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
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