miércoles, 16 de septiembre de 2015

LIVING IN A MATERIALS WORLD

"From concrete to plastics, the megatonnes of stuff in the built environment are mostly manufactured and used with little thought for waste and pollution. Radical moves are afoot to refashion the urban fabric"

To the eco-engineer, the glass is neither half-full nor half-empty. It is simply twice as big as it needs to be. Building with maximum efficiency and minimal materials is increasingly urgent in our resource-strapped times. Many of today’s structural engineers and designers are looking to natural forms and materials as the tried-and-tested guide. The p ower and economy of evolved ‘design’ — eggshell, spiderwebs, bone — are inspiring architects to experiment with solutions that work in harmony with physical forces and mimic biological form. Meanwhile, others are embracing ‘extreme upcycling’ in the flow of materials through the urban fabric, exploring ideas from edible upholstery to walls created from substances sourced in beetle exoskeletons. Here, we look to the design ideas of three top players in the materials world: Olympic Velodrome engineer Chris Wise on lean, intelligent structures; architect and biomimicist Michael Pawlyn on a 3D-printed built environment; and chemist Michael Braungart on manufacturing beyond sustainability

Engineers are taught to design from fear, to avoid failure. The construction industry reinforces this, rewarding those who take the fewest risks, sacrificing our global material and energy stock on the altar of expediency. Dare we hope for wiser engineering, with beautiful performance from the least material? Occasionally, special projects allow us to try. My firm Expedition Engineering was structural designer for the Velodrome in London’s 2012 Olympic Park and the Infinity Bridge in Stockton, UK. Both won Britain’s top prize in structural engineering, the Institution of Structural Engineers’ Supreme Award for Engineering Excellence. Both structures are ‘form-found’, shaped to be in equilibrium with the forces acting on them. Catalonian architect Antoni Gaudí first popularized the technique. His Sagrada Familia cathedral in Barcelona, Spain, begun in the 1880s, was effectively shaped upsidedown — Gaudí’s models were bags of sand hung from tension strings. Form-finding now uses digital-analysis engines for the behaviour of everything from cats’ cradles and soap bubbles to giant basket-like grid shells. This way, structures can be sculpted to carry loads either in pure tension (like a spider’s web) or in pure compression (like an eggshell). Such structures embody the ancient Greek ideal of an inner beauty, carrying maximum load with minimum material in a way that cannot be bettered. Despite humanity’s love of graceful curves and our need to use materials wisely, form-finding is still the exception. It should be the rule. The Velodrome spans 130metres with a tension roof structure only 76 millimetres thick; roofs of other stadia worldwide covering a comparable area are often metres deep. The Velodrome design achieved that lightness by letting nature lead, following the forces until they reached the equilibrium shape of a saddle in pure tension, anchored directly to the curved seating bowl. The forces are carried in harmony completely within the structural geometry, rather than outside it. It’s an old trick much loved by the builders of Gothic cathedrals, although now we use a tension system of machine-woven steel cables, rather than a compression system of individually hand-cut stones. If the Velodrome is a structure acting in tension, Stockton’s double-arched Infinity Bridge is its complementary opposite. Through pure compression, the arches’ shapes carry their own weight and the suspended deck: all the heavy forces are carried down the absolute centre of the structure. Because they are linked into a structure resembling an archer’s bow, the two arches also act like a giant see-saw to resist the much lighter fluctuating weight of crossing pedestrians. (An adaptive bridge geometry, that changes continually in response to pedestrians’ movement, could be coming soon.) The ancient Roman Alcántara Bridge in Spain shows how far arches have evolved. The Romans did not know exactly where their forces went, so hedged their bets by infilling the massive individual masonry arches with cemented rubble to guarantee a pure compression line at least somewhere within the structure. Centuries later, the suspension bridge emerged. From Bristol’s Clifton Suspension Bridge to San Francisco’s Golden Gate, these are structures of great efficiency, but demand extraordinary tension anchorages buried at each end to hold the main suspension cables. Infinity avoids such foundations by using tension cables in the deck to tie the ends of the arches together: the whole bridge just kisses the ground lightly at each end. The flow of the forces is written into the air in ultra-slender structural steel, rather than hidden inside approximately shaped stonework weighing thousands of tonnes. Confident engineering comes from proper understanding of the natural phenomena to which it will be subject, and the more experimental, the more chance there is that something will catch us out. In the late 1990s, I was the engineering firm Arup’s director for London’s Millennium Bridge spanning the River Thames. It, too, was an off-piste, pure-tension natural structure. Too natural, perhaps: on its opening day, it wobbled harmonically like a giant guitar as the lateral sway of pedestrians’ gaits became the vibration of the bridge. That wobble, however, forced a research project to find the cure: energy-absorbing dampers, choreographed by the late Arup engineer Tony Fitzpatrick and published for all to use.


  The lessons learnt there fed into Infinity a decade later. Despite these examples, and others from the likes of German architect and engineer Frei Otto, the late Peter Rice, and Tristram Carfrae at Arup, engineering suffers from a chronic sickness for which the construction industry is both cause and potential cure. ‘Normal’ fees for most engineering commissions are still based on a percentage of the construction cost: the more material you use, the more expensive the project, and the bigger your payout as an engineer. Construction regulations are full of emotive words, such as ‘collapse’ (avoid it) and ‘vibration’ (get rid of it). Beyond these sanctions, they are largely silent. There is nothing in most commissions to encourage engineers to use less material, so they don’t. Yet if engineers were educated to design, say, perfectly tailored beams instead of off-the-shelf steel joists, we would cut about 30% from the millions of tonnes of steel beams used yearly. This should become the industry norm. The huge construction supply chain also requires huge investment in new technologies. If manufacturers will not retool on a speculative basis, engineers need other research partners for innovative alternatives, such as those ‘perfect’ beams whose shape is tuned to the bending in them. Infinity, the Velodrome, Otto’s Olympic Stadium in Munich, Germany, and the Strad violin demonstrate what is possible. It may be ancient, this job of doing for a penny what any fool can do for a pound, but some of us seek performance through harmony between materials and natural forces. We design in hope, not fear — and with an eye on nature.



FUENTES
http://web.a.ebscohost.com.bdatos.usantotomas.edu.co:2048/ehost/results?sid=d9bdc555-1466-4a63-b333-c448f679be8a%40sessionmgr4005&crlhashurl=login.aspx%253fbquery%253d(SO%252b(Nature))AND(DT%252b2013)AND(TI%252bliving%252bin%252ba%252bmaterials%252bworld)%2526direct%253dtrue%2526site%253dehost-live%2526db%253da9h%2526type%253d1&hid=4107&vid=0&bquery=(SO+(Nature))AND(DT+2013)AND(TI+living+in+a+materials+world)&bdata=JmRiPWE5aCZsYW5nPWVzJnR5cGU9MSZzaXRlPWVob3N0LWxpdmU%3d  


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