Tall Building MKA Jan 2011

BLD 510 Construction Technology III

BSc (Hons) Construction Management


TALL BUILDINGS Prepared and Presented By:

MUHAMMAD KAMAL AHMAD Building Department Faculty of Architecture, Planning and Surveying University of Technology MARA

CONTENTS 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0

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INTRODUCTION EVOLUTION OF TALL BUILDING WORLD TALLEST BUILDING PLANNING CONSIDERATION DESIGN FACTORS LOAD ACTION ON TALL BUILDING TALL BUILDING STRUCTURAL SYSTEM VERTICAL LOADING SYSTEMS HORIZONTAL LOADING SYSTEMS FLOOR SYSTEM FOR TALL BUILDING WALLS SYSTEM FOR TALL BUILDING FOUNDATION SYSTEM FOR TALL BUILDING CONSTRUCTION ASPECT OF TALL BUILDING SAFETY SYSTEM FOR TALL BUILDING

Building Department, UiTM

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1.0 INTRODUCTION

The term ‘tall buildings’ is not defined in specific term related to height or the number of storeys. A building is considered tall when its structural analysis and design are in some way affected by the lateral loads, particularly sway caused by such loads.

According to Emporis Standards Committee (ESC) Tall Building is defined as a building 35 meters or greater in height, which is divided at regular intervals into occupiable levels. To be considered a high-rise building a structure must be based on solid ground, and fabricated along its full height through deliberate processes (as opposed to naturally-occurring formations).

According to the regulations of Danish, German and some other European countries, the 72ft. (21.6m = 8 stories buildings), having fire-fighting equipment, are known as tall buildings.

Definitions represented by the U.S. Council on tall buildings and urban settlement refers to tall buildings as these in which the height, influences the planning, construction and spaces application aspects of the building considerably without specifying the number of stories.

1.1 REASON FOR USING TALL BUILDING SPACE LIMITATION • the process migration

urban

• increase in the population density of cities • increasing land prices make it necessary to maximise space utilisation by building upwards.

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PRESTIGE • free imposing advertisements for their owners and even the city it is sited. • as a show of economic power

political

or

• dominate the landscape and easily become landmarks •human ego and competition


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2.0 EVOLUTION OF TALL BUILDING 3 2 1

Reinforced concrete established. Architectural emphasis on reasons, functional and technological facts. Transition of structural systems from rigid frame to more efficient structural systems

Steel structures and sophisticated services such as mechanical lifts and ventilation, limitations on the height of buildings were removed.

Masonry wall bearing structures with thick and messy walls. The horizontal and lateral loads of these structures were mainly Resisted solely by the load bearing masonry walls.

The First Evolution of Tall Buildings

Reliance Building Chicago, 1894

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Guaranty Building, Buffalo, 1895.

Carson Pirie Scott Department Store, Chicago, 1904


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The Second Evolution of Tall Buildings

Woolworth Building, New York, 1930

Chrysler Building, New York, 1930

Empire State Building, New York, 1931 (highest structure in 19th century)

The Third Evolution of Tall Buildings

World Trade Centre, New York, 1972

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Sears Tower, Chicago, 1974

Petronas Twin Tower, Kuala Lumpur, 1996.


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3.0 WORLD TALLEST BUILDINGS

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List of World Tallest Buildings

Refer to Appendix 1. Refer to Appendix 2

4.0 PLANNING CONSIDERATIONS

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The selection of a tall building structure is not based merely on understanding the structure in its own context. The selection may be more function of factors related to cultural, social, economical and technological needs. Some of the factors: a. General Economic Considerations b. Soil Condition c. Height to width Ratio of a Building d. Fabrication and Erection Consideration e. Mechanical Systems Considerations f. Fire Rating Considerations g. Local Considerations h. Availability and Cost of Main Construction Materials


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a. General Economic Considerations

How much the projects costs to build. How much the finished project costs to operate (e.g. expenses associated with utilities, maintenance, insurance, taxes, interest on borrowed money) As the height of the building increases, more and more space is needed for structure, mechanical systems and elevators, leaving less rental space. The costs of elevators and mechanical systems increase with height. Cost for sophisticated construction equipment as building get taller.

b. Soil Condition

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The performance of a building is dependent on the strength of the soil which it is founded. The foundation or substructure binds the superstructure to the soil. If the bearing capacity of the soil is rather low, piles or caissons may be required to reach the proper foundation support.


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c. Height –toto- Width Ratio of Building

As the minimum height-towidth ratio increases, so should the building’s inherent stiffness The stiffness of the building structure is dependent on size and number of bays, structural systems and rigidity of members and connections. The general height-to-width for a plane frame structure in the range of 5 to 7.

d. Fabrication and Erection Considerations

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The planning of fabrication and erection procedures may indicate important factors concerning structural systems selection. Should be a minimum number of structural pieces to shorten construction time, complicated closed form shapes should be avoided and field welding should be minimized.


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e. Mechanical Systems Considerations

Average more than one-third of total tall building costs. Effects on the building overall appearance and economic selection of a structural systems.

f. Fire Rating Considerations

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Almost all floors are beyond the reach of fire truck ladders, fire fighting and rescue action are from the inside of a building. Total emergency evacuation is impossible within a reasonably short period of time. Must be able to ensure the following: * structural integrity for a certain period of time. * confinement of the fire, to prevent it from spreading to certain building areas. * adequate exit systems. * effective smoke and fire detection systems. * sprinklers and necessary smoke and heat venting.


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g. Local Considerations

For example, height limitation, zoning regulations.

h. Availability and Cost of Main Construction Materials

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If a desired material is hard to acquire, it may delay the building schedule and add significantly to building costs.


