Bursic 3:00
R01
Disclaimer—-This paper partially fulfills a writing requirement for first year (freshman) engineering students at the
University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is
based on publicly available information and may not provide complete analyses of all relevant data. If this paper is used for
any purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students
at the University of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk.
COUNTERING THE EFFECT OF WIND ON SKYSCRAPERS
Matthew Lombardo ([email protected])
ENGINEERING STRUCTURES FOR THE
21ST CENTRUY
Brief History of Tall Structures
For over one thousand years, the Great Pyramid of Giza
held the title as the world’s tallest building, standing 481 feet
tall [1]. This mark was then surpassed by many cathedrals in
Europe in the fourteenth and fifteenth centuries, but only by
several meters. It was not until 1889 that the Eiffel Tower
increased the record of world’s highest building significantly,
rising to nearly one thousand feet [1]. The current world
record holder for not only tallest building, but also tallest
structure, now belongs to the Burj Khalifa in Dubai at a
ridiculous 2,722 feet [2]. Although, even that will soon be
surpassed upon the completion of the Jeddah Tower in Saudi
Arabia, which, “will become the world’s first one-kilometer
high structure,” at a massive 3,007 feet [3].
Higher Still?
Yet for the modern world, there is no reason to suspect
that one-kilometer is the limit. William Baker, chief structural
engineer for Skidmore-Owings and Merrill (SOM), one of the
world’s largest architecture firms and the company
responsible for the construction of both the Burj Khalifa and
the Jeddah Tower, has said we will soon have the ability to
build towers perhaps quadruple the height of the Burj Khalifa
[4]. However, creating these structures will be no easy task,
and there is a myriad of engineering problems which must be
overcome to begin construction of those mega-towers. One
such challenge, that becomes increasingly more difficult to
overcome the taller the building is, is that of wind. As
skyscrapers penetrate higher into the atmosphere, wind
becomes stronger and more unpredictable, and it becomes
more challenging to decrease the effects of the forces caused
by wind.
For the modern era, countering this wind effect is an
essential problem to overcome. As humans create more
infrastructure and use up more space, it becomes more
important to construct tall, thin towers to maximize spatial
efficiency. That being said, it is necessary to find methods to
balance the impact of wind so that these buildings can be
developed. The only directions for buildings to move is
upwards, so the future of structural engineering depends on
University of Pittsburgh, Swanson School of Engineering
10.04.2016
the ability to counter the wind force, the main problem faced
by tall structures.
In another perspective, building towards the heavens has
social and philosophical implications as well. Creating taller
and more impressive cities is not just beneficial for practical
use, but it stimulates a sort of excitement in people. There is
a certain importance in keeping people “dreaming,” for lack
of a better term, in allowing the world to see humans advance
higher and higher into the atmosphere. The sense of
amazement that is generated when people look up into the sky
and see buildings taller than some mountains is an invaluable
asset to improving morale, and inspires people to dream large.
Having a monument that can unite a nation together is an
extremely overlooked aspect of the importance of building
incredible structures, and provides social support as to why
building these impressive structures is so essential.
Personally, this engineering difficulty is important to me
because I wanted to be an architect for most of my life. For as
long as I can remember I have wanted to design buildings, and
have therefore kept up to date on skyscraper technology. The
modern construction of megatowers is absolutely fascinating
to me, and is the reason I now want to become a civil engineer.
It is my dream to work on designing the world’s tallest
building, so it is necessary for me to stay informed on relevant
anti-wind engineering. I would love to be able to develop my
own wind-repelling technology as an engineer and apply it to
creating the tallest structure that has ever existed, so it is
crucial that I understand the current approaches to doing so.
What is happening now?
A method of deterring wind that is gaining popularity in
the realm of supertall engineering is that of “confusing the
wind;” that is, designing skyscrapers so that the shapes of the
buildings themselves reduce the effects of wind. Rather than
installing dampers or other structural attachments to
counteract natural forces, engineers are instead constructing
buildings so that their shapes prevent the wind force from
happening in the first place. Because this new approach deters
the wind from becoming harmful in the first place rather than
counteracting the effects of the force while it happens, it has
been informally named “confusing the wind.” One of the first
implementations of this technology can be seen in the
construction of the world’s current tallest building, the Burj
Khalifa in Dubai.
