1.Historical Development In High-Rise Buildings
Ancient Skyscrapers – The Great Ziggurat of Babylon
Perhaps the most impressive structure in the ancient Middle East, the Great Ziggurat of Babylon was built over a span of several decades in the Sixth Century BC. Its seven stories, built upon a square foundation, stretched 300 feet into the sky. Some think it was the inspiration for the infamous Tower of Babel in the Book of Genesis. In this illustration, King Nebuchadnezzar, who ruled Babylon from 604 to 561 BC, is seen overlooking his capital
The towers of Bologna
The towers of and were built in Europe, or together until Bologna are slender, as much as 60 meters (150 feet) tall, by the rich for defense and as status symbols. No other site perhaps the world, had so many tall structures crowded the coming of skyscrapers in the late 19th century.
Fig. 1 The great Ziggurat of Babylon
As many as 180 towers, of many different heights, are thought to have been built in Bologna during the 1100’s and slightly later; now there are barely 20. The two most prominent (seen here) are the symbols of the city and have long been known together as the “Two Towers.”
Fig. 2 The towers of Bologna
The First Safety Elevators
In this period illustration, shoppers ride the elevator in the new Lord & Taylor’s department store on Broadway in New York City sometime during the 1870’s. Around the same time, the first-ever elevator in an office building was also installed in New York. It was designed by Elisha Otis, whose company became synonymous with the new contraption. Elevators revolutionized office buildings, literally turning them upside down. Prior to their invention, the lower floors of a structure were the most valuable rental property because of the difficulty and inconvenience of climbing the stairs. But the elevator made it possible for elite tenants to enjoy the view from the upper floors – and allow buildings to rise higher and higher.
Fig. 3 The first Safety Elevators
Great Chicago Fire
In this illustration, Chicago residents flee the terror of the Chicago fire which devastated their city over a three-day period in October 1871. The fire caused nearly $200 million in damage, killed some 300 people and left another 100,000 homeless. Despite this toll, the destruction cleared the way for Chicago to build scores of modern steel-framed office towers and to become one of America’s most architecturally striking cities.
Fig. 4 Great Chicago Fire
The First skyscraper
Chicago’s 10-story Home Insurance Building, built in 1884 and designed by William Jenney, was arguably the first true modern office tower. It was the first building to use structural steel at least partially in its frame, and was the first tall building to be fireproofed both inside and outside. It was torn down in 1931 but its legacy lives on in thousands of steel-framed and fireproofed buildings around the world.
Fig. 5 Home Insurance Building
The Tribune Tower
Pedestrians walk past the ornate entrance and lower floors of Tribune Tower, home of the Chicago Tribune newspaper, which was built in 1925. The 36-story Gothic Revival structure was designed by John Mead Howells and Raymond Hood, who won a contest held by the newspaper company to create “the most beautiful and distinctive office building in the world.”
Fig. 6 The Tribune Tower
The Chrysler Building
With its majestic spire, New York City’s Chrysler Building is perhaps the most famous Art Deco structure in the world. Built in 1930, the 77-storey structure was briefly the tallest building in the world. The sculptures at the top and around the edges are actually inspired by Chrysler hubcaps and hood ornaments. The building’s tapering profile is perhaps the best example of “form follows zoning” by taking New York City’s setback requirements from 1916 zoning laws – requiring new structures to leave more open space around them – and turning them into an stunning archetype
Fig. 7 The Chrysler Building
The Empire State Building survives a hit
This photo shows the spot where a B-25 bomber struck the Empire State Building in July 1945. The aircraft was ferrying servicemen from Massachusetts to New York’s La Guardia Airport when pilot William Smith veered disastrously off course in heavy fog. Fourteen people – including Smith – were killed when the bomber hit the skyscraper. The building’s 79th floor caught fire, and New York City firefighters bravely rushed up into the building to rescue occupants and put out the blaze. The building’s structure and fireproofing both proved strong enough that the New York landmark reopened the following week.
