Group 1 ABSTRACT The high-rise building is generally defined as one that is taller than the maximum height which people are willing to walk up; it thus requires mechanical vertical transportation. This includes a rather limited range of building uses, primarily residential apartments, hotels, and office buildings, though occasionally including retail and educational facilities. A type that has appeared recently is the mixed-use building, which contains varying amounts of residential, office, hotel, or commercial space. The design and construction of skyscrapers involves creating safe, habitable spaces in very tall 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. One common feature of skyscrapers is having a steel framework from which curtain walls are suspended, rather than load-bearing walls of conventional construction. Most skyscrapers have a steel frame that enables to build taller than load-bearing walls of reinforced concrete. Skyscrapers usually have particularly small surface area of what are conventionally thought of as walls, because the walls are not load-bearing and therefore most skyscrapers are characterized by large surface areas of windows made possible by the concept of steel frame and curtain walls. However, skyscrapers can have curtain walls that mimick conventional walls and a small surface area of windows. The concept of a skyscraper is a product of the industrialized age, made possible by cheap fossil fuel derived energy and industrially refined raw materials such as steel and concrete. The construction of skyscrapers was enabled by steel frame construction that surpassed brick and mortar construction starting at the end of the 19th century and finally surpassing it in the 20th century together with reinforced concrete construction as the price of steel decreased and labour costs increased. The steel frames become inefficient and uneconomic for super tall buildings as usable floor spaces are reduced for supporting column and due to more usage of steel. KEYWORDS: High Rise, High Density Structure, Construction, Skyscraper, Types of Structural Construction, Rigid Frame, Core Structure, Braced Frame
TERMS AND DEFINITIONS Braced frames are cantilevered vertical trusses resisting laterals loads primarily through the axial stiffness of the frame members. Dead loads arise from the weight of the individual construction elements and the finishing loads.
A frame can be classified as non-sway if its response to in-plane horizontal forces is sufficiently stiff for it to be acceptably accurate to neglect any additional internal forces or moments arising from horizontal displacements of its nodes" High rise Structures •A high-rise high-rise is a tall building or structure •Buildings between 75 feet and 491 feet (23 m to 150 m) high are considered high -rises. Buildings taller than 492 feet (150 m) are classified as skyscrapers. •The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most American style skyscrapers have a steel frame, while residential tower blocks are usually constructed out of concrete. •High-rise •High-rise structures have certain features. The structures are high &lead to higher vertical loads and higher lateral loads (mainly due to wind stress) in comparison with lower buildings. Horizontal Loads •Calculation of lateral loads should be carefully scrutinized. •It generally arises from unexpected deflections, wind and earthquake loads Live loads are dependent on use depending on the number of stories, live loads can be reduced for load transfer and the dimensioning of vertical load-bearing elements. Rigid Frame Structure are structure that is consist of columns and girders joined by moment resistant connections. INTRODUCTION A skyscraper skyscraper is a tall, continuously continuously habitable habitable building building of many storeys, usually usually designed designed for office and commercial use. There is no official definition or height above which a building may be classified as a skyscraper. One common feature of skyscrapers is having a steel framework from which curtain walls are suspended, rather than load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete. Modern skyscrapers' walls are not load-bearing, and most skyscrapers are characterized by large surface areas of windows made possible by the concept of steel frame and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls and a small surface area of windows. Skyscrapers since the 1960s use the tubular designs, innovated by Bangladeshi American structural structural engineer engineer Fazlur Fazlur Rahman Khan. This engineering engineering principle principle makes the buildings structurally more efficient and stronger. It reduces the usage of material (economically much more efficient), while simultaneously allows the buildings to reach greater heights. It allows fewer interior columns, and so creates more usable floor space. It further enables buildings to take on various shapes. There are several variations of the tubular design; these structural systems are fundamental to tall building design today.Other pioneers include Hal Iyengar, William LeMessurier, etc. Cities have experienced a huge surge in skyscraper construction. Today, skyscrapers are an increasingly common sight where land is expensive, as in the centres of big cities, because they provide such a high ratio of rentable floor space per unit area of land. They are built not just for economy of space; like temples and palaces of the past, skyscrapers are considered symbols of a city's economic power. Not only do they define the skyline, they help to define the city's identity. In some cases, exceptionally tall skyscrapers have been built not out of necessity, but to help define the city's identity and presence or power as a city.
