German Bridges: 2. Moltke Bridge, Berlin

Heading east along the River Spree, the next bridge is Moltke Bridge (Moltkebrücke).

This is a bridge with a history. A timber swing bridge was constructed here in 1850/1851, but replaced with a multi-span wrought iron arched bridge in 1865, the Unterspreebrücke. That bridge only lasted until 1886/1887, and the present highway bridge was then built in its place, completed in 1891. The bridge is named after Prussian military commander Helmuth von Moltke, who died shortly before the bridge was finished.

The structure was designed under the direction of city architect Otto Stahn, who designed several of Berlin's bridges, most notably the famous Oberbaum Bridge. Stahn worked with urban planner James Hobrecht.

The bridge was the site of a battle between Russian and German forces in 1945, with the Germans detonating charges which damaged but did not completely destroy the bridge. The structure was rapidly restored after the war, with some masonry parts replaced in concrete. A comprehensive restoration took place from 1983 to 1986, including the insertion of structural steel strengthening members.

The casual visitor today would have little idea of the bridge's difficult past. Perhaps the biggest clue is the good condition of the sculptures and red Main sandstone carvings, many of which are replacements for damaged or lost originals.

It's no longer in fashion to decorate bridges in this way, which I think is something of a shame, as it links a bridge to the wider culture, and locates it as part of history. The Moltke Bridge is very well decorated, with carved faces above the crowns of the arch (the grumpy one pictured here is apparently Moltke himself), statues above the pier cutwaters, and carvings and statues at either end.

A damaged statue sits on the north river bank to one side of the bridge: I understand this has been left as a deliberate reminder of the damage that can be caused by war.

The various sculptures were originally designed by Johannes Boese, Karl Begas and Carl Piper, with the restorations by August Jäkel. I like the decoration on the bridge: it's dignified and slightly over-done, but neither gaudy nor kitsch.

Further information:

• Google maps
• Berlin monuments database
• Wikipedia (English, German)
• Structurae
• Ponton's Brücken
• Berliner Brücken (Thiemann and Desczyk, 2012)

German Bridges: 1. Chancellor's Bridge, Berlin

While I was in Berlin recently, I took the chance to visit a number of the city's bridges. A boat cruise along the River Spree provided a prelude to the Footbridge 2017 conference dinner, and I revisited a few of the more interesting bridges as well.

The first of these, the Chancellor's Bridge, or Kanzlersteg / Kanzleramtssteg, is a private pedestrian bridge built for the sole use of the German Chancellor's office and its visitors. The Chancellery sits on the south bank of the Spree here, and is an expansive and to my taste lamentably post-modern establishment, which dwarfs the facilities of the heads of government of many other states (cf. 10 Downing Street or the White House, which are a fraction of the size). The bridge provides exclusive access to the Chancellor's park (and helicopter landing pad) on the north bank. It is only accessible to the public on an open day once a year.

The bridge was completed in 2000, and is a three span structure with spans of 20m, 85m and 17m. The superstructure is of steel box-girder construction, supported on reinforced concrete foundations. It reportedly cost 3.5m euros to build. The designer was engineer GSE with architects Axel Schultes Architekten.

I think this is a decidedly odd bridge.

The bridge links two levels of the Chancellery across the river, and is itself a double-level structure. In cross-section, it is Z-shaped, with the two floors offset either side of the central span girder. This will have made it a tricky beast for the structural engineer to design, with an inbuilt tendency to twist under load, but it's nothing that can't be solved simply by throwing enough steel into the structure.

It seems like a pleasant arrangement, giving both levels the feel of a balcony. At the north end, the lower deck curves to pass below the upper deck. The spine beam element is aligned with a secure wall which protects the Kanzlerpark, so this arrangement allows both decks to pass on the inside of the boundary wall. Access onto the lower deck from adjacent riverside paths is prevented by tall glass screens.

The structural form is very curious. At first, I thought it was an interesting arch, with a feel somewhere between Bauhaus and art deco styles (it also, obviously echoes the simple geometrical shapes used in the Chancellory building itself). It can certainly be seen as a closed-spandrel arch, with the lower deck acting as a tension tie, suspended from the arch with a series of chunky "hangers". Alternatively, it's a bit like a Vierendeel truss. It gives the profound appearance of something not really thought through structurally: it is half wall and half bridge.