Fig. 8 The Empire State Building
World Trade Centre
The famous twin towers of the World Trade Center were built by the Port Authority in the 1960s as part of an effort to revitalize lower Manhattan. The structure was derided by critics as boring. One wag likened it to a giant pair of filing cabinets, but in time it became a popular New York landmark. The original WTC was the first to use “sky lobbies” where people would change from express to local elevators, a setup inspired by the New York subway system. It also had wide-open, column-free spaces that were ideal for Fig. 9 The World Trade Centre the cubicles then becoming popular in office design. The towers were destroyed in the 2001 terrorist attack that killed more than 2,700 people
When the Sears Tower, later renamed the Willis Tower, opened in 1973, the 108-story structure became the tallest building in the world and held that title until Malaysia’s Petronas Towers claimed the distinction in 1998. This skyscraper was able to achieve that height through a spectacular engineering innovation that introduced the “bundled tube structure” – the Sears Tower is really nine square towers bundled together. It was the start of a revolution in structural design that permitted higher and thinner towers than had ever been built before
Fig. 10 The Sears Tower
The Citicorp Building Skirts Disaster
The 59-story Citigroup Center building, completed in 1977, had to undergo a costly strength upgrade the following year after it was discovered that the structure was dangerously vulnerable to strong diagonal winds hitting the building’s corners. This weakness was a consequence of the placement of the main support columns at the centre of the sides rather than on the corners because the building had to float over a church that owned the property. This bold design did win praise for the architect but he subsequently had to suffer the consequences – largely in secret lest panic break out – of experimenting with untested structural elements. If strong dangerous winds had actually toppled the Citicorp building, it is estimated that it might have taken 16 blocks of Manhattan with it.
Fig. 11 The Citicorp Building
The Petronas Tower
Tourists have their picture taken outside the soaring spires of the Petronas Towers in Kuala Lumpur, Malaysia. The 88-story towers, which were completed in the mid-to-late 1990s, were for several years the world’s tallest buildings. The project was the harbinger of a global shift in skyscraper building in which Middle Eastern and Asian countries have been racing to erect the tallest and most majestic towers Fig. 12 The Petronas Tower
The Gherkin, London
One of the more unusual sights in the London skyline is 20 St. Mary Axe, a 41-story office tower opened in 2004, which is nicknamed “The Gherkin” because of its resemblance to a pickle. Though odd-looking, the structure is a prototype for a new generation of innovative, super energy-efficient buildings. Vertical gaps in the building create a natural ventilation system that allows warm air to rise out of the structure. These openings also allow the interior offices to use more Fig. 13 The 20 St. Mary Axe natural light to greatly reducing electrical consumption
The Marina Bay Sands
Singapore’s Marina Bay Sands, a casino and resort complex which opened in 2011, cost an astonishing $8 billion to build. Architect Moshie Safdie’s unorthodox design, with its trio of 55-story towers, reportedly was inspired by card decks on gaming tables. The three towers are connected by a giant terrace that supports the world’s longest elevated swimming pool. The steel for the pool weighs 191,416 kilos (422,000 pounds) and the water it can hold weighs an additional 1,424,098 kilos (3,139,600 pounds). The towers are constructed to allow movement in the wind – up to 50 centimetres – and longer-term settling in the soil.
Fig. 14 The Marina Bay Sands
Dubai’s 160-storey Burj Khalifa, which opened in 2010, is by far the world’s tallest building. Its startling, rocket ship-like appearance, seen in this photo, seems intended to get attention more than anything else. As architectural critic Paul Goldberger has written, “You don’t build this kind of skyscraper to house people… you do it to make sure the world knows who you are.” The tall, tapering design is reminiscent of skyscrapers like the Chrysler Fig. 15 The Burj Khalifa and Empire State buildings although you could put the two New York skyscrapers one on top of the other and they still would not be as tall.
The New World Trade Centre
One World Trade Center (also known as Tower One) rises over lower Manhattan on the site of where the twin towers destroyed in 2001. When completed in 2013, it will have a spire that’s precisely 1,776 feet tall (541 meters), making it the third tallest building in the world and the highest in the Western Hemisphere. The new WTC’s base is enclosed in thick concrete, steel panels and blast-resistant glass, making it one of the toughest skyscrapers ever built, but security concerns have caused the building’s cost to soar, reaching the vicinity of $4 billion.
Fig. 16The New World Trade Centre
Fig. 17 Height Comparison of Noticeable Tall Buildings
2. Classification of Tall Building Structure System
In 1969 Fazlur Khan classified structural systems for tall buildings relating to their heights with considerations for efficiency in the form of “Heights for Structural Systems” diagrams
Fig. 18 Classification of Tall Building Structure System by Fazlur Khan. Left : steel; Right: Concrete
He developed these schemes for both steel and concrete. Khan argued that the rigid frame that had dominated tall building design and construction so long was not the only system fitting for tall buildings. Because of a better understanding of the mechanics of material and member behavior, he reasoned that the structure could be treated in a holistic manner, that is, the building could be analyzed in three dimensions, supported by computer simulations, rather than as a series of planar systems in each principal direction. Feasible structural systems, according to him, are rigid frames, shear walls, interactive frame-shear wall combinations, belt trusses, and the various other tubular systems. Structural systems of tall buildings can be divided into two broad categories: interior structures and exterior structures.