HISTORY Building construction is an ancient human activity. It began with the purely functional need for a controlled environment to moderate the effects of climate. Constructed shelters were one means by which human beings were able to adapt themselves to a wide variety of climates and become a global species. Pre-19th Century Until the 19th century, buildings of over six storeys were rare, as having great numbers of stairs to climb was impractical for inhabitants, and water pressure was usually insufficient to supply running water above 50 m (164 ft). The tallest building in ancient times was the 146 m (479 ft) Great Pyramid of Giza in ancient Egypt, built in the 26th century BCE. It was not surpassed in height for thousands of years, the 14th century CE Lincoln Cathedral being conjectured by many to exceed it.[16] The latter in turn was not surpassed until the 555 feet (169 m) Washington Monument in 1884. However, being uninhabited, none of these structures actually comply with the modern definition of a skyscraper. High-rise apartments flourished in classical antiquity. Ancient Roman insulae there and in other imperial cities reached 10 and more storeys. Beginning with Augustus (r. 30 BCE-14 CE), several emperors attempted to establish limits of 20 – 20 –25 25 m for multi-storey buildings, but met with only limited success. Lower floors were typically occupied by shops or wealthy families, the upper rented to the lower classes. Surviving Oxyrhynchus Papyri indicate that seven-storey buildings existed in provincial towns such as in 3rd century CE Hermopolis in Roman Egypt. The skylines of many important medieval cities had large numbers of high-rise urban towers, built by the wealthy for defense and status. The residential Towers of 12th century Bologna numbered between 80 to 100 at a time, the tallest of which is the 97.2 m (319 ft) high Asinelli Tower. Tower. A Florentine Florentine law of of 1251 decreed decreed that that all urban buildings buildings be be immediately immediately reduced to less than 26 m. Even medium-sized towns of the era are known to have proliferations of towers, such as the 72 up to 51 m height in San Gimignano. The medieval Egyptian city of Fustat housed many high-rise residential buildings, which Al-Muqaddasi Al-Muqaddasi in the 10th 10th century century described described as resembling resembling minarets. minarets. Nasir Nasir Khusraw in in the early 11th century described some of them rising up to 14 storeys, with roof gardens on the top floor complete with ox-drawn water wheels for irrigating them. Cairo in the 16th century had high-rise apartment buildings where the two lower floors were for commercial and storage purposes and the multiple storeys above them were rented out to tenants. An early example of a city consisting entirely of high-rise housing is the 16th-century city of Shibam in Yemen. Shibam was made up of over 500 tower houses, each one rising 5 to 11 storeys high, with each floor being an apartment occupied by a single family. The city was built in this way in order to protect it from Bedouin attacks. Shibam still has the tallest mudbrick buildings in the world, with many of them over 30 m (98 ft) high. An early modern modern example example of high-rise high-rise housing housing was in 17th-century 17th-century Edinburgh, Edinburgh, Scotland, Scotland, where a defensive city wall defined the boundaries of the city. Due to the restricted land area available for development, the houses increased in height instead. Buildings of 11 storeys were common, and there are records of buildings as high as 14 storeys. Many of the stone-built structures can still be seen today in the old town of Edinburgh. The oldest iron framed building in the world, although only partially iron framed, is The Flaxmill (also locally known as the "Maltings"), "Maltings"), in Shrewsbury, England. Built in 1797, it is seen as the "grandfather of skyscrapers”, since its fireproof combination of cast iron columns and cast iron beams developed into the modern steel frame that made modern skyscrapers possible. In 2013 funding was confirmed to convert the derelict building into offices.
