trends and innovations in high-rise buildings over the past decade
TRANSCRIPT
TRENDS AND INNOVATIONS IN HIGH-RISE BUILDINGS OVERTHE PAST DECADE
by
Wenjia Gu
B.S. Civil EngineeringUniversity of Illinois at Urbana-Champaign, 2014
ARCHIVES1MASSACM I TT1 ;r
OF 1*KCHN0L0LGY
JUL 02 2015
LIBRAR IES
SUBMITTED TO THE DEPARTMENT OF CIVIL AND ENVIRONMENTALENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF ENGINEERING IN CIVIL ENGINEERINGAT THE
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
JUNE 2015
C2015 Wenjia Gu. All rights reserved.
The author hereby grants to MIT permission to reproduce and to distributepublicly paper and electronic copies of this thesis document
in whole or in part in any medium now known of hereafter created.
Signature of Author: Signature redactedDepartment of Civil and Environmental Engineering
May 21, 2015
Signature redactedCertified by:
Accepted b
(
v:
Jerome ConnorProfessor of Civil and Environmental Engineering
Thesis Supervisor
Signature redacted?'Hei4 Nepf
Donald and Martha Harleman Professor of Civil and Environmental EngineeringChair, Departmental Committee for Graduate Students
TRENDS AND INNOVATIONS IN HIGH-RISE BUILDINGS OVER
THE PAST DECADE
by
Wenjia Gu
Submitted to the Department of Civil and
Environmental Engineering on May 21, 2015 in
Partial Fulfillment of the Degree Requirements for
Master of Engineering in Civil and Environmental Engineering
ABSTRACT
Over the past decade, high-rise buildings in the world are both booming in quantity and
expanding in height. One of the most important reasons driven the achievement is the
continuously evolvement of structural systems. In this paper, previous classifications of
structural systems are summarized and different types of structural systems are introduced.
Besides the structural systems, innovations in other aspects of today's design of high-rise
buildings including damping systems, construction techniques, elevator systems as well as
sustainability are presented and discussed.
To better understand current high-rise buildings, information about buildings above 200
meter completed within recent ten years and the current 100 tallest building in the world is
collected and analyzed. Structural systems of worldwide 100 tallest buildings are discussed,
from which trends are found. Data shows that tubular systems are in vast majority in recent
high-rise building designs and an increasing number of buildings are using concrete and
composite materials instead of steel. Developments in structural systems also reduce
structures' dependence on auxiliary damping devices. Additionally, sustainability has been
given more and more consideration.
Thesis Supervisor: Jerome Connor
Title: Professor of Civil and Environmental Engineering
3
4
TABLE OF CONTENTS
1. IN TR O D U C T IO N ................................................................................. 7
2. HIGH-RISE BUILDINGS ......................................................................... 9
2.1 D efinition ...................................................................................... 9
2 .2 F acts ........................................................................................... . 10
2 .3 L o ad s ............................................................................................ . 13
3. STRUCTURAL SYSTEMS ...................................................................... 15
3.1 Previous Classifications ................................................................... 15
3.2 Different Types of Structural Systems .................................................... 18
3.2.1 R igid Fram e ........................................................................... 18
3.2.2 Core and outrigger ................................................................ 20
3.2.3 Framed Tube ...................................................................... 22
3.2.4 Trussed Tube ...................................................................... 23
3.2.5 T ube in tube ........................................................................... 25
3.2.6 B undled system ...................................................................... 26
4. INNOVATIONS IN HIGH-RISE BUILDGINS ............................................ 28
4.1 Damping Systems ......................................................................... 28
4.2 Construction Techniques ................................................................. 30
4.3 E levator System s .............................................................................. 32
5
TABLE OF CONTENTS
4.4 Sustainability ................................................................................. 35
5. ANALYSIS OF CURRENT HIGH-RISE BUILDINGS .................................... 37
5.1 Structural System s ........................................................................... 37
5.2 Construction Materials ....................................................................... 39
5.3 Sustainability .............................................................................. 40
6. CASE STUDY OF BURJ KHALIFA ........................................................... 42
7. CONCLUSION ................................................................................. 47
Al. REFERENCES .................................................... 48
A2. 100 TALLEST BUILINGS IN THE WORLD BY 2015 ................................ 50
6
1. INTRODUCTION
Over the past decade, high-rise buildings are both booming in quantity and
expanding in height over the whole world. The number of constructed buildings above 200
meters is increasing every year and the height of the world's tallest building has been raised
from 508 meters in the year 2004 to 828 meters now. Some of the many reasons leading to
this phenomenon include an expanding real estate market that emerges from the steadily
growing global economy, providing investors and contractors with more and more
opportunities, as well as the implicit competitions between countries, metropolitan areas,
and cities to attract more global spotlight.
To fulfill the request of taller and taller buildings, engineers keep working on the
optimization of structural systems to improve the structure's resistance over the load acting
on it. Several studies have discussed the performance of different structural systems from
different perspectives. Over the past decade, a number of high-rise buildings have adopted
integrated structural systems that combined two or more basic structural systems, and
innovative systems such as buttress core system can also be seen in completed buildings.
Besides the aspect of the structural system, structural material also plays an important role in
improving the structural stability and efficiency of the building.
Another important factor that helps pushing the limit of the height of buildings is the
development of construction techniques. With the help of high-tech construction equipment,
concrete can be pumped to a much higher distance than ever, even for high strength concrete.
7
Innovative construction methods also shortened the construction time so that for the owner
the cost of developing a new high-rise building could be reduced.
Other considerations for the design of high-rise buildings including the damping
system, fire design and emergency egress also have some changes over the past decade.
Nonstructural factors such as sustainability of the building are given more and more
importance now.
Information about the 100 tallest completed buildings in the world has been
collected. By studying the structural system as well as other properties of these 100
buildings, the current structural design trends can be found and comparisons between
theoretical analysis and actual can be discussed, which will help engineers break the record
of the most attractive high-rise building.
