Skyscrapers

8086918147
GUIDED BY PRESENTED BY
Mr. JITHIN ubaid
TUTOR S5 C.E ROLL NO:33
MPTC

INTRODUCTION
A skyscraper is a very tall, building. The minimum height requirement
currently to be accepted as skyscraper is 800 feet (244 meters). The word skyscraper
was first known to such buildings in the late 19th century, which reflects public
amazement at the tall buildings that are being built in New York City. The structural
definition of the word skyscraper was later refined by architectural, historians, based
on engineering developments of the 1880s that had enabled construction of tall multi-
story buildings. This definition was based on the steel skeleton as opposed to
constructions of load-bearing masonry, which passed their practical limit in 1891 with
Chicago's Monadnock Building.

DEVELOPMENT OF MODERN SKYSCRAPERS
In the late 19th century, the first skyscrapers
would have been typically an office building
of more than 10 storey’s. The concept was
undoubtedly originated in the USA, in
Chicago and in New York, where space was
limited and where the best option was to
increase the height of the buildings. The
Home Insurance Building in Chicago was
perhaps the first skyscraper in the world. Built
in 1884-1885 its height was 42 m/10 storeys

STRUCTURE, MATERIAL AND BUILDING TECHNIQUE
 FOUNDATIONS AND THE EXCAVATION PIT
• Skyscraper foundations are considerably more complex than
those for normal buildings. The complexity brought is just
because of their height and weight and can be further
depend on the certain specific factors such as nature of soil,
exposure to wind, earthquake and their location in relation to
surrounding property.
• Depending on the nature of the structure, the type of
foundation and the characteristics of the ground, the value of
the foundation / excavation can be as much as the 7.5% of
the total project value.

THERE ARE MANY DIFFERENT TYPES OF RETAINING WALLS
 Interlocking sheet piles; these can be temporary or
permanent
 Contiguous, secant piled walls, the latter more likely to be
used in soft/wet soils
 Diaphragm walls; particularly used in soft ground with high
groundwater and/or adjacent to other structures
 Cross walls; often used in addition to one of the above
where is a particularly high exposure to adjacent properties

 THE CASE OF COVERAGE FOR SKYSCRAPERS
CONSIDERED AREAS ARE
 Piling
 Dewatering
 Vibration, weakening or removal of support
 Dilapidation

Shanghai, China: Possible failure of the Foundation
Moscow, Russia: Excavation / cantilevered Walls

STRUCTURE OF THE MAIN SKELETON,
DESIGN AND MATERIAL
It is the 100 tallest buildings the number using steel has reduced by
at least 15% each decade since 1970, and in 2010 only 22% of the
tallest building is steel.
The key issues with high performance concrete (high performance
concrete is reinforced concrete with a compressive strength at 28
days in excess of 50 MPa) relate to the quality of the material and the
expertise of the contractors.

IN RESPECT OF STRUCTURAL SYSTEMS, IT IS POSSIBLE TO
DEFINE 5 CATEGORIES
 1. The framed tube: system of rigid frames (flatiron building
in 1903)
 2. The bundled tube: combination of framed tubes (Sears
towers, 1974)
 3. Tube in tube: central and peripheral tubes (World Trade
Centre in NY, 1972)
 4. Diagonalised: stressed tubes, diagrids/braced frames
(Alcoa bld. in Chicago)
 5. Core plus outrigger: central lateral system linked to the
perimeter system through outriggers (PETRONAS Tower,
1999 –Taipei 101, 2003)

 VARIOUS TYPES OF SKELETON STRUCTURES
 Super Frame
 Steel Frame Vertical Truss
 Tube In Tube
 Framed Tube
 Bundled Tube
 Exterior Braced Frame Tub
 Turned Mass Damper
 Steel Frame/Belts

 SYSTEM
The facade / cladding systems comprise the external building
envelope or the outer finish. These have evolved over time to reflect
the ambitions of the developers and the creative and innovative
talents of the modern architects
The main objectives being
 Water-tightness, Aesthetics, Wind, Privacy
 Thermal protection (including control of sunlight entry),
 Reduction in noise-level, and Strength / durability.

