River Wear design airbrushed from history

You could be forgiven for thinking that somebody was trying to airbrush the ill-fated New Wear Crossing out of history.

First, the project website www.newsunderlandbridge.com was removed, along with many detailed project documents which, to me at least, remain quite interesting. If you want to know about how Sunderland Council developed the cost estimate for the bridge or analysed the benefits it would bring, you can forget it.

The bridge has also become a ghost on lead designer Techniker's website, removed from their project list and from their news/blog entries. There are no longer any links given to their ICE lecture on the bridge, or to a selection of design drawings. A few ectoplasmic traces remain, in the form of the Stitching Structures lecture, and Google still provides access to both the ICE lecture and some project details, even if the direct links have been edited out.

Of the others involved in the project, Roughan O'Donovan, responsible for much of the detailed design work, make no mention of it on their website, while only Hewson Consulting Engineers, who also provided significant design expertise, seem unembarrassed enough to still feature the scheme on their website. You can also, if you wish, still read about the design's "Very Good" CEEQUAL rating, awarded for sustainability which seems somewhat daft in light of the design's grossly excessive material demands.

I feel sure I had read of plans for an IStructE regional lecture about the project, but can find no sign of it on the IStructE events website.

I think this is all a shame, as whatever the scheme's merits or lack thereof, it was a breathtakingly bold design, and should form a useful case study for students of bridge architecture, engineering and procurement for many years.

There has been little in the way of public analysis of what went wrong, with Sunderland Council clearly determined to bury the whole fiasco as quickly as possible, building a new bridge proposal upon the grave as quickly as they can, bound as they are by a commitment to spend the central government money already granted to them.

One group of gravediggers has been firmly rebuffed, with local Tories refused permission to ask the obvious questions, such as "so, just how much would it have cost?" and "How much money has been wasted?" This may seem somewhat ironic to locals, who will doubtless recall that local Tory leader Robert Oliver was one of the bridge scheme's most enthusiastic promoters. I don't know enough about what has gone on behind the scenes to be able to judge, but given what has happened on several other ultimately unproductive bridge design competitions, I would think that an unwillingness of politicians to put their grandiose ambition aside and to seek out properly critical advice has possibly played a very real part in events.

Update 15th August: Thank you to Matthew Wells for advising that his IStructE evening lecture on the bridge will take place in Manchester on 11th November.

Sunderland's River Wear Crossing: A Post-Mortem

Okay, while the dust slowly settles on this week's announcement that Sunderland's hubristic River Wear Crossing scheme has been cancelled (in its current form, at least), I guess it's time to reflect.

This was a project conceived a few short years after the glitz and the glamour of millennial bridge fever, which saw Sunderland council looking with particular envy at their long-time rivals in Newcastle / Gateshead. The city of Glasgow were another local authority infected by the fever, although in September 2005, when Sunderland announced that their bridge design competition had a winner, it had not yet become apparent quite what a fiasco Glasgow's scheme would become.

The parallels with Glasgow's project are highly pertinent, with both competitions won by designs which were immediately and obviously structurally "challenging"; which were pursued with vigour by their promoters regardless of criticism; which received only two willing tenders, both well above the available budget; and which were binned without a hint of apology for the millions wasted in project development, to be replaced by simpler design-and-build projects where risk was eliminated by letting contractors take the lead.

That's what is to happen now to the New Wear Crossing - a new design-and-build tender stipulating the same alignment, same general principle as the original design (i.e. a cable-stayed bridge), and even the same foundation positions (to avoid having to re-assess any impact on river hydraulics, and land purchase issues, presumably).

Sunderland announced Spence Associates and Techniker as the winners of their RIBA-run contest to design a £43m highway bridge as part of the wider Sunderland Strategic Transport Crossing in 2005, but it would be three years before the winning design would actually be made public.

Quite why it was kept secret has never really been made clear, although I know that the design was subject to independent review from beyond the jury panel and the client's ordinary technical advisers. There was clearly some recognition of the bridge's highly radical departure from the structural engineering norm at the outset (the reviewer concluded that "construction of the bridge is challenging but achievable"). Even when, in November 2008, Sunderland took a positive decision to move ahead with the iconic design, they were still making clear their concern over its feasibility and talking about the possible need to "tone it down".

When the bridge design was finally unveiled, I commented immediately that "The iconic bridge design is simply amazing. Amazingly beautiful. And amazingly daft." Some of what was stated by its designers at the time was hugely misleading e.g. Techniker's patently absurd claim that "the bridge was not a technically difficult or radically new structure", or that a bridge "of similar size and span and of exactly the same construction and arrangement has been constructed a decade ago without any difficulty".

These were not the last statements made which seemed at odds with reality, with Sunderland council on several occasions reporting that the bridge was well-supported by the public, on the basis of a tiny survey which was, in fact, contradicted by a larger survey showing very nearly half of those questioned would have preferred a "tried and tested" design alternative.

In September 2008, I offered this summary of the issues with the design, and I do take some satisfaction from being able to say now that I told you so:

"Amongst all the consideration of cost versus quality that will probably dominate discussions, I think it's important not to forget about risk. Whether it will stand up or not, for a given budget or otherwise, it's undoubtedly a very high-risk proposal. And Sunderland might be wise to look at recent examples from Glasgow and Stratford-upon-Avon for cases where high-risk competition-winning designs were dropped only after first wasting considerable sums of public money."

Following the council's 2008 decision to invest funds in developing the design further, considerable effort was spent first working through the design problems and then preparing a full detailed design, with a number of technically experienced consultants brought alongside Techniker to provide assistance. The cost estimate soon rose well above the original £43m, and it became apparent that central government would only provide Sunderland with enough funding for a conventional bridge alternative, not for an iconic structure.

Nonetheless, the council eventually succeeded in putting together funding to match the cost estimate, and hence to put the highway project (featuring the bridge) out to tender. Indeed, they succeeded in getting the overall project budget down from £133m in 2009 to £118m in 2011.

The £118m estimate was based on a "mean probability" risk allowance, i.e. the council estimated what risks might push their costs up, and allowed for precisely 50% of them, in line with standard government guidance (the P50 risk level). They calculated that if all risks were to materialise in full, the project cost could rise to£130m, and that they would need to make financial provision for this eventuality. Sunderland have now removed the project website, so all their financial reports and other data are no longer shared with the public, although you can still find them, for now at least, via Google's cache.

Signs that the contractors' views of risk differed from the promoter's emerged in February this year, when two of the four firms bidding to build the scheme decided not to return a tender. We are told now that neither of the remaining two tenders returned "were priced within the current funding availability and approved budget for the scheme", and that to pursue them would require "significant additional funding".

What we have not yet been told is precisely what the tender figures are, i.e. to judge whether the original budget estimate or its risk allowance were ever, in fact, realistic. The bidders knew the available budget, and presumably gambled that Sunderland would not wish to lose face and abandon the scheme, finding additional money somehow.

So we are left with a number of unanswered questions:

• What were the tender prices from the two bidders? By how much did they exceed the budget estimate?
• How much of the cost over-run relates to the bridge rather than other aspects of the scheme?
• What was wrong with the budget estimate - what did the bidders price that was not in the estimate?
• How much money has been spent so far on developing the current scheme?
• Looking back to the original competition, why was this design ever chosen?
• Who or what is to blame for the decision to repeatedly press ahead with a project where the risk of failure was ever-present, and never sufficiently mitigated?

