Conference Session C10
Paper 2169
THE BUTTRESSED CORE
Chase Smethurst (cas233@pitt.edu), Billy Green (weg22@pitt.edu)
Abstract - This paper will describe and demonstrate the use
of the buttressed core, the newest and most cutting edge
design being used in the infrastructures of some of the tallest
and the tallest building in the world, these otherwise known
as skyscrapers. The infrastructures and designs of these
buildings will be explained thoroughly as well as the
direction that these skyscrapers and modern buildings are
heading for. Further discussion will show the values of the
known and proven advantages of this innovation of the
‘buttressed core’. It’s ‘three wing design which extend out of
the central core and firmly anchor the skyscrapers will be
described and told as well its use in the future building of
our cities most iconic landmarks.
This conference paper will both describe some of the
techniques and designs currently used in some the earth’s
most famous buildings. The buttressed core will be
examined in detail, describing the different components and
parts which make up the buttressed core and the materials
which go into making it like the use of fly ash in the cement
of the core (Sheath), describing in part how it operates as a
whole, making the world’s tallest skyscrapers more
structurally sound even at their ridiculous heights. The
assessment of how and why this is an invaluable design and
why it is of importance to our future will be described and
discussed as the most advantageous reason for civil
engineers and those building skyscrapers into the future to
use it. This paper will also present examples that the design
was used in the most famous and tallest buildings such as
the Burj Khalifa in Dubai known as the world’s tallest
building, doubling the size of the Empire State Building
(Baker). The buttressed core allows for these skyscrapers to
go up tall and fast with enough usable floor space to
maximize clients chances of making a profit (Blum). The
buttressed core’s design is most prevalent and well
recognized in the beautiful and extravagant building in
Dubai the Burj Khalifa (WebBuildingsDirectory). The Burj
Khalifa offers a social impact as well bringing in extra profit
and much publicity to Dubai (Dowdey) Overall civil
engineering in the future is set to explode and people and
cities want more beautiful and taller buildings, the
buttressed core allows for us to create these buildings of the
future and show engineers that next step in innovation. Our
paper belongs in the Civil Engineering Conference because
it describes and explains important innovations in the world
of civil engineering that are present in the Burj Khalifa.
Even though we only talk about one building, we describe
how it utilizes many new design schemes and techniques that
allow it to become the tallest building in the world.
Key Words – Burj Khalifa, Buttressed Core, civil engineers,
concrete, Fly Ash, structure, Y-design
THE BURJ KHALIFA
The Burj Khalifa (formerly known as the Burj Dubai) gained
the title of the world’s tallest building when it was
completed in 2010. It rises to a maximum height of 828
meters (2716.5 feet), taller than any other man made
structure [1]. It is the crowning achievement in the massive
construction projects in Dubai, UAE, and has become a
symbol for the nation. Dubai has seen a huge amount of
construction in the past few decades. It has built the world’s
tallest hotel, the Burj al Arab, which sits on a man made
island in the Persian Gulf. And speaking of man made
islands, more than 300 have been built in the Persian Gulf.
This is a paradise for architects and engineers who want to
make their wildest dreams come true. This is a place where
you would expect the world’s tallest building to be built.
It is the centerpiece of a $20 billion construction project
in Dubai, UAE. It has been made to bring more business into
the city. The tower is mainly residential, an oddity for
skyscrapers, who are usually used as office space. This is in
an attempt to make urban areas more livable. The building
being connected with transit in the area makes getting from
the tower to the rest of the city easy. But, even being an
excellent place to live, it has remained with a good portion
of its residential space empty [2].
Bill Baker, the designer of the Burj Khalifa, is an expert in
super-tall skyscrapers. He has built many, but in his latest
projects, "He's posing new structural approaches rather than
reworking old ones,” as stated by Carol Willis, director of
the Skyscraper Museum in New York City [1].