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Mobility

Evacuatian

Materials

DESIGN AND CONSTRUCTION CONSIDERATION Earthquakes

Heat

Wind

Speed

5.0 DESIGN the structural elements of the building must responds to all this forces where members must be arranged and connected to one another in such manner as to absorb the forces and guide them safely with a minimum effort to the ground.

building envelope has to accommodate the differences in temperature, air pressure and humidity between exterior and interior environments

requires a team approach between the various disciplines of design, material fabrication and building construction

building must cope with vertical forces of gravity and horizontal forces of wind above grund and the seismic forces below ground

TOTAL DESIGN APPROACH

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Design Parameters

Design Process and Tools

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Design Elements of Tall Building Form

6.0 LOAD ACTION ON TALL BUILDINGS Dead Loads Live Loads Wind Loads Seismic Loading Construction Loads

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Loads Due to Restrained Volume Changes of Materials Rain, Snow & Ice Loads Water and Earth Pressure Loads Impact and Dynamic Loads Blast Loads Combination of Loads


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a. Dead Load

Static forces caused by the weight of every element within the structure. The forces resulting in dead load consists of the weights of the load bearing elements of the building, floor and ceiling finishes, permanent partition walls, façade cladding, storage tanks, mechanical distribution systems etc.

b. Live Load

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‘Occupancy Loads’ : Loads caused by the contents of objects within or on a building. Not part of the structure Include weights of people, furniture, movable partitions, mechanical equipments (e.g computers, business machines) etc. Variable and unpredictable. Change in live loads not only over time but also as a function of location.


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c. Wind Loads

Lateral action caused by winds. Wind velocity in general increases with height. The taller the building is, the more exposed the building to strong winds. Can cause the parts of the external wall or roof to be blown off. If the building is slender, it will sway or vibrate in the wind. Major problem for the designer of tall buildings.

d. Seismic Loading The earth’s crust is not static; its subject to constant motion. Seismic motion acts on the building by shaking the foundation back and forth. The mass of the building resists this motion, setting up inertia forces throughout the structure

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e. Construction Loads

Loads during construction of a building – example contractors commonly stockpile heavy equipment and materials on a small area of the structure. Causes concentrated loads that are much larger than the assumed live loads which the structure was designed.

Spatia Elements

Surface Elements

Linear Elements

7.0 TALL BUILDING STRUCTURAL SYSTEMS

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- Column and Beam - Capable of resisting axial and rotational beam

- Wall : either solid with peforation or trussed, capable of carrying axial and rotational forces

- Floor : solid or ribbed, supported on floor framing, capable of supporting forces in and perpendicular to the plane

- Façade envelope or core for example, tying the building together to act as a unit


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- types of structural systems

Parallel Bearing Walls Cores and Façade Bearing Walls Self Supporting Boxes Cantilevered Slab Flat Slab Interspatial Suspension Staggered Truss Rigid Frame Rigid Frame and Core Trussed Frame Belt-Trussed and Core Tube in Tube Bundled Tube

a. Parallel Bearing Walls

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Comprised of plannar vertical elements that are prestressed by their own weight, thus efficiently absorb lateral force action. Used mostly for apartment building ahere large free spaces are not needed and mechanical systems do not necessitate core structures.


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b. Cores and Facades Bearing Walls

Planar vertical elements form exterior walls around a core structure. This allows for open interior spaces, which depend on the spanning capacities of the floor structure. The core houses mechanical and vertical transportation systems and adds to the stiffenes of the building

c. Rigid Frame

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Rigid joints are used between an assemblage of linear elements to form vertical and horizontal planes. The vertical planes consists of columns and girders mostly on a rectangular grid A similar organizational grid is used is used for the horizontal planes consisting of beams and girders. With the integrity of the spatial skeleton depending on the strength and rigidity of the individual columns and beams, story height and column spacing become controlling design considerations


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d. Rigid Frame and Core

As rigid frame but introducing a core structure to increase the lateral resistance of the building as a result of the core and frame interaction. The core systems house the mechanical and vertical transportation systems.

e. Self Supporting Boxes

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Boxes are prefabricated three dimensional units that resemble the bearing wall when they are place and joined together. The boxes are stacked like bricks in the ’English pattern bond’ resulting in a criss crossed wall beam system.


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f. Cantilevered Slab

Supporting the floor systems from a central core allown for a column-free space with the strength of the slab as the limit of the building size. Large quantities of steel are required especially with large slab projections. Slab stiffenes can be increased by tacking advantage of prestressing techniques.

g. Flat Slab Generally consists of uniformly thick concrete floor slabs supported on columns No deep beams allowing for a mimimum story height

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h. Interspatial

Cantilevered story high framed structures are employed on every other floor to create usable space within and above the frame. The space within the framed floor is used for fixed operations, and the totally free space above the frame can adapt to any type of activity.

i. Suspension Employing hangers instead of columns to carry the floor loads. The cables carry the gravity loads to trusses cantilevering from a central core.

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j. Staggered Truss

Story-high trusses are arranged so that each building floor rests alternatively on the top chord of one truss and the bottom of the next. Besides carrying the vertical loads, this truss arrangement minimizes wind bracing requirements by transferring wind loads to the base through web members and floor slab.

k. Trussed Frame

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Combining a rigid (or hinged) frame with vertical shear trusses provides an increase in strength and stiffenes of the structure. The design of the structure may be based on using the frame for the resistance of gravity loads and the vertical truss for wind loads similar to the riogid frame and core case.


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l. Belt Trussed Frame and Core

Belt trusses tie the façade columns to the core, thus eliminating the individual action of frame and core. The bracing is called cap trussing when it is on the top of the building and belt trussing when around lower sections.

m. Tube in Tube

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The exterior columns and beams are spaced so closely that the façade has the appearance of a wall with perforated window openings. The entire building acts as a hollow tube cantilevering out of the ground. The interior core (tube) increases the stiffenes of the building by sharing the loads with the facade tube.


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n. Bundled Tube An assemblage of individual tubes resulting in a multiple-cell tube. The increase in stiffnes is apparent and allows for the greates height and the most floor area.