 DIFFERENT GROUPS AND THEIR SUB-GROUPS OF FAÇADE
SYSTEMS
Traditional
Brick façade (e.g. Empire State building, Chrysler
building, etc.)
Marble panel system
Ventilated Façade
Aluminum, stone, ceramics, fiber reinforced concrete
Curtain wall (Non-load bearing)
Glass

 MATERIAL WEIGHTS
Flat glass used for window panels – the weight
depends on the glass thickness:
 ¼ of an inch thick glass weighs about 3lbs/ft²
 ½ of an inch thick glass weighs about 6.4lbs/ft²

 BUILDING MATERIAL
 Aluminum – has become the material-of-choice for the outer frames.
 Window Panes – made of high-grade glass filled with noble gases and
a surface coating in order to reflect infrared light.
 Laminated Glass
 “Sandwich” Panels – one of the primary materials used in façade
systems of a building are so called “sandwich” panels or also known
as “composite” panels.
 There is great interest in the combustible-type panels because they
are the most widely used in buildings like apartment/residential,
hotels, office/commercial, hospitals.
 The combustible panels are widely used / installed in countries
situated in the Middle East and the Arabian Gulf peninsula due to the
harsh climatic conditions,

WIND LOADS
Wind engineering analyzes effects of wind in the natural and the built
environment and studies the possible damage, inconvenience or
benefits which may result from wind. In the fields of wind energy and air
pollution it also includes low and moderate winds as these are relevant
to electricity production resp. dispersion of contaminants.
 Wind impact on structures (buildings, bridges, towers).
 Wind comfort near buildings.
 Effects of wind on the ventilation system in a building.
 Wind climate for wind energy.
 Air pollution near buildings.

SEISMIC LOADING
Seismic loading is one of the basic concepts of earthquake engineering
which means application of an earthquake-generated agitation to a
structure. It happens at contact surfaces of a structure either with the
ground, or with adjacent structures, or with gravity waves from tsunami.
 Seismic loading depends, primarily, on:
 Anticipated earthquake's parameters at the site - known as seismic
hazard
 Geotechnical parameters of the site
 Structure's parameters
 Characteristics of the anticipated gravity waves from tsunami (if
applicable).

SEISMIC PERFORMANCE
Earthquake or seismic performance defines a structure's ability to sustain its main
functions, such as its safety and serviceability at and after a particular earthquake
exposure. A structure is, normally, considered safe if it does not endanger the lives and
well-being of those in or around it by partially or completely collapsing.

VIBRATION CONTROL
In earthquake engineering, vibration control is a set of technical means
aimed to mitigate seismic impacts in building and non-building structures.
All seismic vibration control devices may be classified as passive, active
or hybrid where:
 Passive control devices have no feedback capability between them, structural elements
and the ground;
 Hybrid control devices have combined features of active and passive control systems.
 To dissipate the wave energy inside a superstructure with properly engineered dampers;
 To disperse the wave energy between a wider range of frequencies;
 To absorb the resonant portions of the whole wave frequencies band with the help of so
called mass dampers
 Hydraulic snubbers are used on piping systems when restrained thermal movement is
allowed.
 Mechanical snubbers operate on the standards of restricting acceleration of any pipe
movements to a threshold of 0.2 g's, which is the maximum acceleration that the snubber
will permit the piping

CONSTRUCTION TECHNIQUES
The weight of a skyscraper mainly consists of dead load, the load
exerted by the building itself. Any extra weight from people, furniture,
vehicles, etc. is known as live load. In addition, wind and other
unexpected sources can be load providers.