Dubai may be growing into a modern city, but it is also
holding on to its heritage and culture. The Burj Khalifa not
only draws its design from its engineering, but it also pulls
from the culture of Dubai [2].
The Burj Khalifa is the tallest building in the world. And
it is the tallest by an impressive amount. The previous tallest
building is Taipei 101. The Burj Khalifa is Taipei 101 with
the Chrysler Building on top of it. This is a jump in height of
300 meters. The gap between Taipei 101 and its predecessor,
the Petronas Towers, is about 50 meters, and the gap
between the Petronas Towers and its predecessor, the Willis
Tower, is about 10 meters. How could there be such an
unprecedented jump in height? It is all placed within the
secrets of the buttressed core [3].
University of Pittsburgh
Swanson School of Engineering
April 14, 2012
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Chase Smthurst
Billy Green
outside. The shape also makes wind forces much less than
that of a flat edged building, creating less surface area facing
the wind at any one time. The length of the buttresses also
have uses elsewhere [4]. The buttresses take a step pack
every few floors, tapering to a point at the top. This pointed
design emphasizes the height of the building making it seem
taller than it really is, adding to the hugeness of the building.
These set backs also help to reduce the force of the wind [2].
Because the cross section facing the wind changes, as the
building gets taller, the wind cannot form powerful vortexes
on the opposite side as seen in Figure 1. On a flat edge
building, these vortexes cause shaking. This design reduces
the amount of shaking that the Burj Khalifa will be impacted
with [4].
THE BUTTRESSED CORE
In the design and construction of Tower Palace III in Seoul,
South Korea, the Burj Khalifa’s designer, Bill Baker, noticed
that the design was a Y shape and he named it “the
Buttressed Core.” He recognized the strengths of his design
and used it for the construction of the next “world’s tallest
building” [2].
The design consists of a hexagonal core with three
projecting arms. It is built primarily of reinforced concrete,
odd among skyscrapers, which are usually steel. These
“buttresses” have walls that go down their length, ending
with thicker, hammerhead walls. All interior walls are
stacked on top of each other for the height of the building,
giving the building high vertical strength. Columns along the
perimeter of the building connect to outrigger walls on
mechanical floors that connect to the interior walls of the
building. This along with flat plate floors makes all the
vertical concrete work for vertical as well as lateral strength
[4].
It is the innovation that is beginning to be seen all over
the world and in taller and taller buildings. The innovator of
the buttressed core William Baker is becoming more and
more popular in the world of structural and civil
engineering, later in the article more we will see more in
depth to the world of William Baker, but the main part is
that the buttressed core is growing and its efficient way of
helping construct buildings taller, faster, and cheaper, is
really catching on around the world. This is especially
relevant in the world of Dubai, the place where the
buttressed core has made such an impression with its
crowning achievement of the Burj Khalifa.
The buttressed core has the unique and amazing quality
of being strong and sturdy, yet also light and more efficient
to create. Yet it is not only the strength that the buttressed
core provides for these amazingly tall structures but it is also
the appearance that it can give the structure that it designed
to build. The design of the buttressed core allows the
structures to have more window space and can really give
those who are staying at one of William Baker’s amazing
structures that amazing scenery from incredible heights that
may be harder come by in the skyscrapers that do not have
such a favorable design. So not only does the buttressed core
allow a building to built both taller and faster than any other
structure but also allows that structure to have that appeal of
the amazing bird’s eye view it gives to its residents or
visitors.
FIGURE 1
AFFECTS OF THE STRUCTURE ON THE WIND [4]
The buttressed core allows the building to grow to
amazing heights, but not use too much of the building for
strength. If the Willis Tower was as tall as the Burj Khalifa
so much of its floor space would be used for structural
purposes that the building would no be feasible [1].
