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 Key Words – Burj Khalifa, Buttressed Core, civil engineers,
design being used in the infrastructures of some of the tallest concrete, Fly Ash, structure, Y-design
and the tallest building in the world, these otherwise known
as skyscrapers. The infrastructures and designs of these THE BURJ KHALIFA
buildings will be explained thoroughly as well as the
direction that these skyscrapers and modern buildings are The Burj Khalifa (formerly known as the Burj Dubai) gained
heading for. Further discussion will show the values of the the title of the world’s tallest building when it was
known and proven advantages of this innovation of the completed in 2010. It rises to a maximum height of 828
‘buttressed core’. It’s ‘three wing design which extend out of meters (2716.5 feet), taller than any other man made
the central core and firmly anchor the skyscrapers will be structure [1]. It is the crowning achievement in the massive
described and told as well its use in the future building of construction projects in Dubai, UAE, and has become a
our cities most iconic landmarks. symbol for the nation. Dubai has seen a huge amount of
This conference paper will both describe some of the construction in the past few decades. It has built the world’s
techniques and designs currently used in some the earth’s tallest hotel, the Burj al Arab, which sits on a man made
most famous buildings. The buttressed core will be island in the Persian Gulf. And speaking of man made
examined in detail, describing the different components and islands, more than 300 have been built in the Persian Gulf.
parts which make up the buttressed core and the materials This is a paradise for architects and engineers who want to
which go into making it like the use of fly ash in the cement make their wildest dreams come true. This is a place where
of the core (Sheath), describing in part how it operates as a you would expect the world’s tallest building to be built.
whole, making the world’s tallest skyscrapers more It is the centerpiece of a $20 billion construction project
structurally sound even at their ridiculous heights. The in Dubai, UAE. It has been made to bring more business into
assessment of how and why this is an invaluable design and the city. The tower is mainly residential, an oddity for
why it is of importance to our future will be described and skyscrapers, who are usually used as office space. This is in
discussed as the most advantageous reason for civil an attempt to make urban areas more livable. The building
engineers and those building skyscrapers into the future to being connected with transit in the area makes getting from
use it. This paper will also present examples that the design the tower to the rest of the city easy. But, even being an
was used in the most famous and tallest buildings such as excellent place to live, it has remained with a good portion
the Burj Khalifa in Dubai known as the world’s tallest of its residential space empty [2].
building, doubling the size of the Empire State Building Bill Baker, the designer of the Burj Khalifa, is an expert in
(Baker). The buttressed core allows for these skyscrapers to super-tall skyscrapers. He has built many, but in his latest
go up tall and fast with enough usable floor space to projects, "He's posing new structural approaches rather than
maximize clients chances of making a profit (Blum). The reworking old ones,” as stated by Carol Willis, director of
buttressed core’s design is most prevalent and well the Skyscraper Museum in New York City [1].
recognized in the beautiful and extravagant building in Dubai may be growing into a modern city, but it is also
Dubai the Burj Khalifa (WebBuildingsDirectory). The Burj holding on to its heritage and culture. The Burj Khalifa not
Khalifa offers a social impact as well bringing in extra profit only draws its design from its engineering, but it also pulls
and much publicity to Dubai (Dowdey) Overall civil from the culture of Dubai [2].
engineering in the future is set to explode and people and The Burj Khalifa is the tallest building in the world. And
cities want more beautiful and taller buildings, the it is the tallest by an impressive amount. The previous tallest
buttressed core allows for us to create these buildings of the building is Taipei 101. The Burj Khalifa is Taipei 101 with
future and show engineers that next step in innovation. Our the Chrysler Building on top of it. This is a jump in height of
paper belongs in the Civil Engineering Conference because 300 meters. The gap between Taipei 101 and its predecessor,
it describes and explains important innovations in the world the Petronas Towers, is about 50 meters, and the gap
of civil engineering that are present in the Burj Khalifa. between the Petronas Towers and its predecessor, the Willis
Even though we only talk about one building, we describe Tower, is about 10 meters. How could there be such an
how it utilizes many new design schemes and techniques that unprecedented jump in height? It is all placed within the
allow it to become the tallest building in the world. secrets of the buttressed core [3].
