WTC Collapse and My Shower Brush

[CRUE CAB]

I wondered throughout the whole OP: "Who gets dirty enough that they have to use a brush to get clean in the shower?"

Coal miners, diesel techs, oil field guys, axe murderers, train oilers, chicken pluckers, porn actors. muck rakers, chimney sweep.
Dirty dirty jobs.

 

[davidtaylorjr]

This morning I got an lesson on the mysteries of the twin tower collapses.

I was taking my morning shower. I have a long handled shower brush, actually two, one the long hand broke and so I can't hang it by the little loop and can't reach as far either. But the bristles are still good so continue to use it. It's place it on the ledge/top of the tun which is also use as a shower. Sometimes I use this one and others times not. It's older and the bristles are softer so it's better for scrubbing my face for example.

So I pick up the brush and wet it and then get some soap on it to lather up for scrubbing and do the scrubbing and rinse it under the shower and place it back on the tub ledge and resume with the long handled brush for my back. Lo and behold the brush slips from the tub edge after 15 or 20 seconds and ends up in the tub. How did this happen?

Perhaps some water from the shower head came down upon it exerting just enough force to somehow move it laterally and dislodge it. Possible but I don't think so.

I began to imagine that the forces holding the brush perched on the ledge were not enough to move it in any way. It was just like the glass perched on the edge of my desk. One could say in balance. So if it was perhaps just a single drop which changed everything and caused the brush to slip over the edge. Well for starters the brush was wet, perhaps a bit soapy and slippery and this would lesson the force needed to displace it. But the point is that the static condition was clearly very close to changing and then gravity would rule. The top surface of the tub was also rounded and probably a bit wet and likewise not the best surface to balance or support anything. But this clearly was a situation which WAS stable, looked stable and IS stable all the time... the brush lives in this spot until I use it for showering and then replace it. So wet created a very close to failure condition where perhaps... gravity was able to exert enough force in perhaps the right place to just tip it over to unsupportable and it slipped into the tub.

As I picked it up and placed in back in its home, I realized how much this was like the tops of the twin towers which just before they plunged were teetering just above the stable state and it wouldn't take much to change that into a top dropping. I suppose if I had very detailed video of the brush I would be able to see slight movement before release... the forces at work inside the brush. But I was showering and only had my imagination.

With the towers there was no visible BIG event that preceded the top drops. It was standing tall one sec and then it was descending and then soon after it was gone. Failures are often like that... stable until they are not.

Good show!

 

[SanderO]

Why would it lose so much mass out the sides? Gravity vector is down, not sideways.

It didn't loose so much mass out the sides... the facade fell away.. lets of mass... the floors slabs did not.. they came down crushed and pulverized... the contents on the floors was both crushed and came down and blasted out the windows... doesn't take a lot of blasted debris to look like more than it is.

 

[Kat Dorman]

Why would it lose so much mass out the sides? Gravity vector is down, not sideways.

The lower section can exert an eccentric reaction force on impacting debris and freestanding components. As SanderO mentioned, the perimeters peeled away in large sheets and fell outward. This is just like anything tipping over; there's an initial bias towards one direction for whatever reason, then gravity drives the fall with the fulcrum and material providing horizontal reaction force to displace the center of mass of that component away from the footprint.

Even if the towers collapsed entirely straight down, the debris would still assume an angle of repose characteristic of the materials.

What Menard_K expressed, though, was surprise that the collapse could continue while it should be losing "so much" mass outside the footprint. This is incredulity over an unevaluated (by Menard_K) condition. First, what is the theoretical effect of mass shedding on existing models? Second, what are the real circumstances surround mass loss to outside the footprint in the tower collapses?

As far as models go, the various 1D models are really all there are. The best FEA models of tower collapses - and I only know of two, neither of which are full tower replicas - do not offer anything over the 1D models, if as much. These models indicate that fairly high mass loss can be tolerated throughout a continuing collapse, and moderate amounts like 10% don't greatly affect the results.

For the real collapses, two categories of components can be directly seen to have not participated in driving the collapse: the peeling perimeters and core remnants. The perimeters fall over after an interior collapse front has already passed by, stripping the floor slabs and removing critical lateral support. It is because the collapse propagated without the involvement of the perimeters that the perimeters fell. Likewise the core remnants, though lateral support was not so much an issue for the wider surviving remnants; lateral debris pressure at the base likely was. So, as far as reality goes, these masses did not drive the collapses, but neither did the structural capacity of these components contribute to resistive force. Lack of "participation" goes both ways - mass not driving, capacity not resisting.