The height of the Burj Khalifa is really what has made
many marvel at it, and really is what turned the city of Dubai
into what many believe is the first of many super tall
structures. Dubai in its pursuit to create a super tall city is on
the cusp of several new structures because of the Burj
Khalifa’s effect on both the economic and social popularity
of a city that otherwise considered in debt until one of there
local super rich leaders bailed the city out of billions of
dollars of debt. This man was who the amazing structure was
named after and many consider him to be the first to lead
Dubai into this new age where newer and taller buildings
will be built in the hope to attract more and more attention to
the intriguing part of real estate they already have.
Effect on the Structure
The buttressed core is not only used for its strength, but it
has also added to the rest of the structure. The Y-shape
allows for the most unobstructed windows possible, without
leaving much of the interior space closed off from the
University of Pittsburgh
Swanson School of Engineering
April 14, 2012
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Billy Green
The Khalifa itself has a very unique structure to it and
that is also accredited to the ingenious design from the
engineer Bill Baker. The extremely broad base of the
building is necessary for the extreme height that it reaches. It
is said that the taller which you make the building the more
broad of a base you will need to support it. It’s shrinking
width as it gets taller and taller also helps, as there is less
surface area for the wind to grab onto and thus gust into.
Essentially each floor plan as you go further is the Y-shape
of the buttressed core rotated to an exact position different to
that of the floor before it. This adds to both structure an
appearance as the Y design adds the amount of windows that
can be placed on a single floor.
structure itself to sway and this can be very dangerous if
engineers do not use the correct type of structures wen
building these huge buildings. For instance the Burj Khalifa
that is known to all as the tallest building in the world, as
stated earlier uses the buttressed core for its amazing
structural strength. This tri-axial design consists of three
tiers that are staggered throughout construction of each floor
as the building gets taller and taller [6]. This design is the
key to the building itself staying in that safe zone where the
building can sway with the wind but not to the point where it
becomes a dangerous risk. This three-tier design allows the
wind to not hit one side directly or head on, diverting the
wind from the hitting the building straight on at any point
[6].
In the Burj Khalifa specifically each of the wings of the
buttressed core buttresses the others via a six-sided central
core [6]. The corridor walls extend from the central core to
near the end of each wing, terminating in thickened hammer
head walls [4]. The outrigger of these walls is prohibited to
link outlying columns to the inner walls system., which
allows these columns to help with the lateral load resistance
of the structure [6]. What this means is that the concrete
itself in the vertical direction is utilized to support both
gravity and the lateral loads. This amazingly designed part
of the core allows the Burj Khalifa to be very stiff laterally
and torsionally [6].
What this means is that at such extreme heights the things
experience on the surface have to be magnified. The Burj
Khalifa is immense in size and what this means is that
gravity affects it greatly pushing down on all parts of the
incredible building, meaning that to withstand such a large
force of gravity the strength of the building in the upward
direction must be incredibly powerful. The upward force
must be large enough to withstand gravity so that the
structure itself does not collapse in on itself. The buttressed
core allows for structures to become very rigid and give
them the strength vertically to resist the forces that cause it
to collapse [4]. This is directly accredited to the design of
the buttressed core where the three wings are attached to a
very strong central core. The central core is the key factor in
giving the structure the strength to withstand intense weight
of gravity [4].
To be strong vertically as well as torsionally or otherwise
the ability to resist twisting as a result of winds. The Burj
Khalifa was constructed in Dubai where the average wind
speed over fifty years has been just over twenty-two miles
per hour. For the Burj Khalifa to stand at a height where no
other structure has ever been built it would need to have a
design where the resistance of the natural act to twist in the
high winds is fought against. The buttressed core is what
allows the structure to stand at the height of over 800 meters
in the air [7]. The three wings use each other to build that
strength. If one wing is feeing the force of the winds, the
other two wings act as supports to help keep it from twisting.