By my reckoning, the bridge amounts to some £77.5m of the £118m estimate, once you share out project management costs, land purchase, risk and indexation in proportion to actual construction costs. That's some way beyond the original £43m assumed at competition stage, and we must assume that even that figure has been blown past by the actual tender prices.

The financial reports for the bridge stated a figure of £13.3m for "fees" for the project, including items like consultants, designers, public consultation, licenses, consents, surveys, project management etc. Some of this will, I guess, relate to future fees e.g. for project supervision during the construction phase. But most of those headings relate to activities which should already have been completed, and hence I'd guess perhaps some £10m has been spent on developing the scheme to its current state, and the majority of that completely wasted on a design which will never be built.

Looking back to the start of the whole process, I recall emailing Sunderland in 2008 to ask for a copy of the competition jury's minutes, and never received a reply. I think there is much to be said for transparency, and to the opportunity it offers to receive criticism gracefully, and to benefit from it. Perhaps future design competition organisers could consider that.

It looks to me like Sunderland Council will wish to rapidly move on: to put this fiasco behind them and focus on a new, less challenging, possibly far more context-appropriate replacement project. But if others are to learn from this unhappy experience, I hope that answers to the above questions do emerge.

Ding dong

I will hopefully have more to post about this at the weekend, but for now:

Sunderland City Council scraps plan to build £118million bridge across the Wear

Bridge collapse! The rise and fall of Sunderland’s ill-fated Iconic River Wear crossing

Scared off? Sunderland’s landmark bridge architect Stephen Spence reveals his biggest regret over project axe

Sunderland scraps costly Wear bridge plans

£118m Iconic Sunderland bridge was a “ridiculous waste of money” blasts councillor

The official council report can be found online, although it offers few answers to the key questions such as: just how much over budget were the two tenders submitted? How much money has been spent on the abortive design?

River Wear - A Bridge Too Far

As a follow-on to the last post, I found some interesting commentary on the River Wear bridge at New Civil Engineer's website, posted by long-time critic of the bridge, Simon Bourne. With Simon's permission, I am reprinting it verbatim here, and I would be interested to receive comments.

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River Wear - A Bridge Too Far
I have two well-known points regarding this scheme – the first is the cost, but my main objection is actually the complete lack of structural integrity, which is also at the heart of two other concerns about the quality of design and of designers.

1. The Bridge Costs
There are several facts about the costs of the Wear Bridge – facts which, it seems, have not been made available to the client, the residents of Sunderland or the major funder, i.e. the Department for Transport (DfT). One can show very simply that a high-quality and elegant bridge at this location should cost no more than £15-20m.

At the specialist bridge design consultancy that I used to own, Benaim, I have seen the design and construction of two recent bridges of very similar size and location. Both were of similar width (~25m) with one being a little longer (450m) and one being a little shorter (300m). The shorter one had considerable architectural input from a very well-known UK bridge architect. The shorter one cost about £10m and the longer one about £15m. On this basis, and with some adjustments for size and inflation, a high-quality bridge at Wear should therefore cost about £15m. Even with some further sensible premium applied (which I discuss in Section 3), the actual bridge cost should be no more than £20m.

However, the exhibited cost of the bridge is £55m – a factor of nearly three has been adopted. I would suggest that a premium of this size is wholly unacceptable, at any site. This figure may also yet increase further as the real complexity of the construction becomes revealed. This baseline cost of £20m equates to about £2,000-2,500/sq.m, which seems very reasonable compared to all other bridges of its size, a little on the high side if anything. The exhibited scheme though has a cost of around £6,000-7,000/sq.m, which one only finds amongst the very largest and most complex bridges in the world (i.e. major world bridges with spans close to 1,000m that are complex through the engineering necessity of their span, location and scale).

By the time one adds the costs for the highways (~£25m), land (~£10m), fees (~£15m) and the same level of risk/inflation (~£10m), the total cost of the scheme becomes £80m, not the £120m that defines the current scheme. So, the saving attached to a baseline, good-quality solution is thus £40m, not the £5-10m that seems to have been quoted. It would appear that the client, the local residents of Sunderland and the DfT (who provide ~£85m of public funds) are not aware of this potential saving.

It is also noteworthy that around £15m has been spent in fees (over the last 8 years of development since the design competition in 2005) – a figure that is equal to the actual cost of building a sensible bridge.

The original budget for the scheme in 2005 was around £40m, which would suggest that £15m for the bridge was originally expected – this £40m budget has now increased to about £120m. Any publicly-funded scheme that clearly struggles to progress or has a budget that escalates so wildly should certainly be held open to considerable public scrutiny.

2. The Lack of Structural Integrity
The scheme is at face value a cable-stayed bridge, but the lack of connection between the two towers completely transforms the behaviour of the bridge, from elegant engineering in to utter chaos. The two towers are now forced to carry the cantilever moments from the front stays, instead of simply being a means to spread the forces in to the obvious back stays. The public might not appreciate the enormity of this distinction – so, I liken it to a plane being designed with only one wing. Of course, the engineering can be applied to solve even this problem, though the size needed for the jet engines would surely make the plane fly more like a rocket than a plane. This one-winged plane would be a ludicrous piece of engineering, at very high cost – but that is effectively what the Wear scheme has become.

The Wear Bridge has many similarities to Calatrava’s Alamillo Bridge in Seville, which is also an unbalanced cable-stayed structure. I know that this bridge also cost about three times the price of a more traditional solution. It was justified at the time as being part of the development for the Expo 92 in Seville. Though I can support a premium being attached to a bridge that was built as part of Expo 92, and one can observe that the Alamillo Bridge has indeed also become an icon for the city, I cannot support any scheme that has such a high premium (see Section 3).

There is also a common misconception that the two towers of the Wear Bridge are steel fabrications, with a length/width about 5m. They are not anything like this small. Each 140-180m high tower is equivalent to the largest concrete bridge cantilever in the world – the same scale as the 301m span Stolma Bridge in Norway. Each tower is a prestressed concrete box girder around 15-20m deep at its base and about 10m wide, with 1m to 3m thick walls and prestressed with about 120 prestressing cables. I estimate the prestressing force in each tower is around 500MN, i.e. 50,000t, with the tower having to carry a moment of around 7,000MNm – enormous figures that are consistent with the enormity of the task in hand.

The bridge in reality only needs to have 50m spans, or perhaps an elegant 100m cable-stayed span – it does not need to have the equivalent of a 300m span. Not only does the scheme provide a concrete box girder (in the two towers) that is the same as the largest concrete beam bridge in the world, but it then also provides a completely separate steel-composite deck and a complete set of cable-stays to connect the two systems. The scheme effectively has three bridges in one – and so it is not surprising that it costs three times as much.

3. The Quality of Bridge Design
Every bridge or piece of infrastructure should, of course, be a fine piece of engineering of the highest quality. But that desire does not have an additional cost attached to it, and every piece of infrastructure cannot have a premium anyway. However, there will be selected number of major bridges or pieces of infrastructure that do deserve a premium. Society has to decide what premium is acceptable and where or when it is applied, and engineers and architects as representatives of society should formulate those figures. As you can get well-designed bridges at little or no premium, these should be the norm.

