre-conceived notions of what an arch should look like, and is structurally more rational, responding appropriately to the full envelope of possible live load effects. Needle Eye Bridge lacks the sharp angle at the crown of the arch, but overall the bridge is shaped in a similar manner.

It is better than Maillart's bridge, however, in its use of prestressed suspended side spans, preserving a simple, clear geometry. Maillart's designs paired the solid main span with finicky, slender approach structures, often over-fussy in their detailing.

My sense is of a design team very aware of precedent, and enjoying the rare opportunity to experiment with form.

As with the other two M1 bridges I featured recently, at Droppingwell and Smithy Wood, I find it amazing that this bridge is not protected by any kind of heritage status. Sure, it only dates to the 1960s, but the whole set of bridges along this part of the motorway, designed by the West Riding County Council, is remarkable and worthy of wide recognition.

Further information:

26 July 2014

Pedestrian Bridges of London: A Short Guide

Updated 27th July 2014 - THIS OFFER IS NOW CLOSED (see below)

I mentioned this little booklet recently. It was given free to attendees at the recent Footbridge 2014 conference in London. It is based on (much shortened) articles about significant footbridges in London, with all text and photos contributed by The Happy Pontist.

There are twenty pages, covering the following bridges: Bridge of Aspiration; Challenge of Materials Footbridge; Millennium Bridge; Golden Jubilee Footbridges; Chelsea Bridge Wharf Link Footbridge; St Saviours Dock Bridge; Royal Victoria Dock Bridge; South Quay Footbridge; West India Quay Bridge; Plashet School Footbridge; Stratford Town Centre Link; Green Bridge; Rolling Bridge; Merchant's Square Footbridge; Sackler Crossing; Xstrata Treetop Walkway.

The booklet also provides some (very) brief details on significant bridges and structures encountered along the River Thames, the conference's Gala Dinner boat cruise route.

I have eight of these booklets left over from the conference, and I will post them to the first people to email me (happypontist at gmail dot com), having first made a donation to Bridges to Prosperity. I wrote about B2P and their excellent efforts to build low-cost footbridges in the developing world, way back in 2009.

The booklets will never be reprinted, so this is a unique chance to get a copy.

It's very simple:
  1. Donate to B2P whatever amount you wish, although an absolute minimum of US$5 please.
  2. Email me your address and a copy of your B2P donation receipt - if you want to keep any details private, just take a screenshot and cut out any private bits.
  3. This is a bit silly since I blog anonymously, but I will sign the booklet on request. Minimum US$10 donation for a signed copy.
  4. I will post you a copy of the booklet, free of charge. Please bear in mind that I am covering international postage when you decide how much to donate to B2P!
  5. I will post here when all copies are gone, but there can be no refunds - if you donate, and I've run out of copies, never mind, at least B2P will benefit!
  6. Did you attend the conference and already have a copy of the booklet? That's great, but please consider donating to B2P anyway, they're a great organisation.
Updated 27th July 2014 - THIS OFFER IS NOW CLOSED

All the spare booklets are now allocated, many thanks to those who have donated to Bridges to Prosperity! I have also made a donation myself, and together we have raised US$350 to support their excellent work around the world. I'm absolutely delighted to have helped create this opportunity.

24 July 2014

Yorkshire Bridges: 3. Smithy Wood Footbridge

I first became interested in the Smithy Wood Footbridge when Tallbridgeguy posted about it on his blog.

It's another great example of how the West Riding County Council engineers in the 1960s applied real innovation to deal with a specific technical challenge. Their concern when designing new bridges over the Sheffield to Leeds motorway was with possible mining subsidence, which could lead to foundation settlement and severe damage to their new structures.

Three new footbridges were designed as concrete Wichert trusses, possibly the first such designs in concrete, and almost certainly the first such designs in Britain. Only one now survives, the footbridge at Smithy Wood. The concept, originally developed by E.M. Wichert in Pittsburgh in 1930, is for a bridge which is statically determinate but also continuous, such that pier settlement can occur without causing damage.  It achieves this by incorporating a quadrilateral bay within the truss immediately above the support pier or piers.

