Friday, May 6, 2011

ON BRIDGES

. . . . for John, who asked why no one had.

Brisbane has a new bridge.
On 4 October 2009, the Kurilpa Bridge opened across the Brisbane River in Queensland, Australia. The new greenbridge is a multiple-mast, cable-stay structure based on the principles of tensegrity. It is also the largest tensegrity structure in existence.
This entry in Wikipedia (possibly posted by the designers of the bridge – Cox Rayner Architects / Arup - or the government public relations office, as ‘Wiki’ things usually are) refers to the new bridge over the Brisbane River that again joins the art gallery precinct on the south to the CBD/north side of the river. Perhaps the word ‘bank’ should be added here – south bank/north bank - as it reminds one of London and Paris? The article uses some unusual words to describe this ‘world’s-largest’ configuration of its type that is a new pedestrian link: ‘greenbridge;’ ‘multiple-mast;’ ‘cable-stay;’ and ‘tensegrity.’ These terms make the bold claims for this apparently audacious structure look impressive, while suggesting that it might have a colourful nautical theme to it. Brisbane must be proud to have such an iconic structure on its river. But what do these words mean? What is this new wonder? It exists, but there has been very little discussion on it since its opening beyond journalistic hype and blurb. This last word is interesting. As David Astle noted on Letters and Numbers (SBS TV), ‘blurb’ is a word that was invented early last century to describe the descriptive summaries found on the back cover of books – words that seek to entice one to purchase the book. It remains a word that we use today to cover a similar sense of text that babbles on self-consciously in a hyper-promotional, self-interested manner: like much of the journalism in our media.

‘Greenbridge’ can be assumed to be a fabrication used to describe something environmentally positive – or that seeks to be seen as such. In this context one can guess that it has to do with walking and cycling rather than driving, and perhaps to some efficiencies in the making. But what is tensegrity? This word is more obscure and its deconstruction is not so obvious. Buckminister Fuller fashioned this word to describe his idea of creating structures using members with only pure compression or pure tension. These structures were preloaded or prestressed tensionally – intentionally - with the cables always maintaining their rigid tautness, forming a system that was mechanically stable. All elements in the assembly remain in pure tension or pure compression even as stresses on the structure are increased. This design concept meant that no member in the system would experience a bending moment requiring an increase in size to cope with these added stresses. Fuller was interested in these structures because they produced exceptionally rigid structures for their mass and for the cross section of the components. Harvard physician and scientist Donald E. Ingber explains (in Wikipedia):
The tension-bearing members in these structures - whether Fuller's domes or Snelson's sculptures - map out the shortest paths between adjacent members (and are therefore, by definition, arranged geodesically) Tensional forces naturally transmit themselves over the shortest distance between two points, so the members of a tensegrity structure are precisely positioned to best withstand stress. For this reason, tensegrity structures offer a maximum amount of strength.

A different word is again used in this explanation – ‘geodesically.’ It is yet another word - one of many - coined by Fuller. His ‘synergy’ is the one most abused, usually by bureaucrats and managers who seek to sound important when saying very little about anything significant. ‘Geodesic’ has similarly become a part of our general language and understanding of things like different domes, even if few know exactly what the term really involves. Its explanation in this text leaves one with the impression that the Kurilpa Bridge is a crisp and efficient, light-weight assemblage that might prance effortlessly across this River City’s serpentine waterway with a supreme elegance and astonishing wonder.


Fuller’s own simple diagrammatic models used to explain tensegrity are indeed as beautiful as crystals with their intense rigour and efficiency of organised internal relationships and stresses – simply exquisite. The basic models of tensegrity made during one’s student years for class experiments come to mind. There was always a surprise at how a shambles of a few pieces of dowel, some pins and a short length of nylon fishing line could make such surprisingly complex and elegant mathematical forms after a bit of fiddling. This was indeed a marvellous manner to make things minimally – efficient, lightweight and mystically beautiful beyond words. The images that accompany the Wikipedia explanation quoted above show, by way of example, refined and elegant structures with geometric forms shaped by floating, visually disconnected struts held magically in a web of fine tension – effortless weightlessness, as astonishing and intriguing as a hummingbird’s hovering.


In the 1951 Festival of Britain, tensegrity was used to provide the avant-garde sculptural Skylon Tower centrepiece to highlight the possibilities for a bright, post-war future for this country. It was the morale-booster for a saddened, tired people. Fifty-eight years later, this structural concept appears in Brisbane as a bridge to highlight the cleverness of this sunshine capital, of what the Government promotes as ‘The Smart State’ – Queensland, Australia.