At certain key sites (major estuaries, major cities or bridges of national interest or certain bridges with considerable traffic) or at certain key times (the Olympics, for example), one could suggest premiums of 10-25%, say. Most major bridges are dominated by their engineering and environmental challenges, and it is nearly always the resolution of these issues that defines the beauty and success of the bridge. The huge majority of the world’s most fabulous bridges had no premium applied to them and had no architectural input – consider my favourites such as Brunel’s Saltash Bridge across the River Tamar, or Maillart’s Salginatobel Bridge in Switzerland or Freeman Fox’s Humber Bridge.

More recently, architects have indeed become involved, which can be a very welcome addition as long as that architect is skilled in bridge design and respects the considerable forces at work within the bridge. Architects also bring a wider appreciation of social and environmental issues, which can be fundamentally important too.

So, I can see the need for every bridge to be well engineered and carefully designed, with architectural input as the engineer needs it, and the need for a certain number of key bridges to have a premium attached to them, but I cannot see the need for a premium of 2 or 3 to be applied, at any site. It might be possible to play some architectural or sculptural games, or some structural gymnastics with a £2-5m footbridge, where a significant premium might thus be applied, but it is certainly never acceptable to do the same for a £50-100m piece of infrastructure. A footbridge is often more akin to a building, with a shorter lifespan, fewer concerns over its long-term integrity and it is often privately funded. A major bridge though has to last well over a 100 years, be virtually maintenance-free for the same period and justify its existence using public funds.

The client at Wear suggests two reasons for his selection of this scheme – the artistic merits, which I dismiss as they have led to nothing other than a complete lack of structural integrity, and the economic advantages of a landmark bridge. The vast majority of the economic benefit of the scheme lies in the building of a road and a bridge, any bridge in fact. The rather nebulous benefits regarding the further advantages of a landmark scheme are desperately difficult to define and hard to validate, and it is equally hard to find any supporting evidence of such benefit. One has to question the desire of the client to seek a landmark scheme so strongly.

Any publicly-funded client should be seeking to procure a high-quality scheme that fulfils its purpose – the premium to be spent on anything further, such as a landmark solution, should be proportionate to the needs of the area or the value/benefit of the scheme. The client seems to believe that a further £10m benefit might accrue from the creation of a landmark scheme, a scheme which he understands to cost about £5-10m more – that balance might thus make sense, if it were all valid. However, the further benefits of a landmark scheme might equally be zero, and we know from Section 1 above that the additional cost of the landmark scheme is actually around £40m, or more – the cost-benefit equation now makes no sense at all, but the funding authorities do not seem to have appreciated this point yet.

4. The Quality of Bridge Designers
Bridge designers have to use their client’s money wisely as well as leaving an elegant legacy for the benefit of society. I welcome the involvement of skilful architects in this process and indeed the majority of my major bridge designs (many of which have won awards for their elegance, economy and innovation) have been developed with specialist bridge architects – architects who understand the engineering and construction principles, and who work with the engineer to develop forms and details that improve the legacy that we leave behind for society.

In the last 20 years, architects with good bridge expertise have also joined many other engineering teams that design both major and minor bridges, mainly because engineers often do not have this level of aesthetic training or knowledge of the social impacts. This liaison with skilled architects is certainly to be encouraged as it will raise the overall quality of the scheme, generally at little or no cost though. My favourite bridge of the last 20 years, Virlogeux’s Normandy Bridge, rightly had good architectural input too, and the current crop of major bridges (such as the Millau Viaduct in France, the Stonecutters Bridge in Hong Kong or the Forth Replacement Crossing) have also had significant architects involved as part of the design team, though clearly the engineering still dominates with all these schemes.

The key is for the architect to be experienced in bridge design and for their role to be proportionate. On a building, the structural content might only be 25%, and as such the architect leads the design and the engineer supports as part of the team. However, for a bridge where the structural content might be 90%, the engineer must lead and the architect should provide support. On all the major bridges where experienced bridge architects have been involved, they have worked with the engineering to develop overall forms and particular details that work well. On a few occasions though (often with footbridges and rarely with major infrastructure), architects have ignored the engineering and developed their own forms – the Wear Bridge is exactly a case in point.

One has to query the reasoning behind this client appointing a team that seems to have had little major bridge experience. A client commissioning a new hospital or airport would clearly seek an architect, and an engineer, with substantial experience in the design of such buildings. A well-informed client for a major new bridge should only seek an engineer, and an architect if needed, who also has substantial experience of major bridges. Michel Virlogeux noted last month about how the demise of a central client authority in France will lessen the likelihood of further spectacular bridges in that country.

Though I do not entirely support that view (on the basis that design and construct schemes can indeed deliver excellence in all areas – elegance, economy and innovation), it is a good point that the procurement of major schemes can often be best managed when that client body is a national body, with extensive experience and knowledge, the ability to best judge when and where a premium should be applied, and who has control over, and a vision for, the design direction. This would avoid the one-off procurement by a less experienced client, who might be blinkered by his own desires to create an unnecessary and expensive landmark.

Conclusion
I hope that the funding authorities for this scheme (both Sunderland City Council and the DfT) appreciate the enormity of the task ahead of them, with all its attendant risks, and begin to realise that there are very satisfactory, and high-quality, alternatives that are available to them for at least £40m less. A more appropriate scheme of this nature could still be delivered, for the benefit of the whole Sunderland community, more quickly and reliably.

The architect’s role in bridge design is definitely to be encouraged, but that role must be proportionate to the dominance of the engineering forces at work, and that architect must have valid major bridge experience. All infrastructure and bridges must be well-designed and of high quality, with a number of key national projects being worthy of suitable premiums. A central national authority to manage the procurement and design direction of these key projects would make good sense – the DfT would seem the obvious candidate for this role given that they are also the prime source of public funding in this area.

By Simon Bourne, March 2013, reprinted from the New Civil Engineer's website.

River Wear Crossing tenders returned

Tenders were due in for Sunderland's River Wear crossing on 22nd May, and presumably they have now been received. The tender date had been delayed twice, having originally been set as 20th March, and then extended once already to 24th April. The number of tenderers had also dropped, from the original shortlisted four, down to two, after Ferrovial and Balfour Beatty withdrew, leaving the field to Vinci and Graham.

While the bridge building world waits to see whether either tenderer has actually managed to come in below Sunderland Council's £118m project budget, I thought I'd post up a couple of items that are relevant, one in this post and then another to follow soon.

I posted a lengthy update on progress with the bridge almost exactly a year ago. Now, the bridge's lead structural designer, Techniker's Matthew Wells has responded to my post in the comments section.

Wells asks for the bridge to be judged distinctly in architectural, engineering and commercial terms. On the engineering, he notes that "the engineering has been involved and very enjoyable. My associates have demonstrated outstanding skills to realise it", which I don't doubt. Commercially, he says "Is it value for money? Perhaps best left to the client to judge where to spend his/her money." There, we part company. I've argued here in the past that the value a landmark bridge brings to its community is very poorly understood, even in purely economic terms.

