Skyscraper design and construction

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A workman on the framework of the Empire State Building Old timer structural worker2.jpg
A workman on the framework of the Empire State Building

The design and construction of skyscrapers involves creating safe, habitable spaces in very high buildings. 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.

Contents

Basic design considerations

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 be 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.

Substructure

One of the many things that make skyscrapers special is their substructure. For example, the depth of the pit that holds the substructure has to reach all the way to bedrock. If bedrock lies close to the surface, the soil on top of the bedrock is removed, and enough of the bedrock surface is removed to form a smooth platform on which to construct the building's foundation. [1]

Loading and vibration

Taipei 101 endures a typhoon (2005) 101.typhoon.altonthompson.jpg
Taipei 101 endures a typhoon (2005)

The load a skyscraper experiences is largely from the force of the building material itself. In most building 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's setbacks are actually a result of the building code at the time, and were not structurally required. On the other hand, John Hancock Center's shape is uniquely the result of how it supports loads. Vertical supports can come in several types, among which the most common for skyscrapers can be categorized as steel frames, concrete cores, tube within tube design, and shear walls.

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.

Shear walls

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 used 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.

Steel frame

The classic concept of a skyscraper is a large steel box with many 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, steel, a skyscraper could be built with both horizontal and vertical supports throughout. This method, though simple, has drawbacks. Chief among these is that as more 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 becomes inefficient and uneconomic for buildings above 40 stories tall as usable floor spaces are reduced for supporting column and due to more usage of steel. [2] [3]

Tube frame

The Willis Tower showing the bundled tube frame design KM 5939 sears tower august 2007 B.jpg
The Willis Tower showing the bundled tube frame design

A new structural system using framed tubes was developed in the early 1960s. Fazlur Khan 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." [4] Closely spaced interconnected exterior columns form the tube. Horizontal loads (primarily wind) are supported by the structure as a whole. About half the exterior surface is available for windows. Framed tubes allow fewer interior columns, and so create more usable floor space. Where larger openings like garage doors are required, the tube frame must be interrupted, with transfer girders used to maintain structural integrity. Tube structures cut down costs, at the same time allow buildings to reach greater heights. Tube-frame construction was first used in the DeWitt-Chestnut Apartment Building, designed by Khan and completed in Chicago in 1963. [5] It was used soon after for the John Hancock Center and in the construction of the World Trade Center.

A variation on the tube frame is the bundled tube, which uses several interconnected tube frames. The Willis Tower in Chicago used this design, employing nine tubes of varying height to achieve its distinct appearance. The bundle tube design was not only highly efficient in economic terms, but it was also "innovative in its potential for versatile formulation of architectural space. Efficient towers no longer had to be box-like; the tube-units could take on various shapes and could be bundled together in different sorts of groupings." [6] The bundled tube structure meant that "buildings no longer need be boxlike in appearance: they could become sculpture." [7] Cities have experienced a huge surge in skyscraper construction, thanks to Khan's innovations allowing economic skyscrapers.

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, [2] [8] examples including the construction of the World Trade Center, Aon Center, Petronas Towers, Jin Mao Building, and most other supertall skyscrapers since the 1960s. [9] The strong influence of tube structure design is also evident in the construction of the current tallest skyscraper, the Burj Khalifa. [7]

The elevator conundrum

Elevators in the Empire State Building ESB Elevators.JPG
Elevators in the Empire State 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. A taller building requires more elevators to service the additional floors, but the elevator shafts consume valuable floor space. If the service core (which contains the elevator shafts) becomes too big, it can reduce the profitability of the building. Architects must therefore balance the value gained by adding height against the value lost to the expanding service core. [10] Many tall buildings use elevators in a non-standard configuration to reduce their footprint. Buildings such as the former World Trade Center Towers and Chicago's John Hancock Center use sky lobbies, where express elevators take passengers to upper floors which serve as the base for local elevators. This allows architects and engineers to place elevator shafts on top of each other, saving space. Sky lobbies and express elevators take up a significant amount of space and add to the amount of time spent commuting between floors. Other buildings such as the Petronas Towers use double-deck elevators allowing more people to fit in a single elevator and reaching two floors at every stop. It is possible to use even more than two levels on an elevator although this has yet to be tried. The main problem with double-deck elevators is that they cause all elevator occupants to stop when only people on one level need to get off at a given floor.