University of Pittsburgh
Swanson School of Engineering April 14, 2012
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Billy Green

outside. The shape also makes wind forces much less than
THE BUTTRESSED CORE that of a flat edged building, creating less surface area facing
the wind at any one time. The length of the buttresses also
In the design and construction of Tower Palace III in Seoul, have uses elsewhere [4]. The buttresses take a step pack
South Korea, the Burj Khalifa’s designer, Bill Baker, noticed every few floors, tapering to a point at the top. This pointed
that the design was a Y shape and he named it “the design emphasizes the height of the building making it seem
Buttressed Core.” He recognized the strengths of his design taller than it really is, adding to the hugeness of the building.
and used it for the construction of the next “world’s tallest These set backs also help to reduce the force of the wind [2].
building” [2]. Because the cross section facing the wind changes, as the
The design consists of a hexagonal core with three building gets taller, the wind cannot form powerful vortexes
projecting arms. It is built primarily of reinforced concrete, on the opposite side as seen in Figure 1. On a flat edge
odd among skyscrapers, which are usually steel. These building, these vortexes cause shaking. This design reduces
“buttresses” have walls that go down their length, ending the amount of shaking that the Burj Khalifa will be impacted
with thicker, hammerhead walls. All interior walls are with [4].
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 FIGURE 1
AFFECTS OF THE STRUCTURE ON THE WIND [4]
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 The buttressed core allows the building to grow to
core provides for these amazingly tall structures but it is also amazing heights, but not use too much of the building for
the appearance that it can give the structure that it designed strength. If the Willis Tower was as tall as the Burj Khalifa
to build. The design of the buttressed core allows the so much of its floor space would be used for structural
structures to have more window space and can really give purposes that the building would no be feasible [1].
those who are staying at one of William Baker’s amazing The height of the Burj Khalifa is really what has made
structures that amazing scenery from incredible heights that many marvel at it, and really is what turned the city of Dubai
may be harder come by in the skyscrapers that do not have into what many believe is the first of many super tall
such a favorable design. So not only does the buttressed core structures. Dubai in its pursuit to create a super tall city is on
allow a building to built both taller and faster than any other the cusp of several new structures because of the Burj
structure but also allows that structure to have that appeal of Khalifa’s effect on both the economic and social popularity
the amazing bird’s eye view it gives to its residents or of a city that otherwise considered in debt until one of there
visitors. local super rich leaders bailed the city out of billions of
dollars of debt. This man was who the amazing structure was
Effect on the Structure named after and many consider him to be the first to lead
Dubai into this new age where newer and taller buildings
The buttressed core is not only used for its strength, but it will be built in the hope to attract more and more attention to
has also added to the rest of the structure. The Y-shape the intriguing part of real estate they already have.
allows for the most unobstructed windows possible, without
leaving much of the interior space closed off from the
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Swanson School of Engineering April 14, 2012
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Billy Green

The Khalifa itself has a very unique structure to it and structure itself to sway and this can be very dangerous if
that is also accredited to the ingenious design from the engineers do not use the correct type of structures wen
engineer Bill Baker. The extremely broad base of the building these huge buildings. For instance the Burj Khalifa
building is necessary for the extreme height that it reaches. It that is known to all as the tallest building in the world, as
is said that the taller which you make the building the more stated earlier uses the buttressed core for its amazing
broad of a base you will need to support it. It’s shrinking structural strength. This tri-axial design consists of three
width as it gets taller and taller also helps, as there is less tiers that are staggered throughout construction of each floor
surface area for the wind to grab onto and thus gust into. as the building gets taller and taller [6]. This design is the
Essentially each floor plan as you go further is the Y-shape key to the building itself staying in that safe zone where the
of the buttressed core rotated to an exact position different to building can sway with the wind but not to the point where it
that of the floor before it. This adds to both structure an becomes a dangerous risk. This three-tier design allows the
appearance as the Y design adds the amount of windows that wind to not hit one side directly or head on, diverting the
can be placed on a single floor. wind from the hitting the building straight on at any point
[6].
