WTC7 - World Trade Center Building 7

[Rammer]

I would like this discussion to be one of physics & engineering...not politics.

WTC7 had 47 floors and was 570 feet tall. Construction began in 1984 and opened in March 1987.

7 World Trade Center had 1,868,000 square feet of office space. It was a steel frame skyscraper.

It was more than 355 feet north of the World Trade Center North Tower(WTC1).

It was situated between the Verizon and Post Office skyscrapers.

Supposedly, debris from the collapsed North Tower created small fires on floors 6, 7, 8, 10, and 11 of WTC7.

The electrical power was supposedly shutoff at 09:59 AM. The sprinkler system didn't/couldn't activate.

The building was evacuated around 03:00 PM.

The building collapsed at 05:20 PM after the fires had burned for several hours.

I'm looking for scientific minds here, not emotional types.

Questions:

Could debris from WTC1 travel 355 feet to cause fires in WTC7...while the Verizon building only had minor damage & the Post Office building unscathed?

Could fires bring down a 47-story steel framed building?

Could fires bring down a 47-story steel frame building in a demolition style fall that didn't damage the Verizon and Post Office buildings?

Does the governments claim that "the unique design aspect of WTC7, that each outer structural column was responsible for supporting 2,000 sq ft" realistically explain the collapse?

Were firefighters and citizens just imagining the sounds of explosives prior to all three of the World Trade Center building collapses?

Could a 47-story steel building fall in 8.2 seconds in a straight-down implosion style...without being imploded?

Was it a coincidence that WTC7 housed SEC documents related to approximately 3,000 to 4,000 cases (according to the Los Angeles Times)?

Was it a coincidence that Morgan Stanley had 3,500 employees in the WTC complex, the most of any single company?(most escaped death)

Am I pointing the finger at Goldman Sachs?

[Highway6]

You use "supposedly" numerous time.

You bold key words to highlight your skepticism.

When your whole post reeks of conspiracy theory talk, its really hard to take your topic tagline seriously. - A Discussion of Physics & Engineering...Not Politics.

As far as the engineering is concerned. Of course fire can bring down a steel building. Seems there would be lot less conspiracy theories if the wackjobs understood that simple fact.

[BryanS]

Questions:

1. Could debris from WTC1 travel 355 feet to cause fires in WTC7...while the Verizon building only had minor damage & the Post Office building unscathed?

2. Could fires bring down a 47-story steel framed building?

3. Could fires bring down a 47-story steel frame building in a demolition style fall that didn't damage the Verizon and Post Office buildings?

4. Does the governments claim that "the unique design aspect of WTC7, that each outer structural column was responsible for supporting 2,000 sq ft" realistically explain the collapse?

5. Were firefighters and citizens just imagining the sounds of explosives prior to all three of the World Trade Center building collapses?

6. Could a 47-story steel building fall in 8.2 seconds in a straight-down implosion style...without being imploded?

7. Was it a coincidence that WTC7 housed SEC documents related to approximately 3,000 to 4,000 cases (according to the Los Angeles Times)?

8. Was it a coincidence that Morgan Stanley had 3,500 employees in the WTC complex, the most of any single company?(most escaped death)

9. Am I pointing the finger at Goldman Sachs?

1. Yes.

2. Yes.

3. Yes.

4. Yes.

5. Yes. What was heard is the sound of the building.. about to come down.

6. Yes.

7. Yes. This has nothing to do with "engineering" ... why are you moving off topic?

8. Yes. This has nothing to do with "engineering" ... why are you moving off topic?

9. Only you can answer that. This has nothing to do with "engineering" ... why are you moving off topic?

This thread seems pretty useless.

[Rammer]

You use "supposedly" numerous time.

You bold key words to highlight your skepticism.

When your whole post reeks of conspiracy theory talk, its really hard to take your topic tagline seriously. - A Discussion of Physics & Engineering...Not Politics.

As far as the engineering is concerned. Of course fire can bring down a steel building. Seems there would be lot less conspiracy theories if the wackjobs understood that simple fact.

Please name the building and hopefully include a video of the straightdownward total collapse. A frame that remains does not count.