STRUCTURAL SYSTEMS FOR TALL BUILDINGS OF DIFFERENT HEIGHTS

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Efficiency of structural systems of tall buildings Stories

Slender

Empire State Building, New York

Building Cases

1931

Year

102

9.3

2.02

kN/m2

Braced rigid frame

Structural

John Hancock Centre, Chicago

1968

100

7.9

1.42

Trussed tube

World Trade Centre, New York

1972

110

6.9

1.77

Frame tube

Sears Tower, Chicago

1974

109

6.4

1.58

Bundled tube

Chase Manhattan, New York

1963

60

7.3

2.64

Braced rigid frame

US Steel Building, Pittsburgh

1971

64

6.3

1.44

Shearwalls+outrigger+belt trusses

IDS Centre, Minneapolis

1971

57

6.1

0.86

Shearwalls+outrigger+belt trusses

Boston Co. Building, Boston

1970

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4.1

1.01

K-braced tube

Alcoa Building, San Francisco

1969

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4.0

1.24

Latticed tube

John Hancock Centre Empire State Building

U.S Steel Tower

Alcoa Building, San Francisco

Boston Co. Building, Boston

8.0 VERTICAL LOADING SYSTEMS OF TALL BUILDINGS

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The main function of the vertical loading systems is to transfer the dead and live loads of the superstructure to the substructure. Systems of transferring the loads: - Structural Wall System - Skeleton frame System - Suspension System - Composite Wall Frame System - Cantilevered Floor System - Transfers System


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a. Structural Wall System

Loads are transmitted to the ground via floor and wall (designed as load bearing wall). Masonry and brick load bearing were common during the late 19th and late 20th century. Now load bearing walls are made from reinforced concrete ;high performance concrete (HPC) . Usually of precast concrete panels systems and cast in situ concrete buildings using ‘tunnel forms’. Usually residential type because the internal wall layout do not need to be changeable such as in office building.

b. Skeleton Frame System

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Loads are transferred to the beam and column grid to the ground. Using RC or Steel frame. Faster to erect especially when structural steel is used


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c. Suspension System

The floors of the building are suspended over a long span. Ability to provide a column free floor. Three types: i. Hanger system ii. Bridge System iii. Catenary System

i. Hanger System

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Loads are transmitted upwards through vertical tensile members to outrigger arms. The loads are then transferred from the outriggers to one or more piers that transmit the loads to the ground. The tensile members can be hangers or cables and the pier tower are either monolithic reinforced concrete load bearing walls or steel framed tower. e.g Sabah Foundation Building ; Hong Kong & Shanghai Bank Building, Hongkong.

Central Pier Tower

Tension Ring

Hanger Elements

Curtain Wall Facade

Sabah Foundation Building Structural System


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Hongkong & Shanghai Bank Building, Hong Kong

ii. Bridge System

The floor slabs are suspended between two or more towers or mega columns. No intermediate columns used to support the floor slabs. e.g ; Tabung Haji Building, Petronas Twin Towers, OCBC Singapore.

Tabung Haji Building

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OCBC Singapore

Corner core RC tower ; contains either stairs or risers and toilets

Central core RC tower; contains lifts shafts

Floor slab structural girder and beams

Knights of Columbus Building


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iii. Cantenary System

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Example: Federal Reserve bank of Minneapolis Consisted of a pair of catenary members that span between two towers. Both catenary members lie on the long facades of the building


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d. Composite Wall-Frame System

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The skeleton frame and structural load bearing walls are used together. Several arrangements: i. - the wall are arranged to form a core. - the frame surrounds the core walls. - tubes configuration. ii.- the walls are located at opposite ends of square shaped plan; generally Cshaped. - the frame is located between the end walls. iii.- the walls are located at the corners of square shaped or rectangular shaped plan. - the corner walls are L-shaped. - the frame is located within the plan and four corner walls.


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e. Cantilevered Floor System

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Floor slabs rest on beams cantilevering from a central tower. The loads of the building is transferred to the foundation through the central tower. E.g: Nagakin Capsule Tower, Marina Building, Miami & Turnig Torso Malmo


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f. Transfer System

For building where lower floors have lesser columns than the rest of the building. The transfer is in the form of a horizontal elements. Consists of mega column and mega beams at lower floor Skeleton frame is positioned above the transfer mega structures. The loads are transferred from the transfer mega beams to the mega columns and then to the foundation.

8.1 Minimizing Vertical Loads

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Foundations costs may be lower if the total vertical loads can be reduced Some of the ways are: reducing the floor plan area as the building increases using lighter materials in the upper floors using steel instead of R.C for the structural system reducing the cross-section area of the structural members in the upper floors placing the heavier M&E plant in an adjunct building e.g using district cooling system.


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9.0 HORIZONTAL LOADING SYSTEM Horizontal (lateral) forces act on the superstructure and substructure of buildings. Two types of horizontal forces: i. Wind Forces ii. Earthquake Forces

WIND FORCES

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Wind is variable both in direction and strength. Wind exerts loads on the tall structure causing it to oscillate or sway like a pendulum. Oscillations must be kept to a minimum: to ensure occupants’ psychological and physical comfort. to prevent deterioration of joints in the curtain walling and building services.

EARTHQUAKES

Earthquakes create lateral forces on a tall building causing it to sway. Cause the ground to move horizontally and vertically Earthquake-resistant building has to absorb or counteract the forces.


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9.1 Preventing Oscillation of Tall Building Three main ways: 1.

Structural methods by either stiffening or having heavier mass. - Shear Walls - Moment Resistant Frame Systems : eg tube systems - Bracing - Diagrid systems

2.

Counteracting the oscillation by either damping devices or top-to-bottom structural tie members. - Guying methods - Damping Devices : Passive dampers or Active dampers

3.

Aerodynamic methods.

a. Structural Methods i.