CONSTRUCTING THE CORE 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
The buttressed core may seem to many to have a more near the end of each wing, terminating in thickened hammer
‘simple’ design to its structure. To engineers, the buttressed head walls [4]. The outrigger of these walls is prohibited to
core is a thing of incredible ingenuity and there is much link outlying columns to the inner walls system., which
more to what meets the eye when it comes to the allows these columns to help with the lateral load resistance
recognizable, “Y” design. As engineers, to us it is not what a of the structure [6]. What this means is that the concrete
piece of machinery or what a structure may look like as a itself in the vertical direction is utilized to support both
whole but more as to how the whole is made up of from the gravity and the lateral loads. This amazingly designed part
many different parts. The buttressed core is something which of the core allows the Burj Khalifa to be very stiff laterally
is an incredible innovation as a whole but is also something and torsionally [6].
that is made up of many parts and without each and every What this means is that at such extreme heights the things
part accounted for the structure will fail, this is why we experience on the surface have to be magnified. The Burj
found it so important to mention in our conference paper the Khalifa is immense in size and what this means is that
actual construction of a buttressed core and what goes into gravity affects it greatly pushing down on all parts of the
giving it such amazing structural quality. incredible building, meaning that to withstand such a large
One of the major components when it comes to force of gravity the strength of the building in the upward
constructing the buttressed core is the actual cement used to direction must be incredibly powerful. The upward force
make it. One of the interesting things about this structural must be large enough to withstand gravity so that the
innovation is that it actually is not pure cement or concrete. structure itself does not collapse in on itself. The buttressed
What is used to make the buttressed core is a newer and core allows for structures to become very rigid and give
more cost effective way to make cement-like substances them the strength vertically to resist the forces that cause it
known as fly ash [5]. The development and use of mineral to collapse [4]. This is directly accredited to the design of
admixtures like fly ash are becoming more common in the the buttressed core where the three wings are attached to a
construction industry mainly due to the consideration of a very strong central core. The central core is the key factor in
more cost-effective, energy saving, and the environmental giving the structure the strength to withstand intense weight
production and conservation of resources [5]. There is even of gravity [4].
currently a study that is looking at replacing cement in To be strong vertically as well as torsionally or otherwise
concrete more and more with the more flexural fly ash, the ability to resist twisting as a result of winds. The Burj
testing its behaviors in certain support beams and other Khalifa was constructed in Dubai where the average wind
structural uses [5]. In the buttressed core the fly ash is a key speed over fifty years has been just over twenty-two miles
component and is even growing more popular in the entire per hour. For the Burj Khalifa to stand at a height where no
world of construction. other structure has ever been built it would need to have a
Another key component in the construction of the design where the resistance of the natural act to twist in the
buttressed core is its intriguing design. The buttressed core is high winds is fought against. The buttressed core is what
designed in such a way that it makes it perfect for allows the structure to stand at the height of over 800 meters
constructing such amazingly tall heights. One of the major in the air [7]. The three wings use each other to build that
issues when it comes to constructing buildings that challenge strength. If one wing is feeing the force of the winds, the
the heights of the tallest in the world is the wind. At very tall other two wings act as supports to help keep it from twisting.
altitudes the wind can be so strong at times that it causes the
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Billy Green

This design is perfect to have the Burj Khalifa stand at such Khalifa that have countries all over the world building taller
a mind-boggling height without twisting on itself. and more impressive buildings.
All these components of the buttressed core gives What the buttressed core provides that no other structural
structures like the Burj Khalifa a very efficient structure for innovation can provide is such and effective way to reach
the fact that the gravity load resistant system is utilized so it these incredible heights as well giving the building such
can maximize its use in resisting the lateral forces like that incredible rigidity and the lateral strength that allows these
of the incredible wind gusts. On the top of the Burj Khalifa skyscrapers to stand at such tall heights for these long
there is about a 230-meter tall spire and the complete periods of time [4].
structure of the tower founded on a 3700-meter thick As stated earlier in this article Dubai is one of the leaders
reinforced concrete pile supported raft foundation [6]. in the world of designing theses structural super giants.