The characteristics of tensegrity structures that can be seen in these examples are, sadly, not readily revealed in Kurilpa Bridge. The bridge has no obvious weightlessness; the achievement seems to have required far too much effort; and the size and number of members have a quality that is difficult to read as a rigorously refined and minimal outcome for any organisation of pure stresses. It appears to be overdone. Is this why others have not made such structures? The bridge displays little of the organised clarity exhibited in the models or the 1951 sculpture. Its appearance lacks what reads as a certain precision and wonder in these examples. It has what can be seen as a heavy, over-busy presence that confuses the eye and brain, and allows the wandering mind to give rise to a variety of strange interpretations instead of being otherwise engaged in pondering the surprises of internal necessities.

Some see Kurilpa’s complexity of crisscross struts and zigzagging cables as being somewhat like the masts and rigging of a sailing ship, expanding the idea of the previously suggested nautical theme in the description ‘multiple-mast.’ Some see it as a brash and unusually cheeky, spiky form that reminds them of a Mohawk haircut, complete with its linear symmetry. Some choose to talk about it as a random arrangement of ‘pick-up-sticks’ falling - or knitting needles - but with the distinctive colours of the game pieces missing. This is a grey structure where green is used metaphorically - in its cliché mode. Others commenting on the bridge simply struggle to identify any analogous relationship but say safely – lazily- without any commitment, that the bridge is ‘interesting’ and is liked; or, with equal emphasis and lack of dedication, disliked, depending on the point of view taken or perhaps the tolerance or safe manners chosen to be displayed at the time. Some say things that are best not recorded.

It is difficult to see this bridge as a crisp, crystalline form made with refined minimal structural elements as might be expected of things using the principles of tensegrity. Indeed, some have said that the struts look too fat - awkward and too numerous - and that the rigging is too messy - randomly muddled and chaotic; that the bridge looks grossly over-designed. Surely not? It was expensive, but why would any extra or over-sized elements be included? One is left wondering why these comments arise. Is a bridge a natural tensegrity structure? Is a tensegrity structure naturally a bridge? Perhaps the problem lies here? Tensegrity may be better for domes and sculptures – for spanning - enclosure - without having to accommodate loads of horizontal, linear traffic, be these from pedestrian or vehicular movements.

Bridges link – they ‘go between;’ they span. It is their necessity. So it is that one wonders why the new vehicular traffic bridge nearby upstream has been called the ‘Go Between Bridge,’ even if it refers to a local rock band of another era. It all sounds like an overstated understatement of the very obvious. The success of bridges depends not only on their name, appearance or style, but also on what they join. Unfortunately, the Kurilpa Bridge starts at the crowded, freeway-obstructed end of Tank Street, in an area of Brisbane remote from the CBD and distant from any density of necessary pedestrian movement or thoroughfare. It is the ‘backwater’ of central Brisbane. The bridge lands on the other side of the river in front of the new Gallery of Modern Art complex, (GOMA – ‘Modern Art Gallery’ would have given a less catchy ‘MAG’), but with an awkward detour that looks like a large circular corkscrew ramp reaching and stretching only because it has to. This extended path delivers one down to the edge of the river that has just been crossed when walking from the city-side. The worry here is that the bridge links little that has any civic necessity. It is just there bridging from what looks like a randomly chosen point A to another location, B on the opposite bank, the only determinants seeming to be that the bridging can be achieved in this vicinity. There is no obvious civic enhancement here; nothing essential that is connected by this new bridge that is promoted as using the principles of tensegrity - at a ‘world’s-largest’ scale - as if this outcome alone might be the ambition of this exercise: an exhibition of a structural possibility.

London has a new bridge too - The Millennium Bridge. It is the first new bridge across the river Thames in London since Tower Bridge opened in 1894. Like Brisbane’s, it is a pedestrian bridge and would probably also seek ‘green’ credentials. It was designed by Foster + Associates in collaboration with the sculptor, Anthony Caro and structural engineers Arup, the same engineering firm that was involved in the Kurilpa Bridge. This engineering firm investigated and solved the well-publicised problem that the Millennium Bridge encountered – it swayed more than anticipated with cumulative pedestrian movement. Unlike chooks on a perch that can stabilize the swinging movement of their suspension, the movement generated by pedestrian corrections seeking to counter the swaying and to stabilize bodies, only enhanced the structure’s movements. Special buffers were detailed and installed under the bridge to overcome the problem with another piece of subtle engineering by the bridge’s designers. The bridge opened initially on Saturday 10th June 2001, but in order to fully investigate and resolve the swaying issue, the decision was taken to close the bridge on 12th June 2001. After the extensive investigations and corrective work, it was re-opened on 27th February 2002.


