09 June 2016

Seminar on pre-designed bridges by Mario Guisasola, London Friday 10th June

My London-based readers may be interested in this seminar, organised by the Imperial College CivSoc, which takes place from 12-1pm, Friday 10th June, Room 207, Skempton Building, Imperial College, London.

Mario founded design firm Anta IC in 2003, and has designed a number of geometrically interesting and innovative bridges. such as the example depicted above. These are all bridges where the formal geometry is derived from consideration of the span's internal forces, and I've been hoping for some time they'll get some greater attention, so this is a good opportunity to find out more about them - there's also plenty of information on the Anta IC website.

04 June 2016

"Christian Menn: Bridges"

I recently reviewed Philip Jodidio's Calatrava: The Complete Works, a shallow but brain-poundingly flashy review of the Spanish engineer / architect's grandiloquent oeuvre. Now here's a similarly weighty coffee-table recap of Swiss engineer Christian Menn's career. How do they compare?

Christian Menn: Bridges (Scheidegger and Spiess, 2015, 350pp) [amazon.co.uk] is in matching German and English throughout, so a good chance to find out more about the man who is generally recognised as one of Switzerland's finest bridge designers. The previous monograph, Christian Menn - Brückenbauer (2007) was in German only.

The book covers pretty much all of Menn's significant designs, interspersed with various essays, an interview, and tail-ended with a short biography, list of works and the like.

Menn explains his own philosophy of bridge design, which is also a philosophy of bridge procurement, with some thoughts on design competitions and design standards. For Menn, bridge design must be led by engineers, as structures must satisfy all applicable standards and be economical as well as beautiful. His view is that design is the art of achieving an appropriate balance, with economy and aesthetics apparently incompatible, but to some extent reconciled in the choice if appropriate structural form.

I've discussed Menn's philosophy in detail on a previous occasion, so won't repeat that here.

Menn's signature bridge design was the concrete arch, especially in its deck-stiffened guise as pioneered by Robert Maillart. The first project in this book is the magnificent 72.5m span Crestawald Bridge, and there are many more similar examples. They have been beautifully photographed by Ralph Feiner (all the photos I've used here are by Feiner), and generous space is given over to these images, as well as technical diagrams for each bridge in plan, elevation and cross-section.

With the exception of the Crestawald arch, most of Menn's bridges of this type use a polygonal arch, the engineer's rational alternative to a pure curve. The bridges therefore have a Germanic austerity to them which generally sits well within the mountainous Swiss landscape. I particularly admire the way in which they rely on the strength and purity of their structural form: the concrete finishes are sometimes poor and the detailing negligible, but that's simply not what they are about.

Menn has also been responsible for a number of admirable post-tensioned concrete box girder designs, again most notable for their simplicity and clarity of intent - no fussy cross-sections or pier sculpting, they rely on their visual directness for effect.

After a while, it's hard not to feel bludgeoned by repetition - most of Menn's career has been distinguished by monotony, and a number of basically very similar bridges are presented in perhaps more depth than is merited.

I also occasionally find myself doubting his aesthetic judgements. He is highly self-critical, an admirable trait, but is he always right in his view of his own work? He complains that the twin-legged piers of the Felsenau Bridge would have been better as single legs, but I find this hard to credit, as this is a very high quality bridge as built.

In the later years of his career, Menn's work was sometimes uneven. I greatly admire the elegant cable-stayed Sunniberg Bridge but find the Ganter Bridge to be over-rated in the extreme, with its stiff rectangular piers and their clumsy connection to concrete fins in which its support stays are embedded.

The Leonard P. Zakim Bunker Hill Memorial Bridge in Boston, USA, is for the most part a fine design, but it is cursed with a gargantuan 56m wide deck and I can't help wondering whether it would have been better as two smaller, parallel bridges.

Similarly, some of Menn's unbuilt designs in the middle-East show significant departures from the clarity of his earlier work. The pylon for the cable-stayed Al Showah Island Bridge consists of a spindle braced by concrete fins, and seems over-wrought, as does an arch design for the same scheme, where the rise of the arch is much greater than structurally necessary.

Setting all that aside, this is an excellent and well-produced book, and overall Menn's oeuvre certainly deserves this degree of attention. The details of his individual designs are not necessarily something to emulate, but this is largely because few readers will be designing works for the Swiss landscape, and most will be working in forms other than solely reinforced and prestressed concrete. What stays with me the most is his disciplined approach in finding the most appropriate structural form, and in then keeping it simple and unembellished. From experience, that's nowhere near as easy as it sounds, and something that few have achieved as successfully and consistently as Christian Menn.

17 May 2016

French Bridges: 9. Passerelle du Paillon, Nice

Here's a second bridge from the French city of Nice.

The Passerelle du Paillon is a modern addition to the city, completed in December 2010. It's only a short distance from the railway bridge in my previous post, and it carries pedestrians and cyclists across the wide bed of the river Paillon.

The bridge was designed by noted French architect Alain Spielmann. Coyne et Bellier were the structural engineers, and Eiffage and J. Richard Ducros the contractors.

The budget for the 75m long bridge was 3 million euros, but completion of the bridge was delayed by a year when tenders came in 50% higher than expected.