Don't ask me quite how that works: any first-year structural engineering student will look at it and ask why the quadrilateral truss bay doesn't simply "squish". I look at it and I don't really know why either, although I think it has something to do with the feasible displacements of the two adjacent spans. To make it work, the designers had to undertake basic research and testing for the tri-hinge, the point directly above the pier. The upper hinge also has to be prestressed.

It's interesting to think that engineers of the time were designing structures with hinges partly to deal with settlement but also to make them determinate and hence amenable to analysis. Today's engineer would struggle to analyse this bridge: modelling it in any conventional structural analysis software would be fruitless, as the quadrilateral bay will be treated as a mechanism and the software will just output an error and come to a halt.

The bridge looks to be in much worse condition than it really is. It looks like it had a concrete coating which is now peeling away.

Perhaps the thing I found the strangest about this bridge is not its supremely odd structural system, but its incongruity. One end of the bridge is terminated with a series of switchback ramps. This gives the bridge a very urban feel, it's the sort of arrangement you often see in an urban environment. But at Smith Wood, it's in the middle of a field, and it seems completely out of place. This is probably what I liked most about the bridge ...

Further information:

22 July 2014

Footbridge 2014

I thought I'd try to write a brief summary of Footbridge 2014, held over three days last week at Imperial College in London.

Much of the conference was in the usual format: a series of plenary sessions with twelve keynote presentations (substantially more than Footbridge 2011), accompanied by various themed parallel sessions where the bulk of the papers were presented. These ran in triplicate, so I almost certainly missed more amazing presentations than I saw. If I get time, I'll write here about a few of the particularly interesting presentations. I also barely scratched the surface of the exhibition, which was a shame as there were some interesting products and companies on show.

The conference was very busy: I had time to visit a handful of London bridges the day before the event, but once it started there was so much of interest to see, and so many interesting people to meet, that I never had time to go off-campus.

One of the undoubted highlights was the first night, which featured "Footbridge 10-20", a session where presenters had to speak over only ten slides, each shown for exactly 20 seconds. This is a variant on the PechaKucha presentation format, but half the length, and all the better for it. It really forced speakers to be concise, and if they were boring, well, they were gone quickly and on to the next. The four highlights, for me, were presentations on Thomas Heatherwick's absurd Garden Bridge ("Boon or boondoggle?" - I don't think there's much doubt which it is); "freaky London bridge facts" (one of few presentations not by a bridge designer, builder or client); a comparison of the love of "sexy" (i.e. "iconic") bridges with scopophilia, in its sense as a sexual perversion; and a much-applauded tour of bridges in Hollywood action films, particularly science fiction and fantasy films, discussing how they tend to defy the laws of physics. The last was supported by a paper in the main body of the conference, from which this picture of Asgard's rather improbable Bifrost Bridge is taken.

The second night of the conference was the Gala Dinner, a cruise down the River Thames on a glass walled boat. I know London well, but this was a marvellous night, great company, great sights, and the chance to experience very different characters of the city as daylight faded into night.

The keynote presentations were generally of a very high standard, thought-provoking and wide-ranging. Several showed concern with the philosophy and ethics of design, with Andreas Keil, Marc Mimram, Jürg Conzett, Laurent Ney and Martin Knight all addressing the "why" and "how" of footbridge design as much as the "what".

Keil presented ten objectives for a designer, drawn from the vocabulary of a product designer, and illustrated them with examples from the Schlaich Bergermann and Partners portfolio. My favourite objective was to employ "as little design as possible", illustrated by the Bleichwiesesteg (pictured, right).

Conzett's talk addressed the question of how engineers could draw on "inspiration" without having to compromise their essential character and become "artists". Conzett's inspirations are often historic, such as Brunel's Chepstow Railway Bridge, and he often uses images from the past to provide the key to modern design problems, whether of broad conception or with regard to details. Conzett's timber Murau Bridge (pictured, left), was shown as one structure inspired by the Chepstow span. The approach is like that of a detective, treating historical artefacts as clues to discover a hidden and unsuspected new design solution.