[Rammer]

1. Yes.

2. Yes.

3. Yes.

4. Yes.

5. Yes. What was heard is the sound of the building.. about to come down.

6. Yes.

7. Yes. This has nothing to do with "engineering" ... why are you moving off topic?

8. Yes. This has nothing to do with "engineering" ... why are you moving off topic?

9. Only you can answer that. This has nothing to do with "engineering" ... why are you moving off topic?

This thread seems pretty useless.

Thanks for answering the questions...sort of.

I meant to add an asterisk (*) to questions 7-9.

[BryanS]

Please name the building and hopefully include a video of the straightdownward total collapse. A frame that remains does not count.

How about we stick with just WTC 7:

http://www.structuremag.org/Archives/2007-11/SF-WTC7-Gilsanz-Nov07.pdf

Please read. It also has a "video analysis" that you've asked for. No need to discuss any further on here...

[Highway6]

Please name the building and hopefully include a video of the straightdownward total collapse. A frame that remains does not count.

I said that of course fire can fell a steel building... i said nothing about the other bullet points of your wackjob theory.

Thats why we have fire codes, fire protection, fire ratings... because fire can destroy steel.

WTC 1 and 2 ultimately collapsed because of the fire's effect on the steel. There's your proof.

Also... as Bryan pointed out... your wackjob bullet points 7,8 and 9 have zero to do Physics and Engineering. They have everything to do with Politics and wackjob conspiracy theories.

[Highway6]

Rammer..

Do you think that fire can weaken or melt steel ?

[Rammer]

How about we stick with just WTC 7:

http://www.structure...lsanz-Nov07.pdf

Please read. It also has a "video analysis" that you've asked for. No need to discuss any further on here...

There's plenty of need to discuss further.

http://www.bcrevolution.ca/wtc_7.htm

Note the Windsor building in Madrid that burned for 28 hours without collapsing the frame.

Still waiting on the name of a steel skyscraper that totally collapsed (demolition style) due to a fire.

http://www.911blogger.com/node/3231

29 Structural & Civil Engineers Cite Evidence for Controlled Explosive Demolition in Collapses of All 3 WTC High-Rises on 9/11

http://www.911blogger.com/node/20429

http://www.infowars.com/still-standing-the-building-that-proves-wtc-7-was-imploded/

I'm really looking for the opinions of architects(since this is an architectural site), engineers, scientists, physics professors, etc.

[BryanS]

There's plenty of need to discuss further.

http://www.bcrevolution.ca/wtc_7.htm

Note the Windsor building in Madrid that burned for 28 hours without collapsing the frame.

1.) Still waiting on the name of a steel skyscraper that totally collapsed (demolition style) due to a fire.

http://www.911blogger.com/node/3231

29 Structural & Civil Engineers Cite Evidence for Controlled Explosive Demolition in Collapses of All 3 WTC High-Rises on 9/11

http://www.911blogger.com/node/20429

http://www.infowars....7-was-imploded/

2.) I'm really looking for the opinions of architects(since this is an architectural site), engineers, scientists, physics professors, etc.

1.) It's called WTC 7. It had plenty of steel in it. And collapsed, due to fire. No need to find some other example...

2.) Screw the architects. They aren't engineers.

But I am.

Are you?

All I see with WTC 7, from people with your viewpoint, is a bunch of horse crap conspiracy theory. Which you blatantly tried to work into this "engineering" discussion.

For every link you provide, I could provide a corresponding link, debunking the horse crap.

But what point would that serve? There really is nothing to discuss... that has not already been discussed for the past 8 YEARS on this tired, useless topic.

Why argue it here... when you can do a simple google search for "WTC 7" - and wade through countless links and seas of information on this topic...

[barracuda]

Rammer..

Do you think that fire can weaken or melt steel ?

Steel is indeed very susceptible to weakening in extreme heat. People often misunderstand the nature of steel and incorrectly think it's indestructible. It's one of the first things I learned in my building engineering class back in college.

[TheNiche]

Steel is indeed very susceptible to weakening in extreme heat. People often misunderstand the nature of steel and incorrectly think it's indestructible. It's one of the first things I learned in my building engineering class back in college.

You're right about the common conception of the properties of steel. I found out earlier this year as I watched a 40-foot I-beam bow at either end when lifted from the middle. I'd figured that it'd be more rigid. And even then I should've known better, having witnessed steel rails being torn out of an old rail yard and twisting about like noodles.

