27 August 2016

Scottish Bridges: 55. Cambus O'May Bridge (after the flood)

A couple of weeks ago, I visited the River Dee in Aberdeenshire, and returned to three bridges which I had previously seen in the Summer of 2012.

At Christmas 2015, the Dee experienced one of the most severe floods in its history, along with several other rivers in Britain. A number of bridges along the river were severely damaged, and one destroyed.

Cambus O'May Bridge was built in 1905 by James Abernethy & Co., and then substantially rebuilt in 1988. It's a very fine pedestrian suspension bridge, one of many along the River Dee. It looked good on my 2012 visit.

It's amazing that the bridge survived the 2015 flood at all, as the level of water battering the bridge can be seen in the video below:

When I visited in mid-August 2016, the damage to the bridge is clear. Unsurprisingly, it is currently closed, with no sign of any plans for repair work.

The entire structure has been bent sideways by the force of the water.

Several of the bridge hangers are missing or bent.

Most significantly, there is major damage to one bay of the main deck lattice truss, presumably due to impact from debris.

I think the most likely future for this bridge is another reconstruction, as I think it would be inordinately different to cut out and replace the most damaged section and to straighten the remainder of the bridge. That seems unlikely to happen any time soon, as the bridge does not provide critical access to anyone, and I imagine there are other priorities for limited budgets.

04 August 2016

Upper Orwell Crossing Project bridge design competition

I'm struggling to know where to start with what strikes me as one of the worst bridge design competitions to be organised in the UK for quite some time.

First, let's start with the facts.

Suffolk County Council are promoting a £77m scheme to build two new highway crossings of the River Orwell in Ipswich (A and B in the image below), and to refurbish the existing Prince Philip Lock Swing bridge (C in the image below). Working with the RIBA Competitions office, they are launching a design competition to select an architectural team, to work alongside the engineer already appointed, WSP | Parsons Brinckerhoff.

The key aim of the new bridges is to ease traffic congestion, and to promote regeneration in a riverside area which currently has very restricted transport access.

Suffolk's press release invites interested parties to submit a prequalification questionnaire by 1st September. Suffolk then intend to shortlist at least 5 teams to take part in the contest itself. These teams will submit entries by 2nd December, with a winner expected to be announced in week commencing 12th December. Construction would not start until at least 2019.

The shortlisting criteria will be something of a challenge for many very able bridge designers who may be interested in this opportunity. First, and in my view most egregiously, only architects can enter (registration with the Architectural Registration Board is a requirement, or equivalents in other countries). This is quite emphatically not a contest to find the best bridge designer, or indeed the best bridge design team, it's to provide the already-appointed engineer with a partner and skills which Suffolk CC evidently feels they lack on their own. That is, the Council does not consider their engineering consultant to be capable on their own of designing a suitable bridge for the site.

The RIBA Competitions office would support this of course - their role is as much about protection and promotion of the architectural closed shop as it is about serving any client's best interests. Some years ago, RIBA had its arms twisted by the Institution of Civil Engineers and Institution of Structural Engineers to ensure that engineers had a fair opportunity to compete in bridge design competitions (previously, RIBA were insisting that any competitors in their contests had to include a registered architect). WSP|PB will, of course, have been appointed fairly to their role, but it's simply a nonsense to suggest that there are no engineers who can design a decent bridge without the assistance of an architect (there are few, perhaps, but certainly there are some).

(RIBA's history in this area is generally poor. When I examined their track record back in 2009, I reviewed seven of their bridge design competitions, only two of which resulted in bridges actually being built. One more since then has so far fared no better (Salford Meadows), so that's a 75% failure rate.)

A further obstacle to getting the best competitors is commercial. Suffolk's information memorandum explains that they are looking for architects with a turnover of at least £1m per annum and professional insurance cover of £10m, at a stroke eliminating pretty much every specialist bridge architecture firm in the UK and limiting the field to large architectural firms for whom bridges are not a core area of expertise. For anyone who had thought the RIBA wanted to promote the interests of the small practices who make up a huge proportion of its membership, this is a quite unpleasant slap in the face.

