World Trade Center Architecture

Ground Floor Photo ^ | John Jamieson

[ItCanHappenToYou]

Forgot to add that the arch is ubiquitous in architecture because it adds great strength and decreases weight of walls.

[Timesink]

I just can't see how they could believe that [attacks by plane would bring the Towers down.]

I can. There are basically two possibilities: that the terrorists were oblivious to the structural engineering aspects of this or that they were very well-informed about them.

If it's the former, they probably thought the WTC was no different than any run-of-the-mill building, except that it was a lot taller. And as supercat has said, most buildings would have fallen apart almost immediately from such an impact. So, if anything, they were probably surprised it took so long for them to come down.

If it's the latter, then they knew all about the WTC's structural integrity, and what it would take to bring it down. Thus they specifically chose those cross-country flights because those planes had fuel tanks filled to the brim. More fuel = a bigger, hotter fire = higher possibility of getting the steel to buckle.

[truth_seeker]

It would seem the terrorist planners at least had a belief they might bring the buildings down.

My intuition is the terrorist planners expected a big crash and many killed, but not the complete collapse of both towers. The collapse of both towers has effectively started a War on Terrorism, of a magnitude they probably didn't expect.

Maybe I'm wrong. But I somehow feel the unintended consequence of the attack, will be a big blow to Islam. This religion has a lot of ground to make up. It is now tied to this event, and will be suspect for a very long time. What goes around, comes around.

Or in other words, that which they meant to advance, was set back.

[Rome2000]

Of course now, after the fact, every engineer has an explanation and many claim to have known this would happen. I don't buy it

Not every engineer. I didn't think they would come down, of course, no one that wasn't there on the fire floors could know that the sprinkler systems were destoyed by the force of the explosions.

The fireproofing was also compromised by the explosions.

As far as the steel being destroyed by the jet fuel, the fuel burned itself out long before the towers collapsed, the rest of the flammable material was what continued to burn.

It was the lousy fireproofing of the steel, a new process long since discontinued to replace asbestos insulation, which was the primary reason the towers collapsed.

The steel would not have melted so quickly if it was fireproofed in accordance with todays standards.The fire could have been conceivably fought if there had been enough time.The fireproofing was supposed to last 3-4 hours.

The smoke evacuation systems in the stairwells were destroyed as well.

The buidings were designed to withstand fire, not massive explosions that blew out the fire protection systems.

[John Jamieson]

Huh, the arches on the WTC are not structural, but decorative. Main structure is 18" square tubes on 40" centers, with 22" wide windows.

[Arthalion]

Actually there are engineers who now believe that the fire supression system in the north tower, the first to be hit, was working perfectly. I was listening to a couple guys on TV discussing how the water mains for the towers were tied together, and how that one minor design problem may have destroyed the towers. Apparently, the builders of the tower never envisioned a scenario where both towers contained raging fires, so there was neither sufficient capacity or pressure to run the fire sprinklers on multiple floors in both towers simultaneously. After the north tower was hit, fire was burning in about 15 different floors...which was about all the WTC fire system was capable of handling. They noted that the fire did NOT appear to be spreading at that time, and that there was evidence of steam coming from the burning floors which indicated that the system was at least partially functioning.

The towers fate was sealed when the second jet hit the second tower. There wasn't enough capacity or pressure to spray another 15-20 burning floors in the second tower, so when those systems activated, both towers lost water pressure. This is evidenced by the fact that the fire in the north tower began spreading almost immediately after the other tower was hit, and the fact that the steam plumes stopped showing up in the photos and videos.

[Arthalion]

B) If the terrorists goal was to bring the buildings down, they would have dived steeper into a lower part of the building, and not such straight on attack. The best they could have hoped by the angle they hit would have thousands dead, but not the collapse of the buildings.