The main oddity for me, is the bridge's presence in the public realm. Perhaps German citizens feel otherwise, but I get the impression of something very much intended to display as publicly as possible a separation between citizen and government. Political masters can quite literally look down upon those they govern, and they are made visible but shown to be clearly off limits. The materialisation of a political relationship in this highly explicit manner seems to be something few democracies would consider, except perhaps France. It would surely have been simpler just to omit the north bank park and relocate the helipad elsewhere.

I think I'm not entirely alone in this sense of unease.

Further information:

• Google maps
• Wikipedia (German)
• Structurae
• Berliner Brücken (Thiemann and Desczyk, 2012)

"The World's Footbridges for Berlin"

As part of the Footbridge 2017 conference, the organisers invited attendees to submit design ideas for six potential pedestrian bridge sites in Berlin. The aim was to create a space for creativity, and also to stimulate a different type of debate. It was quite clearly something of an experiment: would anyone be willing to "give up" their best ideas for no reward, and pay a conference fee for the privilege of doing so?

It turned out to be a great success. I don't know how many entries were submitted, but 76 designs have been collected in the book "The World’s Footbridges for Berlin". Copies of the book were given free to all conference attendees, and it's also now available for the public to buy. There's also an online app showing the bridge locations and images of submitted designs.

The six sites selected present a wide variety of challenges. In each case, the site description presented to designers is also included in the book, allowing readers to form their own judgement of each design’s success (or otherwise). Most of the sites are for bridges over water, with one over rail (the least popular with entrants), and one which also spans a city highway.

Several of the sites have a historic resonance. Brommy is the location of a former bridge destroyed by German troops in 1945, and also adjacent to a remnant of the Berlin Wall. Waisen is another location with a previous bridge, while the Spandau Citadel is itself a historic fortress.

The book contains multitudes. There are designs which are entirely derived from structural engineering concepts, with a minimum of architectural or contextual gloss, and many of these are surprisingly unworkable or foolish. Other designs have little or no structural engineering, a whisper of a concept without serious practical detail. What's notable is that there are relatively few designs submitted by collaborative architect/engineer teams, so generally what we get is the product of participants freed from having to come up with a competition-winning design. It really is about the taking part, not the winner, in this case.

Given the above, the overall quality of the designs is very high. There are number of duds, mostly from the engineer-only teams, but generally the designs are very well presented, and often fascinating in their inspiration or innovation. What's abundantly clear is the pleasure those taking part have found in being given freedom. It reminds me of the creativity I observe in student projects, which are similarly unconstrained by the need to be "the best solution".

What is also notable is that there are few of the architecturally "crazy" designs which are frequently seen entered in genuine design competitions (there were plenty of these in the Nine Elms to Pimlico contest). I found that a surprise, as you would think that with the freedom involved in "Footbridges for Berlin", there would a greater temptation to go wild.

The entrants are a cross-section of the design community, everything from students to well known bridge designers. Indeed, I was surprised at the number of prominent designers who found time to take part: Brownlie Ernst and Marks, Dietmer Feichtinger, Knight Architects, Schlaich Bergermann, COWI, Moxon Architects, Studio Bednarski, Ney and Partners, Marc Mimram, Dissing + Weitling and many more.

My personal favourite designs tend to have a strong personal story attached, or have shown a greater understanding of the context of each location. I also like those which are something more than a bridge e.g. a love hotel, a roof for riverboat rave parties, or a platform for urban art.

Overall, this is an excellent collection of design ideas, a fascinating insight into how designers of varying background think about their work. It well illustrates the deep subjectivity of the design process, the extent to which context and constraints are a springboard for creativity rather than a straitjacket.

Footbridge 2017: conference report Part 2

Footbridge 2017 had a number of keynote presentations from "big names" in the pedestrian bridge design community: Dietmar Feichtinger, Jan Knippers, Marc Mimram, Jiří Stráský, and Keith Brownlie. For me, the highlight of these was Brownlie's presentation on "Taste (a world of difference)".

Brownlie's design experience spans the globe, and he chose to draw attention to the way in which different styles of bridge design are accepted or promoted in different locations. The aesthetics of bridge design is a topic which has, by now, been pored over extensively, often by engineers seeking to establish a framework of guidance for colleagues. I discussed some of this back in 2009.

