29 October 2013

Bridges news roundup

Ok, I've finished my series of posts on the bridges of Rotterdam.

I'll move on next to various bridges in north east England, the focus of a recent weekend bridges tour, but before I do, here are a few news items that caught my eye ...

Pedestrian Bridge / Miró Rivera Architects
I've probably posted a link to this bridge design before, but it's so great I won't get tired of it any time soon (see picture, right).

Olympic Stadium Amsterdam / René van Zuuk Architects
I think I don't like this bridge, but I'm really not sure.

'Location critical' for River Thames footbridge idea
Bridge proposed between Sunbury and Walton

New footbridge over city canal set to get go-ahead
New bridge at Speirs Wharf in Glasgow.

Revised footbridge designs for Greenwich Reach/Deptford Creek
Flint and Neill and Moxon are brought in to provide some much-needed common sense.

A bridge too far: Dozens of tourists plummet into lake after ignoring 'maximum capacity of 40' warning sign
Brand new footbridge in China unable to carry crowd loading. No serious injuries but plenty of photos of the collapse. The photos appear to show that the upper chord of the bridge truss initially behaved as a catenary, with the floor and lower chord peeling away from the truss web members, suggesting completely inadequate truss connections as the main cause of failure.

Foryd Harbour Bridge opens to public
Here's a nice aerial video of this bridge being opened to the public. According to the contractor's website, it cost £6.5m, which is a greater than 50% increase over the £4m budget stated when the design competition was held. Back in 2009, I said the bridge design was "like to prove a challenge technically, financially, and in achieving the desired programme", and I correctly predicted it would over-run on both budget and programme. I also thought it might prove unreliable in service due to the very unusual opening mechanism. I guess we'll have to wait and see whether that also proves to be true - it may not, as the "drawbridge" mechanism in the contest-winning design appears to have been replaced in the final structure with a more conventional hydraulic ram.

Third-party review reveals design concerns over halted Airport Parkway pedestrian bridge
Ottawa cable-stayed bridge is the subject of considerable embarrassment. A full copy of the critical review findings is online.

28 October 2013

Rotterdam Bridges: 6. Willemsbrug

Of all the bridges I saw in Rotterdam, this last one is easily my least favourite. There's just something about it that is really, really boring. Apparently it won a Dutch Steel Award in 1983. I guess it must have been a quiet year.

Spanning 270m, and 33m wide, it is no small structure. When it was completed in 1981 it replaced a truss bridge dating back to 1878, which was also no small bridge.

The cable-stayed bridge form is one which offers designers considerable opportunities for creative input, so it's particularly disappointing that Willemsbrug makes so little use of this freedom. It's the towers, always the key feature on a cable-stayed bridge, which are the problem. Most cable-stayed bridges use a variation on either a portal-frame tower (sometimes H-shaped), or an A-frame tower (sometimes and inverted-Y). The Willemsbrug towers seem to be an awkward half-way house, somewhere between the two conventional options and with none of the grace of either.

The cables are arranged so that although they pick up the deck along its edges, in a "vertical" row perpendicular to the towers, they connect to the towers in a horizontal row. This requires the fan of the cables to twist in space. I guess it may have been done to create visual interest, because I can't see any other rationale for it, but it seems gratuitous and forced, and from some angles results in a very odd-looking layout, especially for the cables nearest to the towers.

As they enter the towers, the cables pass below eyelid-shaped cowls, which if they didn't disfigure the bridge enough, are accompanied by distracting access gantries. Given that there are access ladders within the towers, I can't see the point of this detail at all.

Overall, this must be one of the least visually successful cable-stayed bridges I can recall seeing, and it's a shame to end this whistle-stop tour of Rotterdam bridges on such a note!

Further information:

24 October 2013

Rotterdam Bridges: 5. De Hef

Officially called the Koningshavenbrug ("King's Harbour Bridge"), this bridge is nicknamed De Hef (“The Lift”) by the Dutch, showing a depressing lack of imagination. Why not “Stilty”? Or “The Old Rustbucket”?