Early Skyscraper In 1852 Elisha Otis introduced the safety elevator, allowing convenient and safe passenger movement to upper floors. Another crucial development was the use of a steel frame instead of stone or brick, otherwise the walls on the lower floors on a tall building would be too thick to be practical. An early development in this area was Oriel Chambers in Liverpool. Designed by local architect Peter Ellis in 1864, the building was the world's first iron-framed, glass curtain-walled office building. It was only 5 floors high. Further developments led to the world's first skyscraper, the ten-storey Home Insurance Building in Chicago, built in 1884 – 1884 –1885. 1885. While its height is not considered very impressive today, it was at that time. The architect, Major William Le Baron Jenney, created a load-bearing structural frame. In this building, a steel frame supported the entire weight of the walls, instead of load-bearing walls carrying the weight of the building. This development led to the "Chicago skeleton" form of construction. In addition to the steel frame, the Home Insurance Building also utilized fireproofing, elevators, and electrical wiring, key elements in most skyscrapers today. Burnham and Root's 1889 Rand McNally Building in Chicago, 1889, was the first allsteel framed skyscraper, while Louis Sullivan's Sullivan's Wainwright Wainwrig ht Building in St. Louis, Missouri, Missouri, 1891, was the first steel-framed building with soaring vertical bands to emphasize the height of the building and is therefore considered by some to be the first true skyscraper. Most early skyscrapers emerged in the land-strapped areas of Chicago, London, and New York toward the end of the 19th century. A land boom in Melbourne, Australia between 1888 – 1888 –1891 1891 spurred the creation of a significant number of early skyscrapers, though none of these were steel reinforced and few remain today. Height limits and fire restrictions were later introduced. London builders soon found building heights limited due to a complaint from Queen Victoria, rules that continued to exist with few exceptions until the 1950s. Concerns about aesthetics and fire safety had likewise hampered the development of skyscrapers across continental Europe for the first half of the twentieth century (with the notable exceptions of the 1898 Witte Huis (White House) in Rotterdam; the Royal Liver Building in Liverpool, completed in 1911 and 90 m (300 ft) high; and the 17-storey Kungstornen (Kings' Towers) in Stockholm, Sweden, which were built 1924 –25, –25, the 15-storey Edificio Telefónica in Madrid, Spain, built in 1929; the 26-storey Boerentoren in Antwerp, Belgium, built in 1932; and the 31-storey Torre Piacentini in Genoa, Italy, built in 1940). After an early competition between Chicago and New York City for the world's tallest building, New York took the lead by 1895 with the completion of the American Surety Building, leaving New York with the title of tallest building for many years. New York City developers competed among themselves, with successively taller buildings claiming the title of "world's tallest" in the 1920s and early 1930s, culminating with the completion of the Chrysler Building in 1930 and the Empire State Building in 1931, the world's tallest building for forty years. The first completed World Trade Center tower became the world's tallest building in 1972. However, it was soon overtaken by the Sears Tower (now Willis Tower) in Chicago within two years. The Sears Tower stood as the world's tallest building for 24 years, from 1974 until 1998, until it was edged out by Petronas Twin Towers in Kuala Lumpur, which held the title for six years.
