Our population globally is growing and our urban population is also growing
rapidly and so we need to find ways to build cities more sustainably
for growing populations.
In the next 30 years about 150 major cities in the world will
double in terms of their urban population. What is going to happen it'll
be really a residential need that will be almost catastrophic in scale unless
we find a new way of building.
Architects can no longer ignore the responsibility
they have towards choosing more eco-friendly materials or sustainable
materials. What we are trying to do is we're trying to show that it is indeed
possible to build structures that are architectural interesting,
using natural materials.
So Oakwood Timber Towers began as a first project
as we were invited by Cambridge University and Smith and Wallwork
engineers. They were interested in the tower of about a hundred meters for study,
but when we were discussing as a group we thought why not just simply go to the
maximum which is 300 meters.
Building with wood, engineered wood at the scale
of skyscrapers, this is the first time we've had a new large-scale, structural
building material in over 150 years since structural steel and reinforced
concrete. We know that global carbon emissions need to come down and building
with wood is an excellent alternative to building with steel or concrete.
What we're really beginning to find though is that it's a new method of construction
that's really has the opportunity to change the industry and bring us into
the 21st century unlike any other material.
CLT is an abbreviation for
cross laminated timber. It's wood glued so they're 90 degree different. Glued
together you get very large panels that architects and engineers currently use
more or less like slabs of concrete. There are lots of advantages to using
cross laminated timber among them it sequesters carbon from the forest,
it is an engineered material so it's the same every time you ask for it.
It's usually cut and pre manufactured in a factory so it comes to site ready to
assemble, it's very light particularly compared to steel and concrete so you
can get taller buildings on the same sized foundations. And we hear a lot
about the change that would be possible to global carbon emissions if all people
became vegetarian, I think we can make an argument that cities
ought to be vegetarian.
When we talk about timber buildings the three most common
questions are of fire, forests and rotting. Wood is combustible and it will burn but
the type of wood that we're using in these very large-scale skyscrapers is
different so these solid wood panels, they behave much more like trunks of trees
so as the wood burns the charcoal is very insulating so protects the unburned
wood underneath. The goal is that if you remove the source of heat,
the fire will go out.
The Center for Natural Material Innovation
at Cambridge University is located in the architecture department.
It's funded by the Leverhulme Trust and it brings together biochemists, plant
scientists, architects, engineers, chemists and mathematicians to try and find ways
to use plant materials at a larger scale in the built environment.
So I'm Paul Dupre
I'm in the Department of Biochemistry in the University of
Cambridge and I work on the structure of wood.
Well there are several reasons why
wood is so strong, there are three main parts to wood: the cellulose xylan and
lignin and it's not been understood how they stick together to make this
remarkable material. And the shape of the xylem molecule, it has evolved we presume
to be precisely complementary to the surface of the cellulose fibers so when
they come close to each other they're able to zip up like two parts of a zip
and that brings the whole molecular structure together and that makes it
remarkably strong. And we might be able to use that
knowledge to improve the properties of wood perhaps by finding components that
we can put in the wood to preserve it or change its structural properties
When you build a tall building you have to be very conscious of how they will
respond to lateral wind loading on the side because they, even though they're
big stiff huge structures they will still flex about to some extent in
the wind. One of the challenges with timber buildings is that a skyscraper
made out of timber will be lighter than it would have been in concrete or
steel and that means that they're more susceptible to moving around in the
wind, to vibrating which could make occupants uncomfortable so we need to
mitigate this and understand how to design appropriately in timber
versus in other materials.
Most failures allow in connections, could be either for concrete
buildings or even for timber buildings so we need to make sure that we provide
safe, reliable and robust connections in any case and this is where research is
needed especially when we need to address higher limits for example in
tall buildings.
So the different colors it's a
visualization of the magnitude of the stresses. Usually red color and indicates
higher stresses, usually at the lowest levels of the building
whereas blue can indicate smaller stresses.
We work on small molecule compounds that
can penetrate into the extremely tiny pores inside of large timber.
We are all made up of extremely small polymers and even smaller molecules right? Our DNA,
our proteins and so you can say that we can engage and interact on a human scale but
of course what's happening are many processes at a much much tinier scale
and in the same way the buildings of the future may be held together through
rapid interactions that are happening at the molecular level but having a
macroscopic effect and on the human scale. And perhaps in the future we'll be
able to completely remove the concept of a nail or a screw holding two timber
joints together. Perhaps they can all be done through small molecules that come
together at very specific interfaces and give the wood unbelievable strength.
We have to ensure that wooden buildings of the future, even wooden buildings today
are made from sustainably managed forests. Deforestation is a big problem
in forests around the world but it is usually a result of cutting forests for
agriculture rather than cutting forests for building materials.
The sustainable forests,
which are not subject to deforestation are planted as crops.
In Europe, in the last few decades the sustainable harvest has grown by an area
the size of Portugal, the amount that can be harvested that hasn't actually been
harvested so the forests are larger by tremendous amount.
There's a new science, called Biophilia
and incorporating timber into cities will improve the
sense of nature returning to human habitations, to cities particularly.
So there's a very strong connection psychologically - our heart rates redo are
reduced or less, less stressed which is something you want in a city centre.
We become more sociable therefore apparently so we see enormous benefits
in using the material.
So I can imagine a future where we're growing our buildings,
where we live in a building that's been made from a tree that was cut down not
too far away and when that tree was cut down, two were planted in its place.
From the first skyscraper in 1885, it was less than 50 years that we got to the 381 meters
of the Empire State Building. In the near future we will see taller and taller
wooden buildings and it will be common for us to accept them and that we will
see some wooden skyscrapers on the skyline of London, New York,
other great cities in the world.
The groups research on timber towers not only pushes the
limits of architectural design, structural engineering and scientific
research but it also synthesises them. We hope to solve a host of problems that
can trickle down to other building typologies
by showing that the very limit of engineering
can be achieved using timber as a natural material.