This is a zombie bridge. The railway line that it once carried is closed, superseded by an underground metro. Accordingly, the bridge is left permanently open, its deck raised high into the air. It is lifeless, but as yet unburied. It survives as a gigantic memorial to the industrial era, and in that respect it offers considerable visual interest.

The two side spans were built in 1878, originally with a swing bridge in the middle. In 1927, it was replaced with the present lift bridge span, to provide greater shipping clearance. It closed to rail traffic in 1993.

When I first drafted this post, I spent some time pondering on how the bridge could be re-animated. Bereft of purpose, it seems unlikely to receive much in the way of maintenance, and could go the way of redundant relics like the Warrington Transporter Bridge, becoming a massive liability for its owner, with only one possible outcome.

I speculated on whether the bridge could offer a home to a modern restaurant, possibly dining al fresco, raising diners up above their surroundings to gaze at Rotterdam’s nightscape while picking listlessly at over-priced hors d’oeuvres. Mindful of the need not to annoy nearby residents by blasting out avant-garde dance music (the kind intended to drown out conversation and thus reduce the chance of awkward words spoiling an intimate meal), patrons would instead have to be entertained by a gentle dinner-jazz trio, adding soft tootles and burbles to the soundtrack of city streets.

As it turns out, I need not have speculated at all, as a local entrepreneur is already way ahead with plans to repurpose the bridge - Hef Experience Rotterdam. As well as access to an elevated public space and a museum, this originally proposed to include activities like bungee jumping and zip wires. From what I can gather, attempts to gain political and financial support have failed.

Perhaps some measure of why the proposal is not widely supported can be found in an article for Vers Beton magazine with a title which could be roughly translated as "Hands off de Hef". This argues that the structure should be left as a monument to industrial heritage, and that maintenance costs should be met by the municipality out of "moral duty".

I think I fall on the side of pragmatism - this will be an extremely expensive bridge to maintain in years to come, and without any source of revenue, there will inevitably be pressure to dismantle such a cumbersome and non-functional structure. Unless it is repurposed, it may survive only for so long as the cost of demolition exceeds the cost of maintenance.

Further information:

22 October 2013

Rotterdam Bridges: 4. Koninginnebrug

Two bridges cross the Koningshaven ("King's Harbour") in the City of Rotterdam. One is a giant, visible for some considerable distance, a monument to the city’s industrial heritage, now disused. The other, the subject of this post, lies low, perhaps asleep, and remains a key conduit for road, cycle and foot traffic.

This bridge, the Koninginnebrug ("Queen's Bridge"), is a twin-leaf bascule bridge, of a type I hadn’t previously encountered. Two steelwork trusses cradle the roadway, while foot and cycle traffic uses walkways cantilevering from either edge. It does not appear to be a particularly modern structure (it was built in 1929, to replace a swing bridge), although it’s not hard to imagine what a contemporary designer could do with this form.

What makes it unusual is the lack of any visible counter-weights for the bascule decks. In most Dutch bascule bridges, the counterweights are made the most obvious feature, part of giant see-saws perched on towers, suspending the deck from hangers. This is sometimes call the “Dutch drawbridge”. There are, of course, many other examples of bascules where the counterweights are hidden below deck level (Tower Bridge in London springs immediately to mind), but probably few where it would have seemed easy to site them above deck. The effect here is to make the trusses appear unbalanced, with the 800-tonne counterweights entirely hidden below road level.

The other notable feature of the bridge is its quartet of control towers, from where shipping can be observed and the bridge opening operation monitored. These have dainty, curved peaked “hats” which at first strike struck me as a little incongruous when set against the more industrial metal trusses. However, it’s the sort of feature which gives a bridge a distinctive identity, and hence provides the reward for any pontist’s travels – if all bridges were made by Ikea, this blog would not exist. It’s constantly fascinating to see how similar problem s around the world have been addressed by highly divergent solutions, each contingent on variations in local resource, expertise, context and custom.

Further information:

20 October 2013

Rotterdam Bridges: 3. Rijnhavenbrug

Other than perhaps the elevated walkway featured in the last post, this is the most recently built of the bridges I visited in Rotterdam. I have discussed it here before, when I explored several of the designs submitted in 2008 to a competition for a new opening footbridge.