There are similarities and differences with Brisbane’s bridge. London’s bridge is held up by tension and lies on a direct axis with St. Pauls – London’s great landmark (well, one of them), linking the City of London near St Paul's Cathedral with the Tate Modern art gallery on Bankside. Kurilpa Bridge uses tension in tensegrity and links the city-side of Brisbane to the art gallery precinct for pedestrians too. The Millennium Bridge stretches from a small, undistinguished pedestrian precinct that meanders through to St. Pauls and, at Bankside on the opposite side of the Thames, splits and comes to an unexpected end in front of Tate Modern’s side wall where the mirrored ramps return to take one back on axis down to the river’s edge. This abrupt termination is somewhat similar to that of the Brisbane bridge. Kurilpa Bridge comes to a point where one is directed off the bridge down a large curved ramp to reach the riverbank below. The explanation for the Millennium Bridge’s abrupt cessation and reversal of pedestrian movement is that here the designers have cleverly redirected pedestrians to look back at St. Pauls. The experience seems to suggest that the reason may have more to do with overcoming an awkward transition defined by some requirement involving levels and structure than anything else, as it does with Brisbane’s bridge. Both bridges feel as though they should be otherwise, perhaps by leading more directly to a predetermined civic location that would allow a less self-conscious and more effortless transition to the art galleries. There seems to be no ‘arty’ explanation for the Brisbane bridge detour – but it may be coming.

Where London’s bridge has a critical necessity in its marvellous location, Brisbane’s seems to have an unresolved anxiety. The Millennium Bridge is anchored with its St. Pauls’ axial precision that overcomes the perceived weakness of the Bankside termination. Brisbane’s bridge seems to have ignored any similar essential placement. Why did it not land between the library and gallery of modern art where it might have gathered location and function together nicely into a civic space that both welcomed and connected city place? Why did it not link with a more vital part of Brisbane’s city side? Maybe it aims to revitalise this rather backward-feeling, uninviting area that holds a sense of being somewhat derelict, lacking in civic energy – shaped, as it feels, by a collection of relics that might be replaced, refurbished or revitalised in the future. How? When?

There is another critical difference in these bridges. Foster wanted the pedestrian to have the benefit of no superstructure interfering with the pedestrians’ enjoyment of the river and the aspects of the city. And it works marvellously – the pedestrian floats over the river, high in open space that might scare the agoraphobics, with the low, tension cables stretching out from the bold ‘Y’ base supports forming the foundation for the huge void of vistas for all to enjoy. In Brisbane, one is again high above the river, but has what looks like a surplus of structure and weight held, looming ominously above and leaning unusually on each side. Here, with a closer inspection of the detail, the sailing ship analogy is tested to the limits. Memories of sailing boats are recalled as an organisation of finer elements with what looks like a more rigorous arrangement of functioning parts and careful connections. Cables never crisscross so much in a ship without one being able to read their sense of having to be there. Their necessary logic and essential patterning becomes self-evident. Here, puzzlingly, tensegrity does not seem to have the readily understood logic that Fuller’s examples display. Is this why it seems ‘messy’? What would Fuller make of this? His examples are so rigorously specific and crystal-clear in their organisation that one has to ask the question. The eye seeks to trace the stresses of this structure that sometimes seem to be those of a familiar suspension bridge - but more unusually complex, while at other times they do fit a pattern that has a quality similar to traditional tensegrity images. Is this bridge a mix of both systems because of the requirements of the bridging functions imposed on tensegrity?

One’s sense of appreciation is challenged by the bridge’s platform. How does the platform fit into the resolution of tensegrity principles? Does it divide the natural stresses in these forms to give a right and a left scaffold, like that in a traditionally-framed bridge? Is this deck in compression or tension – or is it just being held up? How? By what? Is it free of bending moments? What is its role in the philosophy of things geodesic? It becomes a puzzle when, at places, a compressive element seems to be standing on it, or supported by this planar element when we know it cannot or perhaps, should not be so. It is here that the image of the traditional suspension structure appears, leaving one to ask if things might have been more minimal and efficient had this structural system been employed without the added challenges and complications of tensegrity. The lower ends of the compression struts that appear to rest on the deck have cables supporting these extremities that look as though they could support the platform without many of the members above. Has the effort - the commitment - to use tensegrity been so great as to overcome the consideration of the benefits of any possible alternative structural systems?

From the distance the long plank of the pedestrian path looks like a smart, high-tech aerofoil that somehow slots into the equally potentially-slick elements of tensegrity as a sophisticated part of the whole. But as one is swept below the bridge onto the southern bank, it becomes clear that the platform is framed traditionally with fairly basic steel detailing that has an added set of curved forms planted on to each side to provide an illusion of aerofoil elegance, leaving one feeling a little cheated by this charade in much the same manner as one feels on reading the ‘tensegrity’ elements of this bridge, knowing what elegance and refinement geodesic principles can make possible.