However, the issue of taste, the subjective evaluation of aesthetics, has been addressed only in passing. One example that comes to mind is Colin O'Connor's 1991 paper reporting on a series of surveys on bridge aesthetics made with the Australian public. However, the whole issue of what the public think of bridge aesthetics is often ignored by professionals.

Brownlie presented a number of bridge examples from around the world, both built and un-built, loosely tying these together with the thesis that one major determinant of taste is climate, specifically the possibility that 'latitude' correlates with 'attitude'.

Northern-latitude examples include the startling (and, I think, depressing) sobriety which informed the various finalists in the Nine Elms to Pimlico bridge design competition, as well as a number of Nordic designs which are united by their dislike of colour and complexity. At the opposite end of the scale are projects in hotter climes, such as Singapore's bling-laden DNA Helix Bridge (photo courtesy Angelo Pereira), the exuberant Swan River Footbridge (more on this piece of faux-iconic infrastructure some other time, perhaps), or the unsubtle and over-wrought winning design in Miami's I-395 Bridge design contest.

Brownlie's message was simply that the idea of objective aesthetics should be treated with suspicion, and that taste should be acknowledged if not always embraced. He noted that "taste is an ever evolving force", and this is the point I found particularly interesting.

The examples in the paper are all recent designs, largely post-millennial, and so offer a snapshot of current taste. It's easy to find exceptions to the trends set out, but I was left wondering how international tastes in bridge design have emerged, spread, changed, or declined.

One thing that unites Brownlie's examples is that they have been designed and built within a post-modern era. They are not generally representatives of a post-modern philosophy, but they share post-modernism's freedom of treatment of colour, form and style. Playfulness in design has also been greatly facilitated by technological developments, and by economic surplus. This, I think, is one thing that has given rise to the present variety of international taste, and I suspect that economic wealth can also be shown to be prime driver in adoption of some of the more outlandish designs seen in recent decades. Poorer countries generally can't afford to depart so far from pragmatism.

Rationalism is in widespread retreat, and with it the adherence to functionalism that united modernist design. If you look back at many of the nations that Brownlie references, older designs show greater unity. Australia's current taste for the exuberant and irrational (Swan River and Kurilpa Bridge, the latter pictured above left courtesy of Jan Smith) would have been foreign to earlier generations, who had yet to escape the more traditional views inherited from colonial times. The degree of unity seen in the designs of Sydney Harbour Bridge (pictured right), Hell Gate Bridge, and Tyne Bridge is an example: form driven by the practicalities of technology, by the constraints of economy, and by the desire to match form to function.

I think there is also an issue of the desirability of expression of taste, which Brownlie does touch upon, suggesting that in the absence of familiarity with good design, American audiences "literally have no taste". The same is true, I've observed, in Australia, which shares America's frontier heritage: focussed on outcomes, narrow in vision. The result in both nations has often been infrastructure entirely free from any notion of aesthetics, and the current trend towards the overly demonstrative in bridge design in both nations might be seen as a simple over-compensation to their historic cultural deficit.

I think one reason that these developing nations (USA, Australia, along with the Middle-East, much of south-east Asia etc) espouse the irrational, the gigantic, and the frivolous is that they feel left behind by those cultures whose historical continuity has given them a privileged position in the hierarchy of taste. In striving so hard to escape their own inferiority complex, they have ridden a pendulum well beyond what most European cultures would consider tasteful. It is a self-conscious imitation of prestige, almost the very definition of "bling", with inevitable results.

Fashion, in the sense of 'designer' clothing, is increasingly international, with a global audience looking in many cases beyond local tradition towards international brands exhibited in Paris or Milan. The 'brand' influence on taste is less visible in bridge design, with the notable exception of the work of Santiago Calatrava, once (unfairly) derided as the "McDonalds of bridge architecture". Bridge design is inevitably more contextual than fashion, forced by immobility to relate more closely to constraints of geography, climate, history and culture. However, Calatrava makes clear that there is space for brands to set and influence local taste, and indeed I think many of the "exaggeratedly structural" bridge designs seen around the world show the power of the Calatrava brand itself.

In the buildings community, the likes of Gehry and Hadid suggest a wider international acceptance of brand-led design taste, an admiration for freeform extravagance that parallels Calatrava's position closely.

