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Building a 3000m tall building..!! Is it possible?

Fun stuff...!!

A 3000 m tall building is definitely possible. Let us say we have infinite sum of money. Just for the sake of simplifying things so that we can focus on engineering. Challenges?

1. Wind
A structure this tall will be under a giant amount of wind force and I am not saying that it is not possible to resist, we can resist it, but with intelligent engineering. In such cases wind tunnel tests are conducted and the shape of building is put up in such a fashion that we can reduce the wind forces. For example, the current tallest building of the world, Burj Khalifa is standing under the same principle. 


As Will Baker (Bill Baker) says that, the design of the tower is such that it confuses the wind force. The wind force increases as the height of the tower increases, and if the building height is like that of Burj Khalifa, than the allowable deflection is 3m or so which can make the people inside the building uncomfortable. So what they have done is, they have regularly changed the profile of the building so that the boundary layer of wind that is formed around the building is the turbulent one. Also the wind that is flowing will get confused with height because of the change in the shape of the structure. This reduces wind force drastically and helps the tower to remain upright. The lateral forces are simply carried by the tower frame and spinal wall system. This is the most innovative thing that I have seen in my entire life. I did a final year project on wind forces and profile around the structures and found that it is actually the best way to reduce the wind forces. 

Apart from this we can use things like Tuned Mass Dampers which can help in reducing the wind induced deflections at the top. It is just a big chunk of mass suspended at the top of the building which works in direction opposite to the motion of the building. Taipei 101 has a TMD which can help in reducing the story displacements or you can say story movements.


 
2. Earthquakes

As we all know how devastating earthquakes can be. But don't worry, taller buildings perform better and show much more anticipated deformations during earthquakes than a shorter building. So we can design such building pretty efficiently with accurate runs. Before even such building is built, we can test the structure for an actual earthquake and see if it will resist the forces or not. 

For resisting earthquakes and wind we use something called Lateral force resisting systems which can be huge walls in the center and massive columns around the perimeter. Definitely the wall will utilize tremendous amount of space, but anyway we will require such space for 1 reason. Vertical Transportation

3. Vertical Transportation

You know it takes around 10 minutes to reach the top of Burj Khalifa, that it is the highest occupied floor located at 585 m from the ground? It is because no single elevator goes from bottom to top. You will be switching elevators as you switch metro trains. So imagine the same thing for a 3 km tall building. We will require many more elevators with transfer levels. In a building like Burj Khalifa there are 57 elevators. So in such building we will require anywhere around 150-175 elevators assuming that the elevators are much more faster than ever used till now. Or we will have to create a new concept of floating elevators similar to Isaac Gaetz's answer..
Isaac Gaetz's answer to What would you build if you had a dream team of engineers and an unlimited budget?

Thus in order to provide these many elevators and stairs so on, we will require a huge central space around which we can construct a core wall or a Lateral force resisting system. If you do not know what LFRS system is, here is a picture as an example:
The central network of walls is called shear wall or core wall system. These massive walls can resist the lateral forces.

4. Strong soil

Now, if you have to stand strong and tall you require strong foundation. This foundation will be a combination of a Raft and piles. The foundation will be around several feet thick and the piles will be drilled at least 150-175 m deep into the soil. This will make the total depth of foundation equivalent to 175-200m deep from the lowest floor. I am saying lowest floor as the building is so huge, it will require several stories of parking. The foundation of Burj Khalifa which is 828m has piles driven about 50 m into the ground and has raft which is 3.7m thick. Now you can imagine why we require such a giant foundation. The foundation of Burj khalifa looks something like this:
The plate you are looking at is a Mat while the tubes are piles driven into the ground.

5. Parking

It has to be a mixed use building. This means you will require several floors of parking. And in order to make everything quick so that people don't have to drive 15 or 20 or 30 stories into the ground or above the ground, we will have to work with automatic parking system, where in you stop your car at designated location and a whole chain of automated machinery will take the car to an empty spot. This is the only way to make the system efficient. (Automated parking system) Many places have already adopted such parking system. 

6. Fire

In case of a catastrophic fire we will have to think of something innovative where people don't have to come all the way down to the ground in case of fire. A concept of Refugee rooms has been adopted in tall buildings where in there are big fireproof rooms constructed at every few levels where people can lock themselves in and wait for firemen who can rescue them. Apart from this we will require strong pumps to pump water to the top of the building. It can all be done.

7. Construction

If you want to construct 3 km above the ground, you will have to pump concrete up-to that level. Now we have pumped concrete in Burj Khalifa and guess what, it is not up to 828 m, rather it is up to around 600 m. So we will face a tremendous amount of challenge to pump it up to 3000 m without letting the concrete dry. We have methods, but we need to improve those. Let us see till what level we can pump concrete in Jeddah Tower.

If we achieve these feats then rest of the problems are not so big. Imagination is a beautiful thing, it can take us anywhere, but it is reality that limits us. 

Fun fact:
http://www.equipmentworld.com/is... 

Enjoy.