Laurent Ney offered nine design principles, developed in collaboration with Chris Poulissen. These were broadly aligned with Vitruvius's famous three principles of Utilitas, Firmitas and Venustas. Many of Ney and Poulissen's principles are primarily ethical: relating to social integration, minimal waste, recognition of diversity, shared ownership ahead of ego. One principle, "towards an appealing creation narrative", asks for design and construction to embody the culture within which they operate, to create stories with a wider social resonance beyond the specifics of the project.

The conference closed with Martin Knight's talk, "Bridges for places, bridges for people". Like Ney, he was concerned with the role a bridge plays in society beyond the purely functional. The rebuilding of the bridge in Mostar (pictured, right) was offered as an example of a bridge playing both a practical and also a symbolic role, an act of rehabilitation and a site for celebration. He urged designers to "zoom out" and look beyond the bridge itself to its place in a wider context.

I can only scratch the surface of the conference here. Several of the other keynotes were highly informative, and indeed two lectures on footbridge dynamics were both quite amusing, not something often said about this topic. If time permits, I'll pick out a few further papers and projects from the conference, and post here again.

19 July 2014

Footbridge Awards 2014 winners

The winners of the 2014 Footbridge Awards were announced a few days ago at the Footbridge 2014 conference in London. I'll hopefully have more to say about the conference soon, but for now, here are the winning bridges. I posted the full shortlist previously.

I will keep my own comments to a minimum, but would welcome further opinions via the blog comments facility.

Short span
Winner - Smedenpoort Twin Bridges, Bruges, Belgium - Ney and Partners
This is a truly flabbergasting design. I doubt that many engineers other than Ney and Partners would have had the faith that they could make such slenderness work.

Highly Commended - Bleichwiesensteg, Backnang, Germany - Schlaich Bergermann and Partners
I keep staring at this bridge design and wondering about its peculiarly upside-down quality - the compression strut and tension hinge look like they should be a tension tie and compression hinge.

Highly Commended - Campusbrücke Opladen, Germany - Knippers Helbig / Knight Architects
I'm not 100% sure that I understand this bridge, which is geometrically complex and difficult to "get" from just one image, but I do love the use of simple patterns to generate considerable visual interest.

Highly Commended - Vluchthaven Bridge, Amsterdam, Netherlands - Ney and Partners
I'm not sure what I like better about this, the rail-less balustrades, or the folded steel plate deck.

Medium span
Winner - Jarrold Bridge, Norwich, UK - Ramboll
Discussed here back in 2012.

Highly Commended - Geniedijk Bridge, Netherlands -
I can't find a lot of information on this bridge on the internet. The V-shaped theme and use of weathering steel are attractive, as is the detailing, but I do dislike bridges with 3m tall anti-vandal barriers - are they really necessary, or did the client only think they would be?

Highly Commended - Slinky Bridge, Oberhausen, Germany - Schlaich Bergermann and Partners / Tobias Rehberger
When I first saw pictures of this bridge, I found its frivolity, particularly the "slinky" spiral itself, somewhat garish and dispiriting. Closer examination reveals a very well detailed stressed ribbon bridge, and what looks to be an attractive and jolly combination of colour and shape.

Highly Commended - Media City Footbridge, Salford, UK - Wilkinson Eyre / Ramboll
I visited this bridge in 2011.

Long span
Winner - Bow River Bridge, Banff, Canada - StructureCraft
This was up against some pretty impressive competition on the long span shortlist. It's unusual to see timber in bridges this long (an 80m central span), certainly of the beam type.

Highly commended - Peace Bridge, Londonderry, UK - AECOM / Wilkinson Eyre
Sometimes it seems there is little more to be said in the hi-tech, modernist style which Wilkinson Eyre have made their own, but the Peace Bridge is something new within that space (overlapping self-anchored suspension spans), and also a very well detailed example of how it should be done.

Winner - Mala Panew River Bridge, Poland
The write-up in the Awards booklets indicates this to be an exemplary restoration and strengthening of a historic bridge, built in 1827. A paper was presented at the conference, but I can find no useful information on the project online.

Jonathan Speirs footbridge lighting award
Winner - Castle Green Bridge, Taunton, UK - LDA Design / Moxon Architects / Flint and Neill
This strikes me as the sort of design that the late Dan Flavin would have put forward if he were designing visitor access ramps rather than minimalist art installations. That can only be a good thing, in my opinion.