PDA

View Full Version : WTC - Paper imbedded in cement?


Larry Mudd
09-13-2001, 02:20 PM
I saw footage of an interview with an eyewitness on BBC world service who said that office supplies, including copy-paper, hit with enough force to become imbedded in the pavement and vehicles-- blocks away. This is such a remarkable observation that it seems queer to me that only one person (that I know of) mentioned it. Is this true or was it a stress-induced misperception?

Skywatcher
09-13-2001, 02:58 PM
It's certainly plausible. Objects such as playing cards and toothpicks have been known to become lodged in trees by tornado force winds. A post in MSPIMS noted that debris from the WTC was found as far away as Brooklyn.

Una Persson
09-13-2001, 05:06 PM
"Embeded in pavement" means a lot of things, however. It can simply mean it hit the asphalt hard enough to sink into it an inch or so - not a great feat. I daresay none of those items would likely be embedded very far in concrete, if at all.

AFAIK, the "straw embedded in tree trunks" is part urban legend, part misinterpretation. When trees are subjected to the intense winds of a tornado, the trunks are often rended - split open in numerous vertical cracks. Like one would see by taking a brittle stick in their hands and torquing it in opposite directions. While the trees are being torn that way, they are also being hit hard by debris. A lot of it gets stuck in the fissures, which either partially or completely close when the winds die down. Thus leading to the "straw goes into a tree trunk" phenomena.

Let's face it - as strong as the winds of a tornado are (300 mph at most), a .223 bullet going 3100 ft/sec (2113 mph) won't go more than a couple inches into a stout tree (and I've shot many a tree in my time...). There is no way a straw has the combination of the rigidness or the kinetic energy to go into tree bark.

KellyM
09-13-2001, 05:25 PM
Originally posted by Anthracite
[BLet's face it - as strong as the winds of a tornado are (300 mph at most), a .223 bullet going 3100 ft/sec (2113 mph) won't go more than a couple inches into a stout tree (and I've shot many a tree in my time...). There is no way a straw has the combination of the rigidness or the kinetic energy to go into tree bark. [/B]
I question the validity of the foregoing statements. Texas A&M, Purdue University, and other institutions doing research into tornados and the damage they can cause have reproduced this effect in the laboratory. You'd be quite surprised at what happens in high winds, and just how far seemingly weak objects can be imbedded in other, seemingly hard, objects. (Texas A&M has shattered concrete with a 2x4.) The circumstances of straw flying in 300 mile winds are completely different from those of a bullet flying through still air.

That said, on the OP: I have my doubts about paper being imbedded into existing concrete. However, I can easily see the debris from the Tower mixing with firefighting water and other, less mentionable fluids to form a hard mash that might look like concrete. Paper could easily become stuck in this mash.

Una Persson
09-13-2001, 06:53 PM
Originally posted by KellyM
(Texas A&M has shattered concrete with a 2x4.) The circumstances of straw flying in 300 mile winds are completely different from those of a bullet flying through still air.

I've seen that video of the 2x4, and I accept that very easily. They are firing a long, heavy, tough 2x4 with significant mass (and thus significant kinetic energy)straight on its end into a wall. I have no problem with that.

I would really like to see any scientific cite that demonstrates to me how a straw goes into a tree. It simply does not have the kinetic energy, and the rigidity, to do so, IMEO.

KellyM
09-13-2001, 07:36 PM
Originally posted by Anthracite
I would really like to see any scientific cite that demonstrates to me how a straw goes into a tree. It simply does not have the kinetic energy, and the rigidity, to do so, IMEO.
In my opinion, I think straw does have the rigidity to do so. And I question the validity of your claimed expertise in extreme weather conditions or the physical or mechanical characteristics of plants. You are, as far as I know, a power plant engineer; this gives you no more expertise in the foregoing fields than Linus Pauling had in biochemisty.

Una Persson
09-13-2001, 08:15 PM
Originally posted by KellyM
Originally posted by Anthracite
I would really like to see any scientific cite that demonstrates to me how a straw goes into a tree. It simply does not have the kinetic energy, and the rigidity, to do so, IMEO.
In my opinion, I think straw does have the rigidity to do so. And I question the validity of your claimed expertise in extreme weather conditions or the physical or mechanical characteristics of plants. You are, as far as I know, a power plant engineer; this gives you no more expertise in the foregoing fields than Linus Pauling had in biochemisty.

Please calm down. IMEO is "In my Engineering opinion". I have had a wee bit of study in statics, dynamics, analytical mechanics, fracture mechanics, strength of materials, and 7 graduate classes in materials science. It's not hard for me to make a judgement call on the strength of a piece of straw relative to a piece of tree. Or the kinetic energy of said straw. Under any circumstances. The laws of physics do not change in the environment of a tornado.

So, what is the validity of your claimed expertise? I eagerly await your credentials, or your cites. I am happy to admit my judgement is wrong, if you have some facts to counter me, but criticizing me on my experience and knowledge without offering up yours is sorta hypocritical, is it not?

So what is the rigidity of straw again?