8
2. HIGH-RISE BUILDINGS
2.1 Definition
Before looking into the design trends and the innovations behind the increasing
number of high-rise buildings over the past decade, it is important to define what high-rise
buildings mean and what makes them different from other structures.
A tall building is referred as a multi-story structure in which most occupants depend
on elevators to reach their destinations. The most prominent tall buildings are called
high-rise buildings in most countries (Challinger, 2008). Although these terms do not have
internationally agreed definitions, a high-rise building, however, can be defined as follows:
According to the Council of Tall Buildings and Urban Habitat, a high-rise building
is "a building whose height creates different conditions in the design, construction, and use
than those that exist in common buildings of a certain region and period".
"Any structure where the height can have a serious impact on evacuation" (The
International Conference on Fire Safety in High-Rise Buildings).
"For most purposes, the cut-off point for high-rise buildings is around seven stories.
Sometimes, seven stories or higher define a high-rise, and sometimes the definition is more
than seven stories. Sometimes, the definition is stated in terms of linear height (feet or
meters) rather than stories. " (Hall, 2007)
Besides what is listed above, another important feature of a high-rise building is that
it is the lateral load not the gravity load that governs the design of the structure. Lateral loads,
9
including wind load and earthquakes, are crucial for high-rise buildings and can be resisted
efficiently by choosing appropriate structural systems. The exact height above which a
building can be defined as a high-rise building is specified by codes of the particular area
where the building is standing.
2.2 Facts
As a representative of the development in high-rise buildings, the record of the tallest
building in the world keeps being broken over the past decade. The 508-meter Taipei 101
Tower (Figure 1) which was opened on the last day of 2014 kept its title as the world's
tallest building for a mere six years before the Bun Khalifa (Figure 2), standing at nearly
830 meters above the ground, stole its glory in the year of 2010. Yet once again, this glory
will be overshadowed in the near future by the 1000-meter-tall Saudi Arabia's new
landmark, the, which is under construction now (Figure 3).
Figure 1: Taipei 101. Figure 2: Bur Khalifa. Figure 3: Kingdom Tower.
10
At the same time, the number of high-rise buildings completed is also increasing
each year. Information about buildings that are over 200 meters completed each year from
2005 to 2015 is collected and analyzed. Results show that the number of completed
buildings over 200 meters is basically increasing over time, and the average height of these
buildings is increasing as well. As Figure 4 shows, the number of such buildings completed
in 2014 is three times that in 2005, and the number of buildings above 200 meters is
expected to double by the end of 2015. For the height of completed buildings, as Figure 5
indicates, the average height of all buildings that are above 200 meters completed in the year
of 2015 is nearly 50% more than that in the year 2005. It is raised by almost 100 meters -
from 213 meters to 303 meters.
200 t84180
160
140
120
100
807
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2 40. 20
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Year of Completion
Figure 4: Number of completed buildings above 200m each year.
11
350
e 300
250
m 200
-150
100
50
0
Year of Completion
Figure 5: Average height of completed buildings above 200m each year.
For the current 100 tallest buildings in the world, as can be seen in Figure 6, there
are only 28 buildings were completed before the year of 2005. As much as 72 buildings
were completed within the past ten years. Researches in this paper are focused on these 72
high-rise buildings.
Figure 6: Completion time of the 100 tallest buildings in the world.
12
" Number of buildingscompleted between2005-2015
" Number of buildingscompleted before2005
2.3 Loads
The structural design of buildings is governed by all the loads that are acting on
them. A standing structure is supposed to experience loads from two aspects - gravity loads
and lateral loads.
Gravity loads are forces acting vertically on the structure such as the self-weight of
the building, so they are the same for high-rise buildings and low-rise buildings unless the
force will be larger at the bottom of high-rise buildings because of the accumulation of loads
over height.
Lateral loads including wind loads and earthquakes, on the other hand, are crucial
for the design of high-rise buildings. Wind loads will increase as the height of the buildings
rises, and they act as pressures on the structure. Therefore, for buildings over certain height,
there will be large lateral loads acting on it due to the wind. Besides the force resulted along
the direction of the wind, dynamic effects of the wind should also be considered. The
structure will also experience motion perpendicular to the direction of the wind, which is
generated by the formation of vortex shedding acting on alternation sides of the structure.
The maximum displacement in the lateral direction generally occurs in the along-wind
direction, while the peak accelerations of the structure occur in the cross-wind direction.
The earthquake is another important factor to consider in the design of high-rise
buildings because of the intense vibration. This will result in the internal forces within the
structure. To reduce the influence of earthquakes on the structure, the structure is supposed
13
to be as ductile as possible to avoid failure, and dampers are usually implemented in the
structure.
14
3. STRUCTURAL SYSTEMS
The maximum height that a building can achieve is dependent on the ability of its
structure to resist loads that are acting on it. The development of the structural system is a
continuously evolving process. Since 1960 before which the predominant type of structural
system was conventional rigid frame, the emergence of tubular systems, core and outrigger
systems has helped to raise the height of buildings. Over the past decade, new developments
in structural systems such as diagrid systems and buttressed core systems have been applied
to the design of many high-rise buildings and showed satisfying performance in the
resistance of gravity and lateral loads.
3.1 Previous Classifications
In 1969, Fazlur Rahman Khan classified structural systems for high-rise buildings
relating to their heights with considerations for efficiency in the form of "Heights for
Structural Systems" diagrams for the first time (Khan, 1969). Later, these diagrams were
upgraded by way of modifications (Khan, 1972, 1973). He developed these schemes for both
steel and concrete buildings as can be seen in Figure 7. Feasible structural systems,
according to him, are rigid frames, shear walls, interactive frame-shear wall combinations,
belt trusses, framed tubes, trussed tubes, tube-in-tube systems and other tubular systems.
15
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Figure 7: Classification of high-rise building structural systems by F.R.Khan
(above: steel; below: concrete).
