How did they build the Burj Khalifa, think about it, the Burj Khalifa is 2716 feet (828 meters) high, it’s the tallest skyscraper in the world by over 984 feet (300 meters), the problems must have been huge with this one, the advantage is that technology advanced to a point that all kinds of innovations are possible, I’m thinking that it might be a good idea to look at some design and construction difficulties where experience with the Burj Khalifa.
The Burj Khalifa had problems that needed to be solved from the get-go, one of these was the scaffolding, how do you get the scaffolding that high, the foundation, and the fact that the final height of the building was a total secret, the added height created a unique set of engineering challenges, for example how to build high without making the footprint bigger,
The Buttress Core
The core is the center hexagon in the middle of the building to resist the twisting forces on the building, the core has 3 wings coming out on the 3 sides of the building consisting of walls that go down the corridors, the base alone allows the building to be built higher and higher, the buttress steps back inwards as the building goes upward in a spiral. The steady buttress core made it easier to add more and more floors to the building.
Strength of Concrete
Concrete had to be pumped all the way up the Burj Khalifa, the building is cast in place and this created another set of challenges, how do you get the concrete to stay liquid when it’s pumped up the building, it had to be a special mix that could stay liquid when transported and then settle when poured in the molds, easier said than done, the high temperatures in Dubai made it impossible to pour concrete during the day because it would set immediately, the solution was pouring the mix during the night, using 3 pumps to deliver 5826 cubic feet (165 cubic meters) of concrete.
The type of soil on the side of the Burj Khalifa is not what you would normally find on the site of a skyscraper, there had to be another solution, one that could hold up the Burj, even in when there’s a storm, which is a frequent occurrence in Dubai, the solution they went with is a pile foundation, friction piles are ingenious, the idea is that the weight of the building is carried on the friction from the piles against the soil. There are 192 piles to a depth of 50 meters, with a 3,7-meter raft of solid concrete on top of it, holding the whole structure up
Moving materials becomes an enormous task When your plan is to build the tallest building in the world, they hired cranes with a self jacking mechanism to solve the problem of moving materials, the crane lifts higher as each part of the building is completed.
The wind was Another problem, As a building get higher it sways from side to side even with the most moderate winds, the Burj Khalifa is no exception, it had to withstand gust up to 240 km per hour, the Burj Khalifa was designed without mass dampeners, normally found on buildings that are this tall, a mass damper works by moving in the opposite direction of the building’s movement, dissipating the kinetic energy, the solution was to soften the outer buttress edges and reduce the width of the tower higher up and reorienting the tower relative to the prevailing wind direction, resisting vortex shedding.
Every building needs cladding, it gets a bit tricky when it’s a building is as tall as the Burj Khalifa, Dubai is known for its high temperatures, aside from that you get constant winds blowing against the panels, 24348 individual panels had to be hung, to make things worse, the original company that was tasked with the glazing went belly up, pushing them back 18 months, clear glass would turn the building into a sauna, the solution was glass with 2 coatings, silver coating for the outside and titanium coating for the inside, the function of the silver coating is to capture the UV rays and reflect them out of the building while the titanium captures the infrared rays, reducing the amount of heat entering the building.
The spire was the last piece of the structure, getting it to the top of the building was a nightmare
How do you move 350 tons of steel up the tower?
There were no cranes that could lift that high. What the engineers devised was to construct the spire inside the shaft of the building and lift it using strand jacks.
It is clear that advances in technology make building these super tall buildings less difficult, expect to see more and more super tall structures like the Burj Khalifa, as the urban populations explode.