Actually, that would have been rather dumb of them. Like any tall building, the lower you went in the WTC towers, the more load each floor was carrying. Because the lower floors of the WTC carried the load of all the floors above them, they contained quite a bit more structural reinforcement and would have been harder to damage. Osama learned this lesson in the early 90's when he detonated that bomb in the basement...which carried ALL the weight of the building. He discovered then that the lower and heavier parts of the building were nearly impossible to breach, even with high powered explosives. Since the structure of the WTC became progressively lighter as you traveled up through the towers, the upper floors would have obviously been the better target to exact maximum damage.

Interestingly, we're actually rather lucky that the tower WAS hit high. A collapse of that type occuring lower in the buildings could have caused them to fall over like trees, which would have resulted in a MUCH higher number of fatalities.

C) The terrorists strategy was not as sophisticated as it is made out to be. In DC for example, they hit the Pentagon and it does not appear they gave much thought regarding the maximum damage a plane could do crashing into the Pentagon. It was very bad, but it could have been worse if they had more knowledge regarding structure. Whereas, in NYC they got very lucky.

We're fairly certain (based on evidence the pilots left behind) that the Pentagon wasn't the target, the White House was. The White House, surrounded by tall trees and buildings, is a hard target to hit which may have caused the pilot to pick a second target himself. Since he was already in line with the Pentagon and it's such a large, easy target to hit, it may have just been selected by default.

I also wouldn't assume that Osama didn't understand the nature fo the buildings he was hitting. He'd hit them before, and when he failed, he swore he'd hit them again. He spent MANY years planning this attack, and you can be certain that he reviewed it's publically available blueprints and building plans at some point in his planning. He knew EXACTLY what he was doing.

[Rome2000]

I don't know about the accuracy of that report.

From what I remember, each tower supposedly had gravity tanks on the top for supressing fires on the upper floors, as pumping water from the ground floor under any circumstances would not constitute a reliable fire protection system.

Each building would have had separate fire pumps to service the lower to mid tower floors, and they should have not been affected by the initial attack.

I understand that NFPA has prepared a preliminary report on the incident but for some strange reason it has been deleted from their website, probably for security reasons.

[ItCanHappenToYou]

Can you give me the name of a structure in Egypt to look at? I thought the Egyptian temples were hypostyle halls with tiny interior rooms for sacrifice to the gods. The rooms were only large enough to accomodate the priest. With the advent of the arch in Rome, larger interior spaces became possible, allowing larger groups of people to congregate.

Hagia Sophia was a Byzantine cathedral before it was a mosque. The air and light of Hagia Sophia ia a function of the massive dome and the windows in the base of the dome. Hagia Sophia was built in the 5th C; still the pendentives and arches that make it possible were discovered centuries before. The circular design is reminiscent of the Panthenon, with its many entrances and domed center. This structure can not escape its Western roots. JMO, of course. ;-D

[ItCanHappenToYou]

The arches may be more decorative than structural in the WTC, but they certainly don't hurt the building's strength. The ubiquitness of the arch that I mentioned refers to buildings made before the advent of the steel beam and glass skin construction of modern skyscrapers.

[ItCanHappenToYou]

OK, I stopped relying on what I remembered and looked it up, (OK, hastily, so this may not be the definitive word.) The first reference I found was to barrel vaults 2500 BC in the palace of an Assyrian king, Sargon II. I also found a picture of the Ishtar Gate, from Babylon, about 575 BC. So that places the arch/vault much earlier than I remembered, and from the Fertile Crescent area.

I looked and looked for vaults in Egypt and did find post and lintel vaults, but those are obviously not arches.

Maybe you can refresh my memory. Was it Sumeria that had those underground, vaulted, burial chambers?

[pbear8]

Thank you. My husband, whose degrees are in business and history, said a few minutes after the hits that those buildings were going to come down because the steel would melt. If he could figure it out, did not the on site authorities have the same discussion we had?

[ItCanHappenToYou]

Mycenea. I should have known. "Tholos" -- beehive burial vaults.

Here's a Link