Sunderland Council commissioned specialists to put a figure on the value a landmark bridge offered, particularly in how it could encourage investment and hence enhance employment, but this was long after the decision was made to press ahead with the "iconic" design, and comes across somewhat as post facto rationalisation put in place to keep central government funders happy. In short, I believe very few clients can present any real evidence to justify how they spend taxpayers' money once things move beyond simple journey-time benefits, and even those are often grossly miscalculated.

Wells also comments that "like all bridges, it's for 120 years, so questions of design in austerity need careful consideration". Here it may be appropriate to consider that this was a bridge conceived in 2005, at a time when Sunderland were probably still looking enviously at the money lavished on Gateshead's fantastically expensive Millennium Bridge. This was the back end of the millennial boom in iconic bridges, and the winner of Sunderland's design competition exhibited a compellingly flamboyant spirit (as did the designs from other entrants).

Now, in 2013, in a time of austerity, it may seem sensible to question not only the £82m of central government funding allocated to the project, but the £33m of Sunderland Council's own money, which I understood was to come by depleting the Council's financial reserves. Job creation may be cited in its defence, but the Wear Crossing will be nowhere near as effective at that as was, for example, Newcastle's Tyne Bridge, rushed onto site in 1925 largely for the direct employment its construction required.

As always, I'd be interested in readers' views on this subject, please click the Comments link on this post!

River Wear Bridge controversy linked to IABSE competition guidelines

"When engineers get the knife out they can be worse than architects". So says an editorial from Paul Finch in this week's Architects Journal. Finch suggests that "all is not happy in that part of the engineering world which still believes that dreary Freeman Fox box girders were all that were ever required."

The target of his scorn is criticism by bridge engineers of the design for the New Wear Crossing in Sunderland (pictured). The scheme, which has experienced a history of uncertainty dating back to the original bridge design competition, has recently suffered a major blow when two of four tenderers pulled out, almost certainly because of the difficulties determining the cost of building such an unusual structure with sufficient certainty.

Finch asserts that criticism of the "handsome-looking" bridge has been "aggressive" and "moaning", going on to request that "serious competitions with serious winners should not be the subject of professional sniping."

Really? How absurd. Perhaps an appropriate title for this blog post might be "When journalists get the knife out they can be worse than engineers or architects", and perhaps a humble blogger might suggest that "serious engineers should not be the subject of sniping from amateurs".

Although never named, the target of Finch's attack is Simon Bourne, probably the only engineer willing to have his name publicly attached to criticism of Sunderland's vanity project. He has gone on record at least twice. I reported the first occasion, when he told New Civil Engineer that "the bridge is about as structurally inefficient as you can imagine", which strikes me as essentially uncontentious. Two other, anonymous, engineers were happy to attack the bridge at the same time, and these views are consistent with most if not all of those which I have heard privately from other bridge designers. Bourne's more recent comments, in response to the withdrawal of two tenderers, included saying that "the risks of its hugely unique nature are very profound", which strikes me merely as a statement of the obvious.

In Finch's world, engineers should presumably just shut up and fall in line, leaving architects to do the talking. As I've discussed here before, deafness to criticism aligns closely with clients buying closely into a designer's vision, blind to its faults or at least to its risks. At least one high-profile UK bridge design contest came to a miserable end as a result, with a structurally exotic proposal remaining unbuilt, and it's now increasingly possible that the same will happen in Sunderland. Criticism should be welcomed: if a project is well-thought through, responding to challenge will only make its case stronger. What is less helpful, and Bourne's comments fall into this category, is criticism which comes too late to actually make any difference to the decision-making. Participants at all levels have too much personal investment in a project, and positions are too entrenched to change. Careers are staked on making a project succeed, whatever it takes, regardless of whether simpler or better-value alternatives have been discarded along the way.

Finch's attack on honest criticism doesn't end there, however. He goes on to link his point to IABSE's Guidelines for Bridge Design Competitions, which were published earlier this month. This is a document which grew out of widespread dissatisfaction with the conduct and outcome of design contests. In the UK, the subject was extensively aired at the 2007 IABSE Henderson Colloquium, with many of the lessons identified from failed competitions finding their way into the final IABSE guidance.

Finch points to an interview with Naeem Hussain, the chair of the IABSE bridge design competition working group, who discussed the guidelines with New Civil Engineer last year, prior to publication. Hussain was quoted by NCE as saying: "Some of the architects themselves are saying that the pendulum has swung too much and that designs are becoming so outlandish. First you often cannot build them or then the cost is so high that the client abandons the project." The IABSE guidelines are intended to assist clients in properly appraising proposals at the outset so as to reduce the risk of failure, and hence the risk of contest participants wasting their time and money.

In addition to a number of rather petty side-swipes at the content of the guidelines themselves, Finch suggests Hussain's NCE interview "reads like a thinly veiled attack on ‘arty’ structures." Finch isn't wrong to put his finger on the anti-expressive nature of many engineers, a belief instilled by their training and culture that value is the same thing as economy, and that measuring efficiency is tantamount of measuring virtue. I have limited sympathy with this reductionist vision of what bridge design can and should be, but nor would I suggest that the genuinely held views of acknowledged bridge construction experts should be discarded simply because a design competition was somehow "serious", as Finch does. Indeed, I think their views on the subject are probably better-informed than non-professional commentators.

A desire to silence engineering criticism has been reported within the New Wear Crossing's project team itself. In a talk by the design engineer Techniker, reprinted on their website, you can find the following: "One engineering collaborator on the project simply had to go – [they] proved to be subverting the intentions of the designer as at odds with appropriate bridge design. This was a kind of negative professionalism, parochial and ingrowing." Perhaps this is the same anonymous party cited by NCE last year as 'an expert close to the project', saying: "It's a really complicated bridge, and completely unnecessary for a span of this length".

I would have to agree with Techniker, in part. If a professional firm engaged on the project is genuinely attempting to do anything other than use their best professional endeavours to help deliver the client's agreed vision, then they should not be there. The rest of Techniker's talk makes clear that their view is that this is a cultural problem, that many engineers are trapped in what Finch would parody as the box-girder mindset.

More of Techniker's perspective can be understood from a short blog post on their website, which claims that "with modern methods of analysis construction practicalities are receding into irrelevance and the architect is free to organise form as he/she wishes within the geometric constraints of stability." I imagine many contractors would beg to differ, not least the two who have withdrawn from the procurement process.

Techniker's view appears to be simply that some necessary material has been moved up into the sky out of the deck, and if you think I am caricaturing them, here is how they describe the design process: "We worked to justify our proposals as a bigging out of the required steel, spreading it across the sky to make an effect." This is the opposite of the traditional bridge engineering approach, which works from the constraints of the site and of the construction method to determine where material can most efficiently be used. Cable-stayed bridges, of which the New Wear Crossing remains at heart an example, are the epitome of this conventional approach, incorporating within their permanent form all the materials that are also required for temporary support. The River Wear bridge, by contrast, will require extensive temporary support during construction, as material has been disposed for primarily expressive rather than structural effect. Some of the consequences can be seen in Techniker's website postings, and also on their detailed design drawings, a grab bag of which have just been made public.

