Construction of Ultratall (1000m+ ?) Buildings

[Dense_Electric]

So here's my story (if you don't care about the backstory, just skip down a bit): I'm working on a science-fiction project at the moment. Its current incarnation, dubbed 'The Ledyard City Chronicles,' is the latest version of what's been developing in my mind for literally the last twelve years or so (maybe longer). I might even say that the Ledyard City Chronicles is merely part of the larger universe I've created based on the whole decade-plus of imagining, but that's irrelevant for what I want to talk about here.

As you may have guessed from the title, the main setting of the story is Ledyard City, a fictional city set on the border of Michigan's upper peninsula and Montreal, Canada (downtown is on Sugar Island, to be renamed – think of it as the Manhattan of Ledyard City, with the other boroughs being Ledyard City's various wards that extend out for miles in all directions). I want to make this story believable and memorable in part by paying close attention to the details, so I'm asking for your help in figuring out something very important – building construction.

The main story is probably going to take place some time in the late 2090's/early 2100's, and I've decided that I want the average skyscrapers of the city to be somewhere around 1 to 1.5 kilometers high, the taller ones being 2 to 2.5 kilometers (maybe achieving some of that height through spires).

So, two main points of discussion:

One, do you think this is a reasonable height for late-21st century ultratall skyscrapers to reach? This story is toward the harder end of sci-fi, so I want it to be believable. Personally, I think this is a good balance between extremely tall structures and not having them so tall they just become ridiculous, but I'm eager to hear your opinion. (For the record, you can assume that titanium, carbon nanotubes, and other cutting-edge building materials and techniques are cheaper and more common than today).

Two, assuming buildings of the heights I'm discussing are reasonable, how would they be built? What might be some common features of them? Engineering challenges and solutions? Anything else you can think of? Here's a list of a few features I've devised that might be common in Ledyard City (comments and critiques welcome):

- Buildings consisting of multiple cores (maybe four or nine arranged in a square) that can play off each other by way of semi-flexible connectors to counter-act wind forces.

- Buildings built as multiple, narrow towers connected by skybridges.

- Multiple floors of liquid-filled mass dampers spaced up and down the building to counter-act wind.

- Express elevators of five, six, or seven levels and local elevators of two or three, connected by multi-story sky-lobbies so as to reduce elevator footprint size.

- All elevators would have emergency on-board power sources, and could operate independently in the event of building-wide power failure.

- At higher floors, buildings could be pressurized (and have air-locks for roof access).

So, thoughts?

[jigglysquishy]

Buildings over 1000m will never be economically viable. We are just seeing the first economically viable 300m tall buildings and that's in the most expensive place on the planet, Midtown Manhattan.

So it really is science FICTION to have the planet covered in ultra-talls.

[Dense_Electric]

I'm not so concerned with the economics of such structures (I'm hardly considering covering an entire planet with them, merely a few square miles of one island), suffice to say that in the context of the story, that wouldn't be an issue.

The issues I'm more interested in are structural. Imagining that money is no issue, I'm really trying to figure out what such buildings would look like.

I may pull back the average height though (around 400m-ish), merely for the sake of not making the city impenetrable to sunlight. At this average, the taller buildings that stand out against the skyline might be around 600-800m, with the tallest building in the city being around 1.5k (that may be with a spire, I haven't decided).

[Urbana]

I would make sure to stick with the current trend of a large base tapering to a sharp point as we have seen in the burj khalifa and most other hypertall buildings

[Wizened Variations]

Originally Posted by Dense_Electric

I'm not so concerned with the economics of such structures (I'm hardly considering covering an entire planet with them, merely a few square miles of one island), suffice to say that in the context of the story, that wouldn't be an issue.

The issues I'm more interested in are structural. Imagining that money is no issue, I'm really trying to figure out what such buildings would look like.

I may pull back the average height though (around 400m-ish), merely for the sake of not making the city impenetrable to sunlight. At this average, the taller buildings that stand out against the skyline might be around 600-800m, with the tallest building in the city being around 1.5k (that may be with a spire, I haven't decided).

All points to the price of energy and the real cost of materials. Very cheap energy, perhaps 1% per joule of current prices would radically change structural fabrication and construction techniques. If mass could be pulled down from the asteroid belt (imagine a 10 km3 cube of high grade iron), fabrication and construction techniques were change further.

In addition, anti-gravity used in construction would be cool, too. In that case, construction would be far cheaper, and, square cube laws in terms of mass support, etc., would not be necessary (could not resist).

The question for you, sir, would be what social structures would have to evolve to keep human sanity in a vast city.

(I keep thinking of red and blue pills for some reason).

Keep writing.

[uaarkson]

Originally Posted by Dense_Electric

Ledyard City, a fictional city set on the border of Michigan's upper peninsula and Montreal, Canada

Uh. If you're focusing so much on details, you may want to take a quick glance at a map...

[Dense_Electric]

Originally Posted by uaarkson

Uh. If you're focusing so much on details, you may want to take a quick glance at a map...

Derp, Ontario. I was getting Quebec and Ontario switched around.

Originally Posted by Wizened Variations

All points to the price of energy and the real cost of materials. Very cheap energy, perhaps 1% per joule of current prices would radically change structural fabrication and construction techniques. If mass could be pulled down from the asteroid belt (imagine a 10 km3 cube of high grade iron), fabrication and construction techniques were change further.

In addition, anti-gravity used in construction would be cool, too. In that case, construction would be far cheaper, and, square cube laws in terms of mass support, etc., would not be necessary (could not resist).

The question for you, sir, would be what social structures would have to evolve to keep human sanity in a vast city.

(I keep thinking of red and blue pills for some reason).

Keep writing.

I'm liking some of this, perhaps some sort of anti-gravity technology functioning like a modern-day mass damper. Very sci-fi, and yet functional.

I'm also playing with the idea of multiple cores starting spread out at the base and tapering together near the top (sort of like the supports of the Eiffel Tower). From there, a central core for elevators, stairwells, air, water, etc., could be added, and floors spaced in between. The footprint of the building would be large enough that there would be plenty of floorspace even with four or five separate cores like that.

[THE BIG APPLE]

The building of ultratall buildings really doesn't impress me, and I really don't think people know how much of an impact this'll have in the future. It's like putting an entire city in one building, (it's where the phrase "city within a city" comes from). That means people will not live spread out, but instead in one concentrated area. This eliminates the need for parks (I hear those sky gardens are really nice), libraries, schools (why not just put schools in there, there's space), banks, shops, malls, mosques, churches, synagouges (you name it), airports (hey, they have heliports), arenas, stadiums, hospitals, rivers (drainage, you never know), mountains (in china), museums, planetariums, exploratoriums, even transportaions itself (if a city is in a building than what's the need for trains to go to other buildings in a CITY. I think they stop this mega or ultratall concept and build how much is required and necissary and leave it at the Burj Dubai and let it literally say that I'm the only legit building that's twice the height of the Empire State Building. Before anyone says I'm wrong or that I don't know anything. Hey, the nomads didn't know they could domesticate and stay in one area. The farmers didn't know they could spread out from the one area and make many areas. The people of the many areas didn't know they could make even more many more areas. The people of the many more areas didn't know there could one day be even more many areas combined called cities. The people of the cities only thought that buildings could be built only be one floor high. They DIDN'T know that buildings could one day reach 160 floors just like we don't know, if building could become cities themselves and eliminate the need for cities entirely. Get the point?

Phew that was long.