---------

Rammer: pay attention to the following relevent chronology:

1) WTC 7 is evacuated.

2) WTC 1 collapses, unleashing a veritible tsunami of steel and other construction materials upon downtown NYC.

3) Emergency operations are instantly devastated.

4) Debris flow impacts the base of WTC 7, damaging structural members, damaging fire suppression and retardance systems, and setting several floors on fire.

5) Access to WTC 7 is blocked, preventing access by emergency crews, who aren't bothering with putting out the fire anyway because (to the extent that there's still an operation) they have more important issues to deal with than an already-evacuated building.

6) WTC 7 experiences a series of partial collapses leading up to a full-on collapse.

Compare all this to the Windsor tower in Madrid, where a fire broke out in a building with a reinforced concrete core and a functioning fire suppression and retardance system, at a time when there were no concurrent emergencies of that scope, and given that fire crews were not wiped out en masse and that they had easy access to the site. You can't! The events are not comparable.

[Gooch]

I found out earlier this year as I watched a 40-foot I-beam bow at either end when lifted from the middle. I'd figured that it'd be more rigid.

Yes! And the steel gets much more flexy starting as low as 200F. You don't have to melt steel to weaken it tremendously.

Two types- tensioned members and compression members hold the building 'up' vertically. You only need very small distortions in compressed members and singular failue of a tension member to cause incipit collapse. Think of it this way for compressed members... you can stand on a soda can. But the minor distortion caused by plucking causes a complete instantaneous collapse. Building columns are similar. The structure relies on columns being both vertical and straight. Add some heat, and they are not only weakened but distorted by warping. Collapse requires little damage.

Think of tensioned members like a piece of fabric. Tension members are make up a lattice just like fibers in a fabric. Pull on a piece of fabric with a solid edge and it's very strong. Cut a small slit in the edge and pull again, and it rips easily. The WTC Tower collapses and they followed this ripping pattern, starting at the top and continuing until reaching the bottom. Floor-by-floor, lattice-by-lattice. Ripping down from the original small damage locus, pulling away to the sides slightly. Rember the mushroom-top shape of debris as they fell?

Collapse can occur quite slowly too. This it makes it look 'controled' and progressive. First one colum fails, which overloads its two neighbors. Those two neighbors hold for the moment, because we always design building "too" strong. But, eventually they fail because they are carrying the load of the first failed column. This overloads the 4 surrounding members which overloads 8, then 16, then 32, etc.. This is why it's an implosion, and the building doesn't fall over like a Jenga.

Note the Windsor building in Madrid that burned for 28 hours without collapsing the frame.

That's a far too simple comparison. Right off the top, the Windsor did not have parts of it's truss structure compromised by impact. (Remember the fabric & can examples) We don't know what factor-of-safety was used in the steel design loads; or how heavily the members were loaded. Lightly loaded beams would have more excess strength to lose due to heat before failing. We don't know what alloy of steel was used. Diffrent alloys = different heat effects. We also don't know what the truss/column structure design pattern was. The are certainly different. And different load paths will tolerate weakening/warping better than others. Tension members would survive heat better than compressed members for example. Were the colums O-shaped or I-shaped? That too would make a difference on how much distortion they could tolerate before failure. Gussets would also make a huge difference. Did either builing include them? Donno.

IOW there's a lot more to consider than they both had a fire and are both steel framed.

[Highway6]

Steel is indeed very susceptible to weakening in extreme heat. People often misunderstand the nature of steel and incorrectly think it's indestructible. It's one of the first things I learned in my building engineering class back in college.

Yes Cuda.... I know this. Niche knows this. You know this.All the smart people know this.

I'm questioning Rammer if he knows this... because like i said in my first response, "Of course fire can bring down a steel building. Seems there would be lot less conspiracy theories if the wackjobs understood that simple fact."

If Rammer in fact does not know this about steel, then we can correct and educate him.

If he's smart enough to realize that there is a reason for fire codes, fire protection, fire suppression, etc because steel is very susceptible to heat... then all of this is double the load of horse crap. If he's smart enough to know what heat can do to steal, yet still pushes the conspiracy theory crap, then that just proves he has an agenda further making this thread and reasonable dialogue pointless...