Shear Walls

Structural elements to induce stiffenes in the building. Monolithic walls of reinforced concrete, brick or masonry can be used to provide stiffenes ; walls with a moment resistant frame. Location of the shear walls are: - Central core of building - Ends or corners of building - At certain wall position inside the building

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a. Structural Methods ii.

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Moment Resistant Frame Systems (also known as Skeleton Frame) Three dimensional grid of linear column and beams – connected each other using rigid or semi rigid connections. Usually used ‘tubes systems’ – load bearing columns of the exterior perimeter are placed together to form a ‘tube’. - single tube ; tube within tube; bundling of tubes; braced tubes e.g : Xerox Building USA, Sears Towers USA


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a. Structural Methods iii.

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Bracing Adding braces to the frame. The bracing can be in different locations in the structure. The bracing configurations includes: - some vertical and/or horizontal bays of the frame are braced. - solid beam bracing- used to brace shear walls together. - vertical truss – consists of mega column, mega beam and mega brace single plane truss arrangement that is located along the height of the moment resistant frame. - a mega space truss that housed floor slabs, minor columns and beams. E.g: Bank of China, Hong Kong, John Hancock Building, USA, Hong Kong Shanghai bank, Hong Kong


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a. Structural Methods iv.

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Diagrid Systems Consists of a grid of diagonal members that cross each other. The distrubution of the load is similar to that experienced in a single layer grid dome. The diagrid is tied to the core by the floor elements along the height of the building. At the top of the building the diagrid terminates to either a ring beam or the core itself. Hearst Tower ; Swiss Re Building, London; Hubbell Lighting Headquarters Greenville, S.C


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b. Counteracting The Oscillation i.

Guying Method Top-to-bottom structural tie members are installed to the main vertical structure to prevent swaying of the structure. The structural tie members are either steel cables that are stretched or monolithic R.C Fins that are extended between the ground and the top of the tall buildings. Usually used for towers.

b. Counteracting The Oscillation ii. Damping Services

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The devices are used in the structure of lighter tall buildings (normally of steel frame construction) and tall ‘pencil’ thin towers and spires of super tall buildings.

Several types of dampers” * Passive Dampers : is tuned to react to the movement of the building - viscoelastic dampers - passive tuned mass dampers - pendulum tuned mass dampers - liquid tuned mass dampers - viscous liquid dampers * Active Dampers : require sensors to detect the movement and initiate the mechanical hydraulic piston actuators that push against the damper mass and structure.


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Passive Dampers i. Viscoelastic Dampers Viscoelastic material is placed at various points in the structure ; often a rubber or neoprene pad sandwiched between the faces of two steel members. The pad provide shear resistance to the oscillations forces. Eg. Former World Trade Centre New York.

Passive Dampers ii. Passive Tuned Mass Dampers These are sliding or horizontal moving mass of steel or concrete tuned to move in reaction to the horizontal movement of the building. The slab lies on a bed of oil and held in position by heavy springs (or hydraulic pistons) attached to the structural frame of the building. The movement of the building causes the mass to compress some spring and extend the others. The extended springs pulls on the building frame while the compressed springs pushes on the time. This counteracts the movement of the building Usually located at top of building where the swing of the oscillation is most.

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Passive Dampers iii.Pendulum Tuned Mass Dampers A suspended mass acting as pendulum is used. The pendulum mass is held by pistons. Act similar to the passive tuned mass damper. Need high head room E.g : Taipei 101 building.

Passive Dampers iv.Liquid Tuned Mass Dampers Consists of two large tanks or more whose water contents flow from tank to tank in response to lateral forces that sway the building. The sloshing forces of the water on the sides of the tanks as it moves from one tank to another counteract the swaying forces. Water tank for firefighting or air conditioning system of the building can be used for this purpose.

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Passive Dampers v. Viscous Liquid Dampers.

Similar to the use of hydraulic pistons in cars to absorb vibrations from the road. Special hydraulic pistons contains viscous liquid are placed at suitable locations throughout the buildings. E.g: Torre Mayor Building, Mexico City

Active Dampers

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Require sensors to detect the movement and initiate the mechanical hydraulic piston actuators that push against the damper mass and structure. Require external mechanisms and electricity to move them in response to the horizontal movement of the building. Computers are used to fine tune the responses to the swaying of the building.


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Hybrid Damper

Passive active damper that have both the passive damper and active damper The passive damper is used to for the initial movement up to a dynamic movement point where it turns off and the active damper activates to respond to the movement. Now used as an earthquake measure rather than resist wind induced oscillation. E.g: Fukuoka Building, Japan.

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c. Aerodynamics Methods

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The building cross sectional plan is designed to have minimum air turbulence that could cause oscillation. The reduction or air turbulence can be obtained by: i. have circular plan rather than rectangular or square plan of the building. ii cutting or rounding off the corners of the building. iii. Providing for perforation at the corners of the building or in the building. iv. Having channels in the buildings silhouette that allow the wind to be channeled away from the face of the building e.g: Shanghai World Financial Centre


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10.0 FLOOR SYSTEM FOR TALL BUILDING

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Tall buildings has many floors. Have to fulfill several functions – bearing of loads, fire resistance, sound insulation, heat insulation and aesthetics. Divided to three parts: floor structural floor finish ceiling (soffit of floor) finish


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10.1 Floor Structural System

Parts of the building that contribute to the structural stability of the building. Two structural functions: Vertical Loading Function

Horizontal Loading Function

•To carry the live loads and dead loads .

•To act as internal ‘struts’ of the building’s horizontal loading structural systems.

•Has to transfer loads to either support beams of the structural frame or supporting structural walls. •Must stiff enough as to neither noticeably deflect due to the load nor felt to oscillate when repetitive impact loads are applied.

•Depth of the slab and its supporting joists/girders influences the degree of stiffness of the overall building; but more materials and increases the loads exerted on the foundation – foundation costs will increased

Dilemma to the designer ; use of lighter materials (steel or lightweight reinforced concrete, using trusses and creating cavities in the structure ) to reduce loads and costs but building tend to sway in the wind.

Types of Floor Structures: LIGHT WEIGHT OR NORMAL CONCRETE FLOOR STRUCTURES

-the main and structural material is reinforced concrete -the floor plate is supported by r.c joists that span between the perimeter beams of the floor bay. -generally use cast-in-situ concrete floors but sometimes precast concrete is used for the floors. -if have long spans without intermediate supporting columns, prestressed concrete slabs or either prestressed concrete joints are used.

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Types of Floor Structures: COMPOSITE FLOOR STRUCTURES - combination of steel and concrete - may be one of the following: * cast in situ concrete slab on corrugated metal deck. * precast concrete planks on beams * steel joists embedded in concrete

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10.2 Floor Finishes

Screed Floor – usually cement screed which is laid on the concrete slab. tiling or membrane type covers are laid on the screed. access boxes for the m &E ducts laid in the floor slab are positioned relevant to the layout of the floor.

Raised Floor proprietary raised floor are installed onto the floor creating a false floor. space within the raised floor accommodate M & E ducts, cables etc and allows the use of under floor air conditioning plenums.

10.3 Ceiling Finishes

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Wet Construction either plastered or spray finished or cemented acoustic tiling that are clad directly to the floor soffit. usually for residential building.

Dry Construction dry boards or tiles fastened on a frame either suspended from the floor soffit or fixed directly to the floor soffit. dry boards are made from gypsum, wood cement etc ceiling are either attached directly to the floor or suspended with hanging wires or rods from the floors.


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11.0 WALL SYSTEM FOR TALL BUILDING

Walls enclose space and serves the functions of weather exclusion, thermal and sound insulation. It also provides adequate strength, stability, durability, fire resistance aesthetic appeal, etc.

11.1 Factors of External Walls System

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Visual panel, shape and size joint locations, joint sizes daylighting, nightlighting blinds, shades materials, colours, finishes integration with interior design, e.g cabling behind partitions. Integrity air and water tightness ; sealing, drainage, indoor air quality loading; static, dynamic, fatigue movements ; loads, thermal, moisture exceptional loads; blast, intrusion, impact fire ; resistance, reaction, spread verticality and horizontally


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11.1 Factors of External Walls System

Physics/Environment/Comfort heat transfer lighting sound transmission ; noise from street, next room ventilation moisture ; rainwater, humidity, condensation, degradation, mould growth. Buildability tolerance pre-assembly – stick, unitised, panelised quality ; QA, factory work, site work Maintenance access ; cleaning, inspection, repair, replacement life cycle ; component life, inspection cycle, repair, replacement serviceability ; cleaning, repairability, replaceability

11.2 Type of Walls

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Load Bearing walls function as shear walls; generally of reinforced concrete.

Non Load Bearing Walls most walls used in tall buildings are non load bearing. can be reinforced concrete, brick, composite materials, glass, metal sheets etc. used to enclose the building structure and provide a ‘face’ or façade.


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11.3 Type of External Walls a. Curtain Walling b. Infill Panels c. Cladding

a. Curtain Walling

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A form of external lightweight cladding attached to a frame structure forming a complete envelope or sheath around the structural frame. Non load bearing claddings which have to support only their own deadweight and imposed wind loadings which are transferred to the structural frame through connectors which are usually positioned at floor levels. A series of vertical mullions spanning from floor to floor interconnected by horizontal transoms forming openeings into which can be fixed panels of glass or infill panels of apaque materials. Constructed by using a patent or proprietary systems produced by profile metal fabricators.


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- curtain walling details

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- type of curtain walling ‘Stick’ curtain walling ‘Stick and unit’ curtain wall Unitised or panel curtain wall

i. Stick System

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Uses site assembled framing members, mullions (verticals) and transoms (horizontal) Glazing and infill panels are fixed into the carrier framing grid by clamping them into a glazing rebate The infill panels consists of mineral wool insulation. The carrier framework remains visible. E.g. Sears Tower.


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ii. Stick and unit system

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The panels are attached to a stick type or grid type or truss type carrier framework fixed to the building structure.


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iii. Unitised system

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Large, integral factory assembled units, sometimes one storey high incoporating mineral wool insulations, windows, ventilators, doors and opaque facing. The panels are only anchored either to the building structure or to both the structure and adjacent panels.


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iv. Structural Glazing

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Structural glass panels that are supported by a framework of moveable spider connectors steel trusses and outriggers. Popular for the façade of the podium annexes for many tall buildings The system allow for high head room as the glass can be span up to four stories high by an appropriately design framework


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b.Infill Panel

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The wall is installed between the exterior floor slab and columns of the structural frame. The panel layout can be so arranged to expose some or all of the structural members creating various optical impressions. Wide variety of materials or combinations of materials can be employed such as glass, pre cast concrete, aluminium etc.


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c. Cladding

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The wall (in the form of large panel) is attached directly to the structural frame of the buildings or a backing wall. The panels are one to two storey high and span one or more horizontal bays of structural frame. Require large fixings and anchors to hold them on the building.


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12.0 FOUNDATION SYSTEM FOR TALL BUILDING

Refer to foundation notes BLD 310 (Diploma in Building) and basement notes BLD 410 (Degree)

Types of foundation used for Tall Building Piling : Displacement Piles – Steel H Pile, Spun Pile : Replacement Piles – Bored Pile, Barretts Pile Drilled Caisson Buoyancy Raft Foundation

a. Bored Pile

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b. Drilled Caisson

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c. Spun Pile

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d. Barretts Pile

e. Buoyancy Raft Foundation

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13.0 CONSTRUCTION OF TALL BUILDINGS

Nature of Tall Building Construction - Working at Heights : increases the risks of injury or deaths from falling or being hit by falling objects. : personnel and materials have to lifted to their working areas located at elevated heights. - Operating in Restricted Working Area : usually in built up areas on small sites : not much working space at ground level. - Repetitive Work Activities : usually repeating a cycle of activities associated with each floor.

