Post No. 23: Building
Skyscrapers
Building tall skyscrapers has been an old obsession of
engineers, architects and real estate developers between others. To achieve
this dream, it is necessary to gather in harmony several main aspects such as
materials, wind forces, use of the building, wind loads and to face the high
construction costs. All of them, combined with an efficient high tall building
management . We can not forget that errors of any kind can lead to disasters
and many lives can be lost and insurance claims, compensations and legal costs
due to damages may be astronomical.
From the 1960s to the present the technology has changed a
lot and now the digital solutions constitute a methodology that produces
optimal results and that is being widely used but the risks due to nature
continue.
The design and construction of skyscrapers involves creating
safe, habitable spaces in very high building. The buildings must support their weight,
resist wind and earthquakes, and protect occupants from fire. Yet they must
also be conveniently accessible, even on the upper floors, and provide utilities
and a comfortable climate for the occupants. The problems posed in skyscraper design
are considered among the most complex encountered given the balances required
between economics, engineering, and construction management.
Good structural design is important in most building
designs, but particularly for skyscrapers since even a small chance of
catastrophic failure is unacceptable given the high prices of construction. This
presents a paradox to civil engineers: the only way to assure a lack of failure
is to test for all modes of failure, in both the laboratory and the real world.
But the only way to know of all modes of failure is to learn from previous
failures. Thus, no engineer can absolutely sure that a given structure will
resist all loadings that could cause failure, but can only have large enough
margins of safety such that a failure is acceptably unlikely. When buildings do
fail, engineers question whether the failure was due to some lack of foresight
or due to some unknowable factor.
The load a skyscraper experiences is largely from the force
of the building material itself. In most buildings designs, the weight of the
structure is much larger than the weight of the material that it will support
beyond its own weight. In technical terms, the dead load, the load of the
structure, is larger than the live load, the weight of things in the structure
(people, furniture, vehicles, etc). As such, the amount of structural material
required within the lower levels of a skyscraper will be much larger than the
material required within higher levels. This is not always visually apparent. The
Empire State Building
The wind loading on a skyscraper should also be considered.
In fact, the lateral wind load imposed on super-tall structures is generally
the governing factor in the structural design. Wind pressure increases with
height, so for very tall buildings, the loads associated with wind are larger
than dead or live loads. Other vertical and horizontal loading factors come
from varied, unpredictable sources, such as earthquakes.
A shear wall, in its simplest definition, is a wall where
the entire material of the wall is employed in the resistance of both
horizontal and vertical loads. A typical example is a brick or cinderblock
wall. Since the wall material is used to hold the weight, as the wall expands
in size, it must hold considerably more weight. Due to the features of a shear
wall, it is acceptable for small constructions, such as suburban housing or an
urban brownstone, to require low material costs and little maintenance. In this
way, shear walls, typically in the form of plywood and framing, brick, or
cinderblock, are uses for these structures. For skyscrapers, though, as the
size of the structure increases, so does the size of the supporting wall. Large
structures such as castles and cathedrals inherently addressed these issues due
to a large wall being advantageous (castles), or able to be designed around (cathedrals).
Since skyscrapers seek to maximize the floor-space by consolidating structural
support, shear walls tend to be used only in conjunction with other support
systems.
The classic concept of a skyscraper is a large steel box
with small boxes inside it. By eliminating the inefficient part of a shear
wall, the central portion, and consolidating support members in a much stronger
material must be supported ( as height increases), the distance between
supporting members must decrease, which actually, in turn, increases the amount
of material that must be supported. This become inefficient and uneconomic for
buildings above 40 stories tall as usable floor spaces are reduces for
supporting column and due to more usage of steel.
A new structural system using framed tubes was developed in
the early 1960s. Fazlur Kahn and J. Rankine defined the framed tube structure
as “a three dimensional space structure composed of three, four, or possibly
more frames, braced frames, or shear walls, joined at or near their edges to
form a vertical tube- like structural system capable of resisting lateral
forces in any direction by cantilevering from the foundation.
The tubular systems are fundamental to tall building design.
Most buildings over 40-stories constructed since the 1960s now use a tube
design derived from Khan’s structural engineering principles, examples
including the construction of the World
Trade Center ,
Aon Centre, Petronas Towers , Jin
Mao Building
The invention of the elevator was a precondition for the
invention of skyscrapers, given that most people would not (or could not) climb
more than a few flights of stairs at a time. The elevators in a skyscraper are
not simply a necessary utility like running water and electricity, but are in
fact closely related to the design of the whole structure. (1)
References:
(1) Wikipedia
The History of Skyscrapers documentary. Time: 45:43:
Building Tall Skyscraper Lecture Series: How High Can We Go?
Time: 1:11:42:
Deformation Compatibility of Columns in High- Rise
Buildings. Time: 24:12:
(English Narration) Series: A digital design work record of
a high-rise building project. Time: 16:39:
Engineering Disaster: Failing Structure: Best Documentary
2017. Time: 43:41:
Dubai Laser show 2018 I Burj Khalifa I Full HD 1080. Time:
6:31:
How they build the world’s tallest building Burj Khalifa-
Construction Documentary. Time: 44:39:
Constructing tallest building in the World- Burj Khalifa-
Documentary 2015 (HD). Time: 44:46:
Dubai- How to buid in the desert. Time: 45:52:
The Making of Empire
State Building
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