Constructing the buttressed core involves very precise Dubai is located in the Middle East and is one of the richest
and exact measurements, like every other part of a well bit places on earth. Dubai is beginning to be mentioned with the
structure it takes much time and effort to be able to construct major cities of the world as it grows and will continue to
such an integral part of a skyscraper [7]. Every step in the grow. They do not shy away from the possibility of
process of constructing the buttressed core is a key to its designing new super structures and do not see a reason to not
success and holds all the answers to how it allows such continue to build these amazing feats of structural
amazing structural power for these ‘super’ skyscrapers that engineering. Though the United States is not quite as rich
are reaching new heights every day. Giving structures the per capita as the likes of the United Arab Emirates but it still
amazing ability to both resist the vertical force of gravity as has its fair share of skyscrapers. The United States continues
well as having the lateral strength to resist the force of the to have the most popular cities in the world with there own
wind. signature buildings, though they may not be as tall as the
newest skyscrapers, they still hold significance. Dubai is still
SKYSCRAPERS OF T HE FUTURE far off from being known as the New York City of the
Middle East but it is making good process building larger
The need for the buttressed core and innovations like it will and more extravagant buildings by the day.
continue to grow as our society moves further into the The amazing thing is what it is doing for the economy.
future. It seems as if every few years there is a newer and What skyscrapers of this magnitude do, especially when they
taller skyscraper being built. These skyscrapers are are the tallest building in the world, is draw attention to your
something that every country wants, every year making our area no matter where it is. People go to Dubai from all over
cities larger and more attractive to draw business whether it the world to visit the amazing Burj Khalifa as well as their
be a tourist attraction or a skyscraper used for offices. What other attractions. In the base of the hotel alone are more than
the buttressed core allows is the construction of the building a few hotels, which are some of the most extravagant in the
in the quickest and most effective way possible. world. There was even a recent movie shot, which had
With the use of the buttressed core the current tallest scenes shot in and around the Burj Khalifa and Dubai. The
building in the world known as the Burj Khalifa was able to structure itself has done so much for the area that it is hard to
go up much higher than its predecessor the Taipei 101 [8]. dispute the fact that Dubai would be anywhere near as
The Burj Khalifa is over 300 meters taller than the previous popular had it not been for the tallest building in the world.
number one [3]. Skyscrapers not only give the city that amazing scenery and
That amazing statistic gives you a look at how much the a view no one can ever forget but it also gives the people and
buttressed core adds to the heights of these buildings. Not the economy around the area and amazing boost too.
only do these new skyscrapers get put up faster, they are
constructed in a much quicker time. The design of the CIVIL ENGINEERING INNOVATION
buttressed core allows to be put up in a much faster time
period because of how it can be oriented. For buildings to There are so many ways that the buttressed core has helped
reach those heights that have never been thought possible, all civil engineers look at structures differently. It gives
engineers and those who help construct and pay for the engineers the opportunity to expand and push the boundaries
construction of the skyscrapers need the most cost effective of what we have come to believe are the limits of our
and structurally sound innovations, both of which the structural ability. As engineers we continue to look for ways
buttressed core can provide. which we can help improve the way which we construct our
In Dubai the construction of the Burj Khalifa itself has buildings and begin to build the structures of the future
helped the economy boom. Within the amazing skyscraper which reach new heights every day.
there are many different attraction ranging from many hotels The key to help building our future is to have future
to the worlds highest nightclub as well as some residential engineers who push themselves to discover these new
apartments. It is economic advantages like those of the Burj techniques that give us the opportunity to both achieve new

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Billy Green

things and help our society grow in such a way that is effective this would be against the winds at super tall heights
prosperous for the future. These days every year it seems [1].
like a new technology rises up that is the next big thing, and In the amazing “Y”–design Baker so the solution to all of
for the civil engineering world right now that big thing is the his previous problems see that if you were to orient the
buttressed core. The designer of the buttressed core and the buttressed core in such a way that it would be vertically
one who receives most of the credit for its introduction into strong, and by connecting each of the different wings of the
the structural world is William Baker [1]. Y-shape to a very strong central core the twisting and
William Baker is known as one of the premier engineers swaying of the building would be significantly reduced [1].
in the world and many give him the title as the King of Baker himself said back then that “If somebody really
Super Stable Structures. He has designed many large famous wanted to do the world’s tallest building, this would be the
buildings that include the Sears Tower in Chicago, the Time way to go.”
