Why Did the EXTERIOR of WTC 1 & 2 Fail?

You are right, I forgot the numbers I thought it was in the order 20/80 but it looks like the perimeter is even able to handle 40% which makes it even more shocking.

Samkent, yes dynamic loads, very basic. It is like the chicken and egg. You first need speed to build up a thresshold level energy to crush the building. But that thresshold will not be reached when there is no speed.

originally posted by: drommelsboef
crush the building.

"Shear off the truss seats" would be the correct phrase.

a reply to: skyeagle409

Oh my god the logic in this reply may cause my head to explode


Based on the OP, the exterior columns shared the load with the core columns. My understanding (I freely admit I can't find the reference) is that the core however head a much higher load. Also the exterior became progressively thinner because the structure was lighter on the upper floors. When the aircraft impacted the Towers, it did significant structural damage to both the exterior columns and the core transferring the loads to the undamaged columns.

The structure was designed to absorb the impact of a 707 travailing at or near approach speeds. Not an heavier aircraft travailing much faster

originally posted by: waypastvne

originally posted by: drommelsboef
crush the building.

"Shear off the truss seats" would be the correct phrase.

Actually, "crush the building" would be a more accurate description. If it was just "shearing off truss seats" You'd have a hollow shell with 110 floors piled up at the bottom.

originally posted by: waypastvne
Just what caused all those panels to fail at the same time?

Still no answers from the truth movement as to why the walls pulled in before collapse.

I've got a simple question for you. OSer's like to claim that sagging trusses pulled the exterior panels inwards on the towers, so how did the entire internal structure of WTC7 supposedly collapse without affecting the facade at all? In fact, seeing as how 7 used beams instead of trusses and the exterior was nowhere near as robust as the towers, the collapse should have ripped the facade apart.

a reply to: Flatcoat

That would depend on how the interior structure failed in WTC7.

Also you only see the WTC7 from one side.

a reply to: Flatcoat

If it was just "shearing off truss seats" You'd have a hollow shell with 110 floors piled up at the bottom.

The exterior shell needed the lateral support of the floor trusses to prevent buckling.

so how did the entire internal structure of WTC7

This thread is not discussing 7.
Feel free to start a new thread.

Shoot... I was hoping this test was about the interior core structure.
Because the answer would be ACE Elevator company personnel .
well at least I bet they hung around to help people trapped
by their elevators.
usatoday30.usatoday.com...
oh well.
maybe the exterior walls melted?
youtu.be...

Hey, how did the 22nd floor Operations Control Center at 1WTC
blow up if the magic jet fuel from the Car 50 elevator shaft
didn't go to that floor ? youtu.be...

a reply to: Flatcoat

I've got a simple question for you. OSer's like to claim that sagging trusses pulled the exterior panels inwards on the towers, so how did the entire internal structure of WTC7 supposedly collapse without affecting the facade at all?

First of all, the fact that the facade buckled just prior to the collapse, is undeniable proof that fire, not explosives, was responsible for the collapse, not explosives.

We can go here if you missed it before.

originally posted by: skyeagle409
a reply to: Flatcoat

I've got a simple question for you. OSer's like to claim that sagging trusses pulled the exterior panels inwards on the towers, so how did the entire internal structure of WTC7 supposedly collapse without affecting the facade at all?

First of all, the fact that the facade buckled just prior to the collapse, is undeniable proof that fire, not explosives, was responsible for the collapse, not explosives.

We can go here if you missed it before.

Actually no, it's not proof at all. I'd say it's proof the that core columns were suddenly compromised transferring all the load to the exterior columns causing them to buckle.

a reply to: Flatcoat

Actually no, it's not proof at all.

When steel is heated and sit between hard places, this can result.

What Heat Can Do To Steel

Indications of the Imminent Collapse of the World Trade Center Buildings Disprove Explosives Theory

Scientists investigating the Sept. 11, 2001 collapse of the twin towers said, "the World Trade Center towers showed telltale signs they were about to collapse several minutes before each crumbled to the ground." There would not be telltale signs if it was explosives (Controlled Demolition) that caused the buildings to collapse.

