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Check out this plan for the (pre-9/11) World Trade Center: http://en.wikipedia.org/wiki/File:World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangm

by Pitarou 13y ago

Check out this plan for the (pre-9/11) World Trade Center: http://en.wikipedia.org/wiki/File:World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment.svg http://en.wikipedia.org/wiki/File:World_Trade_Center_Buildin... Roughly 1/4 of the area is taken up with elevators, stairwells, and so on. So here's a back of the envelope calculation: Elevator to office ratio: 1 : 3. Proportion of floor area that is usable: 3 / (1 + 3) = 3/4. To join the mile-high club, you need a building that's about 4 times higher. I will make the very crude assumption that, for a building that is 4 times higher, you will need 4 times as many elevators. Elevator to office ratio: 4 : 3 Proportion of floor area that is usable: 3 / (4 + 3) = 3/7 Usable floor area compared to floor area of the old World Trade Center, occupying the same site: 4 * (3 / 7) ÷ (3 / 4) = 16 / 7; or about 2.3 So it's doable, but it's ridiculously inefficient. Where you draw the line is an interesting question. 100 stories is already pushing the limits, but you can alleviate this problem by tapering the building, like the Burj Khalifa. This is remarkably similar to how the pyramid builders solved their problems. But what the pyramid builders really needed was the arch. And what modern engineers really need is an efficient vertical transport system. The obvious thing to do is have more elevators per shaft. Maybe something like a vertical cable car would work. Or even ditch the cables and make each elevator independently mobile within a network of interconnected shafts, like a vertical train system.

JoachimSchipper 13y ago
One high-throughput system is the http://en.wikipedia.org/wiki/Paternoster http://en.wikipedia.org/wiki/Paternoster. Unfortunately, it looks extremely dangerous, and in fact has caused a large enough number of accidents that it's banned in most modern countries.
- Pitarou 13y ago
  That's pretty much what I had in mind as a "vertical cable car". Looks like somebody actually built one in ... um ... 1884!
JoeAltmaier 13y ago
On the same note, in the last century brick buildings were limited in height by the thickness of the walls. If you went much beyond 20 stories, the ground floor walls filled the entire floor, making a sort of pedestal. So further height got zero further floor space. Steel buildings got around this. Hanging each floor from a steel skeleton means the walls don't get thicker at all. As you calculate, elevators are the new brick. The number needed to serve higher floors increase to the point the ground floor is nothing but elevators. So further height is pointless. Its exacerbated by the need to fill/empty the building in bursts - people want to work regular hours, and everybody works the same hours. So you need enough elevators to essentially evacuate the building in under an hour. Ways to work around this? Well, a pyramid structure would help I imagine. Elevators to server higher levels could be distributed evenly about the ground level, more in the center and fewer around the lower edges. That also increases windows-per-volume. And of course if people lived and worked in the building and rarely left it, then the need to 'evacuate' from the ground floor goes away. I imagine an arcology where people live, work and entertain in alternating levels. Fire and services can be located internally in strategic volumes. Air can be drafted up through the building using thermal gradients instead of fans. Need to write a storey involving this kind of structure sometime I guess.

by Pitarou 13y ago

JoachimSchipper 13y ago

One high-throughput system is the http://en.wikipedia.org/wiki/Paternoster http://en.wikipedia.org/wiki/Paternoster. Unfortunately, it looks extremely dangerous, and in fact has caused a large enough number of accidents that it's banned in most modern countries.

Pitarou 13y ago
That's pretty much what I had in mind as a "vertical cable car". Looks like somebody actually built one in ... um ... 1884!

JoeAltmaier 13y ago

On the same note, in the last century brick buildings were limited in height by the thickness of the walls. If you went much beyond 20 stories, the ground floor walls filled the entire floor, making a sort of pedestal. So further height got zero further floor space. Steel buildings got around this. Hanging each floor from a steel skeleton means the walls don't get thicker at all. As you calculate, elevators are the new brick. The number needed to serve higher floors increase to the point the ground floor is nothing but elevators. So further height is pointless. Its exacerbated by the need to fill/empty the building in bursts - people want to work regular hours, and everybody works the same hours. So you need enough elevators to essentially evacuate the building in under an hour. Ways to work around this? Well, a pyramid structure would help I imagine. Elevators to server higher levels could be distributed evenly about the ground level, more in the center and fewer around the lower edges. That also increases windows-per-volume. And of course if people lived and worked in the building and rarely left it, then the need to 'evacuate' from the ground floor goes away. I imagine an arcology where people live, work and entertain in alternating levels. Fire and services can be located internally in strategic volumes. Air can be drafted up through the building using thermal gradients instead of fans. Need to write a storey involving this kind of structure sometime I guess.