Up to this point, the narrative I offer doesn't indicate a preference for natural collapse or CD. There could've been a cascading interior collapse due to damage plus fire, or there could've been charges to separate one or more slabs to get it going and possibly keep it going. Regardless, the mechanics of an interior collapse through the floor area is what needs to be considered, as this is what's observed (it's not necessary to infer that aspect when expulsions are seen passing an area and considerably later the perimeter falls away).

With regards to an interior collapse, the core and perimeter act as temporary "retaining walls" to prevent mass loss from an interior collapse.

 

[shrubnose]

nope... but thanks for caring.

It is wonderful to see one caring human being's empathy for another who is in distress.




"Tolerance is giving to every other human being every right that you claim for yourself." ~ Robert Green Ingersoll.

 

[shrubnose]

I wondered throughout the whole OP:

"Who gets dirty enough that they have to use a brush to get clean in the shower?"

Coal miners and sewer workers?

 

[shrubnose]

I do some of my best thinking when I'm taking a ****.

How about you?

PS - any comments on metastability and its relation to progressive collapse of large buildings? Want to see some fiber bundle models of collapse initiation?

Hearing about someone taking a **** broke my train of thought.I mean where would you take it? To the movies?

Me - I usually leave a **** where it falls in the outhouse or where it's flushed by the toilet.But, to each his,or her own, I guess.

 

[Kat Dorman]

Hearing about someone taking a **** broke my train of thought.

I get what you mean. The guy in your avatar looks like he's taking a ****. When I look at it, my thought processes shut down. Or **** down, as the case may be.

I mean where would you take it? To the movies?

I guess you never saw Borat.

 

[shrubnose]

I get what you mean. The guy in your avatar looks like he's taking a ****. When I look at it, my thought processes shut down. Or **** down, as the case may be.

I guess you never saw Borat

.

Good guess.

I don't waste my time with crap like that.

 

[the_recruit]

It didn't loose so much mass out the sides... the facade fell away.. lets of mass... the floors slabs did not.. they came down crushed and pulverized... the contents on the floors was both crushed and came down and blasted out the windows... doesn't take a lot of blasted debris to look like more than it is.

Dude. Read the context of my comment. I was arguing that we shouldn't expect it to lose significant mass out the sides, which, yes, is in keeping with what we observed.

 

[the_recruit]

The lower section can exert an eccentric reaction force on impacting debris and freestanding components. As SanderO mentioned, the perimeters peeled away in large sheets and fell outward. This is just like anything tipping over; there's an initial bias towards one direction for whatever reason, then gravity drives the fall with the fulcrum and material providing horizontal reaction force to displace the center of mass of that component away from the footprint.

Even if the towers collapsed entirely straight down, the debris would still assume an angle of repose characteristic of the materials.

What Menard_K expressed, though, was surprise that the collapse could continue while it should be losing "so much" mass outside the footprint. This is incredulity over an unevaluated (by Menard_K) condition. First, what is the theoretical effect of mass shedding on existing models? Second, what are the real circumstances surround mass loss to outside the footprint in the tower collapses?

As far as models go, the various 1D models are really all there are. The best FEA models of tower collapses - and I only know of two, neither of which are full tower replicas - do not offer anything over the 1D models, if as much. These models indicate that fairly high mass loss can be tolerated throughout a continuing collapse, and moderate amounts like 10% don't greatly affect the results.

For the real collapses, two categories of components can be directly seen to have not participated in driving the collapse: the peeling perimeters and core remnants. The perimeters fall over after an interior collapse front has already passed by, stripping the floor slabs and removing critical lateral support. It is because the collapse propagated without the involvement of the perimeters that the perimeters fell. Likewise the core remnants, though lateral support was not so much an issue for the wider surviving remnants; lateral debris pressure at the base likely was. So, as far as reality goes, these masses did not drive the collapses, but neither did the structural capacity of these components contribute to resistive force. Lack of "participation" goes both ways - mass not driving, capacity not resisting.