Matthew Lombardo
is people’s arrogance,” and that “engineers will have to get
really good at confusing the wind” to make these towers
possible [6]. The chief structural engineer for SOM, Bill
Baker, has also stated that not only is a one mile tower
possible, but that we could potentially build upwards of two
miles. In fact, in discussing how tall skyscrapers can get,
Baker stated that if he had had unlimited resources in building
the Burj Khalifa, he could have, “doubled what we have. Then
we could have figured out how to double it again [6].” But in
order for these buildings to be constructed, the method of
confusing the wind must be implemented. These infinitely tall
buildings will necessarily adopt the Burj-Khalifa-like slim,
tapered design, but as that taper gets more extreme, so will the
wind, and even more technological developments will need to
occur to counteract it.
CONFUSING THE WIND
How do buildings “confuse” wind?
So, how does this technology work? First, it is important
to understand that buildings have a natural tendency to sway,
and sway at a certain frequency. This is completely
manageable, and safe, but is necessary to consider
nonetheless. Wind, if gathered too much at one area on a
building, can split into two streams that wrap the building,
which push it back and forth in opposite directions in a
periodic force [4]. The problem arises when wind blows on a
structure at the same frequency it naturally sways, because the
combined movement can create tremendous forces that can
topple the towers.
The way engineers implement the wind confusion
technique to prevent this in modern buildings is by designing
the skyscrapers in tapering parts that constantly change the
shape and height of the building. This can be thought of as
several buildings, of different heights, that are combined at
the base to create one tall structure with jagged height
changes. What this does is alter the continuity of the outer
shell of the building, so that there are no large, flat surface
areas where wind could gather. With no large, uniform spaces
to cluster on, the wind cannot coalesce on a large area, or flow
the same on all parts of the building. Because the wind is
prevented from congregating in large pockets, it can never
become the two-stream current, and cannot create a serious
force. Since this design prevents the wind from creating force
in general, there is no need for a wind-prevention device to
counter it.
Along with preventing intense wind force on the
building, this shape also helps to reduce the sway of the tower
that does happen. It is impossible to completely stiffen a
structure so that the building does not move at all, but it is
important to manage this movement so that the people inside
do not feel the motion. If the building sways so that it causes
an acceleration, then the corresponding force would be felt by
the inside occupants, which would naturally cause unease [5].
Another consideration is to prevent the building from swaying
at the same frequency that causes seasickness, to not make
everyone inside nauseous. The slim shape avoids this from
occurring by constantly changing shape, so the effective sway
that would occur on each level of the building is actually
different [4]. Because all parts of the building are diverse and
have tendencies to rock at separate frequencies, it is more
difficult for the building to rock together at one specific rate;
this deters both noticeable leaning and sickening rates of
movement.
THE BURJ KHALIFA
This specific configuration is demonstrated by the shape
of the world’s largest structure, the Burj Khalifa. The building
is constructed in several stalks that rise from the same base,
but all end at different heights. This odd design deflects the
wind at different parts, preventing it from forming strong
currents that would rock the building. Chief structural
engineer of the Burj Khalifa project, Bill Baker, likened the
separate parts of the tower to a swiss army knife, with “every
part working together to resist the forces of nature such as
wind, seismic and gravity” [6]. The Burj Khalifa is built from
a large base to thin top in a tapering design, which is
beneficial in reducing the tower’s movement because the
constant change of height and surface area, from the top of the
skyscraper to the bottom, prevents the wind from merging in
patterns that would result in explicit frequencies of motion.
Its towering shape is easily visible for miles around, as it sits
in a desert landscape that is completely undeveloped aside
from the immediate vicinity of the tower. The Burj Khalifa is
the centerpiece of the Dubai metropolis that is being
constructed out of the desert, standing as a monument to the
power and potential of modern engineering. Its presence
inspires awe and hope that nothing is impossible, and for that
reason it is crucial that we as people support the creation of
more modern skyscrapers, as to provide the world with
centerpieces to express our ability to amaze.
