Amount of explosives used for real CD

[Oystein]

In another thread, there were a few posts touching on the issue of what amount of explosives is required to bring down a highrise building.

Dave Rogers referred to the tallest building demolished by explosives so far, the J. L. Hudson department store in Detroit. I replied, arguing that the rather old and complex Hudson store building would not be a good reference, and suggested the 30-story Landmark Tower:

http://www.dhgt.com/PDF/A talented team of demolition experts.pdf
http://www.emporis.com/application/?nav=building&lng=3&id=122391


So here is some reference data on the Landmark Tower in Fort Worth, imploded in 2006:
Height: 115m
Width: roughly 30x30m
Structure: Steel
Explosives used: 364lb (about 164kg)
Max. size of individual charges: 12 ounces (ca. 340g)


Reference data on the J. L. Hudson department store in Detroit, imploded in 1998:
Height: 134m
Width: ??
Structure: ??
Explosives used: 2,728lb (about 1225kg)
Max. size of individual charges: ??


Anyone got any other such data on highrise implosions, good videos, smart thoughts? Post away!

 

[Scott Jurgenson]

Hey Oystein, can you link me to your blog?

 

[DGM]

Anyone got any other such data on highrise implosions, good videos, smart thoughts? Post away!

I did some "back of a napkin" years ago and also put some thought into what it would take to demo the towers at the height seen. One thing that became clear was you would not want to start at the core. The way the building was designed you would need to "take-out" one parameter wall (with the corners) and then attack the "hat-truss" comprimising the buildings ability to redistribute the load. I came up with a figure of 1400 Lbs of RDX (in the form of shape charges).

My $.02. I'll elaborate later if I get a chance (busy week )

 

[fuelair]

I strongly suggest this book: http://www.amazon.com/Introduction-...=sr_1_1?ie=UTF8&s=books&qid=1307647335&sr=1-1
I am reading it now and it has fun data in it!! Data that sounds quite like what you are looking for and definitely involves controlling explosions/ives. It is not cheap, but most of the stuff in this field (that won't get you killed if you use it) isn't.

 

[Thunder]

what would happen if explosives were only put on say, three floors in the WTC?

I'm gonna guess that if the explosives were put on 3 floors, maybe 30 floors down from the roof, the resulting mass & energy of the above floors crashing down & the accumulating mass....would have been enough to keep the collapse going....ALL the way down.

so explosives would not have been needed on the whole building, let alone 1/2, 1/4, 1/8th, etc etc.

 

[ozeco41]

what would happen if explosives were only put on say, three floors in the WTC?

I'm gonna guess that if the explosives were put on 3 floors, maybe 30 floors down from the roof, the resulting mass & energy of the above floors crashing down & the accumulating mass....would have been enough to keep the collapse going....ALL the way down.

so explosives would not have been needed on the whole building, let alone 1/2, 1/4, 1/8th, etc etc.

Given the advantages of 20/20 hindsight - if we had a Twin Tower clone available for demolition - it would be quite feasible to mimic the ROOSD type collapse process as you describe it.

But knock out three floors at ground level would also work.

Either would be a big job but......

There would be no need to put explosives elsewhere. No need for what seems to be your implicit assumption that there would need to be explosives on many floors.

 

[Dragonrock]

The fact that demo of the WTC towers could be accomplished by blowing up a few parts on a few floors begs the question "why not just crash a plane into the floors and let the fire take it out.

CTs say that "net force equals zero" so the entire tower had to be weakened with explosives. They also speak of "squibs" being seen during the collapse which would not be needed if the collapse could just continue on its own.

 

[ozeco41]

...Anyone got any other such data on highrise implosions, good videos, smart thoughts? Post away!

I cannot help here - my experience is limited to military "set piece" exercises.

Where those exercises involved really using explosives it was usually on steel or reinforced concrete sections of moderate size. We went by the relevant PAM (for "Pamphlet" - the Aussie Army name for the training manuals on all aspects how to fight wars.) You simply looked up the answer in the book.

Experience on bigger targets such as highway bridges was limited to theoretical exercises. It is rare for a government to really want a bridge demolished. In that situation pretending it was in a war scenario you applied "make sure you have overkill". The reason for overkill is simple that the time you want to blow up bridges is when you are "withdrawing to fight on better ground". (Civilians could call it "retreating" but the word "retreat" does not feature in the military vocabulary )

And if you are withdrawing it means the other side are chasing you and you don't get a second chance if the bridge doesn't go down first try. In that situation you care nothing for "collateral damage" to property, other infrastructure or enemy personnel.

 

[ozeco41]

The fact that demo of the WTC towers could be accomplished by blowing up a few parts on a few floors begs the question "why not just crash a plane into the floors and let the fire take it out....

It would depend on detailed understanding of the target building AND 20/20 hindsight post 9/11.