CONSTRUCTING THE CORE
The buttressed core may seem to many to have a more
‘simple’ design to its structure. To engineers, the buttressed
core is a thing of incredible ingenuity and there is much
more to what meets the eye when it comes to the
recognizable, “Y” design. As engineers, to us it is not what a
piece of machinery or what a structure may look like as a
whole but more as to how the whole is made up of from the
many different parts. The buttressed core is something which
is an incredible innovation as a whole but is also something
that is made up of many parts and without each and every
part accounted for the structure will fail, this is why we
found it so important to mention in our conference paper the
actual construction of a buttressed core and what goes into
giving it such amazing structural quality.
One of the major components when it comes to
constructing the buttressed core is the actual cement used to
make it. One of the interesting things about this structural
innovation is that it actually is not pure cement or concrete.
What is used to make the buttressed core is a newer and
more cost effective way to make cement-like substances
known as fly ash [5]. The development and use of mineral
admixtures like fly ash are becoming more common in the
construction industry mainly due to the consideration of a
more cost-effective, energy saving, and the environmental
production and conservation of resources [5]. There is even
currently a study that is looking at replacing cement in
concrete more and more with the more flexural fly ash,
testing its behaviors in certain support beams and other
structural uses [5]. In the buttressed core the fly ash is a key
component and is even growing more popular in the entire
world of construction.
Another key component in the construction of the
buttressed core is its intriguing design. The buttressed core is
designed in such a way that it makes it perfect for
constructing such amazingly tall heights. One of the major
issues when it comes to constructing buildings that challenge
the heights of the tallest in the world is the wind. At very tall
altitudes the wind can be so strong at times that it causes the
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Swanson School of Engineering
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Billy Green
This design is perfect to have the Burj Khalifa stand at such
a mind-boggling height without twisting on itself.
All these components of the buttressed core gives
structures like the Burj Khalifa a very efficient structure for
the fact that the gravity load resistant system is utilized so it
can maximize its use in resisting the lateral forces like that
of the incredible wind gusts. On the top of the Burj Khalifa
there is about a 230-meter tall spire and the complete
structure of the tower founded on a 3700-meter thick
reinforced concrete pile supported raft foundation [6].
Constructing the buttressed core involves very precise
and exact measurements, like every other part of a well bit
structure it takes much time and effort to be able to construct
such an integral part of a skyscraper [7]. Every step in the
process of constructing the buttressed core is a key to its
success and holds all the answers to how it allows such
amazing structural power for these ‘super’ skyscrapers that
are reaching new heights every day. Giving structures the
amazing ability to both resist the vertical force of gravity as
well as having the lateral strength to resist the force of the
wind.
Khalifa that have countries all over the world building taller
and more impressive buildings.
What the buttressed core provides that no other structural
innovation can provide is such and effective way to reach
these incredible heights as well giving the building such
incredible rigidity and the lateral strength that allows these
skyscrapers to stand at such tall heights for these long
periods of time [4].
As stated earlier in this article Dubai is one of the leaders
in the world of designing theses structural super giants.
Dubai is located in the Middle East and is one of the richest
places on earth. Dubai is beginning to be mentioned with the
major cities of the world as it grows and will continue to
grow. They do not shy away from the possibility of
designing new super structures and do not see a reason to not
continue to build these amazing feats of structural
engineering. Though the United States is not quite as rich
per capita as the likes of the United Arab Emirates but it still
has its fair share of skyscrapers. The United States continues
to have the most popular cities in the world with there own
signature buildings, though they may not be as tall as the
newest skyscrapers, they still hold significance. Dubai is still
far off from being known as the New York City of the
Middle East but it is making good process building larger
and more extravagant buildings by the day.
The amazing thing is what it is doing for the economy.
What skyscrapers of this magnitude do, especially when they
are the tallest building in the world, is draw attention to your
area no matter where it is. People go to Dubai from all over
the world to visit the amazing Burj Khalifa as well as their
other attractions. In the base of the hotel alone are more than
a few hotels, which are some of the most extravagant in the
world. There was even a recent movie shot, which had
scenes shot in and around the Burj Khalifa and Dubai. The
structure itself has done so much for the area that it is hard to
dispute the fact that Dubai would be anywhere near as
popular had it not been for the tallest building in the world.