Another classification of the structural system of high-rise building was developed
in 2007 by Mir M. Ali. This classification is based on lateral load-resisting capabilities. He
divided structural systems of high-rise buildings into two broad categories: interior
structures and exterior structures, which was based on the distribution of the components of
16
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the primary lateral load-resisting system over the buildings as shown in Figure 8 (Ali, 2007).
A system is categorized as an interior structure when the major part of the lateral load
resisting system is located within the interior of the building. Likewise, if the major part of
the lateral loading-resisting systems is located at the perimeter of the buildings, this system
is categorized as an exterior structure.
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Figure 8: Classification of high-rise building structural systems by Mir A. Ali (above: interior
structures; below: exterior structures)
3.2 Different Types of Structural Systems
3.2.1 Rigid Frame
The rigid frame structure, also called moment-resisting frame structure, is the most
basic type of framing systems. It consists of horizontal (girders) and vertical (columns)
members that are connected through rigid connections at the joint (Figure 9). Such framing
systems resist loads primarily through the flexural stiffness of the structural members. The
size of columns is mainly controlled by the gravity load, while the size of girders is
controlled by the requirements of lateral sway of the building as well as the vertical
deflection under dead and live loads. Because of the need for space in high-rise buildings,
the number of columns should be minimized, which increases the span of girders. Therefore,
18
the size of girders will be increased to ensure the stability of the structure. Additionally, as
the height of buildings increases, bending rigidity of both girders and columns should be
increased to reduce the lateral deflection. Besides, the expense of the moment-resisting
connections is really high. Therefore, the rigid frame would be an efficient structural system
for buildings under 30 stories (Kowalczyk, Sinn, & Kilmister, 1995).
Connections must becapable of resistingbending moments
Deformed shape Bending moment diagram
Figure 9: Rigid frame.
19
3.2.2 Core and Outrigger
The core and outrigger system is another common structural system in high-rise
buildings. The vertical core elements mostly consist of concrete shear walls or braced
system to resist lateral loads. The outriggers are generally in the form of trusses in steel
structures, or walls in concrete structures, which extend on both sides from the central core
connecting the core to the perimeter of the building. The existence of outriggers can reduce
the overturning moment in the core and can transfer the reduced moment to the outer
elements as shown in Figure 10 (Taranath, 1998).
Shear wall orbraced framecore Outrigger
trussconnecteddirectly
Column to core
20
Moment in core with-- + \outrigger bracing
\.--Moment in core withoutLeeward outrigger bracing
columns incompression
Windwardcolumns in
tension
Figure 10: Core and outrigger system.
Belt trusses are often combined in core and outrigger systems to distribute the
tensile and compressive forces to a large number of exterior frame columns, which are
located at the perimeter of the structure. Belt trusses also help in minimizing differential
elongation and shortening of columns. In the design of existing high-rise buildings,
outriggers are also supported by mega-columns in the exterior perimeter of the structure.
Some other advantages of the core and outrigger system includes that the exterior
column spacing can satisfy more aesthetic and functional requirements. For the aspect of
construction, the exterior framing system consists of simple beams and columns and does
not require moment-resisting connections as in rigid frame system, which is beneficial to the
construction process.
The core and outrigger system may be formed in any combination of steel, concrete
21
_F
and composite construction. Because of the structural benefits of this system and the
advantages listed above, the core and outrigger system has been very popular over the past
decade.
3.2.3 Framed Tube
The framed tube system is the most basic tubular system in high-rise buildings.
The tubular system expresses the concept that a building can be designed as a
hollow cantilever perpendicular to the ground to resist lateral loads by designing it. In the
simplest framed tube system, the exterior perimeter of the structure consists of closely
spaced columns that are tied together with deep spandrel beams through moment
connections (Figure 11).
Closely spaced columns
I :b
Figure 11: Framed tube system.
22
For a framed tube under lateral loads, the corner columns experience the largest
axial forces, and forces are distributed non-linearly along the direction parallel to wind and
perpendicular to wind. This is because the axial forces in the middle columns of the frame
lag behind that in the corner columns because that the structure acts like a hollow tube
instead of a solid one. This phenomenon is called the shear lag effect, as shown in Figure 12.
In the design of framed tube system, the optimal purpose if to limit the shear lag effect.
Cosrmpive
Figure 12: Shear lag effect.
3.2.4 Trussed Tube
The trussed tube is a variation of the framed tube system. By adding large truss
elements around the perimeter of the tube system, the bending stiffness of the structure can
be increased, and the number of exterior columns can be decreased. The truss elements can
also transfer some of the gravity loads acting as inclined column. At the same time, the
23
diagonals of a trussed tube connected to the joints of columns and beams effectively
eliminate the effects of shear lag around the structure. Therefore, the space of columns in the
perimeter of the building can be arranged more widely and the sizes of spandrel beams and
columns can be designed smaller than the framed tubes (Khan, 1967).
Innovative structural systems over the past decade include diagrid systems and
hexagrid systems (Figure 13). The difference between conventional trussed tube structures
and the diagrid system is that almost all conventional vertical columns can be eliminated for
diagrid structures. This is because the diagonal members in diagrid structural systems can
carry both gravity loads and lateral loads through their triangulated configuration (Panchal
and Patel, 2014). The hexagrid system, also called beehive system, is another evolutionary
structural system in the design of high-rise buildings. In addition to eliminating perimeter
columns, another noticeable advantage of the hexagrid systems is that each structural
element can be optimized. This is a relatively new idea and more exploration is required for
the implement of this structural system in the design of high-rise buildings (Askarinejad,
2012).
I
Figure 13: Trussed tube systems (Left: conventional trussed tube; middle: diagrid system;
24
Z N/ NZ
Z NZ
N 4 N
right: hexagrid system).