Another solution, employed by the Shanghai Tower and the under-construction (2019) Jeddah Tower is for buildings to be created for mixed-use, putting floorspace-hogging office suites towards the bottom, but multistory penthouses and atria - which require little cross-sectional floor space - towards the top. [11]

Other difficulties when building skyscrapers

Building skyscrapers can be difficult due to factors other than complexity and cost. For example, in European cities like Paris, the difference between the appearance of old architecture and modern skyscrapers can make it hard to get approval from local authorities to construct new skyscrapers. Building skyscrapers in an old and famous town can drastically alter the image of the city. In cities like London, Edinburgh, Portland,[ which? ] and San Francisco there is a legal requirement called protected view, which limits the height of new buildings within or adjacent to the sightline between the two places involved. [12] [ circular reference ] This rule also makes it harder to find suitable sites for new tall buildings.


See also

Related Research Articles

Central Plaza (Hong Kong) Supertall skyscraper in Hong Kong

Central Plaza is a 78-storey, 374 m (1,227 ft) skyscraper completed in August 1992 at 18 Harbour Road, in Wan Chai on Hong Kong Island in Hong Kong. It is the third tallest tower in the city after 2 International Finance Centre in Central and the ICC in West Kowloon. It was the tallest building in Asia from 1992 to 1996, until the Shun Hing Square was built in Shenzhen, a neighbouring city. Central Plaza surpassed the Bank of China Tower as the tallest building in Hong Kong until the completion of 2 IFC.

Geotechnical engineering Scientific study of earth materials in engineering problems

Geotechnical engineering, also known as geotechnics, is the application of scientific methods and engineering principles to the acquisition, interpretation, and use of knowledge of materials of the Earth's crust and earth materials for the solution of engineering problems and the design of engineering works. It is the applied science of predicting the behavior of the Earth, its various materials and processes towards making the Earth more suitable for human activities and development.

Skyscraper High-rise building

A skyscraper is a continuously habitable high-rise building that has over 40 floors and is taller than 150 m (492 ft). Historically, the term first referred to buildings with 10 to 20 floors in the 1880s. The meaning shifted with advancing construction technology during the 20th century. Skyscrapers may host offices, hotels, residential spaces, and retail spaces.

Seagram Building Office skyscraper in Manhattan, New York

The Seagram Building is a skyscraper at 375 Park Avenue, between East 52nd and 53rd Streets, in Midtown Manhattan, New York City. The integral plaza, building, stone faced lobby and distinctive glass and bronze exterior were designed by German-American architect Ludwig Mies van der Rohe. Philip Johnson designed the interior of The Four Seasons and Brasserie restaurants. Kahn & Jacobs were associate architects. Severud Associates were the structural engineering consultants. The Seagram building was completed in 1958.

Shanghai World Financial Center Skyscraper in Shanghai

The Shanghai World Financial Center is a supertall skyscraper located in the Pudong district of Shanghai. It was designed by Kohn Pedersen Fox and developed by the Mori Building Company, with Leslie E. Robertson Associates as its structural engineer and China State Construction Engineering Corp and Shanghai Construction (Group) General Co. as its main contractor. It is a mixed-use skyscraper, consisting of offices, hotels, conference rooms, observation decks, and ground-floor shopping malls. Park Hyatt Shanghai is the tower's hotel component, comprising 174 rooms and suites occupying the 79th to the 93rd floors, which at the time of completion was the highest hotel in the world. It is now the third-highest hotel in the world after the Ritz-Carlton, Hong Kong, which occupies floors 102 to 118 of the International Commerce Centre.

Curtain wall (architecture) Outer non-structural walls of a building

A curtain wall system is an outer covering of a building in which the outer walls are non-structural, utilized only to keep the weather out and the occupants in. Since the curtain wall is non-structural, it can be made of lightweight materials, thereby reducing construction costs. When glass is used as the curtain wall, an advantage is that natural light can penetrate deeper within the building. The curtain wall façade does not carry any structural load from the building other than its own dead load weight. The wall transfers lateral wind loads that are incident upon it to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, absorb sway induced by wind and seismic forces acting on the building, withstand wind loads, and support its own dead load weight forces.

Seismic retrofit Modification of existing structures to make them more resistant to seismic activity

Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries and late 1970s for many other parts of the world, many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example.

