Skyscraper Foundations

We liked our bridges book so much, we got the companion volume on skyscrapers. It had some great information on the different types of foundations and footings used for skyscrapers on different types of soil. We did this demonstration of how concrete piles in the foundation manage the tower's weight by distributing it among themselves. It works the same way as lying or stepping on a bed of nails! You can see we put toothpicks all throughout this clay "soil," above. A building built right on the clay would slowly sink into the ground. But with these piles making up the foundation. . .

the building is very well-supported!

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We varied this a bit to demonstrate how the weight of a skyscraper is distributed more on the outer edges---allowing "tube" tower construction which makes for very strong towers, such as the Willis tower in Chicago. You can see how if we remove the inner piles, as above . . . 

The outer ones alone are able to support the structure! When we did the opposite thing (removing piles from the outside, leaving only a mass of piles in the center), the piles collapsed under the same load.