I doubt any of us engineers would reasonable have anticipated the Twin Towers collapses before the event. It is so easy with 20/20 hindsight to claim that we did - usually in the form of "once the planes struck I knew that collapse would follow" which isn't a true preview whether it is a true claim or not.

I never had the opportunity to consider the situation in the interval between the first aircraft strike and the first collapse. I saw both on UK television news seconds apart so cannot claim either way whether I would have predicted collapse post the first strike.

Even with hindsight of WTC 9/11 AND a suitable target building (are there any?) I would hesitate to guarantee collapse.

 

[Thunder]

Given the advantages of 20/20 hindsight - if we had a Twin Tower clone available for demolition - it would be quite feasible to mimic the ROOSD type collapse process as you describe it.

we do have just such a building. Its in Tulsa, Oklahoma. Its a 1/3rd scale model of the WTC towers.

http://en.wikipedia.org/wiki/BOK_Tower

http://skyscraperpage.com/cities/?buildingID=3543

 

[Thunder]

CTs say that "net force equals zero" so the entire tower had to be weakened with explosives. They also speak of "squibs" being seen during the collapse which would not be needed if the collapse could just continue on its own.

indeed. every floor that the Truthers claim has a "squib", would have to have explosives.

but back to my point: if we just blew up three floors, 1/4th the way down from the roof, would the ensuing energy and mass be enough to cause a global collapse?

I'm no engineer, but I'd guess YES.

 

[ozeco41]

indeed. every floor that the Truthers claim has a "squib", would have to have explosives.

but back to my point: if we just blew up three floors, 1/4th the way down from the roof, would the ensuing energy and mass be enough to cause a global collapse?

I'm no engineer, but I'd guess YES.

Broadly stated "Yes!" If done carefully it could have the same effect as the actual initiation of the 9/11 collapses.

The key issue being that the way the actual 9/11 collapses initiated all the columns failed and the falling bits of column in the "top block" bypassed the lower parts of those columns. For some of the columns is it obvious why that was so. Recall that the outer perimeter columns were pulled inwards by sagging floor joists and as those columns failed the ends of the top part of columns would automatically brush past the bottom part of the same column. Why all the other columns slipped top end past bottom end is a more complex topic. Take it that in the real 9/11 collapse they did.

Blowing bits out of columns would not guarantee to achieve the same bypassing of the ends of the columns. So the manner in which you took out the three floors would need to ensure column bypass. Details later when you sign the contract for the building you want to take out - its too late for the Twin Towers.

 

[ergo]

Broadly stated "Yes!" If done carefully it could have the same effect as the actual initiation of the 9/11 collapses.

Because those plane crashes were so accurate!

The key issue being that the way the actual 9/11 collapses initiated all the columns failed and the falling bits of column in the "top block" bypassed the lower parts of those columns.... Why all the other columns slipped top end past bottom end is a more complex topic. Take it that in the real 9/11 collapse they did.

Both times! WOW....!

 

[ozeco41]

Because those plane crashes were so accurate!

Nope!

...Both times! WOW....!

Yup!

 

[ergo]

Nope!

So the plane crashes can be messy - doesn't matter, the buildings will come down any old which way, but explosives would need to be carefully placed, and just so, so that they mimic the random haphazardness of the plane crashes?

Yup!

WOW!!

 

[Thunder]

So the plane crashes can be messy - doesn't matter, the buildings will come down any old which way,

err.....the two towers didn't come down EXACTLY the same way.

especially in the beginning, the collapses were different. they both ended up the same kind of collapse, but they started out differently.

 

[ergo]

err.....the two towers didn't come down EXACTLY the same way.

The video record indicates otherwise.

especially in the beginning, the collapses were different. they both ended up the same kind of collapse, but they started out differently.

So what you're really saying is: two completely different collapse initiation events, two different masses of upper building portion, but identical collapse progression and identical collapse times.

WOW!!

 

[ozeco41]

So the plane crashes can be messy - doesn't matter, the buildings will come down any old which way, but explosives would need to be carefully placed, and just so, so that they mimic the random haphazardness of the plane crashes?

No. It is not the plane crash damage which needs mimicking. The plane crashes merely caused some initial damage and started fires. More fire damage then accumulated causing the initial collapse and when that happened the top ends of failed columns went past their bottom ends. That is the feature which would be tricky to mimic. If you simply blew bits of column out you risk the top bit landing on the bottom bit - remember that is where T Szamboti's missing jolt wasn't missing.

 

[Thunder]

The video record indicates otherwise.

you are wrong. the first collapsing tower slightly collapsed to the side and then went straight down. the 2nd collapsing tower went straight down immediately.

identical collapse times.

WOW!!

wow...is right. the collapse times were not identical.

it is IMPOSSIBLE to know for sure what the exact collapse times were, as no video shows the ENTIRE collapse to street level.

only the seismic data can be used to get an accurate reading on collapse times, and while the two times are close..they are not identical.

 

[WildCat]

But remember, truthers claim enough explosives to pulverize concrete and dustify steel.