[Lewis Thomson (OP)]

Donald has been thinking about this recently.

"What prevents skyscrapers from blowing over in high winds or slowly leaning over in time? If abandoned, how long could skyscrapers persist before falling over (life expectancy)?"

Tell us your findings in the comments below...

[alancalverd]

Deep roots. Rust and weathering will gradually erode the structure from the top but it is unlikely that anyone would build a skyscraper with less than 1000 years' predicted structural integrity.

[kelsimcclain]

It's been a question on my mind. In 500-1000 years what will become of skyscrapers? Will they still be safe structurally? When will they begin to fall apart?

I'm assuming they aren't ever replaced or dismantled. I haven't heard of any research on it. Ideas?

[Bored chemist]

I'm assuming they aren't ever replaced or dismantled.

Why assume that?

[evan_au]

Skyscrapers are typically built with reinforced concrete.
- If the sand is poor quality (eg ocean sand rather than river sand), the salt will corrode the steel, the growing salt crystals will crack the concrete, and the building will fail prematurely.
- The concrete protects the iron from attack by atmospheric oxygen and pollutants. The concrete must be maintained to continue this protection.
- I heard one researcher suggest that reinforced concrete would last a lot longer if they included some nickel in the alloy of the reinforcing rods. But this costs money, and 100-year old skyscrapers become a treasured heritage or an eyesore (and often both).

[Petrochemicals]

Dismantelling a steel structure in New York will be much easier than dismantelling a concrete one. You obviously could not blow them up. They have not been around for long enough to know the effects of time opon the foundations but as a guess the foundations will suffer from geological movements, especially in places of tectonic boundaries. I suspect that many will start to lean as the ground they are built on moves.

[Bored chemist]

Dismantelling a steel structure in New York will be much easier than dismantelling a concrete one. You obviously could not blow them up. They have not been around for long enough to know the effects of time opon the foundations but as a guess the foundations will suffer from geological movements, especially in places of tectonic boundaries. I suspect that many will start to lean as the ground they are built on moves.

In reality, we have nearly 100 years of experience of taking down skyscrapers.
https://en.wikipedia.org/wiki/Home_Insurance_Building
And roughly as long experience showing that they don't lean over unless you build them in Pisa.
https://en.wikipedia.org/wiki/Empire_State_Building

[alancalverd]

The concrete protects the iron from attack by atmospheric oxygen and pollutants. The concrete must be maintained to continue this protection.

Looking for somewhere to build a clinic, I was surveying a basement with my mining engineer son. He looked at a section of the reinforced concrete ceiling and described it as "a slab of voids held together by brown stains". 

[Bored chemist]

The concrete must be maintained to continue this protection.

You don't "maintain" concrete. You make it thick enough in the first place.
Roman concrete is still around, doing its job.
And if you do that  the rust resistance of the rebar is irrelevant.