Suffolk then go on to explain that potential competitors need to demonstrate suitable case studies demonstrating capabilities in large infrastructure projects, and information on multi-disciplinary collaborative experience, including BIM level 2 compliance. There are plenty of architectural firms who can claim this, but very few with experience applying these skills to major bridge works.

Successful hoop-jumpers will be delighted to discover they qualify for a £10,000 honorarium, which is very good by RIBA standards and will cover a small part of the costs for their site visit, interview and six presentation boards. These are to include not just one, but two entirely separate designs for each of the two main bridges, which strikes me as quite excessive, like buying one cow and expecting it to provide the milk of two.

You may wonder how the five competing architects will come up with feasible, buildable, and economic bridge design concepts, given that at this stage they will not yet have consummated the intended arranged marriage with the incumbent engineering consultant. Suffolk helpfully suggest that they could invite a friendly neighbourhood structural engineer onto their team. I will be interested to see how many engineers take up this offer, as Suffolk make it repeatedly clear that WSP|PB will be carrying out all the engineering once the project progresses for real. What engineer will pour their creativity into a contest with no carrot of a possible design appointment, only to see another engineer take on their output and gain all the credit?

In the world in which this contest lives, however, engineers are not creative, and their input is not valued. The opportunity for genuine collaborative teams to come up with exciting, attractive and practical solutions may be replaced by a good old fashioned pretty picture parade. I think almost everyone involved in this kind of work on a regular basis knows that this is not how landmark bridge design works best.

Competition entries will be evaluated for quality, appropriateness, buildability etc, and this will account for 60% of each entrant's tender marks. The remaining 40% is for a lump sum fee proposal to provide the necessary architectural services. Yes, a lump sum to undertake design even though they cannot possibly know which of their concepts will be taken forward, or how much those concepts may change during further development. The winner will be the entrant with the highest combined score, raising the very real possibility (as in other similar exercises) that the design taken forward is second or third best, if the fee is low enough.

I will be blunt: I think the way this competition has been set up flies in the face of pretty much everything that is understood about how to procure good bridge design. The prequalification criteria are calculated to exclude the talented and capable, and the promoter's attitude to the value of creative engineering design is simply disgraceful.

Am I disgruntled simply because I'm excluded from a chance to show what I can offer as an engineer? Yes, my grapes are sour, this is true. I will, of course, follow progress with great interest (first, to see whether they back away from any of the currently stated prequalification criteria). For all its flaws, I'm sure interesting designs will be generated by people capable of doing a reasonable job ...

17 July 2016

Bridge: The Heritage Of Connecting Places And Cultures

There's an interesting conference planned for 6th-10th July 2017, to be held at the Museum of Iron, Coalbrookdale, UK.

It's organised by the Ironbridge International Institute for Cultural Heritage (based at the University of Birmingham) and the Ironbridge Gorge Museum Trust, and is intended as an interdisciplinary conference examining the heritage of bridges. The organisers state that "the conference will draw from anthropology, archaeology, art history, architecture, engineering, ethnology, heritage studies, history, geography, landscape studies, literature, linguistics, museum studies, sociology, tourism studies etc."

Proposed discussion themes include:

  • The materials and technologies of bridges – the heritage of form and function
  • National and local iconographies of bridges
  • Narratives of bridge construction and destruction
  • Communities united and communities divided by bridges
  • Poetics of the bridge – representing the bridge in art, literature and film
  • Love and death on the bridge
  • The language of the bridge – metaphors and meanings in social life
  • Touring bridges – travel narratives and tourism economies
  • Alternative bridge crossings – tunnels and ferries

A call for papers has been announced, with a deadline of 1st November 2016 for abstract submission. There are no details on conference prices at present., but you can visit the conference website to keep up to date with plans.

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.