A departure from the ordinary engineering imperative can be economically justified wherever the outcome creates sufficient value to offset the additional expenditure. That's the argument made by Sunderland Council's leader, who in defending the iconic design makes a big noise about the whole scheme's benefit-to-cost ratio (BCR), which is over 4, and therefore far more positive than many other schemes which government is happy to support. The breakdown of the calculated BCR can be found in a document on the New Wear Crossing website (see in particular page 63).

This makes clear that nearly 90% of the expected benefit of the project relates to transport cost savings, with only about 10% relating to the "landmark" nature of the bridge scheme. Of that remaining 10%, the majority relates to the expectation that an "iconic" structure will attract more investment and create more jobs than a cheaper alternative, a belief widely accepted but one for which hard evidence is much harder to come by. What is less clear, and I have been unable to extract numbers from Sunderland's reports which test this, is whether the additional "landmark" benefit is commensurate with the additional cost of a landmark versus a cheap structure. On the figures presented, any "extra over" cost of making the bridge "landmark" rather than conventional, beyond an allowance of £8m, will actually imply that choosing a landmark has reduced the benefit-to-cost ratio of the whole scheme. It doesn't seem plausible to me that the "landmark" cost of this bridge (as against Paul Finch's hated box girder option) is that low.

Ultimately, this is one proper test of the design's appropriateness. Does it add a sufficient proportion of value to justify its cost? While the scheme's engineering critics are right to point out the risks and difficulties of taking forward such a monumentally unique design, they have little if anything relevant to say about the value of the resulting structure to Sunderland's economy.

In one of their website postings, Techniker assert: "We need to set up a critical framework for engineering." This is quite right. Such a framework won't be found solely in the engineering puritans' fear of extravagance; nor in the belief that the desire for economy is irrelevant in an era where anything that can be designed can be built. It certainly won't be found in a world where honest engineering views are dismissed out-of-hand by journalists as "sniping" or "moaning", nor one where IABSE's well-intentioned attempt to encourage better procurement is treated with unjustified paranoia.

River Wear bridge: an update

It seems that the NCE's news story featuring Simon Bourne's criticism of Sunderland's River Wear crossing (see my last post) has attracted quite a lot of comment. I guess that's why the magazine went for it in the first place, the chance to generate some controversy, column inches and pageviews.

First up are the comments on the NCE's website. At the time of writing there are 12 comments, which may not seem much, but is a positive bonanza by the website's normal standards. Civil engineers are normally true to their name, civil, and reluctant to voice strong opinions in a public forum.

The comments are fairly evenly divided between those pro and ante the bridge design. On the pro side are comments like these:

"The bridge is elegant. Difficult to build -yes, but elegant. As a Bridge engineer myself, I can only envy those who will be taking on this design and build challenge."

"It looks exciting, and design is not just about cheapness. It is better to design to please many and offend some, than to design to not offend anyone."

One comment seeks to justify the "iconic" nature of the Sunderland bridge by comparison to past engineering glories:

"The world is scattered with costly design examples, not only of bridges, that are striking, memorable and, by Mr Bourne's theory, should never have been built. A few to ponder are The Eiffel Tower, Sydney Opera House, The Forth Railway Bridge, etc."

That one made me chuckle. The River Wear bridge adopts a design where the structural engineer has taken an entirely submissive attitude to their architect friend, essentially promising to make a vision work, at any cost, regardless of the Herculean structural feats required. Compare the Eiffel and Forth structures, where the engineer led the design and where the geometric form directly responds to the structural imperatives. The Sydney Opera House is, on the other hand, a better comparison: a completely unsuitable structural form, with an architect unwilling to compromise, where the work ran grossly behind programme and over budget. Today we can say this is justified by the enduring presence of an architectural masterpiece, but for the client at the time it was little short of a catastrophe.

I found another comment profoundly depressing:

"If you want, and can afford, to have an 'iconic' structure instead of a bog standard box girder bridge; Good, I'll design and supervise its construction. My brief is to make sure that it doesn't fall down or fail to meet building regulations. It is the promoter's responsibility to meet the cost!"

This is a trait I hate to see in engineers - the view that we are simply the servants of the visions of those better suited, that we should only be the "calculators", in Le Corbusier's notorious phrase. That's not a world I would wish to work in - I'm happier in one where engineers can have their own vision, contribute actively to aesthetic, commercial and political discussions.

Here are some of the comments from those opposing the design:

"I always said that if I was a client I would sue the design team of my project if it won an RIBA award on the basis that it would be over-priced, difficult to build and probably expensive to maintain."

"I'm afraid I have to categorize it as an architect's whim. It is overly complicated and does not present a clear structural statement of what it is trying to achieve."

"... it fits into the architects inflated ego category and an extreme waste of public funds."

"A wonderful monument to architects sticking two fingers up at economic construction - and the councellors all too dazzled to call for sanity. I have no objection to landmark structures and abhor utilitarian design, but surely in these days of economic constraint it is better to get an economically designed project constructed ASAP - and have change left over for the next one - rather than splash out on expensive fantasies."

As I've observed before, a distaste for extravagance is deeply ingrained in the engineering psyche. If a student over-designs the reinforcement in a beam section, they will fail their test - the working assumption throughout an engineering education is that economy is king, and the engineer's job is to minimise materials and cost. The possibility that what we design can have a value beyond the purely functional is rarely if ever acknowledged.

This week's NCE continues to explore the story. In the letters page, architect Martin Knight writes:

"Investment in infrastructure which is well designed, encourages growth, and reinforces social, environmental and economic sustainability is highly valuable."

Knight, of course, was the architect for England's other major current bridge scheme, the Mersey Gateway (pictured, click for full-size image). Like Sunderland's River Wear crossing, this is a cable-stayed bridge design, although far more conventional. The Mersey design is clearly a landmark design with a strong aesthetic vision, but founded on an assessment of what makes engineering sense, in this case towers with balanced cable-stays, and a truss deck which contributes significantly to the overall stability.

There's also a strong contrast in the two schemes' approach to procurement. The promoters of Mersey Gateway accept and encourage their bidders to depart from the original vision in the interests of saving money - the structure which will be built is unlikely to retain either the harp cable layout or the truss deck, although I imagine the single plane of cables has a fair chance of surviving. In Sunderland, the architect's vision appears to be sacrosanct, and must be built however difficult it may become.

This week's NCE also features an opinion piece, which mentions both these schemes and compares them to the eye-wateringly awful ArcelorMittal Orbit (pictured left). This resembles a giant corkscrew onto which a wino is vomiting jets of blood. It is half observation tower, half-giant sculpture, and it's that neither one-thing-nor-the-other quality which makes it such a failure. The economic case for the Orbit is simple: a very rich man is paying for it, so we don't have to, and whatever value it offers is therefore an easy win. The possibility that, carbuncle-like, it actively degrades the aesthetic value of everything around it, is surely too cynical to contemplate.

Other blogs are getting in on the act, with one making the not unreasonable point that debate over the merits of the River Wear bridge is ill-informed without a better understanding of its costs, and the costs of the alternatives, figures which are not easy to extract from publicly available information.