The bridge spans the entrance to a large harbour area, and therefore certainly makes a useful connection in an area which appears to be experiencing long-delayed development. The brief for the design competition was for a bridge which was relatively modest, which eschewed flamboyance. The winning design certainly met that demand, being a simple single-span bascule with a care for detail but an absence of bling.

As built, the bridge has departed little if at all from the competition-winning images. I approached the bridge while it was open to allow a large ship to pass, and as it closed again. This reveals its signature feature, which is that the deck is offset from the pivot point, resembling perhaps a plasterer’s trowel, or a cake slice.

The opening span is counterweighted by what appears to be a massive solid block of steel (presumably a steel box containing adjustable ballast), minimising loads on the opening mechanisms and hence power consumption. This passes down through an opening in the deck when the bridge rises. It is connected to the main span by a steel box spine beam, offering an inviting surface on which to play, and hence likely to require repainting at an earlier date than the rest of the bridge.

The layout of the bridge in plan seems awkward, consisting of a series of straight approach spans to the north, a kink, and a straight main span. This does allow people waiting at either end of the opening span to get a better view of the main deck as it opens.

There are benches on the approach spans, and contemporary parapets which are doing a splendid job of attracting a mass of love-locks, as seems increasingly inevitable on notable pedestrian bridges.

The shaping and size of the main bridge pier struck me as a little unsatisfactory, but my biggest criticism of the bridge relates to the deck lighting. This consists of a series of low-level airport-runway style blisters, which I rapidly discovered to present an unfortunate trip hazard. I’m astonished this detail was considered acceptable.

On the whole, the bridge is eminently reasonable in its lack of spectacle, a trait well-suited to this northern European country. This trait is sadly not present in much of Rotterdam’s modern city centre architecture (which often suggests the output of a stripy-suited banker-turned-architect-wannabe possessed of modelling software with “grandstanding” and “pointless-crumpling” presets). In that company, the bridge deserves praise.

Further information:

17 October 2013

Rotterdam Bridges: 2. Erasmus Bridge Elevated Walkway

I’m including this structure in my series of reports primarily as a curiosity.

It sits a short distance from the south end of the Erasmus Bridge, and I’m unclear to what extent it is intended as a functional walkway, and to what extent it may be a work of art. It’s a bridge in most senses of the word, except that it crosses no obstacle.

The user ascends a staircase at one end, traverses a walkway between two steel girders, and then descends a further staircase.

The experience is largely pointless, except to the extent that it offers an elevated view of the Erasmus Bridge and its environs. It’s a promenade, a chance to survey the urban surroundings.

Although it was unoccupied when I visited, I imagine it as a place to stand and sip a cocktail as the city lights dance on the water in the evening.

I suspect the reality may be just as likely to involve drunkards swigging Heineken, but I am merely speculating.

Further information:

15 October 2013

Rotterdam Bridges: 1. Erasmus Bridge

I managed to find time on a recent trip to Rotterdam to visit a few of the city’s most spectacular bridges, which I’ll discuss over this and the next few posts.

As with many modern city bridges, the Erasmus Bridge serves both a practical and a symbolic purpose. Prior to its construction, transport connections across the river were limited, and the new bridge made generous provision: two single-lane highways, two tramways, two cycleways, and two pedestrian walkways. However, it was also required to satisfy the needs of civic pride, to be the most visible symbol of Rotterdam’s post-war reconstruction and growing economic success. It had to be a landmark both in purely visible terms, signposting the city centre from far and wide, and also as a technological achievement.

The bridge design was proposed by an architect, Ben van Berkel of UN Studio, directly inspired by Calatrava’s Alamillo Bridge in Seville. It was initially hoped that the bridge could be built in the same manner, without back-stays. The backwards-leaning inclination of the inverted-Y-shaped pylon allows the tower to act as a counterweight to the main deck. With a main span of 284m and a tower height of 139m, it proved impossible to make the bridge work without backstays, with even a balance of dead load alone requiring a significantly more substantial pylon.

The cranked arrangement of the pylon is the bridge’s signature feature, seldom replicated (I can think of one obvious example). It apparently provoked controversy amongst engineers not used to being subservient to architects and unhappy with the significant increases in cost required to build such a structure.

