Details of design and construction process of Burj Khalifa

Excavation work began for Burj Khalifa is known as the tallest skyscraper in the world in and it’s excavation work was started in January 2004. It took 1325 days for the completion of the structure.

The superstructure is supported with over 165 stories. The final height of the building is 2,717 feet (828 meters). The 280,000 m2 (3,000,000 ft2) reinforced concrete is used for Dubai tower and employed for retail, a Giorgio Armani Hotel, residential and office.

Structural System Description: 3D Structural Analysis Model of Burj Dubai TowerBurj Khalifa contains "refuge floors" at 25 to 30 story intervals which have great fire resistance capacity as well as individual air supplies to cope up with any emergency situation. With the support of reinforced concrete structure, the building becomes stronger as compared to steel-frame skyscrapers.

Designers intentionally constructed the structural concrete in Burj Dubai as "Y" shaped in plan with the purpose of minimizing the effect of wind forces on the tower along with the intension to retain the structure simple and support constructability. The structural system is defined as a "buttressed" core.

Every section contains its own high performance concrete corridor walls and perimeter columns and supports the others through a six-sided central core, or hexagonal hub. So, a tower is built with enormously rigid lateral and torsion capacity. An inflexible geometry is utilized with the tower that organized all the common central core, wall, and column elements.

Each tier of the building sets back in a spiral stepping pattern up the building. The setbacks are arranged through the Tower's grid, so that the building stepping can be completed by positioning the columns over with walls beneath to set a smooth load path. It facilitates the construction to get rid of the issues resulting from column transfers.

The setbacks are arranged in such way that the Tower's width alters at each setback. The benefit of the stepping and shaping is to "confuse the wind'1. The wind vortices don’t get structured as at each new tier the wind experiences a dissimilar building shape.

Structural Analysis and Design Facts: The center hexagonal reinforced concrete core walls set the torsional resistance of the structure same as a closed tube or axle. The center hexagonal walls are supported with the wing walls and hammer head walls which operate as the webs and flanges of a beam to withstand the wind shears and moments.

Outriggers at the mechanical floors facilitate the columns to contribute to the lateral load resistance of the structure; so, all of the vertical concrete is applied to support both gravity and lateral loads. The wall concrete designated strengths vary from C80 to C60 cube strength and employ Portland cement and fly ash.

To get more information on construction details, go through the following article aboutcivil.org




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Published By
Rajib Dey
www.constructioncost.co
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Brief explanation of wall footing design

Wall footing design is performed on the basis of some theories which must be taken into consideration at the time of designing. The first theory is to examine the soil pressure that is circulated linearly all through design process. This can be obtained, if resultant of soil pressure conforms with the resultant of soil force. Due to this, rotation of footing can be prevented. Usually, the following strength design method is applied while designing the footings.

WALL FOOTING DESIGN EXAMPLE STATEMENT

A 10” thick wall bears a service dead load of 8k/ft and service live load of 9k/ft. At the base of footing the permissible soil pressure is 5000psf and base of footing is 5’ underneath the present ground surface. Now your responsibility is to design the wall footing for;

This construction video highlights 17 various types of roof designs which are generally utilized in building designs, architecture and home construction. The video will provide great advantages to the architects, building designers and custom home builders.

Concrete compressive strength= f’c = 3ksi

Yield strength of steel = fy = 60ksi.

Soil density = 120lb/ft3.

SOLUTION:

Note: Typically low strength of concrete in footing is applied in columns. It necessitates the use of dowel to adapt this modification in strength.

STEP 1: ESTIMATE THE SIZE OF FOOTING AND FACTORED NET PRESSURE.

At the time of designing wall footing, generally one feet strip of the wall and footing is undertaken to simplify the calculation process. The permissible soil pressure is 5ksf. The permissible net soil pressure is 5ksf. As, the thickness of footing is unknown at this stage a acceptable thickness of footing equivalent to (1-1.5)x The wall thickness can be guessed.

1.5 x 9’’ = 13.5’’ take 13’’

STEP 2: FIND THE PERMISSIBLE SOIL PRESSURE

qn=5−[(1.083times0.150)+(5−1.083)times0.120]

[q_{n}=4.367 ksf]

[Area-of-footing=frac{8+9}{4.3676}]

Try 47’’ (3.91’) Wide footing

Factored Net Pressure = qnet = 6.138ksf

STEP 3: CHECK THE TOLERABILITY OF FOOTING DEPTH AGAINST SHEAR

Only one way shear or beam shear is substantial in wall footings. The crucial section for this type of shear is at distance ‘d’ from the face of wall. Where ‘d’ denotes the actual depth of footing.

Supposing that one will use #4 bar.

d = 13 – 3 – ¼ = 9.75″

The Tributary area for one way shear

Tributary area = Shaded area for one way shear

D = H – CLEAR COVER – 1/2 BAR DIAMETER

d = 13 – 3 -1/4

d = 9.75″

To get the complete article visit 

www.engineeringintro.com/concrete/reinforced-concrete/wall-footing-design-example/

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Published By

Rajib Dey

www.constructioncost.co

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Civil Engineering Retaining Wall Design Spreadsheet

A retaining wall refers to a structure designed and built to combat with the lateral pressure of soil once a desired alteration occurs in ground elevation that surpasses the angle of repose of the soil.

The active pressure enhances on the retaining wall in proportionate ratios from zero at the higher grade level to a highest value at the lowest depth of the wall. In order to become functional, retaining walls should be reinforced properly.

Civil Engineering Retaining Wall Design Spreadsheet can be useful to design a retaining wall through an easy to follow process. The spreadsheet consists of tabs to work out stability, moment and shear, reinforcement etc.

A good quality retaining wall design spreadsheet comes with simple interface & various options that can simplify the design process for retaining wall to a great extent. You can download this spreadsheet for free from the below link.

Download Civil Engineering Retaining Wall Design Spreadsheet

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Published By

Rajib Dey

www.quantity-takeoff.com

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