The words ‘clumsy’ and ‘awkward’ come to mind. Why? How is it than the wonder of tensegrity seems to become a little disabled or confused here? Is it that tensegrity principles have been used in this bridge, but only in part? Can one identify the pure tension and pure compression in this scheme without any detailed description or analysis? Unfortunately it looks as though this admirable effort has become just too much of a struggle to achieve without compromise. One must admire the determination, but is left perplexed by the question: why were the potential problems and awkward complexities not addressed during the design stage by changing tack rather than merely beavering on with the aim to achieve a world first? – for, sadly, this is what appears to have happened. Instead of adding to Queensland’s effort to be the ‘Smart State,’ the bridge exhibits an uncertainty of resolution – what looks like a less-than-smart mix of elements seeking to be promoted as Fuller’s dream of an exceptionally rigid and efficient, elegant, light-weight structure using members with a minimal mass and cross-sectional efficacy. The possibility was of an assembly of components that could be really ‘green’ in every way beyond and including colour. This bridge seems to lie in a truly grey area both in relation to any purity of concept and to its simple hue. Sadly, it fails to address the possibilities of colour, and like our other pedestrian bridge – oddly-named ‘Goodwill’ (because most bridges promote goodwill) –  fails to explore how colour can transform and enliven elements; how colour can add life and spirit to even the proverbial grey of the battleship. Here one brings to mind the marvellous dazzle camouflage created for the World War 1 allied ships by the Vorticist group of artists established by Wyndham Lewis and others – one of the few joys that war has ever brought to our world. One is just left imagining how a strategy to use colour and an assemblage of pure geodesic stresses might have danced between necessities to become Brisbane’s different Kurilpa Bridge. But is this an impossible dream? Was it?


P.S.
A word similar to those coined by Buckminster Fuller now comes into play. It is Carl Jung’s ‘synchronicity.’ Wikipedia explains the concept as:
the experience of two or more events, that are apparently causally unrelated or unlikely to occur together by chance, that are observed to occur together in a meaningful manner. The concept of synchronicity was first described by Swiss psychologist Carl Gustav Jung in the 1920s.
A few days after completing this piece on bridges with these questions, a copy of Martin Pawley’s Design Heroes: Buckminister Fuller published by Grafton, London, 1992, was discovered in a second-hand bookshop in Inverell. A quick perusal of the pages revealed some interesting comments, as if to clarify the terminal doubts. Martin Pawley writes:
Unlike the early masterpieces of his architect contemporaries Frank Lloyd Wright, Le Corbusier, Mies van der Rohe and others, Buckminster Fuller’s designs – the Dymaxion House, the Dymaxion Deployment Unit, the Wichita House, the geodesic and tensegrity domes, and the giant projects of the 1960s – were all steps towards the ephemeralization, or rendering insignificant, of the problem of shelter, rather than works of architecture. In this sense they were simply tools, but in another sense they transcended the timescale of mere usefulness and attained another scale of value altogether. Today they are in a literal sense anachronisms – timeless achievements in an age of continuous technical development that ruthlessly gives a shelf-life to even its finest manufactures. (p.172)

Is Kurilpa Bridge an anachronism? It may be. Fuller’s aspiration was described in his concept of ‘ephemeralization’ –
‘the process . . . whereby doing more for less can lead to an implosion of functions, one into another, until only a gossamer thin but steely strong multifunctional envelope takes the place of separate ‘cultures’ of architecture, building and aesthetics.’ (p.152)
Over fifty years have passed and Kurilpa Bridge seems to have made little development with this integral theme of Fuller’s amazing ‘Dymaxion’ world. One might assume the vision is just a far-fetched dream and dismiss it, but there remains a more blatant, latent irony in this tensegrity bridge. Pawley notes of Buckminster Fuller:
His purpose in creating this structural system (tensegrity) was, he (Fuller) wrote in the lucid language of the patent application, ‘to bring the slenderness, lightness and strength of the suspension bridge cable into the realm previously dominated by the compression column of building.’ (p.148)
A new question arises: why, given what looks like the ad hoc patterning of a less-than-refined outcome, has the concept of ‘tensegrity’ been used to supplant the elegance of its inspiration - ‘suspension’ - in Brisbane’s new crossing? The more gracious possibilities of suspension can be seen in London’s new bridge. What has happened in Brisbane – in the ‘Smart State’? Is the tensegrity claim overstretched?


NOTE: 14 September 2016

For more on architecturally designed bridges, see: Exploding the Myths of Modern Architecture by Malcolm Millais, published by Francis Lincoln Limited, London, 2009: Chapter 11 - BRIDGES BECOME SILLY.

22 February 2014 - see: http://voussoirs.blogspot.com.au/2014/02/tensegrity-bridge.html

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