Should designers respond to taste, or look to influence it? Few bridge designers have, or will ever have, the profile of a starchitect. Many espouse a humility and sobriety which is at odds with wider public taste and so are very unlikely to influence it.

Change comes at the point of intersection between design and its recipients, where trends, fashions, philosophies can be influenced or be rejected. Presentation of a compelling vision or a narrative can be powerful. The Footbridge conferences are a great place to cultivate this debate, but the public cannot or do not participate, and clients are also notable by their absence. The difficulty of engagement between the public and those employed to design their environment is nothing new, of course, but I do wonder whether there's a way of getting better public input and understanding not only of specific project issues, but also of wider aspects of aesthetics, value and performance.

Footbridge 2017: conference report Part 1

Every three years, the bridge community gets together to discuss developments in the world of footbridges. Previous events have been held in Paris, Venice, Porto, Wrocław, and London, and this year it was Berlin's turn. I’ve reported on the Wrocław and London events here on this blog.

These are always amongst the most enjoyable events in the conference calendar, largely because they are (in line with their theme) a great opportunity for spanning borders and making new connections. I've met many interesting people at Footbridge conferences, and the problem now is that there are simply too many presentations to see and too many people to meet within the time available.

This year's event was held in the Technical University of Berlin, in one of a series of large buildings originally built for the AEG company. The exhibition part of the conference was located in the Peter Behrens Hall, a giant space now normally used as a structures laboratory. It's a lesson in humility for Anglo-Saxon attendees, as the space showcases the close and purposeful collaboration between industry and academia that is less often found outside mainland Europe.

Tucked away throughout the hall are little experimental concrete-shell bridges, bridge models built by students, and their pride-and-joy, a carbon-fibre supported stress ribbon bridge which was being used during the conference to demonstrate active vibration control mechanisms (see photo, right).

This year, the conference expanded beyond the usual array of technical papers and case study presentations by organising a bridge design "competition", Footbridges for Berlin, with attendees invited to submit their ideas for a bridge at six sites within the city. These have been collected together in a book ("The world’s Footbridges for Berlin"), which I'll review in more detail in a later post.

The presentations of these bridges gave several people the opportunity to explore creative directions that they would normally avoid, as well as the chance to cultivate critique and debate. Unfortunately, this stream was presented at one end of the exhibition hall, a space simply too large and echoing for this to work as well as might have been hoped.

There were some very interesting keynote presentations, most notably the two which departed most from the conference's putative topic. Film director Robert Schwentke presented on how to "tell a story" (addressing the continuing need for designers to improve how they communicate), while photographer Wolfgang Volz gave a splendid overview of Christo and Jeanne-Claude's Floating Piers project. Both these topics reminded all those present of the need to lift their heads up from day-to-day concerns, and consider how to better address the wider world for whom the minutiae of design and construction is irrelevant.

One thing that struck me about the keynotes was that all the presenters were white, European men. In line with the conference as a whole (and much of the wider bridge design and engineering community), this is not a diverse group, and not well aligned with those who enjoy or endure our output. I'd seriously hope that Footbridge 2020, to be held in Madrid, might try to do better.

One positive development is that the conference papers will be made available online (via Structurae) in six months time. I think this is a brilliant move, as far too often conference proceedings are difficult to get hold of, acting as a bar on sharing knowledge more widely. Perhaps other conference organisers could consider adopting a similar approach, as the whole industry's track record on availability of published research and case studies remains very poor.

Ok, that's enough for this post. I'll put together one or two follow-up posts to look in more detail at some of the more interesting papers presented at the conference.

Footbridge 2017 Awards winners announced

The winners of the 2017 Footbridge Awards were announced at the Footbridge 2017 conference in Berlin last week. I previously shared the list of shortlisted entries.

Short span (30m or less)
Winner: Merchant Square Footbridge, London, UK
Highly commended: Cykelsgangen, Copenhagen, Denmark
Highly commended: Waalhaven Bridge, Rotterdam, Netherlands

Medium span (30m to 75m)
Joint winner: Park Bridge Spoor Noord, Antwerp, Belgium
Joint winner: Weinbergbruecke, Rathenow, Germany
Highly commended: Inner Harbour Bridge, Copenhagen, Denmark

Long span (more than 75m)
Winner: Beer Sheva High-Tech Park Bridge, Beer Sheva, Israel

Jonathan Speirs Footbridge Lighting
Winner: George C King Bridge, Calgary, Canada

Historic renovation or reuse
Winner: Como Park Footbridge, Saint Paul, USA

I was struck at the conference by a number of excellent recent bridges which were presented at the event, but not featured on the awards shortlist. From discussion with those involved, it seems several of these were not submitted, which is a shame, as although the award winners all appear to be well-deserving, they offer only a snapshot of what is good out there.