Modern Skyscraper Modern skyscrapers are built with steel or reinforced concrete frameworks and curtain walls of glass or polished stone. They utilize mechanical equipment such as water pumps and elevators. From the 1930s onwards, skyscrapers began to appear around the world - also in Latin America (such as São Paulo, Rio de Janeiro, Buenos Aires, Santiago, Caracas, Bogotá, Mexico City) and in Asia (Tokyo, Shanghai, Hong Kong, Manila, Singapore, Mumbai, Seoul, Kuala Lumpur, Taipei, Bangkok). Immediately after World War II, the Soviet Union planned eight massive skyscrapers dubbed "Stalin Towers" for Moscow; seven of these were eventually built. The rest of Europe also slowly began to permit skyscrapers, starting with Madrid, during the 1950s. Finally, skyscrapers also began to be constructed in cities of Africa, the Middle East and Oceania (mainly Australia) from the late 1950s. After the Great Depression skyscrapers construction was abandoned for over thirty years. German architect Ludwig Mies van der Rohe became one of the world's most renowned architects in the second half of the 20th century. He conceived of the glass façade skyscraper and designed the Seagram Building in 1958, a skyscraper that is often regarded as the pinnacle of the modernist high-rise architecture. In the early 1960s structural engineer Fazlur Khan realized that the rigid steel frame structure that had dominated tall building design and construction so long was not the only system fitting for tall buildings, marking the beginning of a new era of skyscraper revolution in terms of multiple structural systems. His central innovation in skyscraper design and construction was the idea of the "tube" structural system, including the "framed tube", "trussed tube", and "bundled tube". These systems allowed far greater economic efficiency, efficiency, and also allowed efficient skyscrapers to take on various shapes, no longer needing to be box-shaped. Over the next fifteen years, many towers were built by Khan and the "Second Chicago School", including the massive 442 m (1,450 ft) Willis Tower. The tubular systems are fundamental to tall building design. Since 2000, cities such as Chicago, Shanghai, Dubai, and New York have experienced a huge surge in skyscraper construction, thanks to the new tubular design. Chicago, Hong Kong, and New York City, otherwise known as "the big three," are recognized in architectural circles as having especially compelling skylines. A landmark skyscraper can inspire a boom of new high-rise projects in its city, as Taipei 101 has done in Taipei since its opening in 2004. In 2010, The Bank of America Tower at One Bryant Park became the world's first commercial LEED Platinum skyscraper.
TALL BUILDING STRUCTURES As building height increases, the three basic systems of lateral force resistance--- shear wall, braced frame, and rigid frame – may be employed in unique ways. The following tall building configurations are presented in order of suitability for structures of increasing height. The adjacent diagrams illustrate schematically in both plan and section each of the configurations described. CONVENTIONAL STRUCTURAL CONFIGURATIONS The conventional arrangements of stabilizing elements used in low-rise buildings may be extended for use in buildings up to 20 to 25 stories in height. The same considerations that apply to low-rise buildings apply to taller buildings as well: stabilizing elements should be arranged so as to resist lateral forces along all major axes of the building. These elements should be arranged in a balanced manner either within the building or at the perimeter. And such elements must be integrated with the building plan or elevation. Shear walls and braced frames are the stabilizing elements most commonly used in buildings of this height, due to their structural efficiency. They may be used either separately or in combination. The use of rigid frame systems are as the sole means of achieving lateral stability may be feasible in buildings up to 15-20 stories in height in areas of low seismic activity. However, even where feasible, rigid frame structures may be a less attractive option due to the greater difficulty of their fabrication and the increased size of the beams and columns required. More commonly in buildings of this height, rigid frame components are used in combination with either shear walls or braced frames to enhance the lateral resistance of the structure as a whole. RIGID FRAME STRUCTURE A rigid frame structure is is a structure structure made up up of linear linear element, typically beams and columns that are connected to one another at their ends with joints that do not allow any relative rotations to occur between the ends of the attached members, although the joints themselves may rotate as a unit. Members are essentially continuous through the joints. As with continuous beams, rigid-frame structures are statically indeterminate. Many rigid-frame structures resemble simpler post-and-beam systems in appearance, but are radically different in structural behavior, owing to the joint rigidity, which can be sufficient to enable a framed structure to carry significant lateral loads, something a simpler post-andbeam system cannot do without additional bracing elements. Variants of rigid frame structures
have been used for a long time. A common table, for example, typically derives its stability from the rigid joints that are used to connect the legs to the tabletop. The traditional knee-braced timber structure can also be thought of as a type of rigid-frame structure. Still, the rigid frame as a widely used structural device in major buildings is a relatively recent phenomenon. The development of the steel rigid frame in cities such as Chicago during the latter part of the 19 th and early part of the 20 th centuries is a major event in the history of structures. The related movement of separating and differentiating enclosure surfaces from supporting structural skeleton, made possible by the introduction of the rigid frame, also marks a major turning point in the history of architecture. This movement was a marked departure from traditional building practices that made extensive use of dualfunctioning elements, such as exterior load-bearing wall, which served simultaneously as both structural and enclosure. Summary of the Rigid Frame Definition Consist of columns and girders joined by moment resistant connections. Lateral stiffness of a rigid frame bent depends on the bending stiffness of the columns, girders, and connection in the plane of the bents. Ideally suited for reinforced concrete buildings because of the inherent rigidity of reinforced concrete joints. Also used for steel frame buildings, but momentresistant connections in steel tend to be costly. While rigid frame of a typical scale that serve alone to resist lateral loading have an economic height limit of about 25 stories, smaller scale rigid frames in the form of perimeter tube, or typically rigid frames in combination with shear walls or braced bents, can be economic up top much greater heights.
