Knitting Architecture Be Smart about Building Concrete Structures
[Music]
so it’s 2019 and we’re all
very much aware of the fact that climate
change is a serious issue
now if i were to ask everyone in this
room to tell me what we should do
to be more sustainable we’d come up with
the first things
such as using less fossil fuels
flying less maybe driving an electric
car
maybe changing our diets bringing our
bags to the supermarket
using less plastic and recycling and all
of those are valid and good
but there is one sector we almost always
overlook
and this sector in 2017 accounted for
almost
40 percent of the global greenhouse gas
emissions
can anyone think of what this is
it’s the building and construction
industry
and this is not going to get any better
in the future because by 2050 there will
be 2.1 billion people
more on the planet so whether we like it
or not
we’re going to have to build housing and
infrastructure for them
and if we do things the way we do today
we’re going to be faced with
more pollution resource depletion and a
whole lot of waste
so at the block research group at eth
zurich
we develop methods to build and design
build buildings better by intelligently
including
structural performance in architectural
geometry
we can really reduce the amount of
material that you need for a structure
and i can explain that easily using this
piece of paper that i carried in here
so when it’s flat it can barely hold its
own weight
but if we change the geometry and
introduce a little bit of curvature
it can suddenly hold a lot more and the
amount of material has definitely not
changed
now it’s the same principle that allows
that pringle to hold a full glass of
water
and please try this at home also
it’s the same principle that allows for
this structure behind me to span
40 meters with only six centimeters of
concrete
so if we do use structural geometry
intelligently we can
design beautiful structures that use
very little material
but there’s a catch their geometries are
usually complex
and intricate non-repetitive and that
means they can be very challenging to
build
using traditional techniques now
concrete
is the most used material not only here
in bucharest but the world
so it’s also a favorite material when it
comes to these kind of geometries
simply put because it’s liquid stone so
we can mold it into whatever shape we
want if we have a formwork
and the formwork is the catch if we look
at how things are being built today
unfortunately we find a system that has
remained unchanged for hundreds of years
this is roughly the 1960s and while
we’ve gotten better and more precise and
more streamlined
in our manufacturing process the basic
principle stays the same
we need months of milling or carpentry
to produce these heavy
clunky molds that need a lot of support
and ultimately turn into a pile of waste
so really if we want to unlock the full
potential of these kind of
efficient and optimized structures what
we really need to do is not only change
the way that we
design things but we also have to change
the way that we build things
in terms of formwork one solution of
many would be to use a textile
a textile is a lot lighter than wood
it needs a lot less support and finally
it’s also
more sustainable it produces a lot less
waste
my research specifically looks at how we
could use knitted textiles as formwork
for concrete
and knitting is very special in the
sense that we can create
3d geometries directly in a single
process using existing machinery
and we can also make sure that we have
very precise
local material properties or integrated
features
and if it sounds confusing i’ll have you
think of your shoes
your sports shoes all do all of these
things and you’re very familiar with
them
so how this works is we start off with a
design
and then produce a fitting knitted
textile
we then tension that textile into shape
and because textiles and especially
knitted textiles are actually quite soft
so you wouldn’t be able to hold their
shapes when casting
we just coat them with a very thin
special cement paste
to make them strong enough this leads us
to a nice lightweight
structure that can be now used as a
formwork for concrete
one of the tricky parts here was
designing or coming up with a
computational pipeline that allows us to
automatically translate
a 3d design into manufacturing
possibilities for a knitting machine for
existing machinery
so let me show you some examples of
course just because we start off and we
say hey you know knitting could work
that doesn’t mean
everybody believes it so i started off
with this knitting machine which is
something that people in the 90s may
have had in their homes
and we lovingly called her grandma
of course because she’s the ancestor so
we did a bridge
the first bridge we did was a small
structure something about as big as the
circle i’m standing on today
but it was important to be able to test
this kind of principle
it weighed only 200 kilos but the
interesting part about it was that how
much the formwork weighed which was
about one kilo in itself
so the way this worked or the way we
tried out was we started with a textile
that we tensioned using some splines and
ribbons into a corrugated shape
we coated it with the cement paste i
mentioned earlier and then we used it to
cast concrete into normally
if we look at the textile itself you’ll
notice that it has already some channels
in which we could introduce these bars
these black
gfrp rods and cables to get to the shape
and we also had some registry points so
that we would know that we get the right
thickness of concrete
to produce it we used grandma
it took about a week in this very
automated and not manual process as you
can see robots were not yet coming for
our jobs
to produce this very small textile in
three pieces because the width of the
machine was also limited
now what is very interesting about it is
that it is very light so the textile
itself was only 433 grams
in total we put all of the pieces
together into one single piece
introduced all of the splines and
shaping elements so that we could get
a corrugated shape in the end that
flattened piece of textile was then
fixed into a rig
tensioned and gotten to this shape we
took this lovely little bridge into a
climate chamber and applied this
thin cement based coating i was telling
you about
to get a shape that looks something like
this and weighs only 12 kilos
now this was one millimeter thick and it
could
just support another four millimeters of
concrete that we sprayed onto it
those four millimeters together with the
formwork from before became the formwork
for casting concrete normally
so we didn’t change anything about how
we cast the concrete inside
the structure that came out may be small
but what it said about this kind of
technique
was that we can really create a very
have a rather heavy structure with
a significantly lighter mold also
we didn’t need support from underneath
so you could use such a
technique to be able to build in places
where you want to have an
