Construction Cost Estimating


Details about Skyscrapers Foundations

This civil engineering article is about construction process of skyscrapers.

There should be a perfectly planned structure for skyscrapers which should be affixed with the ground. To resist natural forces from falling them over, mega-tall structures require a low center of gravity, obtained by digging deep into the ground to attain a soil robust enough to sustain the weight of the building. The digging is done for some of the world’s tallest buildings up to 85 meters. It all commences with locating for bedrock.

Built on Bedrock: Under the loose surface, stalks of soil and sand settles for a layer of lithified rock, referred to as bedrock.

Getting compacted under pressure, this solid layer of earth belongs to the first building block for developing a strong foundation for skyscrapers. Except this layer, the building is susceptible to moving and shifting with the loose topsoil.

Once the surveying is finished for the construction site for soil composition, construction is started by digging a pit. The size and intensity of the pit is based on how far down the bedrock is located and the numbers of basement levels the building comprises of.

In some areas, just by accessing the bedrock can create a serious engineering challenge. As for instance, at the site of the One World Trade Center in New York City, the bedrock remains almost 20 meters underneath the surface. With adjacent Hudson River drenching the soil, excavating to the bedrock can’t be performed devoid of flooding the site.

Sometimes the bedrock is situated adjacent to the surface. Under this situation, the soil on top of the bedrock is eliminated, and the bedrock is excavated to develop a smooth surface on which the foundation is built up. Footings are then blasted or drilled into the bedrock and set with steel or reinforced concrete columns to secure the building.

When the depth of the bedrock is severe, vertical beams known as piles are plunged through the soil unless they are implanted in the bedrock as footings to tie the structure. Once the beams are affixed, the structures are prepared to resist any natural forces.

Forces of Nature: The skyscrapers are mainly affixed with bedrock to keep the structure safe against gale force winds and seismic activity. The Ancient architects who deal with the pyramids, can find solutions to these issues by utilizing wide foundation to disperse the weight of the building over a greater area. Modern mega-tall buildings, however, encounter space restrictions and unique design demands which are necessary for other solutions.

The lateral forces of wind, and consequent movement of the foundation system, is very much harmful. At the crown of a skyscraper, winds can hit with speeds of up to 100 miles-per-hour. The movement of the foundation system can produced high vertical loads on the structure, specifically on the exterior piles. Therefore, these forces should be considered while making the design of the foundation piles.

Bedrock and the conditions of the soil should be tested to find out the choice of foundation structure along with the type, and number of load bearing strength of footings. In areas containing soft and poor soil conditions, the foundation system may need special rock anchors for withstanding uplift forces from wind or overturning from seismic events.

Together with other design considerations like dampers or shock absorbers, a robust foundation facilitates the skyscrapers to resist even the powerful storms and earthquakes.

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Details about Skyscrapers Foundations