A load-bearing wall or bearing wall is a wall that is an active structural element of a building, which holds the weight of the elements above it, by conducting its weight to a foundation structure below it.

Fazlur Rahman Khan Bangladeshi architect

Fazlur Rahman Khan was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of the Sears Tower, since renamed Willis Tower, the tallest building in the world from 1973 until 1998 and the 100-story John Hancock Center.

Formwork Frame mold in which concrete is poured

Formwork is temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering molds.

The Illinois Vision skyscraper in Chicago, U.S.

The Mile-High Illinois, Illinois Sky City, or simply The Illinois is a visionary skyscraper that is proposed to be over 1 mile (1,600 m) high, conceived and described by American architect Frank Lloyd Wright in his 1957 book, A Testament. The design, intended to be built in Chicago, included 528 stories, with a gross area of 18,460,000 square feet (1,715,000 m2). Wright stated that there would be parking for 15,000 cars and 100 helicopters.

The term structural system or structural frame in structural engineering refers to the load-resisting sub-system of a building or object. The structural system transfers loads through interconnected elements or members.

This is an alphabetical list of articles pertaining specifically to structural engineering. For a broad overview of engineering, please see List of engineering topics. For biographies please see List of engineers.

Construction of the World Trade Center Construction project in New York City (1968–1987)

The construction of the first World Trade Center complex in New York City was conceived as an urban renewal project to help revitalize Lower Manhattan spearheaded by David Rockefeller. The project was developed by the Port Authority of New York and New Jersey. The idea for the World Trade Center arose after World War II as a way to supplement existing avenues of international commerce in the United States.

140 William Street

140 William Street is a 41-storey steel, concrete and glass building located in the eastern side of the central business district of Melbourne, Victoria, Australia. Constructed between 1969 and 1972, BHP House was designed by the architectural practice Yuncken Freeman alongside engineers Irwinconsult, with heavy influence of contemporary skyscrapers in Chicago, Illinois. The local architects sought technical advice from Bangladeshi-American structural engineer Fazlur Rahman Khan, of renowned American architectural firm Skidmore, Owings & Merrill (SOM), spending 10 weeks at their Chicago office in 1968. At the time, BHP House was known to be the tallest steel framed building and the first office building in Australia to use a “total energy concept” – the generation of its own electricity using BHP natural gas. The name BHP House came from the building being the national headquarters of the Broken Hill Proprietary (BHP) Company. BHP House has been included in the Victorian Heritage Register for significance to the State of Victoria for following three reasons:

Tube (structure) system to resist lateral loads in structural engineering

In structural engineering, the tube is a system where, to resist lateral loads, a building is designed to act like a hollow cylinder, cantilevered perpendicular to the ground. This system was introduced by Fazlur Rahman Khan while at the architectural firm Skidmore, Owings & Merrill (SOM), in their Chicago office. The first example of the tube’s use is the 43-story Khan-designed DeWitt-Chestnut Apartment Building, since renamed Plaza on DeWitt, in Chicago, Illinois, finished in 1966.

Shanghai Tower Skyscraper in Shanghai

Shanghai Tower is a 632-metre (2,073 ft), 128-story megatall skyscraper in Lujiazui, Pudong, Shanghai. It is the world's second-tallest building by height to architectural top and it shares the record of having the world's highest observation deck within a building or structure at 562 m. It had the world's second-fastest elevators at a top speed of 20.5 metres per second until 2017, when it was surpassed by the Guangzhou CTF Finance Centre, with a top speed of 21 metres per second. Designed by international design firm Gensler and owned by the Shanghai city government, it is the tallest of the world's first triple-adjacent supertall buildings in Pudong, the other two being the Jin Mao Tower and the Shanghai World Financial Center. Its tiered construction, designed for high energy efficiency, provides nine separate zones divided between office, retail and leisure use.

History of structural engineering

The history of structural engineering dates back to at least 2700 BC when the step pyramid for Pharaoh Djoser was built by Imhotep, the first architect in history known by name. Pyramids were the most common major structures built by ancient civilizations because it is a structural form which is inherently stable and can be almost infinitely scaled.

A building undergoes progressive collapse when a primary structural element fails, resulting in the failure of adjoining structural elements, which in turn causes further structural failure.

Signature Tower is a proposed skyscraper in Jakarta, Indonesia. The proposed height is 638 m (2,093 ft)

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  12. Protected view

Further reading