This classification is based on the distribution of the components of the primary lateral load-resisting system over the building. 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 load-resisting system is located at the building perimeter, a system is categorized as an exterior structure. It should be noted, however, that any interior structure is likely to have some minor components of the lateral load-resisting system at the building perimeter, and any exterior structure may have some minor components within the interior of the building. This classification of structural systems is presented more as a guideline and should be treated as such. It is imperative that each system has a wide range of height applications depending upon other design and service criteria related to building shape, aspect ratio, architectural functions, load conditions, building stability and site constraints.
For each condition, however, there is always an optimum structural system, although it may not necessarily match one of those in the system’s tables due to the predominant influence of other factors on the building form. The height limits shown are therefore presumptive based on experience and the authors’ prediction within an acceptable range of aspect ratios of the buildings, say about 6 to 8. On occasions, an exterior structure may be combined with an interior one, such as when a tubular frame is also braced or provided with core-supported outriggers and belt trusses, to enhance the building’s stiffness 2.1 Interior Structures The two basic types of lateral load-resisting systems in the category of interior structures are the moment-resisting frames and shear trusses/shear walls.
These systems are usually arranged as planar assemblies in two principal orthogonal directions and may be employed together as a combined system in which they interact. Another very important system in this category is the core-supported outrigger structure, which is very widely used for super tall buildings at this writing. The moment-resisting frame (MRF) consists of horizontal (girder) and vertical (column) members rigidly connected together in a planar grid form. Such frames resist load primarily through the flexural stiffness of the members (Kowalczyk, Sinn, & Kilmister, 1995).
The size of the columns is mainly controlled by the gravity loads that accumulate towards the base of the building giving rise to progressively larger column sizes towards the base from the roof. The size of the girders, on the other hand, is controlled by stiffness of the frame in order to ensure acceptable lateral sway of the building. Although gravity load is more or less the same in all typical floors of a tall building, the girder sizes need to be increased to increase the frame stiffness. Likewise, columns already sized for gravity loads need to be slightly increased to increase the frame stiffness as well. MRFs can be located in or around the core, on the exterior, and throughout the interior of the building along grid lines.
Table 1 Interior Structures
Braced frames are laterally supported by vertical steel trusses, also called shear trusses, which resist lateral loads primarily through axial stiffness of the members. These act as vertical cantilever trusses where the columns act as chord members and the concentric K, V, or X braces act as web members. Such systems are called concentric braced frames (CBF).
Eccentric braced frames (EBF) have, on the other hand, braces which are connected to the floor girders that form horizontal elements of the truss, with axial offsets to introduce flexure and shear into the frame (Popov, 1982). This lowers stiffness-to-weight ratio but increases ductility and therefore EBFs are used for seismic zones where ductility is an essential requirement of structural design. EBFs can also be used to accommodate wide doors and other openings, and have on occasions been used for non-seismic zones (Corrin & Swensson, 1992). Braced frames are generally located in the service and elevator core areas of tall buildings.
The frame diagonals are enclosed within the walls. Reinforced concrete planar solid or coupled shear walls have been one of the most popular systems used for high-rise construction to resist lateral forces caused by wind and earthquakes. They are treated as vertical cantilevers fixed at the base. When two or more shear walls in the same plane are interconnected by beams or slabs, as is the case with shear walls with door or window openings, the total stiffness of the system exceeds the sum of the individual wall stiffnesses. This is so because the connecting beam forces the walls to act as a single unit by restraining their individual cantilever actions.
These are known as coupled shear walls. Shear walls used in tall office buildings are generally located around service and elevator cores, and stairwells. In fact, in many tall buildings, the vertical solid core walls that enclose the building services can be used to stabilize and stiffen the building against lateral loads. Many possibilities exist with single or multiple cores in a tall building with regard to their location, shape, number, and arrangement. The core walls are essentially shear walls that can be analyzed as planar elements in each principal direction or as three-dimensional elements using computer programs.
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