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Lecture 8 THigh Rise structures.pdf
- 1. HIGHRISE STRUCTURES- I Lecture 8 Dr Anjali S Patil
- 2. DEMAND FOR HIGH-RISE BUILDINGS High rise buildings are becoming more prominent these days due to following reasons ◻ scarcity of land ◻ increasing demand for business and residential space ◻ economic growth ◻ ◻ ◻ technological advancement ◻ innovations in structural systems ◻ desire for aesthetics in urban settings ◻ cultural significance and prestige ◻ human aspiration to build higher
- 3. High rise is defined differently by different bodies Emporis standards- “A multi-story structure between 35-100 meters tall, or a building of unknown height from 12-39 floors is termed as high rise. Massachusetts, United States General Laws – A high-rise is being higher than 70 feet (21 m). higher than 70 feet (21 m). Buildings higher than 100m is termed as skyscraper according to emporis. Buildings 300m or higher is termed as super tall and buildings 600m or taller is termed as mega-tall.
- 4. Timeline of high rise structures
- 5. STRUCTURE SYSTEMS • Bearing wall structures (upto approximately 28 stories) • Core structures (and bridge structures) • Suspension buildings • Skeleton structures and flat slab building structures • Rigid frame (upto 30 stories) • Braced frame structures : frame with shear wall/ core (45 stories) • Braced frame structures : frame with shear wall/ core (45 stories) • Staggered wall- beam structures (upto 40 stories) • Frame with shear, band and outrigger trusses (upto 60 stories) • Partial tubular frames (upto 65 stories) • Exterior framed tubular (upto 90 stories) • bundled framed tubes (upto 110 stories) • Exterior diagonalised tubes (upto 115 stories) • Mega structures • Hybrid structures
- 6. DEVELOPMENT OF STRUCTURAL SYSTEM M S First Generation1780-1850 ⮚ The exterior walls of these buildings consisted of stone or brick, although sometimes cast iron was added for decorative purposes. ⮚ The columns were constructed of cast iron, often unprotected; steel and wrought iron was used for the beams; and the floors were made of wood. HOME INSURANCE BUILDING and the floors were made of wood. Second Generation 1850-1940 ⮚ The second generation of tall buildings, which includes the Metropolitan Life Building (1909), the Woolworth Building (1913), and the Empire State Building (1931), are frame structures, in which a skeleton of welded- or riveted-steel columns and beams, often encased in concrete, runs through the entire building. ⮚ This type of construction makes for an extremely strong structure, but not such attractive floor space. The interiors are full of heavy, load-bearing columns and walls EMPIRE STATE BUILDING
- 7. DEVELOPMENT OF STRUCTURAL SYSTEMS Third Generation 1940-present ⮚ Buildings constructed from after World War II until today make up the most recent generation of high-rise buildings. ⮚ Within this generation there are those of steel- framed construction( core construction and tube construction ), reinforced concrete tube construction ), reinforced concrete construction(shear wall), and steel-framed reinforced concrete construction . ⮚ Hybrid systems also evolved during this time. These systems make use more than one type of structural system in a building. Burj Khalifa, in Dubai
- 9. TALL BUILDING TRENDS IN 2013 Considering the worlds 100 tallest buildings in 1990: ◻ 80 percent were located in North America. ◻ Almost 90 percent were exclusively office use. ◻ More than half were constructed of steel. ◻ In 2013, for the world's 100 tallest buildings: ◻ The largest share (43 percent) are now in Asia. (Only one new 200-m-plus building was built in North America in 2013, compared to 54 in Asia.) ◻ Less than 50 percent are exclusively office use. Almost a quarter are mixed-use and 14 percent are residential. ◻ Almost half were constructed of reinforced concrete and only 14 percent of steel. (The remaining are composite or mixed structural materials.)
- 10. TALL BUILDING TRENDS IN 2013 A composite tall building utilizes a combination of both steel and concrete acting compositely in the main structural elements. A mixed—structure tall building is any building that utilizes distinct steel or concrete systems above or below each other. Structural material usage from 1930 to 2013
- 11. STRUCTURAL CONCERNS ◻ The primary structural skeleton of a tall building can be visualized as a vertical cantilever beam with its base fixed in the ground. The structure has to carry the vertical gravity loads and the lateral wind and earthquake loads. ◻ Gravity loads are caused by dead and live loads. Lateral loads tend to snap the building or topple it. The building must therefore have adequate shear and bending resistance and must not lose its vertical load-carrying capability. The skyscraper pushes down on into the ground .But when the wind blows, the columns in the windy side stretch apart, and the columns on the other side squeeze together.