3.2.5 Tube in Tube
The tube in tube system uses the core to resist part of the lateral loads in order to
enhance the stiffness of the tubular systems. This structural system consists of an outer tube
in the perimeter and a core tube inside the structure. The core tube inside could be made of a
framed tube, a trussed tube or a solid tube holding elevators and other services. The floor
system connecting the core and the exterior tube transfers the lateral loads to both systems,
while the exterior tube system carries more loads because its greater structural stiffness
(S.R.S.Kuman and A.R.S. Kuman, 2014).
The tube in tube system is flexible in materials because the two tube systems can be
constructed using completely different materials. Current designs of high-rise buildings
combine concrete shear wall core with outer steel framed tube, which is an efficient system
in resisting of different types of loads and has been widely implemented. Figure 14 shows
the floor plan of a typical tube in tube structure, which is the China Trade Center, located in
Beijing, China. The structure of this building consists of a concrete core and the exterior
steel framed tube.
25
Figure 14: Floor plan of typical tube in tube system.
3.2.6 Bundled system
The bundled tube structural systems in a combination of several individual tubes
connected together to act as a single unit. The structural stiffness of the building is notably
increased. In this system, the shear lad effect in the flanges is largely reduced by the
existence of the internal webs. The bundled tube system also allows wider column spacing
in the tubular walls, and the stress in columns is distributed more evenly than that in a single
tube system.
One of the most typical bundled tube systems is the 110-story Willis Tower
completed in 1974 which was also the first buildings using such systems. There are nine
steel framed tubes in total bundled at the bottom of the buildings and they are terminated in
different heights as Figure 15 shows. Such structural system provides the high-rise building
with new possible appearance instead of the simple boxlike shape.
26
D 110
Section D-D 90
66
Section C- C50
30
Section 8 B A
Section A-A
Figure 15: Structural system of Willis Tower.
One innovative structural system using the bundled form over the past decade is the
buttressed core system, which was implemented in the design of Burj Khalifa. The most
important factor of this system is a tripod-shape structure in which a strong concrete core in
the center anchors three structural elements arranged around it. The structure of Burj Khalifa
will be discussed more in the case study section later.
27
4. INNOVA TIONS IN HIGH-RISE B UILD GINS
4.1 Damping Systems
As the evolution of structural systems and development in construction materials
especially high-strength concrete, the weight of the high-rise building has been decreased
considerably than that of earlier ones. Lighter structures reduce cost as well as the
construction time. However, they may cause serious structural motion problem due to the
wind load. An implement of damping systems will help control the structural motion.
Damper can reduce not only the amount of lateral displacement but also the acceleration of
the structure. Structures with more damping can reduce the magnitude of vibration and
dissipate the vibration more quickly (Moon, 2005).
Damping system can be divided into two categories, passive damping systems and
active damping systems. Passive damping systems have fixed properties and they do not
need energy to perform as intended, while active damping systems do need energy input
serving as actuators to modify the damping system properties under different load cases.
Therefore, active damping systems are more efficient than passive systems. However,
passive damping systems are more commonly used in high-rise buildings because of the cost
and reliability.
Passive damping systems can be further divided into two subcategories, auxiliary
mass systems to generate counteracting forces such as tuned mass dampers (TMD) and
tuned liquid dampers (TLD), and energy dissipating materials based systems such as viscous
28
dampers and visco-elastic dampers.
Active damping systems are a more advanced form of performance driven
technologies, which is the tendency of today's high-rise building design. Examples include
active mass dampers (AMD) and active variable stiffness devices (AVSD). Different types
of auxiliary damping systems are summarized in Figure 16 (Connor, 2003).
Tuned Mass Dampers ( TMD)
Tuned Lquid Dampers (TLD)
Vicus Dampers_
Passive System Viscoelassk Dampers
Hysteretic Dampers
Fricton Dampers
-Ete m4Aagne Dampers
Active Mass Dampers (AMD)Acive System
Acive Various Stifless (AVS) Devices
Figure 16: Various types of auxiliary damping systems.
However, it is noticeable that as the continuously evolvement of structural systems
more and more high-rise buildings do not need additional damping systems anymore. The
property of the structure itself is sufficient to protect the building from vibrations due to
29
wind. Such structural factors that will help decrease the dependence of high-rise buildings
on auxiliary damping systems include bundled systems, twisted shape of the building and
opening at the top, as shown in Figure 17. Trump Tower, which is located in Chicago,
implemented no additional damping systems. The stiffness and weight of the building,
combined with the asymmetric setbacks, laterally support and stabilize the tower ad
minimize perceptible motion.
Figure 17: Buildings using geometries to reduce reliance on auxiliary damping systems (left
1 &2: bundled systems; middle: opening at top; right 1 &2: twisted shapes).
4.2 Construction Techniques
While structural engineers managed to find a plan for buildings to rise out of the
ground theoretically or experimentally, it still remains a challenge for contractor to actually
30
build it. As the height of high-rise buildings increases, so does the challenge contractors face.
Construction teams not only have to erect steel and concrete members, they also have to do
it precisely, safely, time and cost efficiently and environmentally friendly. Therefore,
construction techniques have to be developed.
Being time efficient not only means that the building can open to public sooner, but
also means lower construction cost. An innovation applied in the construction of the Shard
in London is the top-down construction method. It allowed the first 23 stories of the
concrete core and much of the surrounding tower to be built before the basement had been
fully excavated. This technique was a world first and saved four months time and a huge
amount of budget on the complex program.
As the development of construction materials especially the creation of
high-strength concrete, more and more high-rise buildings start to use concrete to construct
the structure. Having more powerful pump means high that high-strength concrete is able be
delivered to high levels at greater speed. The KK100 in Shenzhen set a record of pumping
high-strength C 120 grade concrete to the height of 417 meters.
To guarantee workers' safety, precaution for hazard prevention has to be taken
seriously. During construction of Doosan Haeundae We've the Zenith Tower, to prevent
spalling, which is the explosion that can occur when the concrete is exposed to high
temperatures, contractors built the tower with high strength concrete using a spalling failure
prevention method.