So Rammer.. I ask again... Are you aware that fire and heat can easily reduce the strength of steal ?/?

[BryanS]

Steel is indeed very susceptible to weakening in extreme heat. People often misunderstand the nature of steel and incorrectly think it's indestructible. It's one of the first things I learned in my building engineering class back in college.

Yes. And people tend to forget that steel... starts out as a molten liquid. And then solidifies.

...and that old metal... is melted down... and poured into new shapes.

...and if steel... was indestructible, or impervious to fire... then things like this would never work:

...fire cutting steel. AKA cutting torch. But the 9/11 crowd would have us to believe that these things don't work (because fire can't hurt steel). Riiiiight...

[TheNiche]

Ah, there's something about photos of cutting torches and welding equipment in use that's just so invigorating. I'm a pyro I guess. Drove my steel guys crazy with all the photos being taken.

[RedScare]

Yes. And people tend to forget that steel... starts out as a molten liquid. And then solidifies.

...and that old metal... is melted down... and poured into new shapes.

...and if steel... was indestructible, or impervious to fire... then things like this would never work:

...fire cutting steel. AKA cutting torch. But the 9/11 crowd would have us to believe that these things don't work (because fire can't hurt steel). Riiiiight...

You know, I am not going to get into this political trolling thread, but you guys claiming that steel melts so easily while ignoring the burning temperature of the materials in the tower (fuel, paper, wood) don't sound too intelligent either. If you are going to smack down a troll, at least do it in a way that is not so easily refuted.

FTR, paper, wood and fuel burn at temps from 250 to 650 degrees, while steel generally fails at around 110 degrees, depending on carbon content.

[TheNiche]

FTR, paper, wood and fuel burn at temps from 250 to 650 degrees, while steel generally fails at around 110 degrees, depending on carbon content.

Are you talking celsius, fahrenheit, kelvin, or some combination of these?

[UrbaNerd]

You know, I am not going to get into this political trolling thread, but you guys claiming that steel melts so easily while ignoring the burning temperature of the materials in the tower (fuel, paper, wood) don't sound too intelligent either. If you are going to smack down a troll, at least do it in a way that is not so easily refuted.

FTR, paper, wood and fuel burn at temps from 250 to 650 degrees, while steel generally fails at around 110 degrees, depending on carbon content.

And what temp does jet fuel burn at? Over 1000F? That would be significant enough to cause structural damage/warping, right?

Jet Fuel + Massive impact trauma (gross mass of jet plane * velocity in m/s) vs (Stationary object) that resulted in a total penetration of said jet + a few hours + Steel=FAIL. Especially if said impact occurred when the structure of the building is mostly external. This is in regards to the twin towers themselves, of course.

As for WTC7, do remember that some other buildings nearby suffered damage, including one of the IFCs, if I am not mistaken.

Furthermore, there was significant damage to the subsurface levels under the whole WTC site, which could have caused a failure of the WTC 7 foundation.

[TheNiche]

And what temp does jet fuel burn at? Over 1000F? That would be significant enough to cause structural damage/warping, right?

Jet Fuel + Massive impact trauma (gross mass of jet plane * velocity in m/s) vs (Stationary object) that resulted in a total penetration of said jet + a few hours + Steel=FAIL. Especially if said impact occurred when the structure of the building is mostly external.

We're talking about WTC 7, not the twin towers.

[BryanS]

You know, I am not going to get into this political trolling thread, but you guys claiming that steel melts so easily while ignoring the burning temperature of the materials in the tower (fuel, paper, wood) don't sound too intelligent either. If you are going to smack down a troll, at least do it in a way that is not so easily refuted.

FTR, paper, wood and fuel burn at temps from 250 to 650 degrees, while steel generally fails at around 110 degrees, depending on carbon content.

This is misleading....

110 degrees... F? would imply that vehicles in Phoenix, AZ would all "fail" in August.

Steel melts ("fails" completely) at 2500 deg F...

Steel begins to lose strength in the range of your paper/wood range in deg F, but not necessarily "fail" - initially.

Jet A fuel burns at about 550 deg F.