Up to this point, the narrative I offer doesn't indicate a preference for natural collapse or CD. There could've been a cascading interior collapse due to damage plus fire, or there could've been charges to separate one or more slabs to get it going and possibly keep it going. Regardless, the mechanics of an interior collapse through the floor area is what needs to be considered, as this is what's observed (it's not necessary to infer that aspect when expulsions are seen passing an area and considerably later the perimeter falls away).

With regards to an interior collapse, the core and perimeter act as temporary "retaining walls" to prevent mass loss from an interior collapse.

You're completely misunderstanding my comment. There's a reason my comment was directed to Menard rather than you or sanders-whats-his-name, and, considering that, it was rhetorical. I'm not curious as to why most of the mass goes mostly downward or why a relatively small amount can be ejected laterally by gaining kinetic energy through certain collisions. But, don't feel bad, I'm sure someone somewhere will read your post and learn something from it.

And, since you seem to have failed to grasp my sarcasm earlier and still seem intent on dropping terms like "angle of repose" that are only vaguely related to the topic being discussed but are, or so you believe, esoteric and will impress/intimidate me - it doesn't. On the contrary, it makes you come across as an insecure person who cares a bit too much about what an anonymous stranger on the internet thinks of you. Don't take this too hard, but you're not the only person on this forum who learned about angles of repose in college. So, please, do yourself a favor and stop.

 

[Kat Dorman]

Don't take this too hard, but you're not the only person on this forum who learned about angles of repose in college. So, please, do yourself a favor and stop.

I was being kind. You displayed a classic misunderstanding grounded in naive physics. You were quite clear that you felt mass moving horizontally was not to be expected to any large degree since "Gravity vector is down, not sideways." There are plenty of reasons mass went outside the footprint, and plenty of it did.

 

[the_recruit]

I was being kind. You displayed a classic misunderstanding grounded in naive physics. You were quite clear that you felt mass moving horizontally was not to be expected to any large degree since "Gravity vector is down, not sideways." There are plenty of reasons mass went outside the footprint, and plenty of it did.

Again. Reread the context. Menard wasn't implying "plenty" of mass should go sideways. He was implying that more should have than did. Which is not true. And you pointing out that collisions can cause matter to fly in virtually any direction, so long as E and p are conserved, while technically correct, does not mean that more mass should have gone sideways than did.

 

[Kat Dorman]

Again. Reread the context. Menard wasn't implying "plenty" of mass should go sideways. He was implying that more should have than did. Which is not true.

If that's what you get out of it. I frequently have difficulty discerning the meaning of many of his statements. I took it to mean that it was unbelievable that sufficient mass wasn't lost for collapse to arrest. I went back and reread it a half dozen times. I give up.

I took your response to be a dismissal of the notion that significant mass could get off the footprint, on the basis that gravitational force has no horizontal component.

And you pointing out that collisions can cause matter to fly in virtually any direction, so long as E and p are conserved, while technically correct, does not mean that more mass should have gone sideways than did.

True.

 

[Kat Dorman]

And, by the way, what course of study is it that covers angle of repose?

 

[the_recruit]

And, by the way, what course of study is it that covers angle of repose?

Soils. I'm an ME, but I took a soils class to satisfy some general engineering req. Are you a CivE?

 

[SanderO]

Again. Reread the context. Menard wasn't implying "plenty" of mass should go sideways. He was implying that more should have than did. Which is not true. And you pointing out that collisions can cause matter to fly in virtually any direction, so long as E and p are conserved, while technically correct, does not mean that more mass should have gone sideways than did.

Who knows what he was implying and how does he know how much (percentage wise) was inside or outside the footprint? We see the facade panels fall outside... we see some debris being ejected through the windows.. we see the material of the top crush down spill over the side... some of it. We can assume over pressure inside the tower ahead of the crush front and that it would force material out the windows.

The floor destruction/collapse was largely contained by the facade... which fell away from the lateral forces of the gathering floor mass.

 

[Kat Dorman]

Soils. I'm an ME, but I took a soils class to satisfy some general engineering req.

Dig that! Mechanics of granular materials is pretty specialized. Soils, grain storage, food processing... these are about the only disciplines which care about things like that.

Are you a CivE?

No, I'm a software engineer. I did some mechanical stuff many years back, but degree is physics and I never used it.

 

[Kat Dorman]

I will add that I jumped the gun with you, the_recruit, and underestimated your grasp of the situation. You have to understand that a huge preponderance of people talking 9/11 collapses are completely 100% talking out their ass. One of the things I've heard said several times is essentially your reply to Menard_K. In every prior case, the presumption was no horizontal forces were present because only gravity was considered (e.g. the only direction to go is down). The more you said, the less you looked like one of those, rapidly. I have to check the hair trigger; books are not easily judged by one sentence. My apologies.