"In the case of the north tower, police chopper pilots reported seeing the warning signs - an inward bowing of the building facade - at least eight minutes before it collapsed at 10:29 a.m." New York Daily News reporter Paul Shin wrote in his June 19th, 2004 article 9/11 cops saw collapse coming.

"Federal engineering investigators studying the destruction of the World Trade Center's twin towers on Sept. 11 said New York Police Department aviation units reported an inward bowing of the buildings' columns in the minutes before they collapsed, a signal they were about to fall." - NYC Police Saw Sign of Tower Collapse, Study Says

Several minutes before the WTC buildings collapsed, the structures of the buildings were clearly failing and the exterior steel columns could be seen buckling. This simply would not be happening if explosives caused the collapse because explosives don't go off in slow motion for several minutes. Explosives don't slowly buckle steel columns over several minutes.

Obviously, the way an actual controlled explosion happens is the explosives all go off in a matter of seconds. There simply would not be warning signs that the buildings were about to be demolished by explosives, it would of course just suddenly happen. But that is not what happened, the buildings did notsuddenly collapse without any indications that they would. Instead, the fires were compromising the structural integrity of the buildings and the buildings' support structures failed.

Exterior columns buckled because the fires weakened the floor trusses and the floors sagged. The sagging floors pulled on intact column connections so as the floors sagged down, they pulled the exterior columns inward. This inward bowing of the exterior columns was evident to observers such as the police helicopters circling the towers.

"The NYPD aviation unit reported critical information about the impending collapse of the buildings." They could see that the exterior steel beams of the buildings were bowing. You can see the inward bowing of the steel columns in pictures of both WTC 2, (the first building to collapse) and WTC 1 (the second building to collapse.)
Buckling Steel

www.representativepress.org...


Civil & Structural Engineers on WTC Collapse

"The aircraft moved through the building as if it were a hot and fast lava flow," Sozen says. "Consequently, much of the fireproofing insulation was ripped off the structure. Even if all of the columns and girders had survived the impact - an unlikely event - the structure would fail as the result of a buckling of the columns.

The heat from an ordinary office fire would suffice to soften and weaken the unprotected steel. Evaluation of the effects of the fire on the core column structure, with the insulation removed by the impact, showed that collapse would follow whatever the number of columns cut at the time of the impact."

911-engineers.blogspot.com...


Did experts on the scene think WTC 7 was a controlled demolition?

"Several demolition teams had reached Ground Zero by 3:00 pm on 9/11, and these individuals witnessed the collapse of WTC 7 from within a few hundred feet of the event...but I never heard explosions like demo charges.

Another demolition expert who worked at Ground Zero also finds no trouble debunking the claim of explosives."Our team, working at Ground Zero, including myself, never saw indication of explosive use that would have been evident after the event," says Brent Blanchard, senior writer for www.implosionworld.com.

"You just can't clean up all the det cord, shock tube, blasting cap remnants, copper backing from explosive charges, burn marks along clean-cut edges of columns, etc., nor is there any evidence in the thousands of photos taken by the press and dozens of agencies over the following days. I just can't see how it happened that way."

Towers Weakened by Planes; Brought Down by Fire

Analysis by a team of 25 of the nation's leading structural and fire protection engineers suggests that the World Trade Center Towers could have remained standing indefinitely if fire had not overwhelmed the weakened structures, according to a report presented today at a hearing of the House Science Committee.

That finding is significant, said W. Gene Corley, Ph.D., team lead for the ASCE/FEMA Building Performance Study Team, because extreme events of this type, resulting in such substantial damage, are generally not considered in building design, and the fact that these structures were able to successfully withstand such damage is noteworthy.

ARCHITECT Magazine
The Magzine of the American Institute of Architects

All of Gage’s so-called evidence has been rebutted in peer-reviewed papers, by the Federal Emergency Management Agency, by the National Institute for Standards and Technology, by the American Society of Civil Engineers, by the 9/11 Commission Report, and, perhaps most memorably, by the 110-year-old engineering journal Popular Mechanics.