Eviscerating a building's structural support system/members followed by heating the remaining support members will reduce the factor of safety of the design to zero, followed by complete structural failure.

But despite this simple factual explanation, that is not enough for the flat earthers. 8 years is just not enough time for them to process this information...

We're talking about WTC 7, not the twin towers.

They all failed the same way: blunt structural damage, followed by fire, weakening the remaining structure, until complete failure.

[Gooch]

FTR, paper, wood and fuel burn at temps from 250 to 650 degrees, while steel generally fails at around 110 degrees, depending on carbon content.

I'm sure 110 degrees is a typo. Two samples of temperature de-rating tables regularly in use. They are for tubulars, but the stress formula are based on tensile strength of the material.

1) http://www.controlan...4200TS-0604.pdf Scroll to Page 3, Table 8. Steel loses roughly 30% of its design strength by 650F. By 800F it's lost 40%, and it falls offf a cliff after that so fast as to be unrecommended.

2) You can go to http://www.cycla.com...s_GRI000076.pdf Scroll to Page 33, Table 4.3. Roughly same values in the ASME code.

If my somelady wasn't calling me to spoon duty I could come up with more... It's not like it's a big secret.

You simply can't say steel generally fails around any specific temperature. Failure temperature will depend on how it's loaded. And every beam is loaded differently. If the beam is strong enough to sacrifice 20% of its load it would fail somwhere around 700F. If the beam were designed with 30% extra capacity it could endure to about 1000F.

Typically in my industry, we designed for ~50% safety margin. But if a beam were distorted by... say... an aircraft or debris impact... the remaining neighboring beams would be carrying the failed beam's load with no safety margin. Meaning you could see heat induced failure as low as 2-300F.

Perhaps someone can confirm, do building structural engineers typically analyse for damaged columns, beams and trusses? I suspect they don't...

[ricco67]

Yes! And the steel gets much more flexy starting as low as 200F. You don't have to melt steel to weaken it tremendously.

Two types- tensioned members and compression members hold the building 'up' vertically. You only need very small distortions in compressed members and singular failue of a tension member to cause incipit collapse. Think of it this way for compressed members... you can stand on a soda can. But the minor distortion caused by plucking causes a complete instantaneous collapse. Building columns are similar. The structure relies on columns being both vertical and straight. Add some heat, and they are not only weakened but distorted by warping. Collapse requires little damage.

Think of tensioned members like a piece of fabric. Tension members are make up a lattice just like fibers in a fabric. Pull on a piece of fabric with a solid edge and it's very strong. Cut a small slit in the edge and pull again, and it rips easily. The WTC Tower collapses and they followed this ripping pattern, starting at the top and continuing until reaching the bottom. Floor-by-floor, lattice-by-lattice. Ripping down from the original small damage locus, pulling away to the sides slightly. Rember the mushroom-top shape of debris as they fell?

Collapse can occur quite slowly too. This it makes it look 'controled' and progressive. First one colum fails, which overloads its two neighbors. Those two neighbors hold for the moment, because we always design building "too" strong. But, eventually they fail because they are carrying the load of the first failed column. This overloads the 4 surrounding members which overloads 8, then 16, then 32, etc.. This is why it's an implosion, and the building doesn't fall over like a Jenga.

That's a far too simple comparison. Right off the top, the Windsor did not have parts of it's truss structure compromised by impact. (Remember the fabric & can examples) We don't know what factor-of-safety was used in the steel design loads; or how heavily the members were loaded. Lightly loaded beams would have more excess strength to lose due to heat before failing. We don't know what alloy of steel was used. Diffrent alloys = different heat effects. We also don't know what the truss/column structure design pattern was. The are certainly different. And different load paths will tolerate weakening/warping better than others. Tension members would survive heat better than compressed members for example. Were the colums O-shaped or I-shaped? That too would make a difference on how much distortion they could tolerate before failure. Gussets would also make a huge difference. Did either builing include them? Donno.

IOW there's a lot more to consider than they both had a fire and are both steel framed.

Don't forget the one simple fact that the fireproof insulation that surrounded the steel supports was blown away in two of the towers that exposed it to the fires. One has to assume that the same thing happened to WTC7 when the debris crashed into the side of the building. Produce enough shock to a surface and all sorts of things are bound to be shaken loose.