13.1 Method of Construction

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Conventional In Situ Reinforced Concrete Industrialised Building System (IBS) Prefab System Industrialised Formwork System Steel Structures


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a. Conventional – reinforced concrete

Refer to Diploma Notes and Encik Kamran Notes in BLD 460 (Bach of Construction Management)

b. IBS – Prefab System

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Refer to PM Mafozah Murad Notes in BLD 460 (Bach Construction Management)


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b. IBS – Steel Structures

Refer to PM Mafozah Murad Notes in BLD 460 (Bach of Construction Management)

b. IBS - formwork Types of Formwork

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Prefabricated Job Built Forms that can be reused, usually referred to as gang or gang forms. Manufactured Forms, generally purchased or leased, sometimes as a total system.


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i. prefabricated job-built forms

prefabricated forms are usually constructed substantially for the purpose of frequent reuse, commonly used for wall forming, and also for deck forming where multiple floors are being erected. these forms can either be ready made or custom made. Gang or Ganged Forms Flying forms

- gang or ganged forms • are built by assembling a number of small prefabricated panel forms into one large form. • can be used on all types of work, their size being limited only by job conditions and the means for moving them. These large sections are erected, stripped and moved to the next location by cranes. • provides good reuse of equipment, larger concrete placements and decreased erection and stripping time because the sections stay intact. • no dismantling and reassembly of each individual panel for each concrete placement.

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- flying / table forms • are large prefabricated forms for multi-storey building slabs. • contain their own supporting system and levelling jacks, and are easily dropped away from the floor slab when the concrete reaches the specified strength. • the form is then moved to the edge of the building, picked up by a crane, and moved to the next floor for setting and levelling. • the name ”flying formwork” is used because forms are flown from story to story by a crane

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ii. manufactured forms

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speciality manufactured forms that reduce the time and labour formerly required at job sites these systems and panels are durable enough for many reuses. each proprietary panel systems has its own special ties and other accessories.


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- pan forms • made of metal, fibreglass or plastic are used for floor slabs in multi-storey building . • waffle slab floors have waffle-like indentations on the bottom surface formed by rectangular pans in the same manner as in the pan joist floor system. • these forms are reusable and can be either rented or bought. • they come in a wide range of sizes and depths.

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- internal forms • are round or rectangular laminated fibre and cardboard forms placed in deep (or thick) floors or beams and left in place to lighten the dead weight of member • these produce a floor slab similar to the pan joist floor except both top and bottom surfaces are flat. • the duct like void create a space between the joists, inside of the element. • the ends of the tubes and boxes are closed off so that concrete will not flow into them • expanded polystyrene can also be used to create internal voids

- tunnel forms combined the walls on either side of a room and the slab overhead soffit from into a single unit. typically, the wall forms hinge to allow the slab soffit form to be stripped, and the entire assembly is hoisted to the subsequent area to be formed

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- column forms •square or rectangular columns can be built using the same system of form panels as used for walls. •forms for round columns are available in laminated fiber, metal and glass fiber reinforced plastic as complete units

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- slipforms • Slipforms place concrete by extrusion. • The concrete is placed in the forms, which are then pulled or jacked vertically or horizontally, extruding the concrete, in the shape of the forms. • The most spectaculars use of slipforms is for tall towers, silos, elevator shafts in tall buildings and building walls. • The movement of the forms is slow enough for concrete to gain the strength to keep its shape and support its weight.

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- jump forms / climbing forms • similar to slipforms except that rather than extruding the concrete, the form is filled with concrete, stripped and then ‘jumped’ to the next level after the concrete has set. • these gang forms may be lifted by crane or self raised (electrically or hydraulically). • properly designed, they minimize the number of pieces to be handled and simplify the task of resetting the forms while meeting the tolerances specified

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Jump form operation

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Jump form operation

- stay-in-place forms •

• •

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these forms are often steel or thin precast, prestressed concrete units that are placed on supporting formwork (when used for floors) and bonded to become the bottom of the concrete element. become part of the completed structure. they are often used for concrete floor and roof slabs cast over steel joists or beams, for bridge decks, for a top slab over a pipe trench or for other inaccessible locations where it is impractical and expensive to remove forms.


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13.2 Vertical Transportation & Handling / Elevated Access

Access to the interior and exterior of the building is needed for workers, materials and even plant or machinery. Workers have to be lifted to their work areas within the building being built so that they do not tire themselves climbing stairs. Materials have to be lifted to their installation positions within the building being built. The common equipment or machineries used are: Scaffolding Cranes Derricks Gondolas/Swinging Stage Hoists Elevator (lifts) Helicopters Rubbish Chute

a. Scaffolding

A temporary working platform erected around the perimeter of a building structure usually constructed from steel or aluminium alloy tubes clipped or coupled together to provide a means of access to high level working areas as well providing a safe platform from which to work. Supported from the ground or on a floor slab or platform Remain static and difficult to move. Types of Scaffolding:

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Putlog scaffolds Independent scaffolds Cantilevered Scaffolds Truss-out scaffold Gantries


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- component parts of tubular scaffold:

i. putlog scaffolds These are scaffolds which have an outer row of standards joined together by ledgers which in turn support the transverse putlogs which are built into the beds joints or perpends as the work proceeds, they are only suitable for new work in bricks or blocks.

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ii. independent scaffolds

These are scaffolds which have two rows of standards each row joined together with ledgers which in turn support the transverse transoms. The scaffold is erected clear of the existing or proposed building but is tied to the building or structure at suitable intervals.

Tying-in

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All putlog and independent scaffolds should be tied securely to the building structure at alternate lift heights vertically and not more than 6m centres horizontally. Suitable tying-in methods include connecting to tubes fitted between sides of window openings or to internal tubes fitted across window openings.