Advantages: May be place in or around the core, on the exterior, or throughout the interior of the building with minimal constraint on the planning module. The frame may be architecturally exposed to express the grid-like nature of the structure. The spacing of the columns in a moment resisting frame can match that required for gravity framing.
Disadvantages: rigid frames were suitable only at sites where unyielding foundations could be ensured, for uneven settlement produced a "bad effect" on their strength;
placing of steel reinforcement in the concrete required considerable skill; the sequence of concrete placement and removal of formwork was sometimes more complicated; and Design of rigid frame bridges was somewhat more complex because such structures were "statically indeterminate," and analysis was not as straightforward as in the case of statically determinate, simply supported spans. Only suitable for building up to 20 –30 –30 stories only; member proportions and materials cost become unreasonable for building higher than that.
Example
The Osaka World Trade Center Building comprises not only the main tower (with an impressive 76m x 35m footprint) but a low rise block and covered 3000 sq.m atrium as well. The project is park of the Technopark Osako development which comprises almost 800 hectares including three artificial islands in the bay. The tower houses public space, an auditorium, business support centres and office space (7th thru 44th floors). The upper floors house a World Trade Center Museum, restaurants, Cosmo Hall, and other functional components. It is within this building that the "highest" marriages in Japan often take place. The building is capped by the distinctive inverted pyramid which ofers 360-degree views of the city from the "Top of the Bay".
CORE STRUCTURES Core structures are the most commonly used system to stabilize tall buildings. The enclosures at the center of the building, used to house vertical circulation and other building systems, are structured to also serve as stabilizing elements. One of the principal advantages of core structures is that with the placement of the resisting elements in the building core, interference with the surrounding usable space is minimized. In concrete construction, core walls already intended to enclose building systems can easily be designed to also act as shear walls. In steel construction, core structures are usually designed as braced frames. A single core servicing an entire building should be located at the center of the building. In buildings with more than one core, the cores should be located symmetrically in the building plan so as to provide balanced resistance under lateral loads from any direction. Cores typically comprise approximately 20%-25% of the total floor area of a mid- or high-rise building. They should be formed as close elements, approximately square or cylindrical, with openings into the core kept to a minimum. Simple core structures can be used in buildings as high as 35 to 40 stories. Core structures can also be enhanced structurally with hat trusses( at the top of the structures) or belt trusses(at
points lower down) that engage the perimeter’s structural elements in the resistance to lateral loads, thus improving the performance of the building as a whole. These elements may become aesthetically expressed on the building façade or may be preferred locations for mechanical floors. Columns at the perimeter of the building may also increase in size with these systems. These core interactive structures are suitable for buildings up to approximately 60 stories in height. Outrigger serve to reduce the overturning moment in the core that would otherwise act as a pure cantilever, and to transfer the reduced moment to columns outside the core by the way of tension-compression coupled, which take advantage of the increase moment arm between these columns. It also serves to reduce the critical connection where the mast is stepped to the keel beam. In high-rise building this same benefit is realized by a reduction of the base core overturning moments and the associated reduction in the potential core uplift forces. In the foundations system, this core and outrigger system can lead to the need for the following: The addition of expensive and labor- intensive rock anchors to an otherwise “simple” foundation alternative such as spread footing. Greatly enlarged mat dimensions and depth solely to resist overturning forces. Time-consuming and costly rock sockets for caisson systems along with the need to develop reinforcement throughout the complete caisson depth. Expensive and intensive field work connection at the interface between core and the foundation. This connection can become particularly troublesome when one considers the difference in construction tolerances between foundations and core structure. The elimination from consideration of foundation systems which might have been considerably less expensive, such as pile, solely for their inability to resist significant uplift.