CnoteChris
09-13-2001, 08:52 PM
Interestingly enough, here's your exact question with an answer.

From Ask Jack (http://www.usatoday.com/weather/askjack/wasktorn.htm) at USA Today.

Q: There are reports of straw and other debris penetrating cattle, trees and other solid objects during a tornado. Does this occur because of the wind speeds involved, or is there any truth to something I was told which is the "inside" of the tornado is a perfect vacuum that causes solid objects to basically "open up" or pull apart?

A: You're correct, there are confirmed reports of straws penetrating trees or boards in tornadoes. Years ago some thought that tornado winds were fast enough to drive straws into trees, but measurements of tornado wind speeds have shown that they rarely approach 300 mph. The air pressure inside a tornado is lower than the surrounding pressure, but is far from a perfect vacuum. The most generally accepted theory about what happens is that the winds bend trees or boards enough to open up the grains, a straw flies in and the tree straightens up when the tornado moves on. (12-29-96).

* And let me just add that every time I fire up my, "Enough with the 'Got a cite for that?' stuff. Just because you don't have a cite for a comment doesn't mean it isn't true!" speech. Daggumm, everytime I get that sucker loaded and ready to post, I find a friggin cite for whatever's being discussed.

Maybe next time.

GrandfatherTrout
09-13-2001, 09:29 PM
Paper, I don't know. Perhaps it was still bound into a ream?

What I can add to this conversation: I just had dinner with my buddy John. A co-worker of his has been doing excavation/rescue at the WTC site since yesterday. (John is employed by American Express, which is in World Financial Center Building 3.)

Thus far John's co-worker has found four severed heads--one of which had been embedded in the wall of a building some distance away by the force of the blast.

My point is that this was a big-ass kaboom, folks. I'd give the journalist the benefit of the doubt here.

Duck Duck Goose
09-13-2001, 11:19 PM
As a kid growing up in the Illinois section of Tornado Alley, I have many times seen the famous black and white photo of a straw stuck in a tree. Of course, now I can't find it on the Web.

Here is a modern version.
http://www.chesapeake.net/~fireman/_borders/Straw.jpg

Same straw, same tree, different camera angle.
http://www.warnerimages.com/stock/previewimages/top0010.jpg

Different straw, different tree, better photographer.
http://www.sharonandtom.com/weather/wildlife/1998/images/straw.JPG

I would really like to see any scientific cite that demonstrates to me how a straw goes into a tree.
Your wish is Google's command. :) It was Texas Tech that did the research, not A & M.

http://www.weather.com/newscenter/specialreports/tornado/awesome/miracles.html
While the Oklahoma City tornado packed extremely fast winds, lab experiments have shown winds of just over 100 mph are strong enough to drive straw into soft wood. The keys are wind direction and the orientation of the flying object as it slams into the larger object.

http://www.spc.noaa.gov/faq/tornado/
How do tornadoes do some weird things, like drive straw into trees, strip road pavement and drive splinters into bricks?

<snip>

With a specially designed cannon, wind engineers at Texas Tech University have fired boards and other objects at over 100 mph into various types of construction materials, duplicating some of the kinds of "bizarre" effects, such as wood splinters embedded in bricks. Intense winds can bend a tree or other objects, creating cracks in which which debris (e.g., hay straw) becomes lodged before the tree straightens and the crack tightens shut again.

Evidently someone "asked Jack" the same question twice, and he gave two different answers. This is further down the page from Chris's cite.

http://www.usatoday.com/weather/askjack/wasktorn.htm
Q: Can a tornado drive a piece of straw into a tree?
A: Yes. My source is NOAA Technical Memorandum ERL NSSL 82, The Tornado: An Engineering-Oriented Perspective by Joseph E. Minor, James R. McDonald and Kishore C. Mehta of the Institute for Disaster Research at Texas Tech University. On page 174 they note that tornado investigators have found "some cases of straw particles on trees, fence posts, and walls. The few situations where penetration was evident involved soft wood, bark with fissures which accepted the straw, or very slight penetrations."

They also note 1975 experiments that involved propelling broom straws into various types of wood. The researchers found that straw traveling from 143 to 450 mph will penetrate wood samples. Today, tornado scientists generally believe that the fastest tornado winds are around 300 mph. (5-27-96)
Here's the call number for the 1975 experiments, but it's not on the Web.

http://www.wind.ttu.edu/asp_windlib/fullrecord.asp?CN=KellerD-J176
KellerD-J176 < Call Number
Title Wind Speeds Required to Drive Straws and Splinters into Wood
Author David Keller and B. Vonnegut
Month / Year August / 1976
Status Available

NOAA Technical Memorandum ERL NSSL 82, quoted by "Ask Jack", has evidently been reprinted as NOAA Technical Memorandum NWS SR-147 but it's not available on the Web, either.

Una Persson
09-13-2001, 11:29 PM
So, we're both right then? Fair enough.

CnoteChris
09-14-2001, 12:33 AM
My reference was newer than yours was DDG.


Nyah!

Send questions for Cecil Adams to: cecil@straightdope.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright 2018 STM Reader, LLC.