It was put to me by a friend that the bridge is not structurally logical, but this is unfair. The inclined pylon does to some extent balance the main span, reducing loads on the back stays significantly, and the crank is a coherent response to the vertical cluster of anchorages high on the mast. The only obvious enhancement in terms of how it distributes its forces would be for the upper part of the pylon to be curved, a way of reducing tower bending under spread cable forces which has been adopted elsewhere by Calatrava.

Certainly, the temporary propping required during bridge construction will have added to its cost, but I really find it hard to imagine that a more conventional vertical pylon would have looked as satisfactory.

A key element which makes less structural sense is the treatment of the deck girders. In the main span, the steel plate deck sits on transverse ladder beams, which span between and cantilever beyond two primary steel box girders. This allows the deck to appear reasonably slender in elevation, and is probably less expensive overall than allowing the entire deck to span between massive edge girders.

The back span is very different, as it does span between two massive edge girders, these girders forming the distinctive “legs” to the tower, and giving it a kind of abstract resemblance to a person kneeling (I am not sure if this was a conscious intention).

This arrangement has no structural rationale, as it would be more logical to continue the recessed girders. The result is the need to transfer the axial forces in the front span girders into the back-span girders (and pylon foundations) via substantial transfer steelwork. The “legs” are also far larger, at a maximum of 12m deep, than is required to actually carry the back span, with the result that they are largely comprised of fascia elements, with the actual structural girder being much shallower.

Behind the legs, there is a bascule span, designed to provide a shipping clearance of 50m. This is claimed to be the longest single bascule leaf in the world, making it an important structure in its own right, although it is only a small part of the overall structure.

Shortly after the bridge opened, the cables were observed to vibrate under certain combinations of rain and wind. The problem has since been solved by the provision of a hydraulic damper at the foot of each cable.

Close up, the pylon has been detailed largely for architectural effect, with a variety of kinked plate surfaces presumably intended to catch the light and avoid the plainness present on many other cable-stayed bridges. I think it looks good from pretty much almost every angle. There is a slightly odd "lipped" element on the main span face of the pylon, but I think it does need this sort of treatment to avoid looking quite dull.

One issue with cable-stayed bridges at this scale is that the cable sag can get quite significant. This is irrelevant from most perspectives, but disconcerting when you actually look directly along the cables, where the sag leads to the impression that the cables aren't properly tensioned. However, I suspect hardly anyone other than the curious bridge engineer will ever notice this.

Although the deck, cables and pylon are the primary expressive elements of the Erasmus Bridge, I was particularly impressed by the treatment of the substructure, the piers, abutments, and associated ramps and staircases at the north end of the bridge in particular. These take the shape-making desire visible in the steelwork even further in concrete.

There are a couple of twisted pier columns, and the north river pier is in the form of a monolithic "V" with some attractive chiselling. The ramps and staircase which lead from below the bridge up to deck level are also very nicely sculpted. These are all areas where the attention to detail of the architect has paid dividends.

On the whole, I find it hard to see why there's much controversy about this bridge. The design is well-detailed and visually appropriate, given everything the bridge was asked to do. I think it's a fine bridge that deserves to be more highly regarded.

Further information:

10 October 2013

Bridge competition debris part 26: Salford Meadows Bridge

Wow, now these people are quick.

These unsuccessful contest entries were all up on the internet even before the finalists had been announced for this footbridge design competiton, which I first discussed in some detail back in June.

So, here are the submissions which a fairly quick trawl of the internet has found. Follow the links to find more images and details of each design - it really is worth following most of them to see some of the weird and wonderful things that were submitted.

I will make no comment on the individual entries, other than to offer my sympathies to the competition judges.

Update: 21 October 2013: I've added a few more entries found on the internet, and understand RIBA Competitions are preparing their own gallery of all the entries.

ADAPT architects

Atelier Architecture 64 / Laufs Engineering Design

Avery Associates

BAI Design International

Stathis Eleftheriadis

Fala Atelier

InHolD (1)

InHolD (2)





Luca Poian Forms

Pruthiphon Buakaew


Studio 06