how are the weight on the first floor of a skyscraper able to hold the weight of over a 100 floors?
In: 570
Engineering. Piles are drove down into the ground sometimes until refusal (rock) and poured using insanely high psi concrete and rebar. Then the first floor is built on these piles as well as a slab on grade (solid concrete floor). Then columns set on all this to create floors. The floors of 2nd and up are actually mostly suspended except for a column here and there designed by the engineer to hold up X amount. The floors themselves are poured using lightweight concrete that is more porous and has fibers in them to help create tensile strength due to the lack of rebar (weight reduction). The columns are designed and located to withstand the subsequent weight of all floors and are usually located directly atop one another so each floor bare bones is the same. They just add fake walls,panels,etc to make it look like a office or food court or whatever it may be. The most fascinating part is each is given a certain amount of deflection (give) to allow for movement from wind earthquakes and the like. All structures are designed this way and are never rigid. Bridges move around and bend when weight moves across.
Being a construction engineer, I can ensure you that the floors won’t carry the weight of the other floors above. The columns and beams or the walls do this.
A good example is the world trade center. The steel beams melted and the building collapsed. Everything is attached to the pillars on each floor.
https://www.google.com/search?q=twin+towers+steel+structure+behond+sun&tbm=isch&ved=2ahUKEwjq2qqWlo_4AhXGj9gFHTXQBQYQ2-cCegQIABAC&oq=twin+towers+steel+structure+behond+sun&gs_lcp=ChJtb2JpbGUtZ3dzLXdpei1pbWcQAzIECB4QCjoECCMQJzoECAAQHlCpDVi0L2CANGgAcAB4AIABbIgBgQmSAQM3LjWYAQCgAQHAAQE&sclient=mobile-gws-wiz-img&ei=VOOYYurgKMaf4t4PtaCXMA&bih=733&biw=412&client=ms-android-samsung-gn-rev1&prmd=imvn#imgrc=ADnt-50LCgV7zM
For a long time, they couldn’t! Which was why brick and steel skyscrapers were so rare.
Glass and aluminum are pretty darn light, and that means you can build a skyscraper taller than before. Wind can start to be a problem though
Take a look at the floor, go down a floor, take a took at the ceiling. Is the upper floor holding anything up? No.
Imagine a tree. You want to build several platforms around the tree. Instead if building the second, third, fourth etc. platform on top of the first platform, you anker each platform on the tree trunk. So each platform is supported by the tree trunk. Same goes for building, only there are pillars (interior and sometimes exterior) which the floors are ankered to.
To put it simple: Because the load-bearing elements are designed and dimensioned to do just that.
It’s not the first floor that holds the weight, it’s the pillars that support the entire building, along with the foundations in the ground. To make the building strong enough to withstand the entire thing, it’s made up of different types of material throughout . For example, the most common type of pillar is using strengthened concrete, which is just basically steel bars inside a concrete block. This is also why the foundation of a building is super important, otherwise it might collapse on its own weight.
Also keep in mind that skyscrapers often have several floors below, except in NYC, which was blessed with lots of solid granite bedrock, meaning Manhattan skyscrapers need less floors below.
The first floor doesn’t hold up the building. The weight of the building is supported by the ground and the foundation. Each floor only supports itself and the contents of the floor.
Latest Answers