What is impressive about the winning structures is their diversity, representing a good range of superior visual appearance alongside technical achievement and in several cases a degree of eccentricity.

Meanwhile, for anyone who thinks that these awards are terribly lopsided and that bad bridges deserve a share of publicity too, note that the Bridge Awards for Mediocrity and Plain Old Terribleness (the BAMPOTs) are still inviting nominations, until 15th September. I've currently received 19 suggestions, and readers will be pleased to learn that I have appointed a panel of anonymous yet prestigious international judges to sift through them all and come up with a shortlist, to be put to public vote in due course.

Introducing ... the Bridge Awards for Mediocrity and Plain Old Terribleness

The "Carbuncle Cup" has been running for several few years now, a contest to uncover the worst examples of new British architecture, and it's never been short of material. For non-UK readers, the origin of that contest's name can be found at Wikipedia and elsewhere.

Many thanks to Bridge Design and Engineering magazine on Twitter, who recently asked the following question with regard to the Carbuncle Cup:

Do we need a similar award for bridge projects I wonder? https://t.co/NgGb90UsLX

— Bd&e (@bdebridgeweb) August 30, 2017

Do we need it? Not really. Should we do it anyway? Well here it is, the inaugural BAMPOTs. (Again, for readers unfamiliar with the source idiom, see online).

I'm a firm believer that we (the industry that promotes, designs and builds bridges) can learn as much from failure as from success, and we should never be afraid of being honest. The idea of learning from structural failure has a long tradition, but here I'm looking to consider a wider range of failures: function, appearance, delivery etc.

When better to announce this new award than in the week when some of the industry's very best will be celebrated at the Footbridge Awards? The need for some balance feels pressing.

I have some ideas of my own for candidates for this award, but I'm inviting open nominations here: just visit this page on the blog, and add your suggestion(s) in the comments. Please include a link to details of the bridge, and a brief description of why you think it deserves wider attention. Keep it short and to the point. Don't be libellous - I may not publish inappropriate comments.

Bridges should either have been completed within the last decade, or the site of a "failure" incident within that same time (e.g. a botched restoration etc). I'll stretch those limits if a particularly good candidate is put forward.

I'm not including unbuilt bridges, as I think London's Garden Bridge would currently have too large an advantage.

The deadline for nominations is midnight (GMT) on Friday 15th September, although it may be extended if I don't get sufficient response (or this whole exercise may be unceremoniously binned!) Please help get the word out by sharing a link to the BAMPOTs via social media etc: let's make a success out of celebrating failure together.

Subject to getting enough nominations, I'll then organise some kind of voting system to decide on an appropriate winner or winners.

Australian Bridges: 8. Rex Creek Bridge, Mossman

For the last in this series of posts from "down under", I travelled to scenic Mossman Gorge, home of Rex Creek Bridge. Mossman Gorge is part of a World Heritage status rainforest zone, a traditional home to the Indigenous Kuku Yalanii people, and a very popular tourist destination.

The Gorge is accessed via a series of elevated walkways, intended to carefully control visitor access and impact. The trails cross Rex Creek via this 40m long suspension footbridge.

A bridge was first built here in 1986. Constructed by army engineers, this was a catenary suspension bridge, with a timber deck hung from the main cables via a series of steel u-frames.

In 2010, inspections identified defects in the bridge, and a decision was taken to replace it with a new bridge, at a cost of $450,000. The present bridge is a more conventional suspension bridge, although certainly with a number of oddities.

The new bridge also had its own issues with defects, and was closed from July to August 2012 when cracks were found in the parapet posts. Looking at the parapet design, it's not hard to see why they would be vulnerable, as the parapets are in short section lengths with gaps between them.