I'm aware that the bridge's promoter, Sunderland City Council, is pretty unimpressed with the NCE's coverage, stating that the scheme:

"has been rigorously designed, costed, admired and backed within the industry and profession, including the Institution for Civil Engineers which presented the project with a CEEQUAL award ... The project is functional and symbolic, and its regeneration benefits were recognised by the Department for Transport in its decision to award funding."

Sunderland's website for the project reproduces much of the relevant documentation. The most interesting in the context of the present debate are the reports which attempt to put a value on the choice of a bridge with striking rather than commonplace aesthetics. These calculate that the landmark bridge design offers £33m of economic benefits which wouldn't apply to a conventional girder bridge design, most of that in generation of employment.

The document is riddled with flaws, foremost of which is that it calculates the cost-benefit ratio for the chosen landmark design, but doesn't actually compare it with what a conventional alternative would achieve. Many of the figures used are highly debatable, and a series of other landmark bridge case studies are presented, but offer at best anecdotal and certainly no quantitative evidence.

Nonetheless, I'd recommend the report to anyone interested in this debate, which surely needs to move on from the rather simplistic battle between engineering puritans and starry-eyed visionaries which we're faced with at present. There undoubtedly is a case to be made that a bridge as spectacular as Sunderland's will be justified if the additional benefits it brings are sufficiently large, and this would be true irrespective of its structural efficiency, which is not an issue of much interest outside the profession concerned.

The Sunderland promoters are unafraid to make the case that cheapest is not always best, that appearance remains important even in the middle of recession, and that value-generation is the important measure of viability. Anyone arguing against that needs to show not just that the alternatives are much cheaper (as they clearly are), but that the value lost is not significant, and that the end result isn't a blot on the landscape which future generations will look at with regret.

Engineers say £118M Wear bridge is waste of public money

New Civil Engineer magazine has this week found one bridge engineer willing to break cover and criticise Sunderland's River Wear Crossing, an astoundingly bold, astoundingly inefficient cable-stayed design (pictured below) that I've featured on many occasions on this blog.

Simon Bourne is the chap willing to put his head above the parapet. He's described as an "independent bridge expert", although until very recently he was head of bridges at Benaim, part of URS. Presumably with independence comes the ability to speak one's mind much more freely. Benaim were the quintessential contractor's bridge designer, expert at means of construction and ways of building bridges more efficiently.

Bourne describes the bridge as "a gross misuse of public money in a time of austerity", and has written to the government to tell them so. NCE report two other engineers chiming in with support, one noting its complexity makes it "completely unnecessary for a span of this length", and the other "just can't believe it's got this far". I'm always suspicious of anonymous quotes, but these echo views I have heard expressed privately by any number of highly experienced bridge designers, including those often associated with landmark bridges.

Bourne's criticisms of the bridge in terms of its efficiency as a structure are entirely reasonable, although long-time readers of the Pontist will find nothing new there as I've critiqued the bridge in far more detail in the past.

I'm far less convinced by his argument that the expense isn't justified by the economic value that a landmark bridge will trigger. He says that comparisons with the Gateshead Millennium Bridge are invalid because it is a city centre bridge, while the Wear Crossing sits in an industrial estate. I can't see how that's relevant - the Wear bridge will be visible from miles around and its value is as a statement of intent, a trigger for investment which creates value through employment. It's not intended primarily as a visitor destination in its own right. Whether that investment will materialise may quite reasonably be doubted, but I don't imagine Bourne can claim to be an expert in the economics of regeneration. I suspect that the real reason he takes this view is simply the traditional, highly conservative bridge engineer's belief that extravagance is essentially immoral, a narrowly puritan perspective which prevents engineers from contributing more meaningfully into wider cultural discussions on the value of aesthetics.

I've discussed in the past how rarely bridge engineers are willing to publicly criticise the work of their peers in the industry. In that respect, Bourne's intervention is a positive thing, as there is far too little debate on the merits of designs such as this. The NCE quote Sunderland's River Wear project director as saying the bridge has been "rigorously designed, costed, admired and backed within the industry and profession", a statement of such deep complacency that it positively demands more critics to clamber out of the woodwork, brandishing angry manifestoes reading "form follows function" and so on.

Unfortunately, Bourne's complaint also falls into the too little, too late type of criticism which comes at a stage in the project where it is largely pointless. It has been clear throughout the River Wear saga that the promoters are wedded so deeply to their vision that they are happy to ignore opinion, whether expert or non-expert. I recall in particular their reliance on a public survey expressing support for a design, when a much larger survey showed that at least half wanted to avoid expense and favoured a "tried and tested" solution instead. Sunderland have had the design reviewed by experts who agree that it can be built. The most serious test of its feasibility will come when contractors' tenders are finally submitted, and we discover whether they share the client's expectations as to what it will cost.

Bridges news roundup: Mega Edition

It's been some time since I've done a roundup of bridge-related news, so there is quite a bit to cover this time ...

Italy's bridges weighed down by locks of love
I recently wrote about the tradition of adorning Wrocław's Tumski Bridge with padlocks as a symbol of marital or romantic commitment. It appears the Venetian authorities are less than keen on seeing the same tradition applied to the Rialto Bridge. I didn't spot any locks when I visited it, but perhaps this was simply because the authorities were quick on the draw with their boltcutters. It's a shame they are less effective at removing graffiti.

Daredevil takes on Gateshead Millennium Bridge stunt
As this video shows, it's not quite as crazy as the original article makes it sound.

Gateshead Millennium Bridge celebrates 10th anniversary
Designer Jim Eyre interviewed.

Barnard Castle Bridge moves step closer
Plans are afoot for a £1.3m, 265m long pedestrian suspension bridge. That strikes me as too little money for that much bridge, unless it really is done on the cheap, forestry-style.

New Tempe Town Lake pedestrian bridge draws attention
As well it should. See this site for more construction images, or play spot the difference.

Diamond idea for bridge
The suggestion is that the proposed New River Wear Crossing in Sunderland (pictured, right) should be named the Diamond Jubilee Bridge as part of a wheeze to help persuade cash out of the central government in order to support what is undoubtedly a local council vanity project. They are not the first to have this idea - you heard it here first.

New Wear Crossing funding bid
Meanwhile, Sunderland have submitted their revised bid for central government cash for the wider highway scheme of which the bridge is only the most prominent part. The bid cuts roughly £15m off the previous estimated £133m scheme cost. Of the new £117.6m figure, roughly £72m is for the bridge itself, with the rest for highways, land and utilities.

An examination of the documents reveals that considerable "value engineering" has taken place (cost-cutting, in normal parlance). The twisty masts of the bridge have been reduced in height, bespoke parapets and road lighting have been replaced with their bog-standard equivalents, and structural finishes have been reduced in quality. An alternative scheme with a conventional bridge is estimated at £109m, although much of that is due to additional design and land purchase work only necessitated by the fact that Sunderland have already spent large sums on the landmark bridge option. The difference between the landmark and alternative schemes is therefore a mere £8.6m, which is frankly almost impossible to believe. Sunderland have also made a commendable effort to calculate the regeneration and employment benefits of the landmark option, which they put at £33m.

Peace Bridge defenders say Toronto crossing not the same
Calatrava's CAN$25m footbridge in Calgary (the subject of many previous posts on this blog) is compared to the CAN$8m Puente de Lux in Toronto (see here). Both are trusses with curved web members, but the similarity ends there. The Toronto span is essentially a Warren truss with pretensions, while the Calatravan helical truss bridge is a more complex beast. And one is yellow and the other one red. Quite, quite different.