The main mast is supported on a foundation comprising 30m long 1.2m diameter reinforced concrete piles. Two additional stub columns are located on the foundation, presumably to stabilise the bridge deck against twisting.

The bridge is a symmetrical cable-stayed steel structure, with a 25m tall steel pylon supporting twin decks in an "X" configuration. The 3m wide decks appear to comprise steel box girders on the inner edge, with an outer edge supported from cantilever struts.

Planters have been awkwardly placed at the entrance to each arm of the deck, presumably because the designer didn't consider that a 3m wide space might be attractive to drivers of small cars.

The outer edge of each deck is hidden behind a narrow steel fascia strip, presumably added to provide a clean line and hide the tip of the cantilever supports.

The layout of the bridge is much more attractive than a straight-line bridge would be, but strikes me as over-generous for the bridge's location and likely useage. It's well out of the city centre and alternative walking routes are available at a reasonably close distance, so the layout and dimensions appear excessive. I wonder what had to be omitted from the design to bring tenders back within the original budget?

The twin-span solution, with a single pier in the centre of the riverbed, is appropriate to the location. On the west bank of the river, the footway is narrow, but on the east bank it is wide. An asymmetrical design with an offset pylon could therefore have been feasible, with backstays landing on the east bank.

However, the chosen design minimises intrusive construction works to both banks, and the height of the pylon is perhaps more appropriate to the surroundings than would have been the case for an asymmetric solution.

For the most part, the bridge is well-detailed, without undue fuss. I like it.

Further information:

14 May 2016

French Bridges: 8. Railway Bridge, Nice

I'm going to feature a couple of bridges that I found last time I was in Nice, France.

I've done my best to find any information on this three-span masonry arch bridge, which carries a twin-track railway line in Nice across the Paillon, a seasonal river which is exposed here, but buried in a tunnel in most of the city centre.

I don't know when it was built, or by who, so please feel free to add information in the comments, if you can.

What I like most about this bridge is its clear, clean lines. Seen from far enough way, it could be mistaken for a concrete bridge, due to its sharp, hard lines and general lack of texture.

Seen closer to hand, the scale of the facing arch voussoir blocks is impressive. From below, it can be seen that the bridge isn't really made from such large blocks, but from more conventional coursed masonry.

The paleness and the hard edges to the masonry indicate that this is a well-engineered bridge, a work of rigour and certainty.

The bridge deck has been widened in concrete at some stage, but the lightweight balustrades ensure this has little visual impact.

The concrete "boats" which have been placed around the original stone piers are one of the bridge's least attractive features. The original stonework is left marooned, like a giant stepping across a river with her feet in saucepans.

Additional piers have been inserted halfway along the river spans, which help support a lower-level roadway bridge adjacent to the railway structure. Oddly, I don't think these are such a bad feature - they seem sufficiently divorced from the bridge above that it shrugs off their intrusion.

The addition of overhead electrification is less successful, with one support point above a pier, another above an end pilaster, and one in an awkward position part way long a span. It's hard to believe it would have cost much more to position every support symmetrically above the piers.

The bridge is generally in very good condition, except for a few areas of staining and this area of damage to a lower edge.

11 May 2016

Historic bridges widened to add footways or cycleways

One of my readers has written to ask whether I know of any examples of UK historic bridges (ideally Listed ones) which have been widened in modern times to increase capacity for pedestrians and cyclists.

From my previous posts, my personal favourite is Roxburgh Viaduct, with a footbridge added at a low level (although this is, of course, not a modern addition). A poor example is Byker Bridge, while I've covered Hungerford Bridge / Golden Jubilee Bridge on two occasions.

I can think of a few more, but I'd be interested to see what examples any other readers can suggest, both good or bad. Please post in the comments!

03 May 2016

Yorkshire Bridges: 11. University of York footbridges

I'll finish this short series of posts on the bridges of the University of York with a sampling of some of the other footbridges to be found at the University's Heslington Campus.

But first, I found a couple more photographs of the weathering steel footbridge, which make for an interesting comparison with my own photographs. Both of these are courtesy of the University's image library. They show the bridge as it was originally designed and built, not as hidden behind trees as it now is, and with a much more open and attractive parapet. It was clearly a genuine work of art, and deserving of wider recognition. Although it's still an attractive bridge, it's clearly not what it used to be.

Here are a few more of my own photographs of bridges at the University:


30 April 2016

Yorkshire Bridges: 10. Arched footbridge at University of York

Here's a third footbridge at the University of York. This one connects two college buildings across a small highway, and was built some time before 2010, although I can't find any information on the exact date, the contractor, or the designer.

This is a fairly straightforward steel arch bridge, although there are a few features of note.

The first is its asymmetry, with the arch ribs founded at one end close to deck level, and at the other end below deck level. I'm only guessing, but I wonder if this is due to an obstacle to foundations at one end, such as buried services. This may also explain the slightly odd struts supporting the deck at one end.

Joints in the deck edge stringers have been simply detailed, and most of the rest of the bridge is also straightforward and attractive, including the balustrades.

The choice of paving is unfortunate, with some of the paving slabs coming loose. I would think these will be a perennial source of problems.