This puts any of our challenges into perspective

[saveasteading]

"  it’s a steel frame building, so it would not be a total collapse. It would be more of a localised collapse.   "

 

Wishful thinking perhaps, or some words to keep the shareholders and banks happy?

 

Steel buildings can collapse. There is an inherent ability for them to crumple and come to some sort of stability if there is a localised failure. But I don't think this was designed for back in 1960.

in Europe we have to design to prevent "disproportionate collapse" ie one failed element, eg from a gas explosion, would cause only local damage.

see Ronan Point 1968 

 

 

34 minutes ago, ProDave said:

the collapsed columns were likely not reinforced properly and could not support the weight above

That's a fire officer... 

[SteamyTea]

6 minutes ago, saveasteading said:

see Ronan Point

There is a great documentary about RP. One of the contractors still found it funny how they got paid more to put less bolts in. Wankers.

 

8 minutes ago, saveasteading said:

"disproportionate collapse"

Wish I had known that was a 'thing when I was studying engineering. It would have been a hard sell in some companies I have work for, but the opportunity to build models and then destroy them would be great.

[ProDave]

I was surprised at the total collapse of the twin towers of 9/11.  I would have expected the fire compromised floors might just have collapsed down leaving the largely undamaged floors above and below intact.  I can only guess that when one floor collapsed, the momentum of the structure above put too much force on the floor below when it "landed" on it and so a chain of events started.

[SteamyTea]

1 hour ago, ProDave said:

I was surprised at the total collapse of the twin towers of 9/11.  I would have expected the fire compromised floors might just have collapsed down leaving the largely undamaged floors above and below intact.  I can only guess that when one floor collapsed, the momentum of the structure above put too much force on the floor below when it "landed" on it and so a chain of events started.

Maybe the 900 GJ of chemical energy per plane had something to do with it.  That is about 200 tonnes of TNT.

And that is before the kinetic energy of the impacts.  About 200 MJ, about 50 tonnes of TNT.

 

[saveasteading]

2 hours ago, SteamyTea said:

the opportunity to build models and then destroy them would be great.

 

This happened in my uni year one. Tiny portal frames tested to destruction, and thus stuck in my mind thereafter that a frame needs 3 'pins' to form.

(You can see that in the photo... top, middle bottom have all rotated.)

If it had simply been 10 minutes of a lecture it wouldn't have had the same effect.

 

 

1 hour ago, ProDave said:

the momentum of the structure above 

Dead load becomes dynamic load. Also that the loading of the remaining structure becomes out of balance, and in the RP example  the floor collapses are accumulating to be ever increasing  loads.

[Mr Punter]

On 11/07/2026 at 11:16, saveasteading said:

see Ronan Point 1968

 

Ronan point was built with sectional structural slabs of concrete for walls and floors.  I understood the building in the OP was steel framed.

[saveasteading]

The same rules apply.

In efficient structural design concrete beams and slabs would be completely integrated, but these appear to have been designed for speed and tying in has been for location and nothing more.

The NY building probably has concrete floors too, tied to the steel with studs.

 

 

[Alan Ambrose]

Looks like the contractor didn’t put in the required reinforcing. Odd really as it was obviously important…

 

 

[Alan Ambrose]

Maybe it just fell off someone’s project plan. Also odd though that the engineers were not inspecting. Or failed to notice.

[saveasteading]

59 minutes ago, Alan Ambrose said:

contractor didn’t put in the required reinforcing.

Thanks for posting that.

It's not easy to see, but I reckon they've done something like it but not as drawing, and also there probably shouldn't be  a discontinuity.

 

1 hour ago, Alan Ambrose said:

odd though that the engineers were not inspecting.

Yes, I've been the Contractor's Engineer and also the consultant's (acting for the client) on different big projects. In all of these the checking was very thorough by both.

But I've no idea of the US (prob NY own rules) ways. perhaps the contractor and designer were the same ownership.

 

Remember too that it is easy to see now, but during construction this is a birdcage of steel with no floors... No excuse but it would not be for the faint-hearted to check every detail in-situ.