Warner Center in New York, and many other amazing After the story goes on and William Baker completed the
skyscrapers all over the world [1]. As an engineer, many Burj Khalifa and it became the world’s tallest building back
consider him as one of the premier engineers in the world. in 2009. The buttressed core has given so much already to
He is currently working on his next big product in Las the field of civil engineering. Giving structural engineers all
Vegas, Nevada. This project is known as the Crown Las over the world the opportunity to have a hand in building
Vegas Resort and Casino, it will be constructed to an these super structures. The buttressed core’s combination of
amazing 1,888 feet and could include what could be the unmatched strength and lightness gives it an amazing quality
world’s highest gaming room. Being one of the most that no other structural design has. Today Baker still works
important structural engineers in the world, his main on taller and taller buildings and continues to use his famous
contribution has been the buttressed core. design. For all civil engineers this structural design of the
Baker currently has more towers constructed over 1000 ft buttressed core gives us the opportunity to literally reach for
than that of any engineer in history [1]. For a society that is the skies.
racing to win the battle over the skyline of the planet, and
ultimately the bragging rights of having the tallest buildings REFERENCES
in the world, countries all over the world are getting in
contact with William Baker to construct more and more [1] - Andrew Blum (2007, November 27) “Engineer Bill Baker Is the King
buildings. of Superstable 150-Story Structures” Wired [Online] Available:
Before Baker became the famous engineer he is today, as http://www.wired.com/culture/design/magazine/15-
an up and coming engineer he sat in his office, like many 12/mf_baker?currentPage=all#
engineers looking for that new cost effective way to build [2] - William F. Baker (2010, March 1) “Reaching for the Heavens” The
super tall buildings. He looked at three main ideas and Burj Khalifa Triumphs [Online]. Available:
problems and looked for ways to solve them. Calculating http://web.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=3002c401-521e-
and talking about as you increase the height of a building, its 4121-a6ee-9eb3b639782c%40sessionmgr111&vid=2&hid=111
incredible size becomes a bigger target for winds, and these [3] - Hasan. (2008 October) “Ten Tallest Buildings in the World” Info
incredible wind speeds become a large reason for a building Blog [Online] Available: http://www.dirjournal.com/info/ten-tallest-
to topple over. William Baker looked closely at the problem buildings-in-the-world/
of costs and he said that the amount of money that is lost
[4] - Skidmore, Owings and Merrill (2010) “Buttressed Core Central
during additional and unnecessary construction time adds up System for Burj Khalifa” World Buildings Directory [Online] Available:
to a very large amount at the end of the project [6]. The third http://www.worldbuildingsdirectory.com/project.cfm?id=2618
problem being how hard it is to actually fill up these super
tall structures and how no matter how good the economy or [5] - Sunilla George (2011) “Flexural Behavior of Activated Fly Ash
Concrete” International Journal of Engineering Science and Technology
real estate value is, it is very hard to fill up the incredible [Online] Available:
amount of floor space like those of the Sears Tower or even http://www.doaj.org/doaj?func=abstract&id=859078&recNo=44&toc=1&ui
the Empire State Building when it was first constructed. Language=en
The breakthrough for the actual buttressed core came
[6] - J. Sheath. (2010, August). "Fly ash used in the construction of the
when Baker and his team at his engineering firm known as world's tallest building." Civil Engineering. [Online: Article]. Available:
Skidmore, Owings, & Merrill, simply known as SOM, were http://web.ebscohost.com/ehost/detail?sid=19779358-c453-48b1-b0eb
designing a new “Y”-like design which would increase the b0817ae10345%40sessionmgr112&vid=1&hid=127&bdata=JnNpdGU9ZW
amount of windows per apartment. After the plans of that hvc3QtbGl2ZQ%3d%3d#db=bth&AN=60640952
first building never reached potential Baker was still able to [7] - Peter A. Irwin, William F. Baker, Stan Korista, Peter A. Weismantle,
see how amazingly strong the design was and yet very light and Lawrence C. Novak. “The Burj Dubai Tower”. Structure Magazine.
at the same time. He saw that each of the wings acted as [Online Magazine] Available: http://www.structuremag.org/Archives/2006-
support for the other two wings. He realized just how 11/F-Burj-Dubai-Tower-Irwin-etal-Nov_06.pdf

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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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Swanson School of Engineering April 14, 2012
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