 SHEAR WALLS
In a shear wall design, the weight of the structureis
distributed through the walls. These structures are often
made of steel reinforced brick or cinder block–
materials with high compressive strength. The shear
wall design is primarily used in small projects such as
urban brownstones or suburban housing.

 STEEL FRAME
When one thinks of low-rise skyscrapers, the steel frame design
comes to mind. This design is characterized by a large steel box,
containing smaller steel boxes inside. This 3D grid is simple and
efficient for most low-rises, but has its’ drawbacks for high-rise
structures.

 TUBE FRAME
The tube design is a recent innovation used to maximize floor
space and increase resistance to lateral force in any direction. The
buildings skin (outside) consists of closely aligned supporting
columns. This design only leaves about one-half of the building’s
exterior left for windows. Depending on the designer’s outlook, this
can be an advantage or disadvantage.

CONCRETE CORE
This is the most common design for modern
skyscrapers as it is fast to build and provides a strong
center. All the utilities, elevators, and stairwells are
centralized in this design, making it easier for building
modifications and repair.
This design can be dangerous. If a part of the
core is damaged, everything above that section will be
cut off from ground access. This happened in the World
Trade Center towers during the September 11, 2001
terrorist attacks, making it impossible for many people to
escape the burning towers.

EARTHQUAKE RESISTANT CONSTRUCTION
 REINFORCED MASONRY STRUCTURES
A construction system where steel reinforcement is
embedded in the mortar joints of masonry or placed in
holes and after filled with concrete or grout is called
masonry reinforced.
The devastating 1933 Long Beach earthquake
revealed that masonry construction should be improved
immediately. Then, the California State Code made the
reinforced masonry mandatory.
To achieve a ductile behavior of masonry, it is
necessary that the shear strength of the wall is greater
than the flexural strength.

 REINFORCED CONCRETE STRUCTURES
Reinforced concrete is concrete in which steel
reinforcement bars (rebar) or fibers have been incorporated to
strengthen a material that would otherwise be brittle. It can be
used to produce beams, columns, floors or bridges.
Pre-stressed concrete is a kind of reinforced concrete used
for overcoming concrete's natural weakness in tension Pre-
stressing tendons (generally of high tensile steel cable or rods)
are used to provide a clamping load which produces a
compressive stress that offsets the tensile stress that the
concrete compression member would, otherwise, experience
due to a bending load.
Stressed Ribbon pedestrian bridge
Over the Rogue River, Grants Pass, Oregon
Pre-stressed concrete
Cable-stayed bridge over Yangtze River

 PRESTRESSED STRUCTURES
Pre-stressed structure is the one whose overall
integrity, stability and security depend, primarily, on
pre-stressing. Pre-stressing means the intentional
creation of permanent stresses in a structure for the
purpose of improving its performance under various
service conditions.
Naturally pre-compressed exterior
Wall of Coliseum, Rome

 THERE ARE THE FOLLOWING BASIC TYPES OF PRE-
STRESSING:
 Pre-compression (mostly, with the own weight of a structure)
 Pre-tensioning with high-strength embedded tendons
 Post-tensioning with high-strength bonded or un-bonded tendons

 STEEL STRUCTURES
Steel structures are considered mostly earthquake resistant but this isn't
always the case. A great number of welded Steel Moment Resisting Frame
buildings, which looked earthquake-proof, surprisingly experienced brittle
behavior and were hazardously damaged in the 1994 Northridge
earthquake.
After that, the Federal Emergency Management Agency (FEMA)
initiated development of repair techniques and new design approaches
to minimize damage to steel moment frame buildings in future
earthquakes.

PREFABRICATION
Prefabrication is the practice of assembling components of a
structure in a factory or other manufacturing site, and transporting
complete assemblies or sub-assemblies to the construction site where the
structure is to be located. The term is used to distinguish this process from
the more conventional construction practice of transporting the basic
materials to the construction site where all assembly is carried out. The
term prefabrication also applies to the manufacturing of things other
than structures at a fixed site.

