The Foundations of Our Skylines

Where do you start building a skyscraper? Logically, from the bottom – the most critical, and yet often unseen, part of a skyscraper begins underground. To hold such a massive structure in place, a heavy and solid piece of material is needed to anchor it. The foundations of these massive towers can vary depending on the size of the building and where it’s being placed, which may lead to some interesting design challenges.

How Does a Foundation Function?

The main purpose of the foundation is to provide a flat and stable surface to support the rest of the building. If there are large amounts of bedrock near the surface, piers as thick as five feet in diameter are often driven into the bedrock to anchor the building. In areas with loose ground, the foundation may act more like a raft which the tower sits on top of. Often a concrete mat is created at the bottom of these foundations, which is a pour of concrete usually several feet thick and can act as a weight to hold everything in place. In both cases, the foundation creates a stable and solid surface to build on top of, which also provides stability in the case of high winds or earthquakes. 

How are Foundations Designed?

It may seem logical that a taller building demands a deeper foundation, but this assumption doesn’t necessarily carry over into real life. The foundation of the Burj Khalifa consists of hundreds of piers that extend 164 feet into the ground, with a twelve-foot concrete mat. This foundation acts as a wide, stable base with a heavy weight on the bottom to keep the building upright in the unstable and shifting sands of Dubai. Taipei 101, a building over 1000 feet shorter than the Burj Khalifa, has a foundation that reaches 262 feet underground with anchors that are set into bedrock. Because the Taipei 101 foundation is anchored into bedrock, a thick mat is not necessary, and the anchors are extended much deeper than that of the Burj Khalifa in order to reach deep into the rock. In contrast, the Wilshire Grand Center building in Los Angeles has a foundation reaching only ninety feet into the ground but also with an eighteen-foot thick concrete mat, which holds the world record for the largest continuous concrete pour in the world. With such a thick mat, the Wilshire Grand Center foundation can function with a much smaller foundation than either of our other examples, at the cost of material.

While creating a foundation may seem as simple as pouring as much concrete as you can on the spot where you want the building, they pose a difficult challenge for engineers. Creating a foundation that confidently holds a skyscraper in place requires an experienced team, such as our team at DDA Engineers, P.A. Reach out to us for your next big project at (305) 666-0711.


The following two tabs change content below.

DDA Engineers, P.A.

Latest posts by DDA Engineers, P.A. (see all)