8 seconds to bring down a 500 foot tower!

http://www.gazettetimes.com/articles/2006/03/10/news/oregon/friore02.txt

Portland General Electric said Wednesday it is almost ready to destroy the 499-foot cooling tower at Trojan Nuclear Plant. The hourglass-shaped structure, scheduled for implosion on May 21, is one of the most widely recognized icons of Oregon’s only nuclear power plant.

The power plant closed in 1993 after 17 years of operation. Since then, PGE has gradually phased out the facilities at the plant, located roughly 40 miles north of Portland on the Columbia River. Trojan is the first large-scale commercial nuclear plant to be decommissioned in the United States and the cooling tower the largest to be destroyed. Controlled Demolition, Inc., the Maryland-based contractor handling the implosion, said it will take 8 seconds to bring down the 41,000 tons of cement and steel. The company will place roughly 2,000 pounds of explosives at the base of the structure, which is expected to tilt slightly sideways then collapse upon itself.

...

PGE sent a letter to area residents and businesses Friday with details of the upcoming event. The company said debris will be primarily contained to the explosion area. Some fine dust may be caught in the wind, but the company said it does not pose a safety risk. The contractor said vibrations will only be felt in the half-mile radius surrounding the building. The explosion is expected to be no louder than a thunderclap.

“It’s been done before but never this big,’’ said Mark Loizeaux, president of CDI, which also managed the destruction of the Kingdome in Seattle.

I always enjoy watching those things.

- Make7

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Just like they did the South Tower, huh?

I've never had the chance to spec one myself - never needed one quite that big.

It would be cool if we could get the footage.

and WTC7.

(unlike the smartass below that said "On what planet?")

If it takes a 500ft building 8sec to fall, then it would follow that a 1000 ft building would take about twice as long (or maybe less since the longer the objects fall, the higher their velocity). From watching the videos it seems (I've seen a wide variety of interpretations on this) to me that the buildings took about 15-18 seconds to fall. I'll assume 18 seconds for this example. It's hard to tell exactly when the "falls" terminate because of all the dust. But anyway, the WTC 1 & 2 were 1368 ft tall.

Tojan cooling tower: 500ft / 8sec = 62.5ft/sec (average speed of fall)
WTC Towers: 1368ft / 18sec = 76ft/sec (average speed of fall)

It makes sense that the WTC towers would have a higher average fall speed because they had longer to pick up velocity. Like I said, it seems to me that they are falling at almost exactly the same rate/time.

If you have different data or reasoning, please share so we can compare notes! :thumbsup:

Notto be a smartass, but what is "almost exactly"

"very close"
"close resemblance"
"almost identicle"
"virtually identicle"
"very similar"

So, in an attempt to take your question seriously let me rephrase it:
"Like I said, it seems to me that they are falling at a very similar rate/time."

But if you are confused as to what was meant by the phrase "almost exactly", look at the CONTEXT in which it resides: "Like I said, it seems to me that they are falling at almost exactly the same rate/time."

If you can't figure out what was meant by the phrase in that context, then you you are either being a smartass (contrary to your claims) or English is a second language for you (in which case, you are forgiven), or you have very limited analytical abilities.

Not to be a smartass, but what is "Notto"? Oh wait, maybe if I look at the context I could figure that one out.
"Notto be a smartass, but what is "almost exactly" (note: no puncuation)

I'll ASSUME that it is a question even though there is no question ('?') mark. I quickly notice that "Notto", when separated is "Not to". If I replace that NEW phrase in your sentence, it seems to make sense. "Not to be a smartass..."

Wow. Amazing how I did that, eh?

I don't think I've ever seen the average velocities of collapsing buildings compared before - so I wasn't thinking along those lines, but now I see what you are saying.

To be honest, I just don't know if it is useful to be making that comparison. As I am sure you are aware the force of gravity causes falling objects to accelerate. The distance covered is proportional to the square of the time - so given the same rate of acceleration, if a building took twice as long to fall, it would actually be four times as tall. However, the average velocity is directly proportional to the time, so the average velocity for the building that was four times taller would actually be twice that of the shorter building.

I'll add a couple more average velocity measurements to see what you think.

   building      height    time   average velocity 
 Liberty Tower   380 ft   11.0 s     34.55 ft/s    
     WTC2       1362 ft   39.4 s     34.57 ft/s    

We know the Liberty Tower was a controlled demolition - so, hypothetically speaking, if WTC2 took 39.4 seconds to collapse, would it be indicative of a controlled demolition because the average velocity would be the same as the Liberty Tower collapse?

I think it is more useful to compare a buildings average collapse acceleration with gravity. I've seen this done a number of times and have done it myself. Here are the final figures for the two structures from your post (the time used for WTC1 also comes from your post):

   building      height   rate of acceleration   compared to gravity 
 cooling tower   500 ft       15.6 ft/s²              -51.4%         
     WTC1       1368 ft        8.4 ft/s²              -73.7%         

So even though the average velocity for WTC1 is slightly higher than the cooling tower, the average rate of acceleration is quite a bit slower.

I just think it is more useful to say a building fell some percentage amount slower than a free-fall collapse. I've had plenty of people disagree with me about measuring it this way. And they are right - this is just to get a rough idea of how 'fast' or 'slow' a building came down. To really do it accurately would probably require a complex computer simulation - which I don't have the equipment or knowledge to do properly. I've just been using simple physics equations and a spreadsheet - it doesn't give me the precise answer, but I think it at least allows me to make useful comparisons.

- Make7