What were the purpose of the "discolered" floors in the old WTC buildings?

Factual Questions
1

What were the purpose of the “discolored” floors in the old WTC buildings? The dark areas about 1/3 and 2/3 of the way up them?

2

They were for technical services instead of offices. Each section was topped by a “sky lobby” where people switched between local and express elevators.

3

I don’t understand what the OP is referring to, but apparently you do. Would either of you please explain?

4

And “technical services” means they were full of air conditioners, water tanks, electrical switchgear, fire safety gizmos, and the like. IOW, mechanical floors.

5

These things

6

Take a look at this picture of the original towers – you can see darker horizontal “bands” on both towers, as the OP described.

7

As mentioned, look at any photo and you will see band of darker color on floors about 1/3 and 2/3 up (as well as near the bottom and at the top).

8

The color difference is the service floors have no windows

9

Elevators are only part of the answer, but I saw an interesting Nova program once about the problem of elevators in tall buildings. If you run all the elevators the full height of the building, and wish to maintain reasonable wait times, you have to keep putting in more and more elevators. Soon, a huge fraction of the floor space is devoted to elevators. The first solution to this is to introduce sky lobbies as mentioned above. The modern solution is to combine this with a control system in which you tell the system which floor you want to go to and let the computer figure out which elevator stops to pick you up. Apparently, this makes a big difference.

10

Or, of course, you can combine the two. Which is probably necessary anyway, to handle high-volume times (when a lot of people are going to or from their offices).

11

They gave King Kong a better toehold when he climbed up the South Tower back in '76. :smiley:

12

Some buildings have double-decker elevators.

13

The Eiffel Tower has those… plus, they have to travel in curves.

14

Thanks all, for the clarification. I was thinking “discolored” floors was perhaps in reference to um… something else.

15

No one seems to be addressing the obvious question to me.

Why make them look different? Plenty of tall buildings have service floors without making them stand out.

Since keeping a uniform look with windows would not have been difficult, I am guessing they wanted them there to break up the exterior? Maybe they thought it looked too uniform?

16

The mechanical floors needed venting, of course, so they can’t be windows but a screen. Buildings gotta breathe from somewhere. The architect just made the whole floor that way instead of just sections. I found this:

A few questions regarding design and structure of WTC | SkyscraperCity Forum (first answer). The answer includes a photo showing what’s behind the column facade.

17

In a lot of cases they do stand out, but the designs use that difference architecturally as part of the rhythm of the building. In the case of WTC, it looks like they simply swapped out the windows for vents/louvers, which are darker and don’t reflect light the same way as glass does. That’s more a case of “it is what it is.”

18

Thanks for the info, everyone!