Advantages: The outrigger systems may be formed in any combination of steel, concrete, or composite construction. Core overturning moments and their associated induced deformation can be reduced through the “reverse” moment applied to the core at each outrigger intersection. This moment is created by the force couple at the exterior columns to which the outrigger connect. It can potentially increase the effective depth of the structural system from the core only to almost the complete building. Significant reduction and possibly the complete elimination of uplift and net tension forces throughout the column and the foundation systems. The exterior column spacing is not driven by structural considerations and can easily mesh with aesthetic and functional considerations. Exterior framing can consist of “simple” beam and column framing without the need for rigid-frame-type connections, resulting in economies. For rectangular buildings, outriggers can engage the middle columns on the long faces of the building under the application of wind loads in the more critical direction. In corealone and tubular systems, these columns which carry significant gravity load are either not incorporated or underutilized. In some cases, outrigger systems can efficiently incorporate almost every gravity column into lateral load resisting system, leading to significant economies.
Disadvantages The most significant drawback with use of outrigger systems is their potential interference with occupiable and rentable space.
This obstacle can be minimized or in some cases eliminate by incorporation of any of the following approaches: -Locating outrigger in mechanical and interstitial levels -Locating outriggers in the natural sloping lines of the building profile -Incorporating multilevel single diagonal outriggers to minimize the member’s interference on any single level. -Skewing and offsetting outriggers in order to mesh with the functional layout of the floor space. Another potential drawback is the impact the outrigger installation can have on the erection process. As a typical building erection proceeds, the repetitive nature of the structural framing and the reduction in member sizes generally result in a learning curve which can speed the process along. The incorporation of a outrigger at intermediate or upper levels can, if not approached properly, have a negative impact on the erection process. Several steps can be taken to minimize this possibility. Provide clear and concise erection guidelines in the contract documents so that the erector can anticipate the constraint and limitation that the installation will impose. If possible, avoid outriggers locations or design constraints that will require “backtracking” in the construction process to install or connect the outrigger. The incorporation of intermediate outriggers in concrete construction or large variation in dead-load column stresses between the core and the exterior can in some cases result in the need to “backtrack”. Such a need can be minimized if issues such as creep and differential shortening are carefully studied during the design process to minimize their impact. Avoid adding additional outrigger levels for borderline force or deflection control.
Example
Citibank Plaza is a modern office complex that comprises two towers and a retail podium. It is located at 3 Garden Road, Central, Hong Kong. Citibank Plaza is a modern glass and steel office complex in Hong Kong that comprises Citibank Tower, ICBC Tower, a 3 level basement garage capable of accommodating 558 vehicles, as well as a retail podium. With a gross floor area of almost 1,600,000 sq ft (150,000 m2)., Citibank Plaza is one of the biggest
office complexes in Hong Kong, capable of serving a working population of over 10,000. At 205 metres tall, Citibank Tower reaches up to the 50th floor. The highest floor on ICBC Tower is the 40th. Completed in 1992, it was one of the first office buildings in Hong Kong to incorporate intelligent building and environmentally friendly features. Citibank Plaza is considered considere d by many to be one of the Central District’s iconic structures. Besides its two characteristic curved reflective facades, the complex contains many distinct architectural features, such as the flexibility to join 26 floors of both towers to provide an enlarged floor plate of up to 34,000 sq ft (3,200 m2). Two ten-storey tall frameless glass panels provide the main lobby with natural lighting and allow visitors to “look thorough” the building. In recognition of excellence in the area of architectural design, Citibank Plaza was presented with the Hong Kong Institute of Architects’ highest award in 1994, the Silver Medal.
