This may have been discussed before, but after reading the thread about the Brooklyn Bridge maintenance, I wonder about tall buildings in NYC. For instance, the Empire State Building. Say in 50 years or whatever, how would you remove it? I seem to remember that they do not allow explosive implosion in the city. How might they do this?
You have to take it apart from the top down. Here’s a slideshow about dismantling the Deutsche Bank Building, which was damaged beyond repair on 9/11.
What you want is book called UNBUILDING by David Macaulay.
It is a fictional account obout the dismantling of the Empire State Buiding.
You don’t always have to demo a building top-down. I saw a building taken down more-or-less bottom up. It was one of those 60s circular towers (sort of like the old Captiol Records building in LA but much taller). They removed the outer part of the floors from the bottom up, leaving just the center core. As the project neared completion, it started to look like a weird mushroom. The core was surprisingly skinny. Then they took the core down in hardly any time at all.
The only part of a building that counts is the metal (or reinforced concrete) framework. The outer sheathing is irrelevant and can be taken off in any order.
The only real alternatives are top down or explosive implosion.
A big assed airplane?
::: flees:::
Will . . . not . . . laugh. 
Anyway, that wouldn’t work on a building like the Empire State bldg because of the type of construction - steel I-beams forming a series of cages on every floor. WTC was vulnerable because the supporting structure was mainly the external walls. Each floor was supported with trusses IIRC. They never could have built a commercially viable building of that size using traditional methods.
If there were every any doubt though, that would have been removed in 1945 when a B-25 bomber crashed into it.
Fifty years? I’d hope the ESB will last a lot longer than that. Anyone know what the building’s lifespan was intended/estimated to be?
Another two-thumbs-up recommendation for David Macaulay’s Unbuilding. Great book!
The ESB has no planned teardown date. With proper maintenance and barring a meteor strike or supercolossal earthquake, I’m sure they hope it will stand forever. In one of his books, Arthur C. Clarke suggested that its outer shell be covered with a microlayer of crushed synthetic diamonds, which could add centuries to its existence.
Actually, this is a bit off (I worked on the recovery for almost a year, if that counts). The two towers that most folks think of (ignoring the other buildings, oddly) were built with a central core - mostly around the elevator shafts - and the exterior columns (244 of them each) were there for redundant support.
In terms of demolition, as Freido indicates, you usually have to cut the things down layer by layer. Wrecking balls and explosives are highly restricted in NYC, because of the dense arrangements of other buildings and the fact that the whole damned city is essentially hollow below ground (subways, critical infrastructure, etc). A wrecking ball arrangement was, in fact, used (I think on Bldg. 4, if I recall), but it was mostly dropped vertically to separate the wheat from the chaff, as it were. Not enough room for swinging the sucker.
The guys from the demolition companies I worked with (Big Apple Demo was one, the other was from some more Southern state) were awesome. Top notch.
One of the tactics used in demolishing big buildings in NYC is to basically cut the roof off, pull in the walls on the top floor, remove debris, and then repeat until finished. Very risky work (the hordes below hate it when falling debris crushes them).
On the WTC buildings, we also (because there was enough space) “pulled” a building or two down by weakening the structure and, basically tying every damned machine we could find with tracks and yelling “go!”
Actually each WTC building core had 47 vertical steel beams tied together with steel plates on every floor.
Skyscrapers don’t have planned expiration dates. As long as it’s properly maintained and untouched by earthquakes and other massive events, there’s no reason a building couldn’t stand for thousands of years.
What actually happens with vintage buildings is that they become functionally obsolete. Some things can be fixed, but other things–such as the width between columns and the number of elevator shafts–are difficult to change.
ESB has not been considered a great place to locate a business for many years. To rectify this, the owner just got done spending $550 million on a renovation and is now retrofitting the building for high energy efficiency. That is making a positive difference in the office tenancy, but it’s safe to say the building really makes its money on the 4 million observatory visitors every year plus the TV/radio/cellular antenna rights.
I meant to mention in regard to the OP’s question: with the growing emphasis on sustainability, it’s becoming more common to attempt to reuse as much of a building’s materials as possible. “Green” project management aims to divert 50% to 75% of “waste” materials from the landfill. Steel can be recycled, e.g., while some of the concrete can be ground up on-site and used as gravel or whatever on the new project or one nearby.
Under the LEED rating system you get points for reaching (and documenting) the 50% and 75% goals. It also can save money, since you don’t have to pay hauling and disposal fees nor the cost of new materials. It’s not always cost-effective but it certainly can be on a limited basis, and as more cities and states adopt laws requiring LEED equivalent standards on new construction and renovation, taking down buildings brick by brick may become more common.
It was hardly a “skyscraper”, but the 13 story twin tower dorm I lived in at UW-Madison was demolished top-down a floor at a time.
Here’s a youtube video of the East building’s demolition. The West building (where I lived) had already been reduced to a hole in the ground in the foreground.
Here’s a video I came across a few months ago, showing a timelapse look at a “reverse demolition”. The bottom floor is removed, while the building is supported on pillars which then lower so that the one-time second floor becomes the bottom floor… and on and on.
There seem to be some streaming issues on the site that I don’t remember encountering last time I looked at this, so it may take a couple of minutes to get the whole 35-second clip.
I saw on TV that NYC does not allow implosion of buildings. There are too many things underground that can be messed up.