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