Is it all over for £6 million bridge?

Answer: it was probably all over before it ever started. This footbridge in Gainsborough was an ambitious landmark structure (pictured right, and see my previous post for full details) which always seemed at risk of cost escalation, and perhaps over-ambitious for a town which started with no funding in place and remains in the same position. What's odd is that the council granted a local body (now disbanded) £12,000 to develop the initial design but has, apparently, never had any real intention of taking the scheme further. If so, why waste the development cash?

City river footbridge to be lifted into place after year of delays
Hull's £7.5m pedestrian swing bridge (note it was only £6.5m when I last reported, in June) was finally ready for installation after considerable delays due to the local council drip-feeding the finance. It's unclear whether the revolving restaurant will have a tenant yet, or whether lack of cross-river development will make this something of a white elephant.

Critic critiqued

Regular readers will know that the design of a new landmark bridge across the River Wear in Sunderland has a been a topic I've returned to on many occasions. Generally, I've been pretty critical of the entire enterprise, which involves hanging a 336m long bridge deck off two giant prestressed tusks.


The designer, Techniker, has mentioned me in passing as part of a lecture to graduates in Newcastle, available on their own blog. Amongst lots of interesting material on the evolution of their design, they have this to say:

"I have really enjoyed following the blog of the Happy Pontist, a self-appointed critic of bridge design. He is a bit sad but the point is he is genuinely aggrieved. He is not the only one to use their technical authority to say this couldn’t be built then when the figures were out move to the position of it shouldn’t be built then when the cost-benefits come back set up a rear-guard action that it’s just plain ugly. For structures that are permanent, that will effectively be there for all to see forever, across all booms and recessions what is the proper thing to build?"

I'm happy to be "self-appointed", and indeed would hope that no formal license is required simply to go online and post the same views I'd happily share with people in person. I'd also note that I've never called the bridge "ugly" (I have, indeed, called it "amazingly beautiful"), nor suggested it is unbuildable.

But set these aside, because the substantive point at issue here is the final sentence, and the question "what is the proper thing to build?"

The Techniker design is structurally, and hence economically, extravagant, in the service of an essentially architectural vision. Pylons without back-stays (or with "virtual backstays", as Techniker would describe it) do not follow from any purely structural response to the logic of the bridging problem. Here's what Techniker's Matthew Wells had to say on structurally extravagant design back in March 2006 [sorry, that link may only be available to NCE subscribers]:

"'Following the Calatrava route isn't necessarily the best option. Iconic structures don't have to be overweight or over engineered. I believe there is a moral duty not to waste money on infrastructure projects. Efficient structures that give value for money don't have to be dull."

He also identified the demand for such structures to act as beacons for investment in economic regeneration. Discussing the Gateshead Millennium Bridge, Wells went on: "The contribution it's made to the image of the area and the inward investment it's attracted are priceless. That's what clients are looking for, the so-called Bilbao effect - the same impact as the Guggenheim museum had there."

So on the one hand there may be a "moral duty" not to follow (let alone out-do) Calatrava-style flamboyance, and instead to promote efficiency and value for money. On the other, there's the desire to create spectacular icons signposting urban revitalisation. The tension between the two is at the heart of any disagreement on whether, in engineering terms, the River Wear bridge is a "good" design, and at the heart of many a discussion on "iconic" bridges.

The conventional engineering point of view is straightforward, and was aptly summarised by Woodruff and Billington in their review of Calatrava's costly Sundial Bridge: "the drive for landmark bridges has led some engineers to disregard the engineering ethic of economy with some recent footbridges". I've covered this sort of philosophy before, as it has been espoused by most bridge engineers writing on aesthetics: Menn, Leonhardt, Virlogeux and others. As I noted when discussing Woodruff and Billington, value should be more than just a monetary concern, and hence an obsession with economy unfortunately tends to reduce value to a matter of bean-counting. While engineers instinctively like anything that is measurable, there is more to life than a conventional cost-benefit analysis can capture. What price joie de vivre?

Clearly, the River Wear design could be considered visionary, innovative, monumental, even inspiring in its ambition. It puts the "icon" in "iconoclastic". It will have a value both for the spirit of the neighbourhood and for whatever investment in regeneration it can trigger. The question for me is not whether it meets these goals, but whether a different design could also have met them, and whether such a design could be more structurally efficient, and hence offer the taxpayers a better balance between value and cost overall.

I don't see how else you can balance the scales of cost and value other than by comparing a number of alternative options, and I find it hard to believe that in this instance, a more efficient design wouldn't have delivered substantial value for significantly less cost. I think my difficulty with the Wear design also comes down to a bridge engineer's basic instinct: there are other "iconic" bridges which are notable for their extravagance (e.g. the Gateshead Millennium Bridge, one of the most expensive footbridges ever built, for its size), but which have a more conventional structural logic.

Perhaps only posterity will tell whether the Sunderland bridge is destined to be regarded as an engineering marvel along the lines of Eiffel's tower (much criticised when it was first proposed), or simply the bridge world's equivalent of an architectural folly.

River Wear Bridge goes for planning consent

It's been a while since I've had any news to report on Sunderland's River Wear Bridge, the structurally ambitious competition-winning highway bridge design by Techniker and Spence Associates.


Just before Christmas, the project made its planning consent submission, depositing a mammoth package of drawings and reports that must total at least 400 pages. You can find it yourself by visiting Sunderland's planning portal and searching for the application reference 09/04661/LAP.

The reports include a number of interesting engineering documents as well as the normal planning statements, and I've extracted some of the more interesting points here.

It's clear that lead designer Techniker has devoted considerable effort to proving the feasibility of a design that seems by far their most challenging project. They've contracted the prestressed concrete bridge expert Nigel Hewson to provide engineering support, and their design has been peer reviewed both by Roughan O'Donovan and Aecom.

For the first time, we're given a cost estimate for the bridge itself, separated out from the highway scheme's overall cost of £133m. At £46.1m, it's pretty much in line with the budget of £43m specified in the original RIBA bridge design competition (contrary to my previous speculation). The bridge is 336m long, with a maximum span of 144m, and the deck is 25m wide. The cost therefore works out at about £5.5k per square metre in plan, which I would say is pretty cheap for such an unusual design. I've previously noted that it's comparable with Calatrava's Alamillo design, which, although controversial in its own right, is a considerably more structurally efficient bridge.

The planning submission contains a Statement of Community Involvement, which reports on a survey of 161 people, of whom 93% rate the Techniker design as "fairly good" or "very good". That's nice, but it ignores Sunderland Council's previous and larger survey (see council report [PDF]), where out of 1,641 responses, 49% wanted a "tried and tested design", and 58% wanted to minimise the impact on taxpayers (which this design hardly does).

The masts (one 140m high and the other 190m, making it the tallest bridge tower in the UK) are a very interesting construction. At the very bottom, they're of prestressed concrete with a stainless steel skin, but for most of their height they comprise prestressed concrete composite with a 12mm thick painted structural steel skin. The very top section is pure structural steel. Essentially, the prestress cables could be thought of as the "missing" back stays, hidden within the pylon.