THE JEDDAH TOWER
The continued development of wind confusion
technology means the Burj Khalifa’s reign as the world’s
tallest building is coming to an end. Currently under
construction in Saudi Arabia is the Jeddah Tower, which upon
completion will stand a massive 3,281 feet [3]. This will
easily surpass the Burj Khalifa as both the tallest building and
tallest structure in the world, and will also embody the first
one-kilometer skyscraper. It has the same type of Y-shaped
base as the Khalifa, and will follow the same tapering affect
What Do Professionals Have to Say?
The leading experts in the fields of architecture and
structural engineering wholly support the implementation of
wind confusion. Ken Lewis, a partner at Skidmore, Owings &
Merrill, has stated that, “the only limit to how tall we can build
2
Matthew Lombardo
as it rises. The timeline for the completion of the Jeddah
Tower is not definite, but the tower should be completed
within the next several years [3]. This signifies the importance
of the advancement of the confusing the wind technique, as
both the world’s current and future largest tower are adopting
the this practice.
09.24.2015.
Date
Accessed
10.26.2016.
http://www.curbed.com/2015/9/24/9917752/theengineering-tricks-behind-building-slender-taller-towers-and
ACKNOWLEDGEMENTS
I would like to thank my friends Julius Hubby, James
Hennessy, Joe Wrona, Brian Walsh, and Trent Greener for
keeping me company while I wrote the majority of this paper.
I would also like to thank my parents, whose support of my
becoming an engineer and financial support of sending me to
college will allow me to achieve my goal of becoming a
structural engineer.
IN SUMMARY
As the world progresses, the technology we use to build
that world need progress as well. Our increasingly modern
society is getting busier and more populated, so the need for
taller buildings to fit in more cluttered cities is greater than it
has ever been. That need insinuates the need of overcoming
engineering challenges, one of which is the deterrent of wind
forces. The wind confusion technology currently installed in
the Burj Khalifa and Jeddah Tower is the future of skyscraper
technology, and is the most likely procedure that will be used
to finally construct the world’s first one mile tower.
Hopefully, by that time I will be a structural engineer myself,
and will be able to help draw the tapering design of the
world’s tallest building.
SOURCES
[1] “The world’s tallest structures through history.” TravelDestinations.
Accessed
10.26.2016.
http://www.telegraph.co.uk/travel/destinations/europe/france
/galleries/The-worlds-tallest-structures-through-history/
[2] “HISTORY OF THE WORLD’S TALLEST
SKYSCRAPERS.” Emporis. Date of Publication 01.23.2008.
Date
accessed
10.26.2016.
https://www.emporis.com/statistics/history-of-worlds-tallestbuildings
[3] “Jeddah's Kingdom Tower: how much higher can
skyscrapers go? A history of cities in 50 buildings, day 50.”
Cities. Date of Publication 06.04.2015. Date Accessed
10.30.2016.
https://www.theguardian.com/cities/2015/jun/04/jeddahskingdom-tower-how-much-higher-can-skyscrapers-go-ahistory-of-cities-in-50-buildings-day-50
[4] “Confusing the Wind: The Burj Khalifa, Mother Nature,
and the Modern Skyscraper.” Inquiries. Date accessed 1.27.2016.
http://www.inquiriesjournal.com/articles/124/confusing-thewind-the-burj-khalifa-mother-nature-and-the-modernskyscraper
[5] “The World’s Tallest Building Burj Khalifa Sways and
Creaks in a Storm.” Realty Today. Date of Publication
04.17.2013.
Date
Accessed
10.29.2016.
http://www.inquiriesjournal.com/articles/124/confusing-thewind-the-burj-khalifa-mother-nature-and-the-modernskyscraper
[6] “The Engineering Tricks Behind the World's Super Tall
and Super Slender Skyscrapers.” Curbed. Date of Publication
3