31
To make sure the building is in its upright position, GPS technology has been used
over the past decade. This would not have been possible before satellites and GPS
technologies were mature. The Al Hamra Tower, which is located in Kuwait City, utilized
Leica Geosystems Core Wall Survey Control System, a procedure developed by Leica
Geosystems using GPS observations combined with a precision inclination sensor to provide
reliable coordinated points at the top of the building. Another example is used in the
construction of Almas Tower in Dubai, where vortex shedding suppression devices based on
simple principles were used as temporary measures during the construction stage to prevent
excessive wind induced movement of the spire.
4.3 Elevator Systems
As the height of high-rise building increases rapidly, the upgrade of many of its
accessories is required. One of the developed accessories is the elevator system. For
high-rise buildings, efficient mobility is an absolute necessity. Past elevators are
incompatible with today's super-tall buildings, as they have relatively slow rising and
descending rates, causing much time loss when traveling between high levels; some elevator
shafts are so large in size that they take up much of the level's space; some buildings are so
tall that the steel elevator cables are close to the limit where they can no more carry their
own weight.
During the past decade, various technical advancements are seen in the elevator
32
system of high-rise buildings. One smart design is the double deck elevator (Figure 18). As
the name indicates, the double deck elevator consists of two individual cars attached
together, one on top of the other. Both cars operate in the same elevator shaft. Such a
scheme could increase efficiency dramatically during high traffic periods. During such time,
single elevator would stop at every floor, but the double deck elevator will only stop at every
other floor as one of its cars transport passenger on odd floors and the other transport
passengers on even floors. Besides the improved efficiency in elevator shaft usage, the
operation speed of the elevator has also increased throughout the years. Table 1 below
shows the comparison of elevator speed of some of the world's famous buildings. It can be
seen that the speed has increased in the last few decades. The improvement in elevator speed
is accompanied by more powerful magnetic motors, high-tech air pressure adjustment
systems, and lighter and stronger materials. Finnish manufacturer Kone has developed a
carbon fiber dubbed UltraRopeTM that is seven times lighter than steel cables (Figure 19).
The UltraRopeTM will be used in the 1000-meter-tall Kingdom Tower, Saudi Arabia, which
is under construction.
Currently, engineers are picturing elevator systems that will travel both vertically
but also horizontally. As elevators will carry passengers horizontally, vertical shafts could be
reduced, thus saving floor spaces. ThyssenKrupp is poised to revolutionize elevator power
system by using magnetic drive similar to that seen on a Maglev train. The system will be
the world's first cable-free elevator and counter-weight free.
33
Building Completion Year Elevator Speed (m/s)
Chrysler Building, New York City 1930 4.5
Empire State Building, New York City 1931 7.1
Willis Tower, Chicago 1974 8.1
Taipei 101, Taiwan China 2004 16.8
Shanghai Tower, Shanghai 2015 18
CTF Finance Tower, Guangzhou 2016 20 (expected)
Table 1: Comparison of elevator speed of some of the worlds famous buildings.
Coss, 440.MV *kVWwwM
-ofNWe-
we-IR010
Figure 18: Scheme of double deck elevator
Elevator moving masses (kg)108600
13900
Steel Cable UltraRope"
Figure 19: Comparison of traditional steel cable to Kone UltraRopeT M .
34
4.4 Sustainability
Over the past decades, more and more factors besides structural and constructional
aspects are taken into consideration in the design of high-rise buildings. As global warming
and fossil fuel are becoming increasingly concerned topics, engineers are challenged to put
further effort into designing buildings that are more environmentally friendly. Measures that
care most commonly seen in achieving the sustainability of high-rise buildings can be
categorized into two aspects - constructional and operational.
Constructional sustainability is the measures taken during the construction process.
These measures include purchasing construction materials locally or regionally, thus
reducing total mileage of transportation, which in turn reduced carbon footprint. Another
measure is to reuse and recycle excess materials. In excess of 95% of structural steel was
recycled after the construction of New York Times Building, New York City.
Analogously, operational sustainability indicates the measures taken after the
completion of construction and during its normal operation. One of the most common
measure is the use of double-sided windows or double wall curtains with low-emissivity
coating to improve thermal insulation (Figure 20). Additionally, use of LED lights for
signage will reduce electricity consumption significantly. The Shanghai World Financial
Center features over 7000 LEDs, and the power consumption for its signage is merely 220
KW, which is much lower than even the shorter buildings around it. Buildings by rivers or
seas can reduce energy cost by using river or seawater to cool the buildings. An example is
35
the Trump Tower in Chicago that utilizes water from the Chicago River to cool the building.
The cooling system allows the water to recirculate back to the river. Building in high
sunshine areas can install solar panel to heat water. Bun Khalifa features solar panels that
are capable of heating 140,000 liters of water daily. In cities where pollution is heavy,
buildings have air filtration and circulation system to guarantee occupants breathe clean air.
In recognition of and to promote sustainability in building, the U.S Green Building Council
(USGBS) awards the Leader in Energy and Environmental Design (LEED) certificate to
buildings that are outstanding in sustainability. The certification has four levels - certified,
silver, gold, and platinum. The Taipei 101, which is located in Taipei City, has been
awarded the LEED Platinum certificate and will set the quality and performance benchmark
for super-tall buildings.
Figure 20: Double skinned facade curtain wall system.
36
5. ANALYSIS OF CURRENT HIGH-RISE BUILDINGS
To better understand the implement of different structural systems, construction
materials and design critics of high-rise buildings in the actual world, information about
high-rise buildings above 200 meters completed in the past ten years as well as the current
100 tallest buildings in the world has been collected and analyzed.
5.1 Structural Systems
Based on the properties of different types of structural systems which are
introduced in previous section, structural systems of modem high-rise buildings are divided
into seven categories: rigid frames, core and outrigger systems, framed tubes, trussed tubes,
tube in tube systems and bundle systems. The results have been shown in Figure 21 and
Figure 22.
