jonnyboi, 🙂

Add impact damage from an enormous collapsing building, failure of sprinkler systems, withdrawal of the fire department and let the fire burn unchecked for seven hours and yes, that’s what happens in the case of WTC7.

Thermal expansion is a bitch eh?

Thing is though, surely if fire does cause damage to the steel, at best it will only cause localised buckling of the steelwork, which would mean only a small portion of the structure would be likely to collapse…

Even with the additional damage sustained from debris and seismic shock, such complete collapse is surprising, if nothing else.

However, let’s not forget:

The only question is: Was anybody in on it?

For some reason, that reminds me of AIG (American International Group)’s role in the 2008 global financial collapse, but that’s not likely to be relevant here, is it…

I genuinely think that at the time they didn’t consider that it had been necessary. The world had witnessed what happened. It’s easy for us to judge in hindsight

Well apparently not.

? buildings on fire, you couldnít see anything.

So it took us a while (i.5 hrs) and we ended up backing
p
p everybody out, and thatís when 7 collapsed.

Lieutenant William Ryan, Ladder 85

Yet they could see well enough to carry out a structural inspection to determine when it was going to collapse?

Do i think a 100 tonne aircraft doing 500mph could damage the towers?

Seriously? No, i’d expect it to just bounce off without even scratching the paint……

(back of an envelope calc suggest around 4GJ of energy stored in the planes mass at that speed, or about the same as an entire tonne of TNT going off. so yes, plenty enough to damage a building! In fact, it’s more amazing that the Towers even survived the initial impact at all!)

So answer my second question then !

I call that reviewing !

Ive been here since page one Johnny boy

Hit a nerve did i? Imagine how angry you’d be if someone you loved had been killed and some other idiot was talking total rubbish about the way they were killed…….

Have some respect.

So a thin skinned aluminium airplane can penetrate to the core and cause sufficient damage, could you scan in and post your back of an envelope calc, keep it simple eh 😉

In fact, it’s more amazing that the Towers even survived the initial impact at all!)

So was it the fire or the impact that caused collapse ?

Johnny Boy has established it was fire !

I can’t take the credit, but you’d know that if you were paying attention rather than trolling

The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t.

As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. This started the domino effect that caused the buildings to collapse within ten seconds,

No it didn’t. Nothing like a controlled demolition. Nothing like it at all. In a controlled demolition the entire building falls at the same rate. The WTC didn’t. There was a failure over a couple of floors, the top part of the building clearly fell before the bottom part of the building did. Not sure how heavy the top part of the building was – maybe around 10,000 tons? traveling at 20mph, it is going to be pretty hard to stop and can easily over stress steel and reinforced concrete.

The fact aircraft are made of aluminium is utterly irrelevant. A ton of aluminium weighs the same as a ton of steel and has the same energy at the same speed. The fact is 100,000kg of material slamming into the side of the building is going to do some damage no matter what material it is. But what about engines? 10 tons each of pretty much solid titanium, what about undercarriage, again pretty substantially solid projectile, all the motors, systems, boxes of equipment, avionics etc, seats, luggage, they’re all pretty solid structures which became projectiles. The towers were designed to withstand the impact of aircraft anyway. Maybe not a fully laden 747, but upto 727/737 size at least.

The building didn’t have a steel outer skin. It was not armoured in any way. It was a steel girder skeleton so perfectly feasible for the aircraft to penetrate the building – girders are designed to withstand forces in compression and tension – not in bending from a side impact. Have you not seen the footage? aircraft clearly penetrating the side of the buildings. You’ve seen it with your own eyes and yet you doubt it.

Anyway the towers are mostly fresh air with a very skeletal structure. So not that solid or sturdy in relation to impacts from the side:-

Erm, yes….localised ‘buckling’ will do it. A buckled girder no longer has strength in compression. The failure mode of the collapse was an initial collapse localised to one or two floors. The sheer weight of the top part of the building did the rest. Perfectly understandable and explainable with simple engineering principles. The north tower was hit first, but at a higher level, so about 14 floors above the crash level. The south tower was then hit lower down with about 30 floors above the crash level. The South tower collapsed first because of the higher weight of the upper part of the building. Again, perfectly explainable by engineering.

Only to those ignorant of basic structural engineering principles. Steel is not a very good material at elevated temperatures. It looses a significant amount of its strength at a relatively low temperature of 500 ish degs C. Why is it so difficult to grasp the concept that if you significantly weaken the structure of a building it will collapse??? Really, what is so difficult to grasp with that concept?

You really don’t have a coherent argument to make. That is clear

They didn’t. Do some reading

It’s irrelevant that they were aluminium – that mass of water at that speed would have made the same size hole

My calc is near 6GJ – and I did also calculate once that the chemical energy in the fuel is about 3 orders of magnitude bigger.

Unlike most buildings, the cores in WTC 1 and 2 were not the primary structure, that was the perimeter columns.

Until the Ronan Point partial collapse in 1968, nobody really considered progressive collapse, but after that the UK building codes required larger buildings to remain stable if one column was removed. The US codes didn’t make this change until after 2001.

You seem like a gullible chap, care to help out a Nigerian prince looking to hide his money?

Could people stop asking for “things to be explained” and then not listen to that very explanation!

I have explained in multiple posts how, using science, engineering and physics, the events of that terrible day most probably occurred. If you are so blinkered as to choose to ignore those explanations that is fine, that is your decision, but if so, you can’t then ask for it to be re-explained to you.

No it’s not plausible at all. Drone planes???? The location of every 757 and 767 ever made is known. It is tracked. So where would you source a 757 or 767, make it ‘disappear’ only to re-appear as a drone? Also aircraft parts are serialised so the manufacturers have confirmed the serial number of every component retrieved from the site. It’s impossible.

Even if they were drone aircraft you couldn’t fly them accurately to a specific floor. I can’t believe you really think this is more plausible than terrorists hijacking aircraft and flying them into the buildings.