unobstructed passage say over highway or
over a river
and of course because we’re researchers
what we also needed to do we were eager
to load
test it dynamically and in a very
scientific way so we jumped on it
now to the right to my left in the
picture is lex and lex is the researcher
that works on making sure that the
composition of the cement paste is
exactly right so that it is strong
enough to do these kind of things
so he’s our in-house concrete magician
what the project also showed us is that
the textile could possibly be used also
in other ways
i mean it wasn’t coated on one side so
it remained visible
and we leave it in place so it kind of
brings an avenue of doing something
architecturally and aesthetically with
something that is previously just meant
for structure now those experiments were
done with grandma
and you might say hey yeah that’s a
great idea
but in construction we need to do things
that are a lot bigger
and spending a week on this two meter
thing is also not exactly ideal
so we left grandma aside because those
experiments were convincing enough
to get an upgrade to a proper industrial
machine to see that this actually works
at an architectural scale so last year
in october we built a structure to test
these things out it was called nit
candela and it was built in mexico city
it was done in collaboration with
zahadid code group
and it is designed as a homage to the
famous shell builder felix candela
it looked something like this and what
you already see is that it has a
concrete outside and
something interesting on the inside
which is a textile
it weighed five tons of concrete in
total so we went a long way from the
200 kilos and it was built using a cable
net
as a main load-bearing structure and a
knitted textile
that weighed only 25 kilos in total the
cable net and the textile
were 55 kilos and they carried five tons
so that’s quite impressive to do this
what we did was we
made a frame we tensioned the textile
into the frame using those cables that i
talked about
but the interesting part here is just as
with the bridge is that the textile
itself had all of the channels to guide
those cables where they needed to be
guided and another
nifty feature it had pockets so that we
could insert inflatables
when inflated those pockets would create
cavities in the concrete
saving weight what we then did is we
coated it with a very thin cement paste
with a slightly different formulation
because we needed
to use it outside and when that hardened
we coated it with concrete
when the concrete hardens the frame can
be removed and reused for other things
and we’re left with a structure as
before the textile is left inside of the
structure and it’s what you see on the
inside it’s this beautiful aesthetic
thing
so in conclusion the textile that we
used had
two sides a beautiful aesthetic exterior
that needed to be seen
and a technical other side that needed
to fulfill all the functions of guiding
the cables and where all of these
inflatables needed to be and for us to
register the geometry
even though they are two very different
sides they have
they use two different materials and
they behave very differently
they are produced on the machine in one
single process
now of course the machine also has a
limitation in its width
it’s not long enough so we did have to
split the 4 meter geometry into four
parts but when we were done
we created what is arguably the world’s
largest scarf
and we packed that up in four pieces
and put it in our suitcases and took it
in checked in luggage to mexico
well this is first to show that we can
do this very lightly but also as
architects we finish everything the
night before the deadline
so when we get to mexico we put
everything together
we introduced all the cables where they
needed to be and we stretched it in the
frame
we also were very relieved to see that
it does stretch to the size that we
wanted because it looked incredibly
small beforehand
and that means that our pipeline and our
and our whole system
does work at least until this point so
far
and what you can also notice is how
little support it has
otherwise you would need a whole lot of
support to create this geometry
we then coated it with that thin cement
paste layer which was now misted on
as a spray and we were left with this
beautiful swiss chocolate of a texture
on one side
now i just wanted to remind you that
those little boxes that you see there of
the swiss
chocolate there are actually cavities in
the concrete later on
making sure that we don’t have as much
weight otherwise in the structure
we then had very artful craftsmen
which are concrete workers in mexico
that put three layers of concrete onto
this surface in the most traditional
fashion
and made sure that it had an incredibly
incredibly smooth finish
which is absolutely mind-blowing to see
that you get
a concrete finish that probably felix
candela would have also been proud of
so the finished structure has a hard
concrete outside
and a soft textile inside what you don’t
see on this picture
is that the textile is actually soft you
could lean against it
push and it’s soft because there are
cavities behind it
and depending on how the sun would shine
every now and then you could also get a
glimpse of the skeletons of little
balloons that were in there
so i just wanted to leave you with a few
thoughts about a process or a structure
like this
the formwork for this was 50 square
meters
and the cable net and textile so
excluding that frame that can be reused
only cost
2 200 euros it took
it was 25 kilos of weight that the
textile had
and we took it there in a checked
luggage it took a mere
36 hours to knit a surface area that
would have taken about 750 hours to mill
otherwise
and the entire project from the very
first time we sat at a table for design
to the structure standing there was
three and a half months
that would have been impossible with
traditional techniques because those 750
hours i mentioned earlier
that’s about three months of milling
alone so that would have been just the
formwork
now finally the really interesting part
is that those machines that i’m talking
about
they are there are hundreds of them in
factories such as these
all over the world so really we don’t
actually have to take the textile
anywhere though it’s light and all that
we can just send them the data and have
them manufactured locally
moreover these types of feats of
economy and productivity are incredibly
important for the construction sector
that is lagging behind other industries
and the productivity
is at the moment the same as it was 20
years ago
lagging behind average and definitely a
lot lower than what manufacturing can do
so considering that in the next 30 years
we would have to build
the entire amount of construction that
we have today
bill gates earlier this year likened
that to adding a new york
every month for the next 30 years it’s
not
that we can build less but we should
definitely be smarter
about how we build and design those
buildings
thank you
you