TUBE STRUCTURES Many of the world’s tallest buildings are designed as tube structures. In this system, stabilizing elements are located at the perimeter of the structure, leaving the layout of the interior of the building unrestricted by considerations of lateral stability. Either braced frame or rigid frame elements, constructed from either steel or concrete, may be used. Simple tube structures and their variations are generally suitable for buildings approximately 55 stories or greater in height. The use of rigid frame tubes may affect the size and spacing of framing elements at the perimeter of the building. Beams may need to be deeper and columns may need to be larger and more closely spaced than would otherwise be required. When building in steel, the welded joints required in this system may be more costly to construct, although construction systems have been developed that allow the off-site fabrication of these joints, minimizing this disadvantage. And as with core structures, the performance of rigid frame tubes may be enhanced with hat trusses or belt trusses integrated within the perimeter structure. Braced frame tubes are highly structurally efficient lateral load resisting configurations. When built in steel, these structures rely on more easily constructed hinged connections. The diagonal braces that are an integral part of this system often have a significant impact on the appearance of the building façade. Variations on the tube structure and other tall building configurations are also possible. Tube in tube structures allow perimeter tubes to interact with rigid cores. Bundled tube structures allow greater variation in building massing. Space truss structures are similar to braced tubes, with the addition of large scale diagonals that pass through the building’s interior. Diagrid structures rely on latticed frameworks that carry both vertical and lateral loads, with few or no vertical columns. Summary: Braced frames are cantilevered vertical trusses resisting laterals loads primarily through the axial stiffness of the frame members.
The effectiveness of the system, as characterized by a high ratio of stiffness to material quantity, is recognized for multistory building in the low to mid height range. Generally regarded as an exclusively steel system because the diagonal are inevitably subjected to tension for or to the other directions of lateral loading. Able to produce a laterally very stiff structure for a minimum of additional material, makes it an economical structural form for any height of buildings, up to the very tallest. Advantages Girders only participate minimally in the lateral bracing action-Floor framing design is independent of its level in the structure Can be repetitive up the height of the building with obvious economy in design and fabrication.
Disadvantages Obstruct the internal planning and the locations of the windows and doors; for this reason, braced bent are usually incorporated internally along wall and partition lines, especially around elevator, stair, and service shaft. Diagonal connections are expensive to fabricate and erect.
Example ACT TOWER Hamamatsu City, Japan
Act Tower ( アクトシティ浜松 ?) is a skyscraper in Hamamatsu, Shizuoka Prefecture, Japan. It is 213 metres (699 ft) tall, and has 45 floors, making it the tallest building in Hamamatsu, and the tallest building in Japan outside of the Tokyo, Osaka, and Nagoya metropolitan areas.[citation needed] It was constructed in 1994, and houses the Okura City Hotel in its top 17 floors, as well as observation deck on its top floor. The building was designed to resemble a harmonica, in line with Hamamatsu's notable music culture.
OBJECTIVE To provide definitions that makes it possible to point out the essential characteristics of a framed structure. Attention is given to joint behaviour and to the problem of the choice of structural model depending on the loads acting on the structure. CONCLUSION Selection of frame Structures of the high rise building is due to the versatility and advantages over the normal traditional load bearing structures. Actually, the performance of load bearing structures is usually dependent on the mass of the structures. To fulfill this requirement of load bearing structures, there is the need of increase in volume of the structural elements leads toward the construction of thick wall. Due to such type of construction, labor and construction cost increases, in construction of thick wall there will be the need of great attention, which will further reduce the speed of construction. If we make the contrast of load bearing structure with the framed structures appear to be more flexible, economical and can carry the heavy loads. Frame structures can be rehabilitated at any time. Different services can be provided in frame structures. Thus frame structures are flexible in use.