Even a small house fire can produce a substantial amount of heat if there is enough fuel inside.

[Rammer]

And what temp does jet fuel burn at? Over 1000F? That would be significant enough to cause structural damage/warping, right?

Jet Fuel + Massive impact trauma (gross mass of jet plane * velocity in m/s) vs (Stationary object) that resulted in a total penetration of said jet + a few hours + Steel=FAIL. Especially if said impact occurred when the structure of the building is mostly external. This is in regards to the twin towers themselves, of course.

As for WTC7, do remember that some other buildings nearby suffered damage, including one of the IFCs, if I am not mistaken.

Furthermore, there was significant damage to the subsurface levels under the whole WTC site, which could have caused a failure of the WTC 7 foundation.

Keep in mind, WTC7 was not hit by a jet plane.

I have found one reference that steel melts at 2500 degrees farenheit...but it depends on the alloy of steel.

From the AISC website: In common circumstances, the maximum temperature of a fully developed building fire will rarely exceed 1800°F.

(The average gas temperature in a fully developed fire is not likely to reach 1500°F. Temperatures of fires that have not developed to post-flashover stage will not exceed 1000°F)

(More science, less namecalling please. Pretend you are Spock explaining it to Captain Kirk.)

[RedScare]

That was a typo. Steel generally loses its strength at 1100 degrees F.

Jet fuel burns in open air at 550 degrees F.

(I can't edit the original post.)

[Gooch]

Note the Windsor building in Madrid that burned for 28 hours without collapsing the frame.

Something else I thought about... the Windsor didn't have two massive collapsing buildings adjacent to it. We think of buildings as static and immovable. They are not. The WTC1 and WTC2 collapse no doubt shook the crraapp out of WTC7. Given that earthquakes are not common in NYC, the building likely wasn't designed for this type of motion.

[BryanS]

Keep in mind, WTC7 was not hit by a jet plane.

I have found one reference that steel melts at 2500 degrees farenheit...but it depends on the alloy of steel.

From the AISC website: In common circumstances, the maximum temperature of a fully developed building fire will rarely exceed 1800°F.

(The average gas temperature in a fully developed fire is not likely to reach 1500°F. Temperatures of fires that have not developed to post-flashover stage will not exceed 1000°F)

(More science, less namecalling please. Pretend you are Spock explaining it to Captain Kirk.)

What was it hit by though? I am guessing debris from a gigantic building right next to it that also fell into the ground.

...and for some reason... in your mind... you cannot comprehend that metals lose strength when heated.

They do not have to be heated to cutting torch temperatures (2500+deg F) in order to "fail."

[TheNiche]

(More science, less namecalling please. Pretend you are Spock explaining it to Captain Kirk.)

Even Spock was half human. I'd suspect that if Spock initially claimed that some particular theory was illogical, it probably was intended as a mixed up interspecies equivalent of, "Yo mamma so fat..."

EDIT: Oh, wait...apparently Spock has something to say about a similar matter. Let's watch, shall we:

http://www.youtube.com/watch?v=cL5Yu3Ub9nA

[Gooch]

Steel generally loses its strength at 1100 degrees F.

Unfortunately, that's misleading to some folks that can't (or won't) read a table. Steel doesn't suddenly lose its strength at this magic temperature. It's strength slowly degrades with increasing temperature starting as low as 250F (4% loss) By 800F it's lost 40% and by 1100F it has no practical elastic strength. It's plastic.

[TheNiche]

Ynfortunately, that's misleading to some folks that can't (or won't) read a table. Steel doesn't suddenly lose its strength at this magic temperature. It's strength slowly degrades with increasing temperature starting as low as 250F (4% loss) By 800F it's lost 40% and by 1100F it has no practical elastic strength. It's plastic.

And plastic is made from oil, and the Saudis control lots of oil, and most of the hijackers were Saudi. And this guy, Osama Bin Laden, he was also a Saudi...and his family owns a huge construction company. OH MY GOD, IT ALL MAKES SENSE NOW! It was Bin Laden after all. And he must've masterminded the construction of WTC 7 when it was built in 1983 with plastic structural members so that it could be brought down 18 years later. It's so obvious! Why didn't anybody think of this before?