Figure 21 shows the distribution of structural systems of high-rise buildings above
200 meter completed during each period over time. As the figure shows, tube in tube
systems have been more and more used in the design of high-rise buildings, while rigid
frame systems is no more been used within the past five decades.
Figure 22 shows the distribution of structural systems of the current worldwide 100
tallest buildings. As can be seen, vast majority of the structural system consist of tubular
systems and core and outrigger systems, in which the tube in tube system has the largest
percentage of 38%.
37
16
14
12
10
5* -
6
4,
2... ... ...
" Bundled system
" Tube in tube
" Trussed tube
" Framed tube
N Core and outrigger
* Rigid Frame
Figure 21: Distribution of structural systems of buildings over 200m over time.
2%
0 Bundled system
U Tube in tube
8 Trussed tube
a Framed tube
M Core and outrigger
0 Rigid Frame
Figure 22: Distribution of structural systems of the current 100 tallest buildings.
Taking the average stories of different types of structural systems of the current 100
tallest buildings in the world, comparison can be conducted with previous theoretical
analysis of structural systems. As Figure 23 shows, bundle system has the highest average
38
number of stories, while core and outrigger system has the lowest average number of stories.
Rigid frame system has the second highest average number of stories, which is quite
different from previous analysis, because of relatively small sample size.
100
90
; 80
70
60
s0
40
30
20
10
0Core and Tube in Framed Trussed Rigid Bundled
outrigger tube tube tube Frame system
Figure 23: Average number of stories of different types of structural systems.
5.2 Construction Materials
To study the trend of construction materials, information about worldwide 100
tallest buildings in each period is collected. Result is shown in Figure 24.
A steel building is defined as a building where the main vertical and lateral
structural elements and floor systems are constructed from steel. Similarly, a concrete
building is defined as one where the main vertical and lateral structural elements and floor
systems are constructed from concrete. A composite building utilizes a combination of both
steel and concrete acting compositely in the main structural elements. A mixed-structure
39
building is any building that utilizes distinct steel and concrete systems above or below each
other.
As the figure indicates, a high percentage of buildings are using composite materials
in the past few decades. The most common combination is a steel building with a concrete
core. At the same time, the number of buildings using concrete as the construction materials
is increasing as well. One possible reason behind the increasing number of concrete
buildings is the development of high-strength concrete and concrete pumping techniques
which have been discussed previously.
100
* Unknown75
" Mixed
50 a Composite
" Concrete25
" Steel
01960 1970 1980 1990 2000 2005 2010 2015
Figure 24: Distribution of construction materials of 100 tallest buildings in each
period.
5.3 Sustainability
Since the matter of sustainability has been given more and more consideration in
recent years, the sustainable design of 72 buildings completed in the past decade that are
40
listed in the current 100 tallest buildings is studied besides the aspects of structural systems
and construction materials. Result is shown in Figure 25.
As the result shows, 43 percent of buildings have considered sustainability in their
design, and most of them are awarded LEED certificates. According to the data collected,
most popular measures of sustainable design of high-rise buildings include double-sided
windows or double curtain walls to provide thermal protection and water recycling and air
filtration systems.
Figure 25: Distribution of buildings considering sustainability.
41
* Number of buildingsconsideringsustainability
* Number of buildingswithout consideringsustainability
6. CASE STUDY OF BURJ KHALIFA
At 828 meters, the Burj Khalifa (formerly the Burj Dubai) has 163 stories and is the
world's tallest freestanding structure as well as the world's tallest building (Figure 26).
Construction of the tower began in January 2004 and the structure was topped out in
October 2009. It was officially opened in January 2010. The architectural and engineering
designer of this tower was Skidmore, Owings and Merill (SOM) of Chicago and its primary
contractor is Samsung Engineering and Construction Group of South Korea.
Figure 26: Bur Khalifa.
The structural system of Buj Khalifa is buttressed core system that is mentioned
above. It is designed to efficiently support a super-tall building utilizing a strong central core,
buttressed by its three wings. The vertical structure is tied together at the mechanical floors
through outrigger walls in order to maximize the building's stiffness. It is an inherently
42
stable system in that each wing is buttressed by the other two. The central core provides the
torsional resistance for the building, while the wings provide the shear resistance and
increased moment of inertia. The result is an efficient system where all of the building's
vertical structure is used to resist both gravity and lateral loads (Figure 27).
wing
central core
corridor wall
Figure 27: Typicalfloor plan of Bur Khalifa.
The structural integrity of the building itself can also serve as the damping system.
The building rises to the heavens in several separate stalks, which top out unevenly around
the central spire. This somewhat odd-looking design deflects the wind around the structure
and prevents it from forming organized whirlpools of air current, or vortices, that would
rock the tower from side to side and could even damage the building. The variation of the
tower shape, and width, resulted in wind vortices around the perimeter of the tower that
behaved differently for different shapes at different frequencies, thus disorganizing the
43
interaction of the tower structure with the wind (Figure 28). Over 40 wind tunnel tests were
conducted on Burj Khalifa to examine the effects wind would have on the tower and its
occupants. Engineers determined that no tuned-mass damping was needed.
VM T~-
Lower Pan
PWoo
Figure 28: Wind profile around Bur] Khalifa.
During the construction process, over 45,000 m3 of concrete weighing more than
110,000 tons were used to construct the concrete and steel foundation, which features 192
piles. Each pile is 1 .5m in diameter and 43m long buried more than 50m deep. The
construction of Burj Khalifa's used 330,000 m3 of concrete and 39,000 tons of steel rebar.
Special mixes of concrete are made to withstand the extreme pressure of the massive
building. It was difficult to create a concrete that could withstand both thousands of tons
bearing down on it and high Persian Gulf temperatures that can reach 50 0C (122 0F). To
44
combat this problem, the concrete was not poured during the day. Instead, it was poured at
night when the air is cooler and the humidity is higher, and during the summer months ice
was added to the mixture. In November 2007, the highest reinforced concrete core walls
were pumped using 80 MPa concrete from ground level to the height of 606 meters, which
broke the previous pumping record of 470m in the Taipei 101.
At the aspect of elevator systems, eight escalators and 57 elevators were installed in
Burj Khalifa, of which two are double-deck elevators used exclusively for the travel to the
observation deck. Engineers of Bun Khalifa considered triple deck elevators at first, but the
final design called for double deck elevators. With the rising and descending speed up to
1Om/s, these are the world's fastest double-deck elevators. The elevator system of this tower
is also awarded as the longest travel distance elevator in the world that is 504 meters, and the
world's highest elevator which lands at 638 meters (Otis, 2010).
Burj Khalifa is also considered as a sustainable building. Solar panels are capable of
heating 140000 liters of water daily. A special performance glazing glass with low
emissivity provides the tower with advanced thermal protection. Due to its significant height,
the building is able to utilize ventilation from where air temperature is cooler and humidity
is relatively lower. When air is drawn in at the top of the building, it requires less energy for
air conditioning, ventilation, and dehumidification system. LED modules used for signage
throughout to ensure reliable low maintenance lighting with low energy consumption.
Additionally, Burj Khalifa has one of the largest condensate recovery systems in the world.
45
Collecting water from air conditioning condensate discharge prevents it from entering the
wastewater stream and reduces the need for municipal potable water (Burj Khalifa,
CTBUH).
46
7. CONCLUSION
Over the past decade, both the number of high-rise buildings and the average height
of high-rise buildings have increased rapidly. Continuously evolving structural systems
creates opportunities for structures to be more efficient. Other developments in construction
techniques, accessory systems as well as structural materials have enabled the structure to
actually stand taller and taller.
Based on the study of recent high-rise buildings and the current 100 tallest buildings
in the world, following trends can be summarized: By the year of 2015, tubular structures
are in vast majority of the structural systems in recent high-rise buildings, in which tube in
tube system is the most popular one and has been applied in the design of a large number of
high-rise buildings. Advancements in structural systems also help to reduce buildings'
dependence on auxiliary damping devices. For structural materials, there is an increasing
trend to use concrete and composite materials to construct the structure. Additionally,
sustainability has been given more consideration in modem high-rise building designs.
47
Al. REFERENCES
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Askarinejad, P. (2012). "Beehive (Hexagrid): Innovative Structural System of Tall
Buildings". Council on Tall Buildings and Urban Habitat.
Baker, W. F. (2001). "Structural Innovation." Sixth World Congress on Tall Buildings and
Urban Habitat. Melbourne, Australia.
Challinger, D. "From the Ground Up: Security for Tall Buildings CRISP Report".Alexandria, VA: ASIS Foundation Research Council; 2008.
Connor, J.J. (2003). Introduction to Structural Motion Control.
Hall, Jr JR (2005). "High-Rise Building Fires". Quincy, MA: National Fire ProtectionAssociation.
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Otis (2010). "Burj Khalifa, the world's tallest building, inaugurated: Global press and firstvisitors ride Otis elevators to observation deck".<http://www.otis.com/_layouts/ProjectNewsPopup.aspx?ID= 1 3&siteURL=http://www.otis.com/site/in/pages/OtisNews.aspx> (May 20, 2015)
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49
A2. 100 TA LLEST BUILINGS IN THE WORLD BY 2015
# Building Name City Height Floors Completed Material(m)
1 Buj Khalifa Dubai (AE) 828 163 2010 steel/concrete
2 Shanghai Tower Shanghai (CN) 632 128 2015 composite
Makkah Royal Clock3 Mecca (SA) 601 120 2012 steel/concrete
Tower Hotel
New York4 One World Trade Center 541.3 94 2014 composite
City (US)
5 TAIPEI 101 Taipei (TW) 508 101 2004 composite
6 Shanghai World Financial6 Shanghai (CN) 492 101 2008 compositeCenter
International Commerce
7 Centre Hong Kong (CN) 484 108 2010 composite
Kuala8 Petronas Tower 1 451.9 88 1998 composite
_____Lumpur (MY)
Kuala9 Petronas Tower 2 451.9 88 1998 composite
_____Lumpur (MY)
10 Zifeng Tower Nanjing (CN) 450 66 2010 composite
11 Willis Tower Chicago (US) 442.1 108 1974 steel
12 KK100 Shenzhen (CN) 441.8 100 2011 composite
13 Guangzhou Intemnational13 Cnter Guangzhou (CN) 438.6 103 2010 composite
Finance Center
14 Marina 101 Dubai (AE) 426.5 101 2015 concrete
15 432 Park Avenue New York (US) 425.5 88 2015 concrete
16 Trump International Hotel16 ter Chicago (US) 423.2 98 2009 concrete
& Tower
17 Jin Mao Tower Shanghai (CN) 420.5 88 1999 composite
18 Princess Tower Dubai (AE) 413.4 101 2012 steel/concrete
19 Al Hamra Tower Kuwait City (KW) 412.6 80 2011 concrete
Two International Finance
20 Centre Hong Kong (CN) 412 88 2003 composite
21 23 Marina Dubai (AE) 392.4 88 2012 concrete
22 CITIC Plaza Guangzhou (CN) 390.2 80 1996 concrete
23 Capital Market Authority Riyadh (SA) 385 76 2015 compositeTower
24 Shun Hing Square Shenzhen (CN) 384 69 1996 composite
50
25 Eton Place Dalian Tower 1 Dalian (CN) 383.1 80 2015 composite
26 Burj Mohammed Bin Abu Dhabi (AE) 381.2 88 2014 concreteRashid Tower
New York27 Empire State Building City (US) 381 102 1931 steel
28 Elite Residence Dubai (AE) 380.5 87 2012 concrete
Concrete29 Central Plaza Hong Kong (CN) 373.9 78 1992
Federation Towers -30 Vostok Tower Moscow (RU) 373.7 95 2015 concrete
31 Bank of China Tower Hong Kong (CN) 367.4 72 1990 composite
32 Bank of America Tower New York (US) 365.8 55 2009 composite
33 Almas Tower Dubai (AE) 360 68 2008 concrete
34 JW Marriott Marquis Dubai (AE) 355.4 82 2012 concreteHotel Dubai Tower 1
35 JW Marriott Marquis Dubai (AE) 355.4 82 2013 concreteHotel Dubai Tower 2
36 Emirates Tower One Dubai (AE) 354.6 54 2000 composite
37 OKO - South Tower Moscow (RU) 353.6 85 2015 concrete
38 The Torch Dubai (AE) 352 86 2011 concrete
39 Forum 66 Tower 1 Shenyang (CN) 350.6 68 2015 composite
40 The Pinnacle Guangzhou (CN) 350.3 60 2012 concrete
41 T & C Tower Kaohsiung (TW) 347.5 85 1997 composite
42 Aon Center Chicago (US) 346.3 83 1973 steel
43 The Center Hong Kong (CN) 346 73 1998 steel
44 John Hancock Center Chicago (US) 343.7 100 1969 steel
45 ADNOC Headquarters Abu Dhabi (AE) 342 76 2015 concrete
Ahmed Abdul Rahim Al46 Aed Tb wer Dubai (AE) 342 76 2015 steel/concrete
Attar Tower
Wuxi International47 Finnaioal Wuxi (CN) 339 68 2014 composite
Finance Square______________
48 Chongqing World48 F in Cnr Chongqing (CN) 338.9 72 2015 compositeFinancial Center
49 Mercury City Tower Moscow (RU) 338.8 75 2013 concrete
50 Tianjin World Financial50 Tianjin (CN) 336.9 75 2011 composite
Center P S C 3 6
51 Shimao International Plaza Shanghai (CN) 333.3 60 2006 concrete
51
52 Rose Rayhaan by Rotana Dubai (AE) 333 71 2007 composite
53 Minsheng Bank Building Wuhan (CN) 331 68 2008 steel
54 China World Tower Beijing (CN) 330 74 2010 composite
Keangnam Hanoi55 Hanoi (VN) 328.6 72 2012 concrete
Landmark Tower
56 Longxi International Hotel Jiangyin (CN) 328 72 2011 composite
57 Al Yaqoob Tower Dubai (AE) 328 69 2013 concrete
58 Wuxi Suning Plaza 1 Wuxi (CN) 328 68 2014 composite
59 The Index Dubai (AE) 326 80 2010 concrete
60 The Landmark Abu Dhabi (AE) 324 72 2013 concrete
61 Deji Plaza Nanjing (CN) 324 62 2013 composite
Yantai Shimao No. 1 The62 Yantai (CN) 323 59 2015 composite
Harbour
63 QI Tower Gold Coast (AU) 322.5 78 2005 concrete
64 Wenzhou Trade Center Wenzhou (CN) 321.9 68 2011 concrete
65 Burj Al Arab Dubai (AE) 321 56 1999 composite
66 Nina Tower Hong Kong (CN) 320.4 80 2006 concrete
New York67 Chrysler Building City (US) 318.9 77 1930 steel
New York68 New York Times Tower 318.8 52 2007 steel
City (US)
Riverside Century Plaza69 Wuhu (CN) 318 66 2015 composite
Main Tower
70 HHHR Tower Dubai (AE) 317.6 72 2010 concrete
71 Bank of America Plaza Atlanta (US) 311.8 55 1992 composite
72 Moi Center Tower A Shenyang (CN) 311 75 2014 composite
73 U.S. Bank Tower Los Angeles (US) 310.3 73 1990 steel
Kuala74 Menara Telekom 310 55 2001 concrete
Lumpur (MY)
75 Ocean Heights Dubai (AE) 310 83 2010 concrete
76 Pearl River Tower Guangzhou (CN) 309.4 71 2013 composite
77 Fortune Center Guangzhou (CN) 309.4 73 2015 composite
78 Emirates Tower Two Dubai (AE) 309 56 2000 concrete
79 Burj Rafal Riyadh (SA) 307.9 68 2014 concrete
The Franklin - North80 Chicago (US) 306.9 60 1989 composite
Tower Chi (U) 306.9 60 1989 composte
81 Cayan Tower Dubai (AE) 306.4 73 2013 concrete
52
53
82 One57 New York (US) 306.4 75 2014 steel/concrete
East Pacific Center Tower83 A Shenzhen (CN) 306 85 2013 concrete
84 The Shard London (GB) 306 73 2013 composite
85 JPMorgan Chase Tower Houston (US) 305.4 75 1982 composite
86 Etihad Towers T2 Abu Dhabi (AE) 305.3 80 2011 concrete
Northeast Asia Trade87 t e r Incheon (KR) 305 68 2011 composite
Tower
88 Baiyoke Tower II Bangkok (TH) 304 85 1997 concrete
89 Wuxi Maoye City - Wuxi (CN) 303.8 68 2014 compositeMarriott Hotel
90 Two Prudential Plaza Chicago (US) 303.3 64 1990 concrete
91 Shenzhcn Changcheng Shenzhen (CN) 303 61 2014 compositeCenter
92 Greenland Puli Center Jinan (CN) 303 60 2015 composite
93 Leatop Plaza Guangzhou (CN) 302.7 64 2012 composite
94 Wells Fargo Plaza Houston (US) 302.4 71 1983 steel
95 Kingdom Centre Riyadh (SA) 302.3 41 2002 steel/concrete
96 The Address Dubai (AE) 302.2 63 2008 concrete
Capital City Moscow97 Moscow (RU) 301.8 76 2010 concrete
Tower
98 Aspire Tower Doha (QA) 300 36 2007 composite
99 Arraya Tower Kuwait City (KW) 300 60 2009 concrete
Doosan Haeundae We've100 the Zen We Busan (KR) 300 80 2011 concrete
the Zenith Tower A