The reports acknowledge the difficulties of fabricating the very complex steel plates involved, which are constantly changing in cross-section, rotating in plan and elevation, and hence much of the steel plate is curved in two directions (see drawing extract on the left, all drawings are taken from the planning submission).

Given the size of the towers, the steel skin will provide very little structural benefit. Indeed, its interaction with the tower prestress and with the creep behaviour of the internal concrete make it a significant complication in the design.

It seems to be there partly to provide an ultra-smooth finish sought by the architect (welds are to be ground flush up to 40m height, which strikes me as rather pointless), and partly to act as permanent formwork for the hollow concrete tower cores, which would otherwise be very awkward to form. The downside of course is the enhanced maintenance cost associated with painted steel. Compare the steel-clad concrete pylons on Stonecutters Bridge: these use a 20mm thick stainless steel skin providing a genuine composite benefit (indeed, the composite system replaced the original steel-only design), but I presume the budget at River Wear ruled out stainless steel.

The pylons sit on a caisson foundation 40m by 24m (or alternatively, on a grid of 78 1.2m diameter piles, they haven't made their mind up yet). Quite a bit of thought seems to have been devoted to carefully positioning the foundation relative to the pylons so that the forces, including massive torsions, are as well balanced as possible.

The deck is a steel and concrete composite ladder-beam system (see image below right), with short outriggers picking up the cables. That's a reasonably economic choice, although it struggles near the pylons, where the hogging bending moment is highest. At these locations, the designer suggests the deck concrete may need to be post-tensioned, which strikes me as an unusual and interesting approach.

The deck is likely to be launched, with the pylons built at the same time and the cables stressed only after both are complete. That seems at first to be very odd choice for a cable-stay bridge, particularly given the expense involved: a number of temporary launching props will need to be installed in the river, and subsequently cut off or pulled out through holes in the deck. The normal approach for a cable-stay bridge is to cantilever the deck in segments from the pylon, as was done on Alamillo (where the pylon and deck were both cantilevered segmentally in phase). The ability to use the stay cables both as the temporary and permanent support for the deck is normally the great economic advantage of this type of bridge.

At River Wear, however, the lack of back stays means that the cantilevers would be unbalanced, and the loads imposed on the pylon and foundation during construction could substantially exceed those in the final condition (where the deck acts as a continuous beam, or propped cantilever). The design is therefore entirely driven by the architectural rather than the structural logic - a cable-stay bridge is a means to an end (the production of an icon), rather than the logical response to the engineering challenge.

Despite the bridge's utter lack of any basic structural rationale, I found myself strangely impressed reading though the documentation. If you accept the architectural vision as sacrosanct (Ove Arup style), it's clear that the designers have risen to the challenge posed by this deeply unconventional, flagrantly contrary structure. I understand that detailed design is now underway, and no doubt the technical challenges which remain are tremendous but perfectly capable of being resolved. Once complete, the bridge will be a major engineering achievement.

I think I can admire that, without in any way liking the bridge.

Horny bridge keeps on going

A proposed "iconic" bridge in Sunderland, designed by Spence Associates and Techniker, is moving forwards, following a meeting of Sunderland's city council cabinet yesterday. Claiming the structure would be a "people's bridge", the council leader revealed that the design is likely to be submitted for planning consent in November. The bridge features twin cable-stayed masts shaped a little like antelope horns.


A report available on the council's website makes for interesting reading, and is perhaps worth dissecting in some detail (just a dissection - not quite a full scale fisking).

It notes that "the design aligns with the City's brand values of 'smart', 'life-enhancing' and 'balanced'". I nearly snorted my cup of tea when reading that - what's so smart about a cable-stay bridge with no back-stays? It's balanced only in the sense that a man standing on one leg is balanced - he can stand up, but the effort to remain so is harder than it needs to be.

The report reveals that Techniker have now done considerable design development, backed up by peer review by their own subconsultants, consultation with possible contractors, and validation by the Council's normal cost and engineering consultants. It would be nice to know who the peer reviewers are, in particular, as they would be expected to include specialist long-span bridge engineers, but I can't imagine many of those wanting their names too closely associated with this design.

This is all very good - given the extravagantly unusual structural behaviour of this design, a detailed consideration of technical issues and risks is vital to confirming its feasibility and ability to be built within cost. The report certainly suggests substantial risk management is being undertaken. Hydraulic and wind tunnel testing have both been carried out.

The report still doesn't shed much light on the bridge's actual cost, reporting only the overall scheme cost of £133m, which include 3km of highway, land acquisitions, and utility diversions as well as the bridge itself. It makes clear that funding is not yet secured: the Department for Transport (DfT) have agreed £98m of funds, but those are dependent on construction tenders falling within the budget estimate. £6m comes from development agency One North East. The Council calculates it has to provide the remaining £29m of the total.

That's made up by sticking a £10m dent into their five-year Local Transport Plan funding (presumably that means cutting cycle and bus schemes), with the rest drawing down on the city's strategic reserves. Council tax payers therefore don't see any rise in their tax to pay for the bridge, but at the cost of exhausting considerable sums of money which could have been spent locally on other projects. It also means (as with many regeneration projects) that the Council financing is heavily geared, such that a 10% increase in overall scheme costs could lead to a near doubling of what the Council actually has to pay (although in reality some of that increase would be bailed out by central government). The risks to local finances are therefore not insignificant.

The report does give some simple dimensions for the bridge (336m long by 30m wide), which confirm that square metreage costs estimates I've previously made are based on the right information.

The document also suggests that there is evidence that landmark bridges accelerate and lead to higher quality regeneration and development in their vicinity. This is the assumption made by most commissioning authorities, and it may well be true, but I've never seen any proper quantitative evidence to support it. In any event, greater development would need to be measured against greater cost to make a serious financial case for a landmark structure, a calculation yet to be made.

The cabinet report repeats the statement that "public opinion is overall in favour of having a landmark design ... and to do so while minimising the impact on council tax". This has been said several times in Sunderland, but I've noted previously that the council's own surveys tell a very different story, with half the populace preferring a "tried and tested" solution instead.

The report also offers insight into Techniker's appointment. The council have clearly considered the possibility that their appointment could be ended, with the remaining design carried out by another firm, most probably via design-and-build. The report states that "as this is a landmark design, Techniker have insisted that they must remain as the exclusive designers ... for the full duration of the design services".

It's good to see the designer taking such a strong position, as there have certainly been design competitions in the past where the original designer has been discarded in favour of others, perhaps most controversially on Stonecutter's Bridge. At River Wear in Sunderland, it would seem that Techniker retained design copyright throughout, giving them a strong negotiating position, even in the face of their very limited track record in designing major structures of this type.

So, the choice of bridge is now finally confirmed, four years after the Techniker design won in competition, and the next step is to secure all the necessary consents from statutory bodies and seek final confirmation of funding. I have to admit I thought this was a bridge that would never get built, and it's remarkable that such a bizarre design has survived the design development phase intact. The next real obstacle in its path is likely to come when construction tenders are submitted in 2011 or 2012, when we'll find out whether the budget estimates are right or not (for a classic example of another unconvential structure which failed at that hurdle, see the Neptune's Way scheme).