Construction Planning and Techniques used

in Skyscrapers

K.SNEHAROLL NO:131564

Contents

Introduction Construction planning and management Integration of Super tall building systems Foundation Structural system selection approach Wind engineering Earthquake engineering Structural Health Monitoring Skyscrapers Implications Conclusion

Introduction

A skyscraper is a super tall, continuously habitable building of many floors, usually designed for office, commercial and residential use.

For buildings above a height of 300 m (984 ft), the term Super tall can be used.

1.Construction Planning

Owner, architect and principals of the design team establish functions for which the structure must serve. Building use areas and major building parameters are determined

Management strategies

These are proposed for defining the different stages of planning and to reduce the time in overall construction duration.

2.Integration of Super tall building systems

Integration involves the coordination and design of building systems to work together in a holistic manner.

Integration is a method to help simplify the tall building’s design process intelligently meshing different elements together into an effective functioning entity.

Integration Web for super tall structures

3.Construction Techniques

FOUNDATION : The following issues will generally need to be addressed

in the design of foundations for high-rise buildings:1) Ultimate capacity of the foundation under vertical,

lateral and moment loading combinations.  2) The influence of the cyclic nature of wind,

earthquakes and wave loadings (if appropriate) on foundation capacity and movements.  

3) Overall settlements. 4) Earthquake effects, including the response of the

structure-foundation system to earthquake excitation, and the possibility of liquefaction in the soil surrounding and/or supporting the foundation.

3.1 Piled raft foundation

Using Combined Piled Raft Foundation (CPRF) as a foundation for high-rise buildings in the settlement-sensitive Frankfurt clay, a considerable settlement reduction of more than 50% compared to raft foundations can be achieved.

3.2 Structural system selection approach

• Select and optimize the building structural system for strength, stiffness, cost effectiveness, redundancy, and speed of construction.

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.

1)Framed Tube system2)Bundled Tube system3)Tube in tube system4)Diagrids /braced frames system5)Core plus outrigger system

3.3 Wind engineering

Wind produces three different types of effects on tall buildings: static, dynamic, and aerodynamic.

Structurally, static effect is a term of analysis independent of time; but dynamic analysis is an attempt to take into account how the system responds to the change through the period of time; and when the building is very flexible, it interacts with the wind load and affects its response; that is called aerodynamic effect.

Strategies to mitigate wind effect

To reduce the impact of wind on a tall building and mitigate the response of the structure of tall building, there are two main concepts: Architectural and structural .

Structural strategies:1) Increasing the structural stiffness by

considering the structural systems 2) Damping sources (vibration

absorbers)

Device mounted in structures to reduce the amplitude of mechanical vibrations. Their application can prevent discomfort, damage, or outright structural failure.

• Aerodynamic(Geometric modifications)

Modifications on cross-sectional shapes, such as slotted, chamfered, rounded corners, and notching on a rectangular building, can have significant effects on both along wind and across wind responses of the building,

Tapering setback

Porosity or openings Twisting Slotted and chamfered corners Corner roundness and recession

3.4 Seismic Design Considerations

Seismic loading  means application of an earthquake-generated excitation on a structure (or geo-structure). It happens at contact surfaces of a structure either with the ground, with adjacent structures, or with gravity waves from tsunami.

Earthquake or seismic performance defines a structure's ability to sustain its main functions, such as its safety and serviceability, at and after a particular earthquake exposure.

Vibration control

Seismic vibration control is a set of technical means aimed to mitigate seismic impacts in building and non-building structures.

  After the seismic waves enter a superstructure,

there are a number of ways to control them in order to soothe their damaging effect and improve the building's seismic performance, for instance:

1) To dissipate the wave energy inside a superstructure with properly engineered dampers;

2) To disperse the wave energy between a wider range of frequencies;

3) To absorb the resonant portions of the whole wave frequencies band with the help of so-called mass dampers

Lead Rubber Bearing or LRB is a type of base isolation employing a heavy damping. Heavy damping mechanism incorporated in vibration control technologies and, particularly, in base isolation devices, is often considered a valuable source of suppressing vibrations thus enhancing a building's seismic performance.

