Is it possible for a skyscraper to be constructed such that it can survive it's floors burning?

Factual Questions
1

A certain major motion picture was recently released, staring one of Hollywood’s most moneymaking actors at the present.

A central plot point was a kilometer+ high tower that has a raging inferno, starting at a floor about halfway up and growing to consume all the flammable materials in each floor above it.

A tower at this ~1000m height would have tremendous structural load. And for movie plot related reasons, none of the fire sprinklers are working, so the blaze is out of control.

Anyways, would the tower definitely be at risk of structural collapse? Or do construction methods exist to protect the structural elements from the fire so that the building remains standing?

2

Have any steel and concrete skyscrapers fallen because of fire? I remember the 911 people saying it never happened before.

3

“Definitely be at risk”? I suppose there is some risk, but they don’t “definitely” collapse. See Grenfell Tower fire in London last year.

Yes.

4

The 17-story Plasco Building in Tehran collapsed after a fire last year. The 24-story Edifício Wilton Paes de Almeida in São Paulo collapsed after a fire earlier this year. (The Edifício Wilton Paes de Almeida had been abandoned and was occupied by squatters; various things may have been done, or alternatively were no longer being done, that compromised the building’s structural integrity and resistance to fire.) Of course, both collapses took place years after the 9/11 attacks.

5

So there’s a Quora on this. https://www.quora.com/How-many-steel-buildings-have-collapsed-from-fire-besides-WTC

Apparently, yes, it’s happened a number of times. It doesn’t require jet fuel, burning offices is enough.

But it primarily depends on whether it’s steel or concrete. Apparently, concrete - and concrete coated steel - does pretty well in fires and rarely fails from the heat. But steel is enormously vulnerable, Quora shows a figure that indicates steel loses 90% of it’s strength at half the melting temperature.

So, in reality, conspiracy nuts are just nuts. If an aircraft slams into a building and starts a fire that weakens the structural steel of a building to 10% of it’s normal value, that’s enough. And in WTC, the girders were coated with a spray on material that had gaps, not to mention the aircraft impact no doubt damaged a lot of the fire protection. It also caused immediate structural damage to portions of the steel columns, just from the aircraft collision, further weakening the margins supporting the structure.

Anyways, the problem with a 1 kilometer structure is that concrete is far too heavy. At that height, you probably would need to use structural aluminum to save weight. And a quick bit of googling says that structural aluminum has less resistance to heat than steel does.

The only way I can think to do a mega-tall building and have it be fire resistant would be to use something semi-sci fi. Something like structural elements manufactured from the factory with a vacuum ceramic insulation. Vacuum ceramic (the stuff they use on space shuttle tiles) would be basically immune to the fire that could burn in a skyscraper, the problem is the stuff is very fragile and ironically would be destroyed from an aircraft impact.

Or, the other way, and this is the solution they had in the movie, it just didn’t work - would be active defenses. Basically building scale fire extinguishers. Not just sprinklers, special nozzles that can spray that fire suppressing powder that dry fire extinguishers have in them.

6

Not really. The Burj Khalifa is 828 m tall; almost a kilometer already. It used C80 concrete, which more or less means a compressive strength of 80 MPa. However, fiber reinforcement and other factors can yield concrete with >200 MPa strength. Even without higher strength concrete, tweaks to the shape and internal density distribution could get you well over a kilometer (the Burj Khalifa is rather slender).

7

In the history of steel-framed buildings, only 3 have ever collapsed. And they happened on the same exact day, were all heavily insured, and owned by the same person. So i guess collapse is possible

8

Good info.

:smiley: I guess since they fell after 911, it’s part of the cover up. :smack: :smiley:

9

That shouldn’t happen in any decent building built in the last 100 years. Of course it /does/ happen, but when it happens something has been done wrong.

10

Movie plot spoilers : the automated dampers to cut off ventilation in the case of a fire were built by incompetent Chinese engineers who made them all centrally controlled and thus hackable…

11

… if you don’t count the other 2 that have already been mentioned in this (GQ) thread.

12

Plus the tower in Spain that collapsed except for its concrete core - the Windsor Tower in Madrid - also quoted to people who claimed that 9/11 was a conspiracy. In fact, steel towers are a lot more difficult to blow up than concrete ones, since steel is more resistant to crumbling.

And in fact, there were two minor fires few miles from my house around the same time as 9/11 and in both cases, the main steel I-beam (previously) supporting the second floor was visibly sagging in the damaged property. It does not take much to turn steel into taffy.

13

Windsor specifically did not collapse. Everything which could burn pretty much did, but the whole structure (including floor/ceilings) resisted. Even the crane which had been sitting atop the building for the two years it had been under remodel was ok. The building was later dismantled from the top down.

14

There is a pretty spectacular video of Edifício Wilton Paes de Almeida collapsing.

15

As I understood it, the steel structure part of Windsor collapsed (due to fire weakening the structural steel) while the concrete core part did not… which demonstrated the vulnerability of structural steel. But generally, unless the building is packed with flammables, or they are delivered by the plane-load to the middle of the structure, there should not be enough material to create a significant fire that can outrace the sprinkler system. …should…

16

In that particular case, one of the things that was being done waaaaas…

set up the sprinkler system.

And I’m not even sure what do you mean by the steel structure part vs the concrete core part. Are you thinking I-beams surrounding a central concrete part? I’ve seen those in multiple American buildings but the Windsor didn’t use that kind of setup; beams were cemento armado, concrete on rebar.