- 12. Variation of wind load with the variation of forms Round shape Minimum wind pressure Irregular shape Maximum wind pressure Plan view
- 13. LOAD DISTRIBUTION SYSTEM : All type of loads can be considered as_ • Vertical load & • Lateral load Vertical loads transfer through_ • Bearing wall • Column • Column • Core • Diagonal frame Lateral loads transfer through_ • Shear wall • Slab • Beam • Diagonal Frame
- 14. Structural member: Beam : Beam is a rigid structural member designed to carry and transfer loads across spaces to supporting elements. Column : A rigid relativity slender structural member designed primarily to support axial compressive loads applied at the member ends. In high rise buildings it can be use as mega column, In high rise buildings it can be use as mega column, concrete filled tubular(CFT) etc. Shear wall: A vertical diaphragm or wall acting as a thin, deep cantilever beam in loads to the ground foundation. Bracing : It is a structural element for positioning, supporting, strengthening or restraining the member of a structural frame.
- 15. Core : Core is one of the most important structural and functional elements of the high rise building. The core of a building is the area reserved for elevators’ stairs, mechanical equipments and the vertical shafts that are necessary for ducts, pipes and wires. Its wall are also the most common location for the vertical wind bracing. The placement of the service core stems from four generic types which are : which are : - Central core - Split core - End core - Atrium core Central core End core Atrium core split core
- 16. Type I : Shear Frames Type II : Interacting Systems Type III: Partial Tubular Systems Type IV: Tubular Systems (CTBUH, 1980) Structural typology: According to ‘Council on Tall Buildings and Urban habitat’ there are four types of structural system- According to Mir M. Ali and Kyoung Sun Moon, Structural systems of tall buildings can be divided into two broad categories- 1.interior structures and 2.exterior structures. According to material it can be also- 1. Concrete type and 2. steel type
- 17. INTERIOR STRUCTURES By clustering steel columns and beams in the core, engineers create a stiff backbone that can resist tremendous wind forces. The inner core is used as an elevator shaft , and the design allows lots of open space on each floor Interior structure 1. Rigid Frames 2. Shear Wall Hinged Frames 3.Shear Wall (or Shear Truss) - Frame Interaction System 4. Outrigger Structures Interior and exterior classification is based on the distribution of the components of the primary lateral load-resisting system over the building. 4. Outrigger Structures EXTERIOR STRUCTURES In newer skyscrapers, like the Sears Tower in Chicago, engineers moved the columns and beams from the core to the perimeter, creating a hollow, rigid tube as strong as the core design, but weighing much, much less. Exterior structure 1. Tube 2. Diagrid 3. Space Truss Structures 4. Super frames 5. Exo-skeleton
- 18. INTERIOR STRUCTURES By clustering steel columns and beams in the core, engineers create a stiff backbone that can resist tremendous wind forces. The inner core is used as an elevator shaft , and the design allows lots of open space on each floor EXTERIOR STRUCTURES In newer skyscrapers, like the Sears Tower in Chicago, engineers moved the columns and beams from the core to the perimeter, creating a hollow, rigid tube as strong as the core design, but weighing much, much less.
- 20. INTERIOR STRUCTURAL SYSTEM 1)RIGID FRAME ◻ A rigid frame in structural engineering is the load- resisting skeleton constructed with straight or curved members interconnected by mostly rigid connections which resist movements induced at the joints of members. Its members can take bending moment, shear, and axial loads. ◻ Consist of columns and girders joined by moment Seagram building ◻ Consist of columns and girders joined by moment resistant connections. ◻ Can build upto 20 to 25 floors 2)SHEAR WALL STRUCTURE ◻ Concrete or masonry continuous vertical walls may serve both architecturally partitions and structurally to carry gravity and lateral loading. Very high in plane stiffness and strength make them ideally suited for bracing tall building ◻ Usually built as the core of the building ◻ Can build upto 35 Floors Shear wall core
- 21. 3)OUTRIGGER STRUCTURES ◻ The core may be centrally located with outriggers extending on both sides or in some cases it may be located on one side of the building with outriggers extending to the building columns on the other side ◻ The outriggers are generally in the form of trusses (1 or 2 story deep) in steel ◻ form of trusses (1 or 2 story deep) in steel structures, or walls in concrete structures, that effectively act as stiff headers inducing a tension- compression couple in the outer columns. ◻ Belt trusses are often provided to distribute these tensile and compressive forces to a large number of exterior frame columns. ◻ An build upto 150 floors Shangai World financial centre
- 22. EXTERIOR STRUCTURES 1)Tube system ◻ The tube system concept is based on the idea that a building can be designed to resist lateral loads by designing it as a hollow cantilever perpendicular to the ground. In the simplest incarnation of the tube, the perimeter of the exterior consists of closely spaced columns that are tied closely spaced columns that are tied together with deep spandrel beams through moment connections. This assembly of columns and beams forms a rigid frame that amounts to a dense and strong structural wall along the exterior of the building. ◻ The different tubular systems are- ◻ 1)Framed tube 2)Braced tube 3)Bundled tube 4)Tube in tube
- 23. 2)Diagrid systems ◻ With their structural efficiency as a varied version of the tubular systems, diagrid structures have been emerging as a new aesthetic trend for tall buildings in this era of pluralistic styles. ◻ Early designs of tall buildings recognized the effectiveness of diagonal bracing members in ◻ effectiveness of diagonal bracing members in resisting lateral forces. ◻ Most of the structural systems deployed for early tall buildings were steel frames with diagonal bracings of various configurations such as X, K, and chevron. However, while the structural importance of diagonals was well recognized, the aesthetic potential of them was not appreciated since they were considered obstructive for viewing the outdoors. ◻ Efficiently resists lateral shear by axial forces in the diagonal members but have Complicated joints Hearst tower , New York
- 24. 3)Space truss ◻ Space truss structures are modified braced tubes with diagonals connecting the exterior to interior. In a typical braced tube structure, all the diagonals, which connect the chord members – vertical corner columns in general, are located on the plane parallel to the facades. ◻ However, in space trusses, some diagonals penetrate the interior of the building. ◻ Bank of China, Hong Kon ◻ 4)Exo skeleton structure ◻ In exoskeleton structures, lateral load-resisting systems are placed outside the building lines away from their facades. ◻ Due to the system’s compositional characteristics, it acts as a primary building identifier – one of the major roles of building facades in general cases. ◻ Fire proofing of the system is not a serious issue due to its location outside the building line. Hotel de las Atres
- 25. 5)Super frame structures ◻ Superframe structures can create ultra high-rise buildings upto 160 floors. ◻ Superframes or Megaframes assume the form of a portal which is provided on the exterior of a building. ◻ The frames resist all wind forces ◻ The frames resist all wind forces as an exterior tubular structure. The portal frame of the Superframe is composed of vertical legs in each corner of the building which are linked by horizontal elements at about every 12 to 14 floors. ◻ Since the vertical elements are concentrated in the corner areas of the building, maximum efficiency is obtained for resisting wind forces.
- 26. CONCLUSION ◻ With the present technology and known materials , it is possible to build more higher and faster. ◻ It is now possible to build skyscrapers so fast using pre- fabricated units that it can lead to environmental problems, stress on resources and overcrowding if not controlled. ◻ To build higher the base of the building will have to be made ◻ To build higher the base of the building will have to be made wider. The bundled tube system was a great innovation and was able to span great heights during it's time , to attain the height of burj khalifa the bundled tube system will need a bigger base when compared with the buttressed core system. ◻ New improved structural systems and new materials in the future can lead us to even greater heights and more stable buildings. It’s not technology holding buildings back. It’s money.
- 27. References : • Council on Tall Buildings and Urban Habitat. (CTBUH) • Structural Developments in Tall Buildings: Current Trends and Future Prospects -Mir M. Ali† and Kyoung Sun Moon • http://www.aij.or.jp/jpn/symposium/2006/loads/Chapter7_com.pdf • High-rise building structure -Wolfgang Schueller www.greatbuilding.com . • www.greatbuilding.com . • www.riba.com .