 ADVANTAGES OF PREFABRICATION
 Self-supporting ready-made components are used, so
the need for formwork, shuttering and scaffolding is
greatly reduced.
 Construction time is reduced and buildings are
completed sooner, allowing an earlier return of the
capital invested.
 On-site construction and congestion is minimized.
 Less waste may occur
 Advanced materials such as sandwich-structured
composite can be easily used, improving thermal and
sound insulation and air tightness.
Prefabrication

DISCUSSION
 Burj Khalifa – Dubai (2010) 829 m
Key Facts:
 Constructed in 6 years.
 World’s tallest building.
 163 Storeys.
 45,000 square meters of concrete weighing 110,000 tonnes
 12,000 workers.
 Cost USD $1.5billion.
 Tallest service elevator.
 Tallest free standing structure
 31,400 metric tonnes of steel used.
 Construction started in 2004
 58 number of elevators
 Top elevator speed 10m/s
 900 number of apartments
 Previously known as Burj Dubai.
 Highest outdoor observation Deck (440m)
 Peak Electricity demand of tower is 5 MVA
 946,000 litres of water used every day.
 The tower’s architect and engineer is Skidmore, Owings and Merrill (Chicago).

 The Imperial II (Mumbai) 2010, 254m
Key Facts:-
 Tallest Residential Building in India.
 Also called as SD Towers or Tardeo Twin Towers.
 60 floors.
 Construction started in 2005
 #189 tallest in World
 #17 Elevators.
 Top elevator speed 6m/s.
 A private observation deck is present at the top of each
building by the cone spires.
 Use of M50 grade cement which is usually used in building
dams and bridges.
 228 luxury homes.
 Fe 500 iron used instead of regular Fe 450 to give the slabs
added tensile strength allowing longer spans in between the
beams.
 Clear ceiling height of 10.8 and 11.8 feet.
 A grand triple height lobby.

SKYSCRAPERS – IMPLICATIONS
 ADVANTAGES OF SKYSCRAPERS
Throughout the world, the population of the major cities are increasing at a fast rate
and where land for building is not available; there is a pressure to build upward rather than
sideways.
The main advantage of building higher building is that they can take pressure of the
need to build just outside large cities, thus preventing the spread outwards and the
destruction of the countryside.
 Skyscrapers are known as modern answer for lack of space.
 Each Skyscraper has their own unique architectural feature.
 These features often made the skyscrapers the icon of their city.
 These skyscrapers attract millions of tourist each year, and bring profit to local business.
 Radio, television and cell phones require signal receivers from broadcasters.
 By placing an antenna at a highest point in the city broadcasters can send a power
full signal for many miles.
 Skyscrapers provide excellent site for antenna and other equipment.

 DISADVANTAGES OF SKYSCRAPERS
 High cost of investment, construction, maintenance, and operation.
 Negative effect on indoor and outdoor environment.
 Destruction of natural environment.
 Noise pollution.
 Poor Ventilation.
 Rely on Elevators.
 Fireproofing Problem.
 Evacuation difficulty when fire broke out.
 Poor Fire resistance of Steel Structure System.
 Land Subsidence.
 The development of high rise buildings destroyed the harmony of the local cultural
landscape.
 The last reason is economy; the skyscrapers can’t be cleaned or repaired by normal
people.

CONCLUSION
From this t seminar I conclude that the SKYSCRAPERS are known to
be super tall building either residential, work place or of mix use. They are
not built just for the economy of space, they are considered to be symbol
of city’s economic power. The first skyscrapers would have been typically
an office building of more than 10 stories. The concept was originated in
USA, in Chicago and in New York, where space was limited and where
best option was to increase the height of building. The building up to
about 4 stories can be supported by their walls, while skyscraper’s are
larger buildings that must be supported by skeleton frames.

Skyscrapers

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