Lead Rubber Bearing

Tuned mass damper

• Typically the tuned mass dampers are huge concrete blocks mounted in skyscrapers or other structures and moved in opposition to the resonance frequency oscillations of the structures by means of some sort of spring mechanism.

Simple Roller Bearing

• Simple roller bearing is a base isolation device which is intended for protection of various building and non-building structures against potentially damaging lateral impacts of strong earthquakes.

3.5 Super structure and Equipment

1) Auto Climbing formwork system (ACS) 2) Rebar pre-fabrication 3) High performance concrete suitable for

providing high strength, high durability requirement, high modulus, and pumping

4) Advanced concrete pumping technology 5) Simple drop head formwork system that can

be dismantled and assembled quickly with minimum labor requirements

6) Column/Wall proceeding method, part of ACS formwork system

3.6 Major equipment

Aerial cranes: Aerial crane or 'Sky cranes' usually are helicopters designed to lift large loads. Helicopters are able to travel to and lift in areas that are difficult to reach by conventional cranes.

Tower cranes: tower cranes often give the best combination of height and lifting capacity and are used in the construction of tall buildings

• Self erecting cranes : Generally a type of

tower crane, these cranes, also called self-assembling, jack-up, or "kangaroo" cranes, lift themselves from the ground or lift an upper, telescoping section using jacks, allowing the next section of the tower to be inserted at ground level or lifted into place by the partially erected crane itself.

4.Structural health monitoring

The process of implementing a damage detection and characterization strategy for engineering structures is referred to as Structural Health Monitoring (SHM).

Extensive structural health and survey monitoring program has to be installed during construction of skyscrapers and it includes

1) Strain gauges at the columns, walls and beams, 2)Foundation settlement survey, strain guages in

the piles, horizontal and vertical survey system, accelerometers, and GPS system to monitor the dynamic behavior of the skyscrapers during construction and for permanent buildings conditions.

5.Skyscrapers Implications

Advantages of Skyscrapers 

1. Skyscrapers are known as modern answer for lack of space.

2. These skyscrapers attract millions of tourist each year, and bring profit to local business.

3. Radio, television and cell phones require signal receivers from broadcasters.

Disadvantages of Skyscrapers 4. High cost of investment, construction, maintenance, and

operation. 5. Negative effect on indoor and outdoor environment. 6. Poor Ventilation, Rely on Elevators, Fireproofing Problem

Conclusion

Throughout the world, the population of the major cities are increasing at a fast rate and where land for building is not available; there is a pressure to build upward rather than sideways.

The structures offer some major advantages but also pose serious challenges to designers and builders.

The need for office workers was increasing at a spectacular rate as business like banking, insurance etc hired more people, not only the partners at these firms but huge numbers of office workers too.

So it was the expansion of office market that went hand in hand with expansion of the skyscraper.

References•

• Abbas Aminmansour, A.M.ASCE (2010 ). “Integrated Design and Constructuction of Tall Buildings”. 

• Ahmad Abdelrazaq, SE ,Structural Congress (2010 ). “ Design and Construction Planning of Burj Kalifa, Dubai, UAE” . 

• M. Alagmandan, M. Elimeriri , (2013), “Reducing impact of wind on Tall buildings through Design and aerodynamic modifications”. 

• Sam Lee1, Dasui Wang, Yun Liao and Neville Mathias (2010) “Performance Based Seismic Design of a 75 Story Buckling Restrained Slender Steel Plate Shear Wall Tower”. 

• M. M Ali, Ph.D., S.E., F. ASCE and P. J. Armstrong, R.A, (2006). “Integration of Tall Building Systems”. 

• Harry G. Poulos, Dist. MASCE. GEOTECHNICAL ENGINEERING STATE OF THE ART AND PRACTICE 787 . “Foundation Design for Tall Buildings”.

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