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iii. cantilever scaffolds

These are a form of independent tied scaffold erected on cantilever beams and used where it is impracticable, undesirable or uneconomic to use a traditional scaffold raised from ground level. Requires special skills and should therefore always be carried out by trained and experienced personnel.

iv. truss-out scaffold

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A form of independent tied scaffold used where it is impracticable, undesirable or uneconomic to build a scaffold from ground level. The supporting scaffold structures is known as the truss out. Requires special skills and should therefore always be carried out by trained and experienced personnel.


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v. gantries

These are elevated platforms used when the building being maintained or under construction is adjacent to a public footpath. A gantry over a footpath can be used for storage of materials, housing units of accommodation and supporting an independent scaffold.

b. Cranes

These are lifting devices designed to raise materials by means of rope operation and move the load horizontally within their limitations of any particular machine. The range of cranes available is very wide and therefore choice must be based on the loads to be lifted, height and horizontal distance to be covered, time periods og lifting operations, utilisation factors and degree of mobility required Types of crane:

Mobile Crane Static Crane Tower Crane

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- types of crane

i. Mobile Crane – Self Propelled Cranes Mobile cranes mounted on a wheeled chassis and have only one operator position from which the crane is controlled and the vehicle driven

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i. Mobile Crane – Lorry Mounted Cranes

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Mobile cranes consists of a lattice or telescopic boom mounted on a specially adapted truck or lorry. Have two operating positions: the lorry being driven from a conventional front cab and the crane being controlled from a different location. The lifting capacities can be increased by using outrigger stabilizing jacks.


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i. Mobile Crane – Lorry Mounted Lattice Jib Cranes

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These cranes follow the same basic principles as the lorry mounted telescopic cranes but they have a lattice boom and are designed as heavy duty cranes with lifting capacities in excess of 100 tones.


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i. Mobile Crane – Track Mounted Cranes

These machines can be a universal power unit rigged as a crane or a purpose designed track mounted crane with or without a fly jib attachment. The latter type are usually more powerful with lifting capacities up to 45 tonnes. Can travel and carry out lifting operations on most site without the need for special road and hardstands provisions but they have to be rigged on arrival after being transported to site on a low loader lorry.

ii. Static Crane - Mast Cranes

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Similar in appearance to the familiar tower cranes but they have one major difference in that the mast or tower is mounted on the slewing ring and thus rotates whereas a tower crane has the slewing ring at the top of tower and therefore only the jib portion rotates. Self erecting, of relatively low lifting capacity and are usually fitted with luffing jib.


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iii. Tower Cranes

Most tower cranes have to be assembled and erected on site prior to use and can be equipped with a horizontal of luffing jib. Wide range of models available often makes it difficult to choose a crane suitable for any particular site but most tower cranes can be classified into one of four basic groups:

Self Supporting Static Tower Cranes Supported Static Tower Cranes Travelling Tower Cranes Climbing Cranes

Example of Tower Cranes Details:

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iii. Tower Cranes – Self Supporting Static Tower Crane High lifting capacity with the mast or tower fixed to a foundation base. Suitable for confined and open sites.

iii. Tower Cranes – Supported Static Tower Cranes

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Similar in concept to self supporting cranes and are used where high lifts are required, the mast or tower being tied at suitable intervals to the structure to give extra stability.


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iii. Tower Crane – Travelling (Rail Mounted) Tower Crane

Mounted on power bogies running on a wide gauge railway track to give greater site coverage. Only slight gradients can be accommodated therefore a reasonably level site or specially constructed railway support trestle is required.

iii. Tower Crane – Climbing Cranes

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Used in conjunction with tall buildings and structures. The climbing mast or tower is housed within the structure and raised as the height of the structure is increased. Upon completion the crane is dismantled into small sections and lowered down the face of the building


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- parts of a Tower Crane

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All tower cranes consist of the same basic parts: The base is bolted to a large concrete pad that supports the crane. The base connects to the mast (or tower), which gives the tower crane its height. Attached to the top of the mast is the slewing unit -- the gear and motor -that allows the crane to rotate:


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On top of the slewing unit are three parts: The long horizontal jib (or working arm), which is the portion of the crane that carries the load. A trolley runs along the jib to move the load in and out from the crane's center: The shorter horizontal machinery arm, which contains the crane's motors and electronics as well as the large concrete counter weights: The operator's cab:

The machinery arm contains the motor that lifts the load, along with the control electronics that drive it and the cable drum, as shown here: The motors that drive the slewing unit are located above the unit's large gear:


- how do they grow?

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Tower cranes arrive at the construction site on 10 to 12 tractortrailer rigs. The crew uses a mobile crane to assemble the jib and the machinery section, and places these horizontal members on a 40foot (12-m) mast that consists of two mast sections. The mobile crane then adds the counterweights. The mast rises from this firm foundation. The mast is a large, triangulated lattice structure, typically 10 feet (3.2 meters) square. The triangulated structure gives the mast the strength to remain upright.


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To rise to its maximum height, the crane grows itself one mast section at a time! The crew uses a top climber or climbing frame that fits between the slewing unit and the top of the mast. Here's the process:

The crew hangs a weight on the jib to balance the counterweight. The crew detaches the slewing unit from the top of the mast. Large hydraulic rams in the top climber push the slewing unit up 20 feet (6 m). The crane operator uses the crane to lift another 20-foot mast section into the gap opened by the climbing frame. Once bolted in place, the crane is 20 feet taller!

- how much weight can they lift?