Why the World Trade Center Buildings Collapsed: A Fire Chief ’s Assessment

When the jet liners crashed into the towers based upon knowledge of the tower construction and high-rise firefighting experience the following happened: First the plane broke through the tubular steel-bearing wall. This started the building failure. Next the exploding, disintegrating, 185-ton jet plane slid across an open office floor area and severed many of the steel interior columns in the center core area. Plane parts also crashed through the plasterboard-enclosed stairways, cutting off the exits from the upper floors.

The jet collapsed the ceilings and scraped most of the spray-on fire retarding asbestos from the steel trusses. The steel truss floor supports probably started to fail quickly from the flames and the center steel supporting columns severed by plane parts heated by the flames began to buckle, sag, warp and fail.

vincentdunn.com...

There is something very wrong with that simulation of the trusses pulling in the perimeter columns at 1:56, which should be called an animation. Those trusses connections are always referred to as the weakest link of the tube-in-tube structure, but they pull the thick external columns in (even the intact ones) and you don't see them snap in the animation, but what the hell, at 2:19 the connection still doesn't snap but the perimeter columns snap! Looks like Wile E. Coyote physics that silly animation.

a reply to: Informer1958

Why not pour jet fuel on the top floors of any building and watch it burn for an hour and the whole building should fall down in it's own foot print

Why do people keep repeating this falling into its own footprint yet the same people talk about bombs blowing steel beams horizontally out of the building when it was collapsing.

A plane didn't hit buildings and just did a fuel dump?

I really have to scratch my head when I read some posts authored by those claiming inside job, bombs bla bla bla.

I might be mistaken but didn't you ask in another thread how steel beams could be thrown out of the buildings when they were collapsing if bombs weren't an explanation, and for another poster to point out the obvious, gravity and force of the floors above crushing down caused the beams to be expelled where there was the least resistance for them or something along those lines.

If so how does steel beams that were thrown at a distance away from the building equal falling into its own footprint?

How does damage to surrounding buildings equal falling into its own footprint?

Or was the damage to the surrounding buildings not caused by the collapse in your opinion if the towers fell into their own footprint?

a reply to: InhaleExhale

Why do people keep repeating this falling into its own footprint yet the same people talk about bombs blowing steel beams horizontally out of the building when it was collapsing.

I think what people mean by that is that it fell vertically through itself. It didn't topple over, the collapse was vertical and symmetrical. this in itself presents a problem for the debunkers who like to claim that the falling mass of the top section crushed the rest of the building, but when someone says "fell into it's own footprint", they say " Rubbish! It was spread over a 400 foot radius around the building." Can't have it both ways....

Dont know if it has ever been investigated, and maybe it is easy disproven. But I have always wondered if the real conspiracy/cover-up around 9/11 is that the WTC was built using sub-standard materials (and I said this at the time, though it was never, to my knowledge, picked up). I dont thnk anyone expected the towers to collapse.

a reply to: AndyMayhew

Dont know if it has ever been investigated, and maybe it is easy disproven. But I have always wondered if the real conspiracy/cover-up around 9/11 is that the WTC was built using sub-standard materials (and I said this at the time, though it was never, to my knowledge, picked up). I dont thnk anyone expected the towers to collapse.

There was nothing wrong with the steel, but inspections have uncovered substandard application of fire protection on the structures.

"FIREPROOFING" AT THE WTC TOWERS

I investigated the fireproofing in both World Trade Center towers over approximately a 10-year period between the early 1990s and early June 2000, the last time I was in the towers.

There were problems with the fireproofing in the World Trade Towers that may have rendered them vulnerable to fire. These problems are not unique to the WTC; I have observed similar problems with the fireproofing in many high-rise buildings in the United States and Europe.

www.fireengineering.com... wtc-towers.html

Photo 1

Photo 2

originally posted by: soulpowertothendegree
a reply to: samkent

They didn't all fail at the same time, rather they were turned to dust and crumbled one at a time.

Turned to dust

originally posted by: Flatcoat

originally posted by: waypastvne

originally posted by: drommelsboef
crush the building.

"Shear off the truss seats" would be the correct phrase.

Actually, "crush the building" would be a more accurate description. If it was just "shearing off truss seats" You'd have a hollow shell with 110 floors piled up at the bottom.

Only someone with a cartoon level of knowledge would expect this.