Skyscrapers not only give the city that amazing scenery and
a view no one can ever forget but it also gives the people and
the economy around the area and amazing boost too.
SKYSCRAPERS OF T HE FUTURE
The need for the buttressed core and innovations like it will
continue to grow as our society moves further into the
future. It seems as if every few years there is a newer and
taller skyscraper being built. These skyscrapers are
something that every country wants, every year making our
cities larger and more attractive to draw business whether it
be a tourist attraction or a skyscraper used for offices. What
the buttressed core allows is the construction of the building
in the quickest and most effective way possible.
With the use of the buttressed core the current tallest
building in the world known as the Burj Khalifa was able to
go up much higher than its predecessor the Taipei 101 [8].
The Burj Khalifa is over 300 meters taller than the previous
number one [3].
That amazing statistic gives you a look at how much the
buttressed core adds to the heights of these buildings. Not
only do these new skyscrapers get put up faster, they are
constructed in a much quicker time. The design of the
buttressed core allows to be put up in a much faster time
period because of how it can be oriented. For buildings to
reach those heights that have never been thought possible,
engineers and those who help construct and pay for the
construction of the skyscrapers need the most cost effective
and structurally sound innovations, both of which the
buttressed core can provide.
In Dubai the construction of the Burj Khalifa itself has
helped the economy boom. Within the amazing skyscraper
there are many different attraction ranging from many hotels
to the worlds highest nightclub as well as some residential
apartments. It is economic advantages like those of the Burj
CIVIL ENGINEERING INNOVATION
There are so many ways that the buttressed core has helped
all civil engineers look at structures differently. It gives
engineers the opportunity to expand and push the boundaries
of what we have come to believe are the limits of our
structural ability. As engineers we continue to look for ways
which we can help improve the way which we construct our
buildings and begin to build the structures of the future
which reach new heights every day.
The key to help building our future is to have future
engineers who push themselves to discover these new
techniques that give us the opportunity to both achieve new
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Swanson School of Engineering
April 14, 2012
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Billy Green
things and help our society grow in such a way that is
prosperous for the future. These days every year it seems
like a new technology rises up that is the next big thing, and
for the civil engineering world right now that big thing is the
buttressed core. The designer of the buttressed core and the
one who receives most of the credit for its introduction into
the structural world is William Baker [1].
William Baker is known as one of the premier engineers
in the world and many give him the title as the King of
Super Stable Structures. He has designed many large famous
buildings that include the Sears Tower in Chicago, the Time
Warner Center in New York, and many other amazing
skyscrapers all over the world [1]. As an engineer, many
consider him as one of the premier engineers in the world.
He is currently working on his next big product in Las
Vegas, Nevada. This project is known as the Crown Las
Vegas Resort and Casino, it will be constructed to an
amazing 1,888 feet and could include what could be the
world’s highest gaming room. Being one of the most
important structural engineers in the world, his main
contribution has been the buttressed core.
Baker currently has more towers constructed over 1000 ft
than that of any engineer in history [1]. For a society that is
racing to win the battle over the skyline of the planet, and
ultimately the bragging rights of having the tallest buildings
in the world, countries all over the world are getting in
contact with William Baker to construct more and more
buildings.
Before Baker became the famous engineer he is today, as
an up and coming engineer he sat in his office, like many
engineers looking for that new cost effective way to build
super tall buildings. He looked at three main ideas and
problems and looked for ways to solve them. Calculating
and talking about as you increase the height of a building, its
incredible size becomes a bigger target for winds, and these
incredible wind speeds become a large reason for a building
to topple over. William Baker looked closely at the problem
of costs and he said that the amount of money that is lost
during additional and unnecessary construction time adds up
to a very large amount at the end of the project [6]. The third
problem being how hard it is to actually fill up these super
tall structures and how no matter how good the economy or
real estate value is, it is very hard to fill up the incredible
amount of floor space like those of the Sears Tower or even
the Empire State Building when it was first constructed.