A typical tower specifications:

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crane

has

the

following

Maximum unsupported height - 265 feet (80 meters) The crane can have a total height much greater than 265 feet if it is tied into the building as the building rises around the crane. Maximum reach - 230 feet (70 meters) Maximum lifting power - 19.8 tons (18 metric tons), 300 tonne-meters (metric ton = tonne) Counterweights - 20 tons (16.3 metric tons)

The maximum load that the crane can lift is 18 metric tons (39,690 pounds), but the crane cannot lift that much weight if the load is positioned at the end of the jib. The closer the load is positioned to the mast, the more weight the crane can lift safely. The 300 tonnemeter rating tells you the relationship. For example, if the operator positions the load 30 meters (100 feet) from the mast, the crane can lift a maximum of 10.1 tonnes.


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The crane uses two limit switches to make sure that the operator does not overload the crane:

The maximum load switch monitors the pull on the cable and makes sure that the load does not exceed 18 tonnes. The load moment switch makes sure that the operator does not exceed the tonnemeter rating of the crane as the load moves out on the jib. A cat head assembly in the slewing unit can measure the amount of collapse in the jib and sense when an overload condition occurs.

- why don't they fall over?

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The first element of the tower crane's stability is a large concrete pad that the construction company pours several weeks before the crane arrives. This pad typically measures 30 feet by 30 feet by 4 feet (10 x 10 x 1.3 meters) and weighs 400,000 pounds (182,000 kg) -these are the pad measurements for the crane shown here. Large anchor bolts embedded deep into this pad support the base of the crane:


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c. Derricks The Derricks crane is a simple and inexpensive solution for lifting heavy weights (10 tonnes or more) at long radius (up to 30m) Two types:

Guy

Derrick Scotch Derrick

i. Guy Derrick

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Guy Derrick has several guys (cable ties) that holding up the mast and to help slewing of the cranes boom. The other ends of the guys are anchored to the building structure. The boom is hinged to the base of the mast. Winches located at the mast base.: use to derrick the boom and hoisting the load


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ii. Scotch Derrick Similar in design to the guy derrick except that it has no guys (cable ties), has a shorter mast and a longer boom. It is stabilized by having its two backstays to be loaded with ballast.

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d. Gondolas or Swinging Stage

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These consists of a working platform in the form of a cradle which is suspended from cantilever beams or outriggers from the roof of a tall building to give access to the façade for carrying out light maintenance work and cleaning activities. The cradles can have manual or power control and be in single unit or grouped together to form a continuous working platform. If grouped together they are connected to one another at their abutment ends with hinges to form a gap of not more than 25mm wide. Many high rise building have a permanent cradle system installed at roof level and this is recommended for all buildings over 30m high.


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e. Hoists

These are designed for the vertical transportation of materials, passengers or materials and passengers.

Materials hoists are designed for one specific use (i.e. the vertical transportation of materials) and under no circumstances should they be used to transport passengers. Most material host are of a mobile format which can be dismantled, folded onto the chassis and moved to another position or site under their own power or towed buy a haulage vehicle.

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Passenger hoists are designed to carry passengers although most are capable of transporting a combined load of materials and passengers within the lifting capacity of the hoist. A wide selection of hoists are available ranging from a single cage with rope suspension to twin cages with rack and pinion operation mounted on two sides of a static tower.


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f. Elevators (lifts)

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These move on tracks. They are more stable and have higher capacities as compared with a gondola.


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g. Helicopters

When it is not possible to use crane to lift the topmost part of the building (such as telecommunication tower mast) helicopter becomes a viable solution despite its very high cost.

g. Rubbish Chutes

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Used to direct disposals of debris from various floor to the bin on the ground floor The simple concept of connecting several perforated dustbins. The tapered layered cylinders are produced from reinforced rubber with chain linkage for continuity. Overall length are generally 1100mm, providing an effective length of 1m. Hoppers and side entry unit are mede for special applications.


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13.3 Working Space Space is limited. Among approaches to provide sufficient work space so that work can be done safely and efficiently:

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multistory site accommodation. elevated site accommodation and platforms. use part of uncompleted structure. use nearby properties and public spaces. maximising prefabrication and standardisation


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a. Multi story site accommodation

Usually portable container cabins stacked up.

b. Elevated site accommodation and platform

site accommodation build upon scaffolding / gantry such that the site accommodation opens up to the street level. Gantry to support cabin

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c. Use part of uncompleted structure

When the building is partially complete, it may be feasible to use some of the completed floor as site accomadati on.

d. Use nearby properties and public spaces

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Rent space in an adjacent building for site accommodation.


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e. Maximising prefabrication and standardisation If the contractor uses prefabricated components for the building, there is no need for space at site to store the raw materials. The components are built off site and transported to the site to be assembled into their final positions

14.0 Safety System For Tall Building Construction

The great heights, strong winds at heights and constricted working space make fatal falls and collisions very possible. Most accidents in a worksite are categorized under :

Accidents may result in high direct and indirect costs:

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“falls of person” “workers struck by falling objects”

Direct Costs : medical costs, workers’ compensation and other insurance benefits. Indirect Costs : reduced productivity, job schedule delays, damage to equipment and facilities, low morale among workers and possible additional liability claims.


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14.1Falls of Person

Measures against fall of persons:

A working platform should be provided to workers whenever practicable : should be of adequate width, carrying capacity and with sufficient guardrails to afford a safe and steady foothold and handhold. The width should not be less than 635mm and toe-boards must be provided. Safety belts and lifelines; in the case where platform cannot be provided for reasons of space constraint.

Safety Belt

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14.2 Falling Objects

Measures against person struck by falling objects include:

Good housekeeping and minimizing debris being generated, hence less falling materials. Systematic and regular disposal of accumulated debris, provisions of perimeter overhead shelter. Access and egress shelters to building: provision of safety nets and provision of pedestrian walkway or hoarding The compulsory wearing of safety helmets.

Safety Helmet

Sidewalk Shed Protection

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Safety Netting


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Safety Net Catch Platform

CASE STUDY:

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PETRONAS TWIN TOWERS…. TURNING TORSO, SWEDEN…. BURJ HOTEL, DUBAI……


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THANK YOU

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Tall Building MKA Jan 2011

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