As well as rendering the parapets more vulnerable to damage, this has implications for the stiffness of the bridge, and unsurprisingly it is very vibration-prone. Depending on the visitor's perspective, this is either a bit of a thrill, or a serious difficulty. For my part, I think it's a significant design failing, making it difficult or unpleasant for some visitors to proceed further into the Mossman Gorge area. It would easily have been prevented or reduced by using the parapets as stiffening members.

The bridge deck is suspended via hangers from twin suspension cables on each side. The hangers pass through a connecting clamp,, which prevents sliding along the main cables. The hanger connection itself is just a simple threaded nut.

The main cables are connected to steel framed towers. A beefy crossbar at the top houses connections for the cables on either side, and is bolted onto a Y-frame portal.

It's an ugly arrangement, and I think part of a general philosophy amongst Australian bridge designers which favours robustness and pragmatism over beauty. It possibly derives from an American rather than European tradition, a hang-over from a frontier mentality.

However, this is a bridge which had to be assembled in a difficult location, and having selected steel for reasons of strength, the bridge needed to be transportable in small selections which could be lifted over the forest via helicopter.

The "industrial" detailing continues to all parts of the bridge. The anchorage at one end comprises a cross-braced frame, picking up the forces from the main cables and carrying them back into the ground via compression struts. I can only guess that the issue here is that the ground is falling steeply away from the bridge, and that anchoring the cables directly into the ground at their normal angle would have been impossible.

At the other end of the bridge, there's a more conventional anchorage arrangement, with box frames taking the force from the twin suspension cables into a single threaded rod anchored directly into the ground (I don't know whether there's a concrete anchorage or whether this is simply a rock anchor).

Overall, I like this bridge a lot less than Lloyd's Bridge (see my previous post). Lloyd's Bridge was somewhat ramshackle and wobble-prone, but it was locally funded and is not a major tourist site. The Rex Creek bridge is crossed by hundreds of visitors every day, and it would have added little or no cost to make it stiffer and more visually attractive.

It begs the question of the extent to which visual appeal is necessary in this setting - the bridge is not a destination in its own right, merely a means to an end. However, that's the same philosophy used to justify ugly bridges everywhere. I think the best that can be said of the bridge is that it is an authentic representative of Australian bridge culture.

This concludes my posts on Australian bridges, until a further visit. Next stop, Berlin, for the Footbridge 2017 conference later this week, which looks like being as stimulating an event as ever.

Further information:

• Google maps

Australian Bridges: 7. Lloyd's Bridge, Yungaburra

The last three bridges are all located in Australia's largest city, Sydney. The next two are from further north, in Queensland.

Head inland from the north Queensland coast to find the delightful historic town of Yungaburra. One of the attractions here is the walking track along Peterson's Creek, from where it's possible to see platypus and tree-kangaroos (although not when the Happy Pontist visited).

In 2008, local man Lloyd Abell provided funding for a new bridge to connect the walking trail across the Creek, a structure now and hopefully forever known as Lloyd's Bridge. There's a commemorative plaque on one of the bridge masts, and an explanatory sign nearby.

The suspension footbridge spans 30m over the creek. A sign makes clear that the maximum load is 10 persons - this is not a bridge suitable for the absurd 5 kPa of normal footbridge design, nor should it be.

The bridge comprises a deck of longitudinal planks supported on timber cross-bearers. These are suspended via 8mm hangers from the 16mm main cables. A cable in a rough plastic sheath is clamped to the hangers to form the handrail and to hold up mesh infill balustrades.

The main cables are anchored into turpentine poles forming the bridge towers, and then into concrete anchorage blocks.

Some people may wonder why I'm covering such a seemingly minor structure and non-notable structure here. Well, firstly, I just have a soft spot for small-span pedestrian suspension bridges. Secondly, I think they illustrate how much variety is possible even with a seemingly small niche. If you look at the minor details on this and similar bridges (how the main cables attach to the tower, or how the hangers attach to the main cables), you'll find every one is different, and I think there's endless fascination in seeing how others have solved the same problems in such a variety of different ways.

The bridge lacks stiffness and moves considerably under load, but the mesh balustrades effectively damp vibration. The bridge creaks very noticeably when used, the level of noise being proportional to the success of the damping, and therefore reassuring, to a structural engineer at least.

It's a pragmatic structure, blessed with a minimum of design, and well done.

  

  

Further information:

• Google maps
• Weekend Notes