The breakthrough for the actual buttressed core came
when Baker and his team at his engineering firm known as
Skidmore, Owings, & Merrill, simply known as SOM, were
designing a new “Y”-like design which would increase the
amount of windows per apartment. After the plans of that
first building never reached potential Baker was still able to
see how amazingly strong the design was and yet very light
at the same time. He saw that each of the wings acted as
support for the other two wings. He realized just how
effective this would be against the winds at super tall heights
[1].
In the amazing “Y”–design Baker so the solution to all of
his previous problems see that if you were to orient the
buttressed core in such a way that it would be vertically
strong, and by connecting each of the different wings of the
Y-shape to a very strong central core the twisting and
swaying of the building would be significantly reduced [1].
Baker himself said back then that “If somebody really
wanted to do the world’s tallest building, this would be the
way to go.”
After the story goes on and William Baker completed the
Burj Khalifa and it became the world’s tallest building back
in 2009. The buttressed core has given so much already to
the field of civil engineering. Giving structural engineers all
over the world the opportunity to have a hand in building
these super structures. The buttressed core’s combination of
unmatched strength and lightness gives it an amazing quality
that no other structural design has. Today Baker still works
on taller and taller buildings and continues to use his famous
design. For all civil engineers this structural design of the
buttressed core gives us the opportunity to literally reach for
the skies.
REFERENCES
[1] - Andrew Blum (2007, November 27) “Engineer Bill Baker Is the King
of Superstable 150-Story Structures” Wired [Online] Available:
http://www.wired.com/culture/design/magazine/1512/mf_baker?currentPage=all#
[2] - William F. Baker (2010, March 1) “Reaching for the Heavens” The
Burj
Khalifa
Triumphs
[Online].
Available:
http://web.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=3002c401-521e4121-a6ee-9eb3b639782c%40sessionmgr111&vid=2&hid=111
[3] - Hasan. (2008 October) “Ten Tallest Buildings in the World” Info
Blog [Online] Available: http://www.dirjournal.com/info/ten-tallestbuildings-in-the-world/
[4] - Skidmore, Owings and Merrill (2010) “Buttressed Core Central
System for Burj Khalifa” World Buildings Directory [Online] Available:
http://www.worldbuildingsdirectory.com/project.cfm?id=2618
[5] - Sunilla George (2011) “Flexural Behavior of Activated Fly Ash
Concrete” International Journal of Engineering Science and Technology
[Online]
Available:
http://www.doaj.org/doaj?func=abstract&id=859078&recNo=44&toc=1&ui
Language=en
[6] - J. Sheath. (2010, August). "Fly ash used in the construction of the
world's tallest building." Civil Engineering. [Online: Article]. Available:
http://web.ebscohost.com/ehost/detail?sid=19779358-c453-48b1-b0eb
b0817ae10345%40sessionmgr112&vid=1&hid=127&bdata=JnNpdGU9ZW
hvc3QtbGl2ZQ%3d%3d#db=bth&AN=60640952
[7] - Peter A. Irwin, William F. Baker, Stan Korista, Peter A. Weismantle,
and Lawrence C. Novak. “The Burj Dubai Tower”. Structure Magazine.
[Online Magazine] Available: http://www.structuremag.org/Archives/200611/F-Burj-Dubai-Tower-Irwin-etal-Nov_06.pdf
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Swanson School of Engineering
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Billy Green
[8] - Sarah Dowdey (N/A) “What’s the New Tallest Building in the World”
How
Stuff
Works
[Online]
Available:
http://adventure.howstuffworks.com/burj-dubai.htm
ACKNOWLEDGMENTS
We would like to thank all the workers at the library who helped us find and
acquire this information. We’d also like to thank our friend and families
who have helped give us the tools to study and work hard to become
engineering majors. This paper would not have happened without them.
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