I had to ask about the angle of repose thing because there isn't 1 in 100 people with engineering or physics degrees who'd know the term. Most would know the concept, but not the term.

 

[the_recruit]

I will add that I jumped the gun with you, the_recruit, and underestimated your grasp of the situation. You have to understand that a huge preponderance of people talking 9/11 collapses are completely 100% talking out their ass. One of the things I've heard said several times is essentially your reply to Menard_K. In every prior case, the presumption was no horizontal forces were present because only gravity was considered (e.g. the only direction to go is down). The more you said, the less you looked like one of those, rapidly. I have to check the hair trigger; books are not easily judged by one sentence. My apologies.

I had to ask about the angle of repose thing because there isn't 1 in 100 people with engineering or physics degrees who'd know the term. Most would know the concept, but not the term.

Likewise. No hard feelings. eace

Generally, I can't stand WTC threads. Too many troofers with their cardboard scale models trying to explain things they know nothing about. I've found my blood pressure stays much lower if I avoid these threads. :mrgreen:

 

[Morrigi]

Meh, wrong WTC thread.

 

[Woodman909]

I once took a glass baking dish from the dishwasher and set it into the cupboard, not gingerly but certainly gently. Within moments, it explosively shattered into hundreds of small shards scattered all around the kitchen. It's reasonable to assume that it was manufactured with a defect (not apparent to the eye) which imposed large internal stresses. .

Sorry to be off point, but if this was a Corning Vision piece, what you experienced is a known problem that happens in one of every 2k pieces sold. You are very lucky to have avoided being injured. We got rid of all our Vision cookware.

 

[SanderO]

Likewise. No hard feelings. eace

Generally, I can't stand WTC threads. Too many troofers with their cardboard scale models trying to explain things they know nothing about. I've found my blood pressure stays much lower if I avoid these threads. :mrgreen:

I wouldn't let it get to you... these sorts of debates should be looked at as enjoyable... mental exercises and to see how others think or can't think. i have to admit that some of the forums and some of the threads have been very instructive to me... I've learned many things and many of them about thinking, analysis, psychology and so forth. I participate because at the times that I do... I have nothing more interesting or productive to do. I got myself involved in the truth movement because I naively believed that this group was hunting down the truth. But when I realized that they were not... that they were advancing a political agenda toward some rather undefined goal posts and using 9/11 as a football I withdrew to my PC and these discussions. People can get very exercised and show very poor manners online. They can do it because they can get away with it... lying or cyber bullying or just jerking people around. You can spot them... and engage or ignore...but you won't change them. The only person you can ever change is YOU and only if you want to and are open to change.

I've learned enormous amount from Kat Dorman, femr2, Tom and others and been exposed to how intelligent people can do and say dumb things knowingly or not. The good thing, you can shut the PC off and go sailing and this all doesn't matter.

 

[Menard_K]

Likewise. No hard feelings. eace

Generally, I can't stand WTC threads. Too many troofers with their cardboard scale models trying to explain things they know nothing about. I've found my blood pressure stays much lower if I avoid these threads. :mrgreen:

I have presented NO cardboard models of the WTC, The simple fact of asking WHY it is that chaotic damage could cause coherent "collapse" is sufficient to cause all sorts of lame excuses for how things happened the way they did.

The only three buildings in the complex to be completely destroyed
by the "terrorist attack" are WTC 1,2 & 7
Note that in the case of complete & total destruction of anything, the law-enforcement investigators are supposed to step in and declare the whole place a crime scene and control the access to it and indeed INVESTIGATE, however ... WHY was the Mayor of NYC allowed to get away with evidence tampering & obstruction of justice?

A! Bust the emperor for indecent exposure!

 

[Thoreau72]

I was being kind. You displayed a classic misunderstanding grounded in naive physics. You were quite clear that you felt mass moving horizontally was not to be expected to any large degree since "Gravity vector is down, not sideways." There are plenty of reasons mass went outside the footprint, and plenty of it did.

Amen Brother!

The biggest reason mass went outside the footprint, as far as several hundred feet with enough energy to impale pieces in WFC, was explosive devices. :2razz: