QUOTE (OneWhiteEye+Jan 29 2008, 06:08 PM)
I leeched!
Yeah. Wonder why. Makes me want to take the discussion elsewhere. This is no longer a happy medium.
I've noticed it, too. Comments forthcoming, within a few months...
User posted image: http://i26.tinypic.com/2i050ex.gif
User posted image: http://i28.tinypic.com/2iha32f.png
User posted image: http://i27.tinypic.com/wrzvo2.jpg
You really posted the last inline image here, it is also extension independent.
George W. knows it: “One of the great things about books is sometimes there are some fantastic pictures.”
And that is the same for a forum.
Yeah. Wonder why. Makes me want to take the discussion elsewhere. This is no longer a happy medium.
I've noticed it, too. Comments forthcoming, within a few months...
User posted image: http://i26.tinypic.com/2i050ex.gif
User posted image: http://i28.tinypic.com/2iha32f.png
User posted image: http://i27.tinypic.com/wrzvo2.jpg
You really posted the last inline image here, it is also extension independent.
George W. knows it: “One of the great things about books is sometimes there are some fantastic pictures.”
And that is the same for a forum.
einsteen --- Allo three of your links simply say test. Is that correct?
"Zoctober,
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
To self quote my 1st post, in this series, that you, BTW, found so amusing, "[...], I'm not talking about the pocket oscillator device associated with Tesla's urban mayhem. No, I'm talking about modern 'industrial strength' shakers, suitable for stress testing bridges, etc., bolted up to columns at critical position(s) along the vertical height".
To reiterate:
What if an infrasonic device, normally used by civil engineers for structural testing purposes, was (mis)used to provoke and prolong the excitation of a (steel) building's resonant frequency? Admittedly, the initial structural damage would, in itself, cause the building's frequency to change, thus causing the calibration to drift, and therefore the diminishing of the effect. The feedback search function, however, would continuously re-calibrate, and the periods of resonant excitation would continue to cycle, until the source units were destroyed, presumably, as the consequence of the buildings collapse.
There are two levels of application in a MIHOP scenario.
The first would be, just, to cause the building to shudder, sufficient to prompt initiation. This assumes, the upper section(s) had sufficient accelerated mass to displace and crush the lower section(s) to the ground.
The second would be a prolonged effort, for the (additional) purpose of snapping the connections of the vertical columns, and in the process, the lateral support of such.
Tesla claimed, that the dedicated application of mechanical resonance could destroy any structure, including the earth.
So, we have the following collapse scenario's:
Impact, damage, fire, and gravity.
Impact (controlled), damage, fire, and gravity
Impact (controlled), damage, fire, explosives (initiation), and gravity
Impact (controlled), explosives and or Thermite or Thermate, and gravity
Impact, damage, fire, mechanical resonance, and gravity
Impact (controlled), damage, fire, mechanical resonance, and gravity
Impact (controlled), mechanical resonance, and gravity
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
To self quote my 1st post, in this series, that you, BTW, found so amusing, "[...], I'm not talking about the pocket oscillator device associated with Tesla's urban mayhem. No, I'm talking about modern 'industrial strength' shakers, suitable for stress testing bridges, etc., bolted up to columns at critical position(s) along the vertical height".
To reiterate:
What if an infrasonic device, normally used by civil engineers for structural testing purposes, was (mis)used to provoke and prolong the excitation of a (steel) building's resonant frequency? Admittedly, the initial structural damage would, in itself, cause the building's frequency to change, thus causing the calibration to drift, and therefore the diminishing of the effect. The feedback search function, however, would continuously re-calibrate, and the periods of resonant excitation would continue to cycle, until the source units were destroyed, presumably, as the consequence of the buildings collapse.
There are two levels of application in a MIHOP scenario.
The first would be, just, to cause the building to shudder, sufficient to prompt initiation. This assumes, the upper section(s) had sufficient accelerated mass to displace and crush the lower section(s) to the ground.
The second would be a prolonged effort, for the (additional) purpose of snapping the connections of the vertical columns, and in the process, the lateral support of such.
Tesla claimed, that the dedicated application of mechanical resonance could destroy any structure, including the earth.
So, we have the following collapse scenario's:
Impact, damage, fire, and gravity.
Impact (controlled), damage, fire, and gravity
Impact (controlled), damage, fire, explosives (initiation), and gravity
Impact (controlled), explosives and or Thermite or Thermate, and gravity
Impact, damage, fire, mechanical resonance, and gravity
Impact (controlled), damage, fire, mechanical resonance, and gravity
Impact (controlled), mechanical resonance, and gravity
QUOTE (zoktoberfest+Jan 30 2008, 01:45 PM)
"Zoctober,
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
I notice you go to great lengths to NOT actually answer the question.
Do you believe there is ANY device, now or in the past, built by Telsa or not, the size of an Alarm Clock which could destroy a 5 story Steel building?
Arthur
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
I notice you go to great lengths to NOT actually answer the question.
Do you believe there is ANY device, now or in the past, built by Telsa or not, the size of an Alarm Clock which could destroy a 5 story Steel building?
Arthur
QUOTE (David B. Benson+Jan 30 2008, 05:21 PM)
einsteen --- Allo three of your links simply say test. Is that correct?
Das stimmt! I was testing several formats.
Das stimmt! I was testing several formats.
QUOTE (zoktoberfest+Jan 30 2008, 06:45 PM)
"Zoctober,
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
To self quote my 1st post, in this series, that you, BTW, found so amusing, "[...], I'm not talking about the pocket oscillator device associated with Tesla's urban mayhem. No, I'm talking about modern 'industrial strength' shakers, suitable for stress testing bridges, etc., bolted up to columns at critical position(s) along the vertical height".
To reiterate:
What if an infrasonic device, normally used by civil engineers for structural testing purposes, was (mis)used to provoke and prolong the excitation of a (steel) building's resonant frequency? Admittedly, the initial structural damage would, in itself, cause the building's frequency to change, thus causing the calibration to drift, and therefore the diminishing of the effect. The feedback search function, however, would continuously re-calibrate, and the periods of resonant excitation would continue to cycle, until the source units were destroyed, presumably, as the consequence of the buildings collapse.
There are two levels of application in a MIHOP scenario.
The first would be, just, to cause the building to shudder, sufficient to prompt initiation. This assumes, the upper section(s) had sufficient accelerated mass to displace and crush the lower section(s) to the ground.
The second would be a prolonged effort, for the (additional) purpose of snapping the connections of the vertical columns, and in the process, the lateral support of such.
Tesla claimed, that the dedicated application of mechanical resonance could destroy any structure, including the earth.
So, we have the following collapse scenario's:
Impact, damage, fire, and gravity.
Impact (controlled), damage, fire, and gravity
Impact (controlled), damage, fire, explosives (initiation), and gravity
Impact (controlled), explosives and or Thermite or Thermate, and gravity
Impact, damage, fire, mechanical resonance, and gravity
Impact (controlled), damage, fire, mechanical resonance, and gravity
Impact (controlled), mechanical resonance, and gravity
Sono Chemistry ring a bell Zoctober, that is what your talking about, you do understand that do you not?
Do you REALLY think Telsa had a device, no larger than an alarm clock, that could shake the bottom 5 stories of a 10 story steel building till it failed or destroy the Brooklyn bridge?
Arthur"
Tesla was the greatest inventor of the modern age. Some extend his importance even further.
If anyone could develop such a device, it would be him. He was conspicuously grounded in the the realm of applied science. It was within his nature to unleash, in order to ascertain, the full potential of his invention. He had little reason to misrepresent the actual or potential outcomes. At least, in the earlier phase of his career, he could always "walk the talk". There also exists, in the archives of the local periodicals, accounts of authorities arriving at his address, after unusual physical disturbances, in the surrounding neighborhood, were attributed to activities at his labs.
To self quote my 1st post, in this series, that you, BTW, found so amusing, "[...], I'm not talking about the pocket oscillator device associated with Tesla's urban mayhem. No, I'm talking about modern 'industrial strength' shakers, suitable for stress testing bridges, etc., bolted up to columns at critical position(s) along the vertical height".
To reiterate:
What if an infrasonic device, normally used by civil engineers for structural testing purposes, was (mis)used to provoke and prolong the excitation of a (steel) building's resonant frequency? Admittedly, the initial structural damage would, in itself, cause the building's frequency to change, thus causing the calibration to drift, and therefore the diminishing of the effect. The feedback search function, however, would continuously re-calibrate, and the periods of resonant excitation would continue to cycle, until the source units were destroyed, presumably, as the consequence of the buildings collapse.
There are two levels of application in a MIHOP scenario.
The first would be, just, to cause the building to shudder, sufficient to prompt initiation. This assumes, the upper section(s) had sufficient accelerated mass to displace and crush the lower section(s) to the ground.
The second would be a prolonged effort, for the (additional) purpose of snapping the connections of the vertical columns, and in the process, the lateral support of such.
Tesla claimed, that the dedicated application of mechanical resonance could destroy any structure, including the earth.
So, we have the following collapse scenario's:
Impact, damage, fire, and gravity.
Impact (controlled), damage, fire, and gravity
Impact (controlled), damage, fire, explosives (initiation), and gravity
Impact (controlled), explosives and or Thermite or Thermate, and gravity
Impact, damage, fire, mechanical resonance, and gravity
Impact (controlled), damage, fire, mechanical resonance, and gravity
Impact (controlled), mechanical resonance, and gravity
Sono Chemistry ring a bell Zoctober, that is what your talking about, you do understand that do you not?
calcium sulfate + carbon dioxide --> calcium carbonate + ??
Also, is this reaction exothermic or endothermic?
Thanks.
Also, is this reaction exothermic or endothermic?
Thanks.
QUOTE (David B. Benson+Jan 31 2008, 12:18 AM)
calcium sulfate + carbon dioxide --> calcium carbonate + ??
Also, is this reaction exothermic or endothermic?
Thanks.
Hi DBB!
IIRC, Sulfuric Acid displaces Carbon diOxide from Calcium Carbonate to produce CaSO4 plus heat energy plus Steam plus free CO2 gas. So the reverse would be against the chemo-thermodynamic 'arrow'.
Calcium Carbonate 'naturally' forms in a watery medium containing Carbonic Acid (CO2 in water).....it cannot form 'naturally' as a hot/dry reaction because the Carbonic Acid dissociates readily at elevated temps and the CO2 escapes as gas out of solution.
Since sulfuric acid is VERY stable and does not begin to dissociate before at least 360+ degrees C, the Carbonic Dioxide component is displaced easily by the sulfur TriOxide component of the sulfuric acid at those temps.
That was from 'old' memory. Please correct me if I mis-remembered anything!
RC.
.
Also, is this reaction exothermic or endothermic?
Thanks.
Hi DBB!
IIRC, Sulfuric Acid displaces Carbon diOxide from Calcium Carbonate to produce CaSO4 plus heat energy plus Steam plus free CO2 gas. So the reverse would be against the chemo-thermodynamic 'arrow'.
Calcium Carbonate 'naturally' forms in a watery medium containing Carbonic Acid (CO2 in water).....it cannot form 'naturally' as a hot/dry reaction because the Carbonic Acid dissociates readily at elevated temps and the CO2 escapes as gas out of solution.
Since sulfuric acid is VERY stable and does not begin to dissociate before at least 360+ degrees C, the Carbonic Dioxide component is displaced easily by the sulfur TriOxide component of the sulfuric acid at those temps.
That was from 'old' memory. Please correct me if I mis-remembered anything!
RC.
.
QUOTE (David B. Benson+Jan 31 2008, 12:18 AM)
calcium sulfate + carbon dioxide --> calcium carbonate + ??
Also, is this reaction exothermic or endothermic?
Thanks.
http://www.terrapub.co.jp/journals/GJ/pdf/...01/40010087.pdf
http://www.freepatentsonline.com/3640682.html
http://www.freepatentsonline.com/3640682.html
1. A process for increasing the rate of reaction in a process wherein calcium sulfate is reduced to calcium sulfide in a reaction vessel by the reaction between calcium sulfate and a gaseous reductant wherein the reductant consists essentially of hydrogen, carbon monoxide and mixtures thereof, said gaseous reductant being further characterized in that it is obtained from a first source whereby said gaseous reductant contains substantially less than 0.1 percent by volume of compounds containing one sulfur atom per molecule and substantially less than 0.05 percent by volume of compounds containing two sulfur atoms per molecule, which comprises supplying to said reaction, from an external second source, an accelerator agent selected from the group consisting of compounds which will provide in said reaction vessel a sulfur compound selected from the group consisting of sulfur vapor, sulfur dioxide and gaseous sulfide in an amount sufficient to provide a concentration of at least 0.1 percent by volume in the gaseous reductant in the case of sulfur compounds containing only one sulfur atom per molecule and at least 0.05 percent by volume in the gaseous reductant in the case of sulfur compounds containing two sulfur atoms per molecule, while maintaining the reaction temperature in said vessel within the range of 1,300° to 1,900° F.
http://www.osti.gov/energycitations/produc...osti_id=6593993
Also, is this reaction exothermic or endothermic?
Thanks.
http://www.terrapub.co.jp/journals/GJ/pdf/...01/40010087.pdf
QUOTE
Organic-inorganic reactions during thermochemical sulfate reduction (TSR) are the main cause for the destruction of
hydrocarbons in deep carbonate sediments. In this paper, thermal simulation experiments on C
1
–C
3
hydrocarbons and
solid calcium sulfate were carried out using an autoclave operated at high temperature and high pressure. The gas and
solid products were characterized by advanced analytical methods including microcoulometry, gas chromatography and
FT-IR. The kinetics and thermodynamics were investigated on the basis of the experimental data, and the results showed
that the reactions of C
1
–C
3
hydrocarbons and solid calcium sulfate can proceed spontaneously in the laboratory to produce
H
2
S, H
2
O, and CaCO
3
as the main products. From the kinetic calculation, it is found that these three reactions are zero
order reactions with activation energies of 152.9 kJ/mol, 131.0 kJ/mol and 120.6 kJ/mol, respectively. When extrapolated
to geological temperatures, the time needed to reach 50% conversion at the temperature of 200°C for the reaction between
CH
4
and CaSO
4
is 1.44 million years
hydrocarbons in deep carbonate sediments. In this paper, thermal simulation experiments on C
1
–C
3
hydrocarbons and
solid calcium sulfate were carried out using an autoclave operated at high temperature and high pressure. The gas and
solid products were characterized by advanced analytical methods including microcoulometry, gas chromatography and
FT-IR. The kinetics and thermodynamics were investigated on the basis of the experimental data, and the results showed
that the reactions of C
1
–C
3
hydrocarbons and solid calcium sulfate can proceed spontaneously in the laboratory to produce
H
2
S, H
2
O, and CaCO
3
as the main products. From the kinetic calculation, it is found that these three reactions are zero
order reactions with activation energies of 152.9 kJ/mol, 131.0 kJ/mol and 120.6 kJ/mol, respectively. When extrapolated
to geological temperatures, the time needed to reach 50% conversion at the temperature of 200°C for the reaction between
CH
4
and CaSO
4
is 1.44 million years
http://www.freepatentsonline.com/3640682.html
QUOTE (->
| QUOTE |
| Organic-inorganic reactions during thermochemical sulfate reduction (TSR) are the main cause for the destruction of hydrocarbons in deep carbonate sediments. In this paper, thermal simulation experiments on C 1 –C 3 hydrocarbons and solid calcium sulfate were carried out using an autoclave operated at high temperature and high pressure. The gas and solid products were characterized by advanced analytical methods including microcoulometry, gas chromatography and FT-IR. The kinetics and thermodynamics were investigated on the basis of the experimental data, and the results showed that the reactions of C 1 –C 3 hydrocarbons and solid calcium sulfate can proceed spontaneously in the laboratory to produce H 2 S, H 2 O, and CaCO 3 as the main products. From the kinetic calculation, it is found that these three reactions are zero order reactions with activation energies of 152.9 kJ/mol, 131.0 kJ/mol and 120.6 kJ/mol, respectively. When extrapolated to geological temperatures, the time needed to reach 50% conversion at the temperature of 200°C for the reaction between CH 4 and CaSO 4 is 1.44 million years |
http://www.freepatentsonline.com/3640682.html
1. A process for increasing the rate of reaction in a process wherein calcium sulfate is reduced to calcium sulfide in a reaction vessel by the reaction between calcium sulfate and a gaseous reductant wherein the reductant consists essentially of hydrogen, carbon monoxide and mixtures thereof, said gaseous reductant being further characterized in that it is obtained from a first source whereby said gaseous reductant contains substantially less than 0.1 percent by volume of compounds containing one sulfur atom per molecule and substantially less than 0.05 percent by volume of compounds containing two sulfur atoms per molecule, which comprises supplying to said reaction, from an external second source, an accelerator agent selected from the group consisting of compounds which will provide in said reaction vessel a sulfur compound selected from the group consisting of sulfur vapor, sulfur dioxide and gaseous sulfide in an amount sufficient to provide a concentration of at least 0.1 percent by volume in the gaseous reductant in the case of sulfur compounds containing only one sulfur atom per molecule and at least 0.05 percent by volume in the gaseous reductant in the case of sulfur compounds containing two sulfur atoms per molecule, while maintaining the reaction temperature in said vessel within the range of 1,300° to 1,900° F.
http://www.osti.gov/energycitations/produc...osti_id=6593993
QUOTE
The reductive decomposition of calcium sulfate pellets with both hydrogen and carbon monoxide was studied experimentally in the range of 900 to 1100/sup 0/C.^The conditions of the reaction were controlled in order to enhance the formation of calcium oxide while the production of the undesirable calcium sulfide was inhibited; carbon dioxide was used to prevent calcium sulfide formation.^Cylindrical calcium sulfate pellets were prepared at a constant compression pressure and reduction was carried out initially at a constant temperature and various reductant gas concentrations.^Additional experiments were made with a constant gas phase concentration and various reaction temperatures.^Stabilization of the pellet through heating prior to initiating the reduction process was required in order to obtain reliable data.^Treatment of the pellet at elevated temperatures caused sintering which reduced the pellet surface area to a value that changed little with additional heating time.^Conversions of about 100% were obtained in several hours with both reductant gases at temperatures around 1000/sup 0/C and higher.^The rate of calcium sulfate reduction with hydrogen was consistently found to be higher than that with carbon monoxide.^The grain model was used to first determine the mechanism controlling the reduction process, then the grain shape factor was evaluated by fitting the data, and finally the parameters involved in the controlling mechanism were calculated.^A first-order chemical reaction was found to be the predominant resistance limiting the rate of reduction.^The highest correlation factors, around 0.99, were always obtained when a spherical grain shape factor was used in plotting the numerical solution of the governing equation.^42 figures, 3 tables.
RealityCheck and Chainsaw --- Thanks. I asked because it seems that calcium sulfate is a component of wood ash.
"Sono Chemistry ring a bell Zoctober, that is what your talking about, you do understand that do you not?"
"sonochemistry
In chemistry, the study of sonochemistry is concerned with understanding the effect of sonic waves and wave properties on chemical systems. Since acoustic waves have unique physical properties, the corresponding atomic and molecular chemistry is unique as well. Often these effects are most apparent in ultrasonic systems. This is demonstrated in phenomena such as ultrasound, sonication, sonoluminescence and sonic cavitation.
For example, in chemical kinetics, it has been observed that ultrasound can greatly enhance chemical reactivity in a number of systems; effectively acting as a catalyst by exciting the atomic and molecular modes of the system (such as the vibrational, rotational, and translational modes). In addition, in reactions that use solids, ultrasound breaks up the solid pieces from the energy released from the bubbles created by cavitation collapsing through them. This gives the solid reactant a larger surface area for the reaction to proceed over, increasing the observed rate of reaction. Ultrasound produces radicals in liquids due to the high temperatures and pressures experienced locally when a bubble collapses.
While the application of ultrasound often generates mixtures of products, a paper published in 2007 in the journal Nature described the use of ultrasound to selectively effect a certain cyclobutane ring-opening reaction.[1]"
http://en.wikipedia.org/wiki/Sonochemistry
Chainsaw,
Sonochemistry utilizes sonic (40-20kHz) and ultrasonic (>20kHz) frequencies to influence chemical reactions. Exciting the fundamental resonance of the WTC would require a wave length some where in the infrasonic range (0-20Hz). Secondary harmonics could extend into the subsonic range (20-40Hz).
Allow me to recount an experience, that led me to speculate on the possible use of mechanical resonance as a destructive force.
I supplemented my HT system with a small bass shaker (50W). It's a surface mount transducer that extends the low end of the system into the infrasonic range (<20Hz). It introduces inaudible, but visceral and tactile sensations through solid mediums, and into the listener's body. I inherited this device without the documentation, so my placement options were limited only by my own foolishness. I attached it to the main beam (4"x10") supporting the floor joists in the basement. During "Saving Private Ryan", I could feel the explosions on Normandy Beach, as if I were there, and then it happened. During a subsequent explosion scene, the house seemed to jump on its' foundation. I killed the power to the shaker unit immediately.
A frequency on the sound track, must have matched the resonant frequency of my small house. I had turned the floor system, momentarily, into a massive live diaphragm. I understand, first hand, the force that Tesla unleashed with his small, pneumatic oscillator. Mechanical resonance.
Arthur
Yes, I believe that Tesla could excite a 5 story building with his small pneumatic device. Not as effortlessly as I, unintentionally, did. I will acknowledge, that a source of pressurized air, not mentioned in the accounts, either from a hand pump or a canister, would be required to sustain its' operation.
"sonochemistry
In chemistry, the study of sonochemistry is concerned with understanding the effect of sonic waves and wave properties on chemical systems. Since acoustic waves have unique physical properties, the corresponding atomic and molecular chemistry is unique as well. Often these effects are most apparent in ultrasonic systems. This is demonstrated in phenomena such as ultrasound, sonication, sonoluminescence and sonic cavitation.
For example, in chemical kinetics, it has been observed that ultrasound can greatly enhance chemical reactivity in a number of systems; effectively acting as a catalyst by exciting the atomic and molecular modes of the system (such as the vibrational, rotational, and translational modes). In addition, in reactions that use solids, ultrasound breaks up the solid pieces from the energy released from the bubbles created by cavitation collapsing through them. This gives the solid reactant a larger surface area for the reaction to proceed over, increasing the observed rate of reaction. Ultrasound produces radicals in liquids due to the high temperatures and pressures experienced locally when a bubble collapses.
While the application of ultrasound often generates mixtures of products, a paper published in 2007 in the journal Nature described the use of ultrasound to selectively effect a certain cyclobutane ring-opening reaction.[1]"
http://en.wikipedia.org/wiki/Sonochemistry
Chainsaw,
Sonochemistry utilizes sonic (40-20kHz) and ultrasonic (>20kHz) frequencies to influence chemical reactions. Exciting the fundamental resonance of the WTC would require a wave length some where in the infrasonic range (0-20Hz). Secondary harmonics could extend into the subsonic range (20-40Hz).
Allow me to recount an experience, that led me to speculate on the possible use of mechanical resonance as a destructive force.
I supplemented my HT system with a small bass shaker (50W). It's a surface mount transducer that extends the low end of the system into the infrasonic range (<20Hz). It introduces inaudible, but visceral and tactile sensations through solid mediums, and into the listener's body. I inherited this device without the documentation, so my placement options were limited only by my own foolishness. I attached it to the main beam (4"x10") supporting the floor joists in the basement. During "Saving Private Ryan", I could feel the explosions on Normandy Beach, as if I were there, and then it happened. During a subsequent explosion scene, the house seemed to jump on its' foundation. I killed the power to the shaker unit immediately.
A frequency on the sound track, must have matched the resonant frequency of my small house. I had turned the floor system, momentarily, into a massive live diaphragm. I understand, first hand, the force that Tesla unleashed with his small, pneumatic oscillator. Mechanical resonance.
Arthur
Yes, I believe that Tesla could excite a 5 story building with his small pneumatic device. Not as effortlessly as I, unintentionally, did. I will acknowledge, that a source of pressurized air, not mentioned in the accounts, either from a hand pump or a canister, would be required to sustain its' operation.
QUOTE (zoktoberfest+Feb 1 2008, 08:35 PM)
Yes, I believe that Tesla could excite a 5 story building with his small pneumatic device. Not as effortlessly as I, unintentionally, did. I will acknowledge, that a source of pressurized air, not mentioned in the accounts, either from a hand pump or a canister, would be required to sustain its' operation.
Well then there is apparently little you WON'T believe.
But, be my guest, prove me wrong, show a link to an alarm clock size device that has the ability to destroy a 5 story steel building by shaking it to pieces.
Heck, I'll accept a link to an electro/mechanical device 100 times the volume of an alarm clock.
But I won't hold my breath.
Arthur
Well then there is apparently little you WON'T believe.
But, be my guest, prove me wrong, show a link to an alarm clock size device that has the ability to destroy a 5 story steel building by shaking it to pieces.
Heck, I'll accept a link to an electro/mechanical device 100 times the volume of an alarm clock.
But I won't hold my breath.
Arthur
These guys do some funny experiments
http://www.youtube.com/watch?v=DgqkJ7do1wk
http://www.youtube.com/watch?v=pP98X-ar2mA
worth watching
http://www.youtube.com/watch?v=DgqkJ7do1wk
http://www.youtube.com/watch?v=pP98X-ar2mA
worth watching
QUOTE (einsteen+Feb 4 2008, 10:18 AM)
worth watching
Since I can't, a brief description?
Since I can't, a brief description?
User posted image: User posted image
QUOTE (einsteen+Feb 4 2008, 12:18 PM)
These guys do some funny experiments
http://www.youtube.com/watch?v=DgqkJ7do1wk
http://www.youtube.com/watch?v=pP98X-ar2mA
worth watching
For LAUGHS?????
I doubt this could be less realistic if they tried.
Just a few obvious observations:
A ) the loads have to be such that at ~ twice the gravity load the structure will fail.
B ) the floors can't be integral to the structure, they have to be supported by much smaller tabs to represent the truss seats.
C ) the materials can't flex like that without breaking (consider the SCALE amount of flexing the observed bending represents)
D) the drop distance can't be scaled, regardless of how small you make the towers you still have to drop the top section ~ 9 ft.
Arthur
http://www.youtube.com/watch?v=DgqkJ7do1wk
http://www.youtube.com/watch?v=pP98X-ar2mA
worth watching
For LAUGHS?????
I doubt this could be less realistic if they tried.
Just a few obvious observations:
A ) the loads have to be such that at ~ twice the gravity load the structure will fail.
B ) the floors can't be integral to the structure, they have to be supported by much smaller tabs to represent the truss seats.
C ) the materials can't flex like that without breaking (consider the SCALE amount of flexing the observed bending represents)
D) the drop distance can't be scaled, regardless of how small you make the towers you still have to drop the top section ~ 9 ft.
Arthur
QUOTE (einsteen+Feb 5 2008, 12:07 AM)
User posted image: <a target='_blank' href='http://i32.tinypic.com/2hfqrd5.jpg'>User posted image</a>
Thanks.
Such attempts are doomed to failure since the force of gravity cannot be scaled.
I had earlier suggested building a horizontal model, but even this would not (quite) take all the inertial effects into account. The main virtue of the model is that both metamars and reasonwhy poopooed it, which demonstrated to my satisfaction that neither of them actually understand physics.
Thanks.
Such attempts are doomed to failure since the force of gravity cannot be scaled.
I had earlier suggested building a horizontal model, but even this would not (quite) take all the inertial effects into account. The main virtue of the model is that both metamars and reasonwhy poopooed it, which demonstrated to my satisfaction that neither of them actually understand physics.
QUOTE (David B. Benson+Feb 5 2008, 06:03 PM)
Thanks.
Such attempts are doomed to failure since the force of gravity cannot be scaled.
I had earlier suggested building a horizontal model, but even this would not (quite) take all the inertial effects into account. The main virtue of the model is that both metamars and reasonwhy poopooed it, which demonstrated to my satisfaction that neither of them actually understand physics.
Oh, Benson, how could you say such a thing? How COULD you?
You know perfectly well that, if anything, I've suggested that your vision was too limited. Why, with just the right amount of tweaking, rail cars and velcro could still yield, for you, proof of the Higgs boson. If you hurry, you can still beat out the Large Hadron Collider, and the Nobel Prize will be yours!
Such attempts are doomed to failure since the force of gravity cannot be scaled.
I had earlier suggested building a horizontal model, but even this would not (quite) take all the inertial effects into account. The main virtue of the model is that both metamars and reasonwhy poopooed it, which demonstrated to my satisfaction that neither of them actually understand physics.
Oh, Benson, how could you say such a thing? How COULD you?
You know perfectly well that, if anything, I've suggested that your vision was too limited. Why, with just the right amount of tweaking, rail cars and velcro could still yield, for you, proof of the Higgs boson. If you hurry, you can still beat out the Large Hadron Collider, and the Nobel Prize will be yours!
Of course that experiment doesn't work but the challenge is to get something like that to work. Since gravity doesn't scale in the same way one could try a centrifuge for example... or maybe try to create a weak construction, put one story on a table, try to find a weight that is able to destroy that one, then start dropping an amount of stories on another amount of stories in which the collapsing amount has the same weight as your test weight. Initiation is still a mystery, nobody dropped the titanic on the twin towers.
einsteen
It is no mystery, instead of the weight increasing(or being dropped on it), the structural strength decreased due to heating(in addition to the damage done by impact) to the point of failure. To an engineer or physicist(in fact, to most fairly well educated people), this is so simple they fail to understand how anyone could logically or reasonably dispute this.
Grumpy
QUOTE
Initiation is still a mystery, nobody dropped the titanic on the twin towers
It is no mystery, instead of the weight increasing(or being dropped on it), the structural strength decreased due to heating(in addition to the damage done by impact) to the point of failure. To an engineer or physicist(in fact, to most fairly well educated people), this is so simple they fail to understand how anyone could logically or reasonably dispute this.
Grumpy
QUOTE (einsteen+Feb 6 2008, 02:52 AM)
... nobody dropped the titanic on the twin towers.
The top portion of WTC 1 massed about the same as a fully loaded handysize cargo ship.
The top portion of WTC 1 massed about the same as a fully loaded handysize cargo ship.
QUOTE (einsteen+Feb 6 2008, 04:52 AM)
Of course that experiment doesn't work but the challenge is to get something like that to work. Since gravity doesn't scale in the same way one could try a centrifuge for example...
einsteen,
Please describe for us the approximate dimensions and capabilities of this centrifuge and the corresponding model of the WTC tower that you think that you could try.....
Arthur
einsteen,
Please describe for us the approximate dimensions and capabilities of this centrifuge and the corresponding model of the WTC tower that you think that you could try.....
Arthur
QUOTE (Grumpy+Feb 6 2008, 05:06 PM)
einsteen
It is no mystery, instead of the weight increasing(or being dropped on it), the structural strength decreased due to heating(in addition to the damage done by impact) to the point of failure. To an engineer or physicist(in fact, to most fairly well educated people), this is so simple they fail to understand how anyone could logically or reasonably dispute this.
Grumpy
The story looks so self-evident that 99% of the population (who only thinks briefly about it) can understand it, therefore it is a big success.
It is no mystery, instead of the weight increasing(or being dropped on it), the structural strength decreased due to heating(in addition to the damage done by impact) to the point of failure. To an engineer or physicist(in fact, to most fairly well educated people), this is so simple they fail to understand how anyone could logically or reasonably dispute this.
Grumpy
The story looks so self-evident that 99% of the population (who only thinks briefly about it) can understand it, therefore it is a big success.
QUOTE (adoucette+Feb 6 2008, 06:05 PM)
einsteen,
Please describe for us the approximate dimensions and capabilities of this centrifuge and the corresponding model of the WTC tower that you think that you could try.....
Arthur
Ok, I had to check my paper (that is on hold for almost a year now) back
If you scale g times the height of a story by a factor alpha, then you also have to scale E1/M by the same factor alpha, the velocity then goes as the square of alpha. This gives a lot of possibilities for the 1d model
summary
gh ---> gh/alpha
E1/M ---> E1/M*alpha
v ---> v/sqrt(alpha)
Please describe for us the approximate dimensions and capabilities of this centrifuge and the corresponding model of the WTC tower that you think that you could try.....
Arthur
Ok, I had to check my paper (that is on hold for almost a year now) back
If you scale g times the height of a story by a factor alpha, then you also have to scale E1/M by the same factor alpha, the velocity then goes as the square of alpha. This gives a lot of possibilities for the 1d model
summary
gh ---> gh/alpha
E1/M ---> E1/M*alpha
v ---> v/sqrt(alpha)
einsteen
Yeah, the facts have a way of doing that, you know, it only takes a brief look to ascertain that the scientists and engineers DO know what they are talking about, after all. Glad we finally got that straight.
Grumpy
QUOTE
The story looks so self-evident that 99% of the population (who only thinks briefly about it) can understand it, therefore it is a big success.
Yeah, the facts have a way of doing that, you know, it only takes a brief look to ascertain that the scientists and engineers DO know what they are talking about, after all. Glad we finally got that straight.
Grumpy
QUOTE (einsteen+Feb 6 2008, 03:09 PM)
Ok, I had to check my paper (that is on hold for almost a year now) back
If you scale g times the height of a story by a factor alpha, then you also have to scale E1/M by the same factor alpha, the velocity then goes as the square of alpha. This gives a lot of possibilities for the 1d model
summary
gh ---> gh/alpha
E1/M ---> E1/M*alpha
v ---> v/sqrt(alpha)
That doesn't answer the question I asked.
Try again.
Arthur
If you scale g times the height of a story by a factor alpha, then you also have to scale E1/M by the same factor alpha, the velocity then goes as the square of alpha. This gives a lot of possibilities for the 1d model
summary
gh ---> gh/alpha
E1/M ---> E1/M*alpha
v ---> v/sqrt(alpha)
That doesn't answer the question I asked.
Try again.
Arthur
I think it does, maybe it's no explicit answer and a very general one, but you could try what you want with those values, probably you don't even need a centrifuge for the effect.
QUOTE (einsteen+Feb 6 2008, 05:36 PM)
I think it does, maybe it's no explicit answer and a very general one, but you could try what you want with those values, probably you don't even need a centrifuge for the effect.
einsteen, we are talking about building a REAL scale model.
Velocity comes from the force of gravity so your term: v/sqrt(alpha) makes no sense to me at all as it relates to a scale model.
Maybe I don't understand your very SPARSE answer.
Could you take a FEW more seconds from your busy schedule and describe what you mean to solve the problem of scaling Gravity?
Arthur
einsteen, we are talking about building a REAL scale model.
Velocity comes from the force of gravity so your term: v/sqrt(alpha) makes no sense to me at all as it relates to a scale model.
Maybe I don't understand your very SPARSE answer.
Could you take a FEW more seconds from your busy schedule and describe what you mean to solve the problem of scaling Gravity?
Arthur
from http://pdf.aiaa.org/preview/CDReadyMASM03_582/PV2003_241.pdf
In another study, Aumann et al. (1995) examined the oxidation behavior of aluminum nanopowders. They suggest that Al powder mixtures with average particle sizes of 20-50 nm can react 1000 times faster than conventional powdered thermites..
Recall that the red/gray chips have a layer that Professor Jones believes is thermite that is only 40 microns thick.
Also, at JREF, Mackey has pointed out to me that a 100 mph wind will only create a .17 psi overpressure. The idea of a thermobaric, even a muted one, explaining pulverization seems, ahem, unlikely.
I'm still uncertain as to what a fast burn of a nanopowder thermite would look like. In particular, I'd like to know whether an explosive "bang" is to be expected, the speed and momentum of the iron-containing explosive front (as a function of space and time), and it's connection to any concomittant pressure wave of gas. Probably a chemical engineer is better to ask than a physicist.
Also, BTW, Fe2O3 is used as a catalyst in solid propellants (where something else is the oxidizer). See http://www.allfreeessays.net/student/Solid_Propellants.html .
Perhaps, if an aluminotheric nanopowder was used, there was relatively few ferrous spheres, because there was relatively little ferrous compound used for the reaction. While a catalyst technically doesn't get used up in a reaction, if it's catalyzing another reaction hot enough to melt it, I suppose that we'd get ferrous microspheres, anyway.
QUOTE
In another study, Aumann et al. (1995) examined the oxidation behavior of aluminum nanopowders. They suggest that Al powder mixtures with average particle sizes of 20-50 nm can react 1000 times faster than conventional powdered thermites..
Recall that the red/gray chips have a layer that Professor Jones believes is thermite that is only 40 microns thick.
Also, at JREF, Mackey has pointed out to me that a 100 mph wind will only create a .17 psi overpressure. The idea of a thermobaric, even a muted one, explaining pulverization seems, ahem, unlikely.
I'm still uncertain as to what a fast burn of a nanopowder thermite would look like. In particular, I'd like to know whether an explosive "bang" is to be expected, the speed and momentum of the iron-containing explosive front (as a function of space and time), and it's connection to any concomittant pressure wave of gas. Probably a chemical engineer is better to ask than a physicist.
Also, BTW, Fe2O3 is used as a catalyst in solid propellants (where something else is the oxidizer). See http://www.allfreeessays.net/student/Solid_Propellants.html .
Perhaps, if an aluminotheric nanopowder was used, there was relatively few ferrous spheres, because there was relatively little ferrous compound used for the reaction. While a catalyst technically doesn't get used up in a reaction, if it's catalyzing another reaction hot enough to melt it, I suppose that we'd get ferrous microspheres, anyway.
Arthur, for you I have always time. I've tried to check it with the
crush-down equation with lambda=0, m(z)=constant, Fc=F=constant
but I'm currently not sure how to do that, maybe DBB could help out
m * z''(t) - mg=-F
if we use F=E1/h we can rewrite it as
h*z''(t)-gh=-E1/m
For
gh ---> gh/alpha
E1/M ---> E1/M*alpha
I'm at the moment NOT sure how to rewrite it but that
should give
h*z''(t) --> h*z''(t)/alpha
and if g=constant that should become maybe h*z''(t)/alpha^2 ?????
TRY #2
======
The thing that I derived is not v(t) but v(k), i.e. the velocity as function
of the floor which is an index and I took the discrete model and also no
uniform force distribution
When a mass M falls a distance h and E1 is consumed due to a resistive force then
that relation is
v=sqrt(2[gh-E1/M])
In that case
gh ---> gh/alpha
E1/M ---> E1/M*alpha
leads to v ---> v/sqrt(alpha)
and I think I wrote it wrong last night, not the square of the velocity but the square
of alpha... And I thought that this process can be scaled for the whole v(k) function
including momentum transfer, I will later verify it with maple.
Cheers,
Ed
crush-down equation with lambda=0, m(z)=constant, Fc=F=constant
but I'm currently not sure how to do that, maybe DBB could help out
m * z''(t) - mg=-F
if we use F=E1/h we can rewrite it as
h*z''(t)-gh=-E1/m
For
gh ---> gh/alpha
E1/M ---> E1/M*alpha
I'm at the moment NOT sure how to rewrite it but that
should give
h*z''(t) --> h*z''(t)/alpha
and if g=constant that should become maybe h*z''(t)/alpha^2 ?????
TRY #2
======
The thing that I derived is not v(t) but v(k), i.e. the velocity as function
of the floor which is an index and I took the discrete model and also no
uniform force distribution
When a mass M falls a distance h and E1 is consumed due to a resistive force then
that relation is
v=sqrt(2[gh-E1/M])
In that case
gh ---> gh/alpha
E1/M ---> E1/M*alpha
leads to v ---> v/sqrt(alpha)
and I think I wrote it wrong last night, not the square of the velocity but the square
of alpha... And I thought that this process can be scaled for the whole v(k) function
including momentum transfer, I will later verify it with maple.
Cheers,
Ed
Einsteen, is this what you had in mind in reference to centrifuge testing?
A geotechnical centrifuge is used for research in geotechnical science, an area of civil engineering concerned how geological materials (dirt and rock) interact with the foundations of built structures such as bridges, roads, and houses. In a research laboratory, engineers use centrifuges to study the affect of gravity on soil samples or small-scale models of structures. The experiments serve to measure properties such as the strength, stiffness and capacity of foundations for bridges and buildings, the stability of hillsides and seawalls, etc. Small models do not weigh the same as a full size structure, of course, but the forces created by the centrifuge can artificially recreate the affects of gravity to provide accurate results.
http://www.nees.org/Research_Activities/centrifuge/
A geotechnical centrifuge is used for research in geotechnical science, an area of civil engineering concerned how geological materials (dirt and rock) interact with the foundations of built structures such as bridges, roads, and houses. In a research laboratory, engineers use centrifuges to study the affect of gravity on soil samples or small-scale models of structures. The experiments serve to measure properties such as the strength, stiffness and capacity of foundations for bridges and buildings, the stability of hillsides and seawalls, etc. Small models do not weigh the same as a full size structure, of course, but the forces created by the centrifuge can artificially recreate the affects of gravity to provide accurate results.
http://www.nees.org/Research_Activities/centrifuge/
QUOTE (metamars+Feb 7 2008, 02:57 AM)
I'm still uncertain as to what a fast burn of a nanopowder thermite would look like. In particular, I'd like to know whether an explosive "bang" is to be expected, the speed and momentum of the iron-containing explosive front (as a function of space and time), and it's connection to any concomittant pressure wave of gas. Probably a chemical engineer is better to ask than a physicist.
Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation
At: http://etd.lib.ttu.edu/theses/available/et...Kyle_Thesis.pdf
Table 8 (truncated): Mach number calculations for the flame speed of the reactions
Al Size Composition Ma in gas medium at reaction temp
50 nm Al/Teflon 1.18
50 nm Al/MoO3/Teflon 0.90
50 nm Al/MoO3 0.87
1-3 micron Al/Teflon 0.49
1-3 micron Al/MoO3/Teflon 0.15
1-3 micron Al/MoO3 0.22
Initially looking at the flame speeds, the reactions appear to approach Mach 3 as shown by the Mach number calculation at room temperature shown in Table 8. If this was the case acoustical effects may play a huge role and detonation in the reaction would be imminent. However, considering the reaction occurs in air at the reaction temperature yields Mach numbers on the subsonic regime and would be more consistent with a deflagration. The actual Mach numbers will most likely be somewhere in between and may be best represented by the Mach number calculation in the gas byproduct medium at the reaction temperature. The number is probably slightly high as the gas will not be at the adiabatic flame temperature but it will be much higher than that of room temperature. These Mach numbers are on the order of Mach 1 and would suggest a reaction that is still a deflagration but may be nearing detonation. This is consistent with the comparison of the optical and acoustical propagation rates from above.
(emphasis mine)
Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation
At: http://etd.lib.ttu.edu/theses/available/et...Kyle_Thesis.pdf
QUOTE
Table 8 (truncated): Mach number calculations for the flame speed of the reactions
Al Size Composition Ma in gas medium at reaction temp
50 nm Al/Teflon 1.18
50 nm Al/MoO3/Teflon 0.90
50 nm Al/MoO3 0.87
1-3 micron Al/Teflon 0.49
1-3 micron Al/MoO3/Teflon 0.15
1-3 micron Al/MoO3 0.22
Initially looking at the flame speeds, the reactions appear to approach Mach 3 as shown by the Mach number calculation at room temperature shown in Table 8. If this was the case acoustical effects may play a huge role and detonation in the reaction would be imminent. However, considering the reaction occurs in air at the reaction temperature yields Mach numbers on the subsonic regime and would be more consistent with a deflagration. The actual Mach numbers will most likely be somewhere in between and may be best represented by the Mach number calculation in the gas byproduct medium at the reaction temperature. The number is probably slightly high as the gas will not be at the adiabatic flame temperature but it will be much higher than that of room temperature. These Mach numbers are on the order of Mach 1 and would suggest a reaction that is still a deflagration but may be nearing detonation. This is consistent with the comparison of the optical and acoustical propagation rates from above.
(emphasis mine)
QUOTE (einsteen+Feb 6 2008, 11:49 PM)
... maybe DBB could help out
m * z''(t) - mg=-F
Sure. You left out the inertial term regarding momentum. Scaling so that Z lies between 0 (top) and 1 (bottom) and assuming constant density so that Z also represents the mass from the top down to height Z, and also scaling so that g = 1 (all three together are possible):
ZZ" + (1/2)Z" - Z = -F(Z,Z')
Now do note that assuming F(Z,Z') is independent of Z and Z' gives a resistive force does agrees but poorly with the data, especially when the stretch is assumed to be zero. A more accurate resistive force function is
F(Z,Z') = k0 + k1*Z + k2*Z*(Z')^2
m * z''(t) - mg=-F
Sure. You left out the inertial term regarding momentum. Scaling so that Z lies between 0 (top) and 1 (bottom) and assuming constant density so that Z also represents the mass from the top down to height Z, and also scaling so that g = 1 (all three together are possible):
ZZ" + (1/2)Z" - Z = -F(Z,Z')
Now do note that assuming F(Z,Z') is independent of Z and Z' gives a resistive force does agrees but poorly with the data, especially when the stretch is assumed to be zero. A more accurate resistive force function is
F(Z,Z') = k0 + k1*Z + k2*Z*(Z')^2
Again from Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation
http://etd.lib.ttu.edu/theses/available/et...Kyle_Thesis.pdf
The pressure wave propagation will tell how fast the pressure is moving through the confined space. This can be used to determine if the reaction reaches the point of detonation or if it is a deflagration. If the pressure wave proceeds equal or faster than that of the optical propagation wave the reaction can be considered to have reached detonation. If the pressure wave propagates slower than the optical wave the reaction will be a deflagration.
The optical propagation rate, or flame speed, is deduced from the high-speed camera data. It is primarily used as a quantification for the speed of the reaction, but can also give indication of detonation when compared to the pressure wave propagation rate as described above. Another interesting characteristic derived from the optical propagatioin rate is the Mach number achieved by the reaction. In many MIC reactions, flame speeds can approach and exceed 1000 m/s, which would be in excess of Ma 3 if the surroundings were considered to be air at room temperature. The achieving of such Mach numbers could mean that there are significant acoustic effects in the reaction. However, reaction proceeds within the flame zone assumed to be at the adiabatic flame temperature for the reaction. This extreme temperature environment reduces the Ma number calculation significantly.
.
.
.
.
Peak flame speeds of 4.249 m/s, 410.636 m/s, and 456.559 m/s were obtained for the nano Al samples of Al/Teflon, Al/MoO3/Teflon, and Al/MoO3 composites, respectively.
Note: the flame propagation rate varied enormously as a percentage of aluminum. For example, from Figure 11, which plots flame propagation rate vs. % Al for Al/MoO3/Teflon, there are not only supersonic flame rates of about 410 m/s and 360 m/s, there are also flame rates of ~ 230, 80, 10 and 10 m/s.
In other words, we can get both supersonic and subsonic flame rates, the speed of sound in air being 344 m/s.
I'm not sure if this holds for rapid, yet subsonic flame rate regimes, but for the case of 50 nm Al burns of 40% Al, we can see from Table 5 that supersonic, optical propagation rate exceeds the pressure propagation rate for all of the species being studied. Perhaps the same will be true, for example, for a 230 m/s flame propagation rate, but I haven't seen the data for that.
What you really need to do is scale the gravity UP so that the top block hits at the same velocity as if it was dropped the full scale distance.
I have to be careful how I express myself here. I understand the issue with the uniform acceleration of gravity. Always have, and cannot emphasize it enough. I agree that it is a problem in modeling the behavior of the towers - but ONLY if your goal is to directly match some parameter over time such as (obviously normalized) collapse front velocity in your scale model. I don't believe that's necessary.
And, to be clear: I say the house of cards is a representative scale model of progressive collapse of a real building, not that one can actually build a collapsing model of either real tower and make any direct correspondences.
A generalized model verified by scaled experiments could be quite meaningful. My contention is that the dynamics can be modeled mathematically and real instances, assumed to conform to the model and for which constituent parameters are known, can be observed/tested empirically for purposes of calibration, verification and test for predictive power. These instances could be composed of posterior analyses of CDs (still sketchy in assumptions) and by scale models with known properties and precisely recorded dynamics.
The way to solve that problem is to make the forces required to progressively crush or otherwise disintegrate the lower portion accordingly smaller. I mean, you can play with material and connection strengths as well as dead load. And other parameters, I'm sure. These are all constituent parameters that have potential for being aggregated meaningfully into a generalized parameter like effective resistive force and coefficients analagous to coefficients of drag for a given shape or modulus of elasticity for a material, etc.. You know, I don't care if someone were to cry foul if a scale model were to be top-loaded to force collapse, it's the derivation and applicability that matter! Is it good science or junk science? Not - is it built like the towers and did it collapse at 2/3 - 7/8ths g?
The house of cards proves, almost comically, that resilient but self disintegrating structures are possible on a small scale.
The way to solve that problem is to make the forces required to progressively crush or otherwise disintegrate the lower portion accordingly smaller. I mean, you can play with material and connection strengths as well as dead load. And other parameters, I'm sure. These are all constituent parameters that have potential for being aggregated meaningfully into a generalized parameter like effective resistive force and coefficients analagous to coefficients of drag for a given shape or modulus of elasticity for a material, etc.. You know, I don't care if someone were to cry foul if a scale model were to be top-loaded to force collapse, it's the derivation and applicability that matter! Is it good science or junk science? Not - is it built like the towers and did it collapse at 2/3 - 7/8ths g?
The house of cards proves, almost comically, that resilient but self disintegrating structures are possible on a small scale.
Hence the use of a centrifuge.
I was grooving on what einsteen was saying actually, but it seemed quite impractical for a model of any substantial size. It could be extremely useful to investigate small scale cascade failure of materials which would not normally yield without a lot of help.
http://etd.lib.ttu.edu/theses/available/et...Kyle_Thesis.pdf
QUOTE
The pressure wave propagation will tell how fast the pressure is moving through the confined space. This can be used to determine if the reaction reaches the point of detonation or if it is a deflagration. If the pressure wave proceeds equal or faster than that of the optical propagation wave the reaction can be considered to have reached detonation. If the pressure wave propagates slower than the optical wave the reaction will be a deflagration.
The optical propagation rate, or flame speed, is deduced from the high-speed camera data. It is primarily used as a quantification for the speed of the reaction, but can also give indication of detonation when compared to the pressure wave propagation rate as described above. Another interesting characteristic derived from the optical propagatioin rate is the Mach number achieved by the reaction. In many MIC reactions, flame speeds can approach and exceed 1000 m/s, which would be in excess of Ma 3 if the surroundings were considered to be air at room temperature. The achieving of such Mach numbers could mean that there are significant acoustic effects in the reaction. However, reaction proceeds within the flame zone assumed to be at the adiabatic flame temperature for the reaction. This extreme temperature environment reduces the Ma number calculation significantly.
.
.
QUOTE (->
| QUOTE |
The pressure wave propagation will tell how fast the pressure is moving through the confined space. This can be used to determine if the reaction reaches the point of detonation or if it is a deflagration. If the pressure wave proceeds equal or faster than that of the optical propagation wave the reaction can be considered to have reached detonation. If the pressure wave propagates slower than the optical wave the reaction will be a deflagration. The optical propagation rate, or flame speed, is deduced from the high-speed camera data. It is primarily used as a quantification for the speed of the reaction, but can also give indication of detonation when compared to the pressure wave propagation rate as described above. Another interesting characteristic derived from the optical propagatioin rate is the Mach number achieved by the reaction. In many MIC reactions, flame speeds can approach and exceed 1000 m/s, which would be in excess of Ma 3 if the surroundings were considered to be air at room temperature. The achieving of such Mach numbers could mean that there are significant acoustic effects in the reaction. However, reaction proceeds within the flame zone assumed to be at the adiabatic flame temperature for the reaction. This extreme temperature environment reduces the Ma number calculation significantly. |
.
.
Peak flame speeds of 4.249 m/s, 410.636 m/s, and 456.559 m/s were obtained for the nano Al samples of Al/Teflon, Al/MoO3/Teflon, and Al/MoO3 composites, respectively.
Note: the flame propagation rate varied enormously as a percentage of aluminum. For example, from Figure 11, which plots flame propagation rate vs. % Al for Al/MoO3/Teflon, there are not only supersonic flame rates of about 410 m/s and 360 m/s, there are also flame rates of ~ 230, 80, 10 and 10 m/s.
In other words, we can get both supersonic and subsonic flame rates, the speed of sound in air being 344 m/s.
I'm not sure if this holds for rapid, yet subsonic flame rate regimes, but for the case of 50 nm Al burns of 40% Al, we can see from Table 5 that supersonic, optical propagation rate exceeds the pressure propagation rate for all of the species being studied. Perhaps the same will be true, for example, for a 230 m/s flame propagation rate, but I haven't seen the data for that.
duplicate post deleted
Capracus,
Nice find, they are really used
David,
What's your opinion about a real scale model then ? I mean if you don't fit drop functions but use the DE with a constant force, could a similar DE be valid for a small scale model ?
Nice find, they are really used
David,
What's your opinion about a real scale model then ? I mean if you don't fit drop functions but use the DE with a constant force, could a similar DE be valid for a small scale model ?
QUOTE (Capracus+Feb 7 2008, 06:37 AM)
Einsteen, is this what you had in mind in reference to centrifuge testing?
A geotechnical centrifuge is used for research in geotechnical science, an area of civil engineering concerned how geological materials (dirt and rock) interact with the foundations of built structures such as bridges, roads, and houses. In a research laboratory, engineers use centrifuges to study the affect of gravity on soil samples or small-scale models of structures. The experiments serve to measure properties such as the strength, stiffness and capacity of foundations for bridges and buildings, the stability of hillsides and seawalls, etc. Small models do not weigh the same as a full size structure, of course, but the forces created by the centrifuge can artificially recreate the affects of gravity to provide accurate results.
http://www.nees.org/Research_Activities/centrifuge/
That's fine for scaling up gravity for testing static forces, but it won't work in a collapse model because acceleration over a distance is a critical factor.
Arthur
A geotechnical centrifuge is used for research in geotechnical science, an area of civil engineering concerned how geological materials (dirt and rock) interact with the foundations of built structures such as bridges, roads, and houses. In a research laboratory, engineers use centrifuges to study the affect of gravity on soil samples or small-scale models of structures. The experiments serve to measure properties such as the strength, stiffness and capacity of foundations for bridges and buildings, the stability of hillsides and seawalls, etc. Small models do not weigh the same as a full size structure, of course, but the forces created by the centrifuge can artificially recreate the affects of gravity to provide accurate results.
http://www.nees.org/Research_Activities/centrifuge/
That's fine for scaling up gravity for testing static forces, but it won't work in a collapse model because acceleration over a distance is a critical factor.
Arthur
QUOTE (einsteen+Feb 7 2008, 10:53 AM)
What's your opinion about a real scale model then ? I mean if you don't fit drop functions but use the DE with a constant force, could a similar DE be valid for a small scale model ?
The crush-down equation is valid for any structure satisfying the four assumptions of B & V. It does not depend upon size. But attempting to build a 1:100 scale model, 4.16 meters tall, appears to be quite the engineering challenge. One the one hand it has to be strong enough to stand up under its own weight; on the other, weak enough so that the collapse propagates.
Now Galileo Galilei used inclined planes to aid in studying terrestrial gravity. I suggest doing the same in this case: watch flowing snow avalanches to observe well-studied similar behavior.
The crush-down equation is valid for any structure satisfying the four assumptions of B & V. It does not depend upon size. But attempting to build a 1:100 scale model, 4.16 meters tall, appears to be quite the engineering challenge. One the one hand it has to be strong enough to stand up under its own weight; on the other, weak enough so that the collapse propagates.
Now Galileo Galilei used inclined planes to aid in studying terrestrial gravity. I suggest doing the same in this case: watch flowing snow avalanches to observe well-studied similar behavior.
yeah that is cool, then the gravity component in that directory becomes very small.
You can even get energy from nothing with this device....
http://www.lhup.edu/~dsimanek/museum/stevin.gif
You can even get energy from nothing with this device....
http://www.lhup.edu/~dsimanek/museum/stevin.gif
QUOTE (David B. Benson+Feb 7 2008, 06:54 PM)
One the one hand it has to be strong enough to stand up under its own weight; on the other, weak enough so that the collapse propagates.
An interesting statement. Maybe this is why the notion of progressive collapse is difficult for some to grasp. The behavior of structures at the scale of the towers is beyond the realm of normal experience and intuition. The challenge of constructing a scaled-down model to achieve similar behavior to the towers parallels the limits of everyday experience with structures, most of which would not fully collapse under the driving force of only an upper fraction unless the structure were top-loaded in some manner.
Remember the house of cards video that newton posted a while back? That was a small, uniform structure strong enough to stand under its own weight, yet weak enough for the collapse to propagate once started. It even withstood repeated impacts and partial collapse before finally succumbing, but it went to completion after that. The top disintegrated first, but there's ONE scaled-down model for a buliding collapse, a house of cards. There's no need to have the same collapse speed, only self-sustaining collapse. The model in this case prescribes very strong material as compared to connections, but how is this case so different from the prep work companies do to pre-weaken a building before a CD, other than size (and by extension, total mass)?
Isn't a top-down collapse of a house of cards a vertical avalanche, if anything is?
The potential for a broadly applicable model of progressive collapse seems obvious. Given a suitable form with a few fundamental parameterizations, solutions should be obtainable numerically for any sort of progressive collapse, including many sorts of CDs as well as towers of cards. It's only a matter of proper characterization within the framework, whatever that turns out to be. Between this forum and the papers we all know and love around here, a foundation in dynamics has been laid for exploring possible forms of solutions.
Of course, it's necessary to 'calibrate' against as many known instances as possible over the spectrum of parameter ranges. The analysis thus far is limited by reasonable assumptions (i.e., swamped by unknowns), not just for parameter values but the time-varying character of parameters, whereas a fully developed model should be tested against systems composed exclusively of knowns when possible. Turning that inside out for a given model, once parameter values for a range of configurations are determined empirically, the model should have predictive power at least within the range defined by previous experiment, if not the ability to extrapolate some small degree outside that range, particularly if the model should prove stable and well-behaved on the known range and remain so outside.
Yes, I am looking for the equivalent of a Hooke's Law for progressive collapse. Too ambitious or optimistic? I don't think so, though I admit the lack of (collective) motivation might prevent the idea from becoming reality. The immediate utility of such a model may not be obvious, though countless academics have made careers studying things I personally consider to have no merit other than intellectually satisfying a pool of people with mutual interest. A working model, leading to equations expressed parametrically in terms of strength of materials and geometric properties, should have predictive powers given conditions and constraints. Seems useful to me.
Where is the boundary in solution space between self-arresting and self-disintegrating collapse? Initial conditions contribute to the demarcation as well as values for properties. I realize the question has already been answered by NEU-FONZE and others against particular contexts. I'll elaborate more on this as time allows.
An interesting statement. Maybe this is why the notion of progressive collapse is difficult for some to grasp. The behavior of structures at the scale of the towers is beyond the realm of normal experience and intuition. The challenge of constructing a scaled-down model to achieve similar behavior to the towers parallels the limits of everyday experience with structures, most of which would not fully collapse under the driving force of only an upper fraction unless the structure were top-loaded in some manner.
Remember the house of cards video that newton posted a while back? That was a small, uniform structure strong enough to stand under its own weight, yet weak enough for the collapse to propagate once started. It even withstood repeated impacts and partial collapse before finally succumbing, but it went to completion after that. The top disintegrated first, but there's ONE scaled-down model for a buliding collapse, a house of cards. There's no need to have the same collapse speed, only self-sustaining collapse. The model in this case prescribes very strong material as compared to connections, but how is this case so different from the prep work companies do to pre-weaken a building before a CD, other than size (and by extension, total mass)?
Isn't a top-down collapse of a house of cards a vertical avalanche, if anything is?
The potential for a broadly applicable model of progressive collapse seems obvious. Given a suitable form with a few fundamental parameterizations, solutions should be obtainable numerically for any sort of progressive collapse, including many sorts of CDs as well as towers of cards. It's only a matter of proper characterization within the framework, whatever that turns out to be. Between this forum and the papers we all know and love around here, a foundation in dynamics has been laid for exploring possible forms of solutions.
Of course, it's necessary to 'calibrate' against as many known instances as possible over the spectrum of parameter ranges. The analysis thus far is limited by reasonable assumptions (i.e., swamped by unknowns), not just for parameter values but the time-varying character of parameters, whereas a fully developed model should be tested against systems composed exclusively of knowns when possible. Turning that inside out for a given model, once parameter values for a range of configurations are determined empirically, the model should have predictive power at least within the range defined by previous experiment, if not the ability to extrapolate some small degree outside that range, particularly if the model should prove stable and well-behaved on the known range and remain so outside.
Yes, I am looking for the equivalent of a Hooke's Law for progressive collapse. Too ambitious or optimistic? I don't think so, though I admit the lack of (collective) motivation might prevent the idea from becoming reality. The immediate utility of such a model may not be obvious, though countless academics have made careers studying things I personally consider to have no merit other than intellectually satisfying a pool of people with mutual interest. A working model, leading to equations expressed parametrically in terms of strength of materials and geometric properties, should have predictive powers given conditions and constraints. Seems useful to me.
Where is the boundary in solution space between self-arresting and self-disintegrating collapse? Initial conditions contribute to the demarcation as well as values for properties. I realize the question has already been answered by NEU-FONZE and others against particular contexts. I'll elaborate more on this as time allows.
To anyone and everyone: I'd like to pose a few hypothetical scenarios and some questions. The questions are rhetorical but I'd welcome answers.
Imagine there exists a device which is capable of instantaneously removing a planar section of a building, in any desired thickness down to nanometers, effectively zero thickness. The device could be used to instantly remove a floor or number of floors from a building, allowing whatever is above to free fall until impacting the portion below. Or it could be used to simply cut a building in two by removing an infinitesimal thickness in the plane of the cut.
Now imagine you are on the top floor of one of the Trade Center towers when this device is used to cut the building on a perfectly horizontal plane at say, the 90th floor, and you happen to know about it. Forget about elevator cables, wiring, plumbing, glass, and fascia, just focus on the structural components - the beams and columns, pretend that other stuff is OK. After the cut, which is sugically (no, magically) clean and imparts no force, the top portion rests on the bottom. No drop.
Do you feel safe? Do you want to complete your workday up there? Or do you want to get the hell out of there immediately, before the wind blows?
Take it a step further. Let the device remove one centimeter of material in making the cut, which allows the top to fall freely until it impacts the portion below in a perfect axial strike.
Same questions, plus: What would that sound like? What would it feel like? How long would it take you to decide you needed to get out? Would it be time enough for your co-workers to notice the smell emanating from your drawers? What would happen to the building, over the short and long term?
For the last two scenarios, return to the magical cut that removes infinitesimal material and leaves no gap: instead of cutting on the horizontal, though, imagine the cut in one case being one centimeter higher on one side than the opposite side and, in the last case, the cut one centimeter higher on a given diagonal than the other. Same questions.
I'm not trying to say the above means anything at all, it's just something I've thought about.
Imagine there exists a device which is capable of instantaneously removing a planar section of a building, in any desired thickness down to nanometers, effectively zero thickness. The device could be used to instantly remove a floor or number of floors from a building, allowing whatever is above to free fall until impacting the portion below. Or it could be used to simply cut a building in two by removing an infinitesimal thickness in the plane of the cut.
Now imagine you are on the top floor of one of the Trade Center towers when this device is used to cut the building on a perfectly horizontal plane at say, the 90th floor, and you happen to know about it. Forget about elevator cables, wiring, plumbing, glass, and fascia, just focus on the structural components - the beams and columns, pretend that other stuff is OK. After the cut, which is sugically (no, magically) clean and imparts no force, the top portion rests on the bottom. No drop.
Do you feel safe? Do you want to complete your workday up there? Or do you want to get the hell out of there immediately, before the wind blows?
Take it a step further. Let the device remove one centimeter of material in making the cut, which allows the top to fall freely until it impacts the portion below in a perfect axial strike.
Same questions, plus: What would that sound like? What would it feel like? How long would it take you to decide you needed to get out? Would it be time enough for your co-workers to notice the smell emanating from your drawers? What would happen to the building, over the short and long term?
For the last two scenarios, return to the magical cut that removes infinitesimal material and leaves no gap: instead of cutting on the horizontal, though, imagine the cut in one case being one centimeter higher on one side than the opposite side and, in the last case, the cut one centimeter higher on a given diagonal than the other. Same questions.
I'm not trying to say the above means anything at all, it's just something I've thought about.
QUOTE (OneWhiteEye+Feb 7 2008, 05:17 PM)
An interesting statement. Maybe this is why the notion of progressive collapse is difficult for some to grasp. The behavior of structures at the scale of the towers is beyond the realm of normal experience and intuition. The challenge of constructing a scaled-down model to achieve similar behavior to the towers parallels the limits of everyday experience with structures, most of which would not fully collapse under the driving force of only an upper fraction unless the structure were top-loaded in some manner.
But you can't do it.
If you scale the size and the mass, you have to keep the velocity at impact the same.
It makes no logical sense to also scale the velocity at impact down.
If you think it does, than take it to its conclusion.
Let's make a 1/300 scale model.
Conveniently this makes each storey 1/2 inch tall.
The tower now stands a managable 54 inches tall and is ~ 8.4" on a side.
The PROBLEM is when you let the top block drop ONE STORY it hits with a velocity of but 0.5 meters per second, but since you have scaled the mass down, you've now made the impact forces proportionally way to small.
What you really need to do is scale the gravity UP so that the top block hits at the same velocity as if it was dropped the full scale distance.
Hence the use of a centrifuge.
But this is why I asked about the model size, since you can see, even a 1/300 scale model is over 4 ft tall, but consider the construction difficulties in building a scale version with the same physical properties as the tower since in this case a 4 inch concrete slab is but 0.013 inches thick.
Arthur
But you can't do it.
If you scale the size and the mass, you have to keep the velocity at impact the same.
It makes no logical sense to also scale the velocity at impact down.
If you think it does, than take it to its conclusion.
Let's make a 1/300 scale model.
Conveniently this makes each storey 1/2 inch tall.
The tower now stands a managable 54 inches tall and is ~ 8.4" on a side.
The PROBLEM is when you let the top block drop ONE STORY it hits with a velocity of but 0.5 meters per second, but since you have scaled the mass down, you've now made the impact forces proportionally way to small.
What you really need to do is scale the gravity UP so that the top block hits at the same velocity as if it was dropped the full scale distance.
Hence the use of a centrifuge.
But this is why I asked about the model size, since you can see, even a 1/300 scale model is over 4 ft tall, but consider the construction difficulties in building a scale version with the same physical properties as the tower since in this case a 4 inch concrete slab is but 0.013 inches thick.
Arthur
QUOTE (OneWhiteEye+Feb 7 2008, 03:17 PM)
Isn't a top-down collapse of a house of cards a vertical avalanche, if anything is?
Yes, I am looking for the equivalent of a Hooke's Law for progressive collapse.
Where is the boundary in solution space between self-arresting and self-disintegrating collapse?
I doubt it. For a house of cards I would suspect that the dissipative term in the resistive force would be k2(Z')2, which is not the vertical avalanche form. I could be wrong.
The Seffen crush-down equation, which I gave just previously in a simplified form, is it (for structures satisfying, close enough, the four B & V conditions).
If the resistive force on the right side of the equation is greater than the sum on the left side, the collapse halts (assuming this condition lasts long enough).
Yes, I am looking for the equivalent of a Hooke's Law for progressive collapse.
Where is the boundary in solution space between self-arresting and self-disintegrating collapse?
I doubt it. For a house of cards I would suspect that the dissipative term in the resistive force would be k2(Z')2, which is not the vertical avalanche form. I could be wrong.
The Seffen crush-down equation, which I gave just previously in a simplified form, is it (for structures satisfying, close enough, the four B & V conditions).
If the resistive force on the right side of the equation is greater than the sum on the left side, the collapse halts (assuming this condition lasts long enough).
QUOTE (adoucette+Feb 7 2008, 03:58 PM)
The PROBLEM is when you let the top block drop ONE STORY it hits with a velocity of but 0.5 meters per second, but since you have scaled the mass down, you've now made the impact forces proportionally way to small.
...the construction difficulties in building a scale version with the same physical properties as the tower since in this case a 4 inch concrete slab is but 0.013 inches thick.
If you just want to see a vertical avalanche, let the initial drop be larger. It certainly was more like 3 stories for WTC 2.
When scaling down, don't try to keep all the dimensions exactly the same. The essential features are:
(1) Satisfies, close enough, the four B & V assumptions;
(2) Most of the mass is on the scaled 'floors', but lightly connected to the supporting walls (and core).
...the construction difficulties in building a scale version with the same physical properties as the tower since in this case a 4 inch concrete slab is but 0.013 inches thick.
If you just want to see a vertical avalanche, let the initial drop be larger. It certainly was more like 3 stories for WTC 2.
When scaling down, don't try to keep all the dimensions exactly the same. The essential features are:
(1) Satisfies, close enough, the four B & V assumptions;
(2) Most of the mass is on the scaled 'floors', but lightly connected to the supporting walls (and core).
QUOTE (adoucette+Feb 7 2008, 10:58 PM)
What you really need to do is scale the gravity UP so that the top block hits at the same velocity as if it was dropped the full scale distance.
I have to be careful how I express myself here. I understand the issue with the uniform acceleration of gravity. Always have, and cannot emphasize it enough. I agree that it is a problem in modeling the behavior of the towers - but ONLY if your goal is to directly match some parameter over time such as (obviously normalized) collapse front velocity in your scale model. I don't believe that's necessary.
And, to be clear: I say the house of cards is a representative scale model of progressive collapse of a real building, not that one can actually build a collapsing model of either real tower and make any direct correspondences.
A generalized model verified by scaled experiments could be quite meaningful. My contention is that the dynamics can be modeled mathematically and real instances, assumed to conform to the model and for which constituent parameters are known, can be observed/tested empirically for purposes of calibration, verification and test for predictive power. These instances could be composed of posterior analyses of CDs (still sketchy in assumptions) and by scale models with known properties and precisely recorded dynamics.
QUOTE
The PROBLEM is when you let the top block drop ONE STORY it hits with a velocity of but 0.5 meters per second, but since you have scaled the mass down, you've now made the impact forces proportionally way to small.
The way to solve that problem is to make the forces required to progressively crush or otherwise disintegrate the lower portion accordingly smaller. I mean, you can play with material and connection strengths as well as dead load. And other parameters, I'm sure. These are all constituent parameters that have potential for being aggregated meaningfully into a generalized parameter like effective resistive force and coefficients analagous to coefficients of drag for a given shape or modulus of elasticity for a material, etc.. You know, I don't care if someone were to cry foul if a scale model were to be top-loaded to force collapse, it's the derivation and applicability that matter! Is it good science or junk science? Not - is it built like the towers and did it collapse at 2/3 - 7/8ths g?
The house of cards proves, almost comically, that resilient but self disintegrating structures are possible on a small scale.
QUOTE (->
| QUOTE |
| The PROBLEM is when you let the top block drop ONE STORY it hits with a velocity of but 0.5 meters per second, but since you have scaled the mass down, you've now made the impact forces proportionally way to small. |
The way to solve that problem is to make the forces required to progressively crush or otherwise disintegrate the lower portion accordingly smaller. I mean, you can play with material and connection strengths as well as dead load. And other parameters, I'm sure. These are all constituent parameters that have potential for being aggregated meaningfully into a generalized parameter like effective resistive force and coefficients analagous to coefficients of drag for a given shape or modulus of elasticity for a material, etc.. You know, I don't care if someone were to cry foul if a scale model were to be top-loaded to force collapse, it's the derivation and applicability that matter! Is it good science or junk science? Not - is it built like the towers and did it collapse at 2/3 - 7/8ths g?
The house of cards proves, almost comically, that resilient but self disintegrating structures are possible on a small scale.
Hence the use of a centrifuge.
I was grooving on what einsteen was saying actually, but it seemed quite impractical for a model of any substantial size. It could be extremely useful to investigate small scale cascade failure of materials which would not normally yield without a lot of help.
Well, here is another model which ought to be buildable: Use Lego blocks to construct the outer walls (and a core if desired); there is no expectation these will collapse. Arrange for some places regularly up the tower walls to insert cardboard pegs, the sheets of lightweight corrugated cardboard being inserted across between the walls as the tower is constructed. Place weights on the cardboard, but not enough that these either kink nor sag.
Now use some dropped starting mass on the top cardboard, enough to sag or kink the cardboard so that the pegs pull out of the holes. Progressive collapse ensues.
But yawn. This is precisely what one obtains from a computer calculation using the Seffen crush-down equation. The results could then be animated if desired.
Now use some dropped starting mass on the top cardboard, enough to sag or kink the cardboard so that the pegs pull out of the holes. Progressive collapse ensues.
But yawn. This is precisely what one obtains from a computer calculation using the Seffen crush-down equation. The results could then be animated if desired.
QUOTE (OneWhiteEye+Feb 7 2008, 06:34 PM)
I have to be careful how I express myself here. I understand the issue with the uniform acceleration of gravity. Always have, and cannot emphasize it enough. I agree that it is a problem in modeling the behavior of the towers - but ONLY if your goal is to directly match some parameter over time such as (obviously normalized) collapse front velocity in your scale model. I don't believe that's necessary.
And, to be clear: I say the house of cards is a representative scale model of progressive collapse of a real building, not that one can actually build a collapsing model of either real tower and make any direct correspondences.
That's my point though.
We've seen a number of these various attempts to "model" the towers, and in every case they scale the towers down AND then they scale the drop distance.
Then they say, SEE, it doesn't collapse (like in the video that einsteen posted)
The fact is, if you want to get a more intuitive idea of what happened, then simply make a scale tower, with scale masses, and then drop the top block ~ 9 ft onto the bottom block.
I can assure you when the velocity goes back up to what it should be, the top block WILL crush the bottom portion.
Arthur
And, to be clear: I say the house of cards is a representative scale model of progressive collapse of a real building, not that one can actually build a collapsing model of either real tower and make any direct correspondences.
That's my point though.
We've seen a number of these various attempts to "model" the towers, and in every case they scale the towers down AND then they scale the drop distance.
Then they say, SEE, it doesn't collapse (like in the video that einsteen posted)
The fact is, if you want to get a more intuitive idea of what happened, then simply make a scale tower, with scale masses, and then drop the top block ~ 9 ft onto the bottom block.
I can assure you when the velocity goes back up to what it should be, the top block WILL crush the bottom portion.
Arthur
QUOTE (David B. Benson+Feb 7 2008, 11:07 PM)
I doubt it. For a house of cards I would suspect that the dissipative term in the resistive force would be k2(Z')2, which is not the vertical avalanche form. I could be wrong.
OK, I can see that. I probably got too specific. This raises some questions I'll post in a few.
Maybe a house of cards could be constructed, based on theory, that more closely conforms to avalanche. (I'm not proposing this but) Perhaps tack welds of crazy glue would allow sufficient size, and testing in a vacuum chamber would allow dynamics besides air resistance to show at non-trivial velocities. Perhaps using cards with abrasive or sticky surfaces or gossamer thread tying them together in small clumps, or cards made of inflexible material, lead, etc. Whatever. It's a general theory of progressive self-disintegration of previously intact structures I'm thinking of, where there is more than one regime, of which vertical avalanche is one. The general solution is a superposition of terms, some of which overwhelm the others in certain contexts, like fluid resistance would overwhelm other terms in a long drop of cards in air.
I'm willing to bet a mountainside of playing cards would bear strong resemblance to snow, on some level, if it started to slide.
I'm going to obtain the normalized position versus time for the crush front on the card collapse, no promises when. Maybe in a few hours, maybe in a few weeks but, whenever, I'll post it.
OK, I can see that. I probably got too specific. This raises some questions I'll post in a few.
Maybe a house of cards could be constructed, based on theory, that more closely conforms to avalanche. (I'm not proposing this but) Perhaps tack welds of crazy glue would allow sufficient size, and testing in a vacuum chamber would allow dynamics besides air resistance to show at non-trivial velocities. Perhaps using cards with abrasive or sticky surfaces or gossamer thread tying them together in small clumps, or cards made of inflexible material, lead, etc. Whatever. It's a general theory of progressive self-disintegration of previously intact structures I'm thinking of, where there is more than one regime, of which vertical avalanche is one. The general solution is a superposition of terms, some of which overwhelm the others in certain contexts, like fluid resistance would overwhelm other terms in a long drop of cards in air.
I'm willing to bet a mountainside of playing cards would bear strong resemblance to snow, on some level, if it started to slide.
I'm going to obtain the normalized position versus time for the crush front on the card collapse, no promises when. Maybe in a few hours, maybe in a few weeks but, whenever, I'll post it.
QUOTE (adoucette+Feb 8 2008, 12:09 AM)
Then they say, SEE, it doesn't collapse
An unjustified leap. I see we're not in any fundamental disagreement. Scale tests are a means to an end, and that is the characterization of a quantity like collapse front coordinate by means of other generalized quantities that have non-physical interpretation yet subsume, in aggregate, many physical quantities like material strength, connection strength, collision frequency, mass shedding, and so on. I've no expectation there should be the same results unless 'the model' predicted it. I'm guessing, if enough of the parameters were known, the similarity between WTC1 and the Landmark (two entirely different static and dynamic configurations) could be predicted.
You can get buried in terms, or you can find a good fit empirically that covers the range of observations and has less degrees of freedom than the real underlying form, if it's so amenable.
Now, see, I'm OK with that. That's valid tweaking of the conditions.
An unjustified leap. I see we're not in any fundamental disagreement. Scale tests are a means to an end, and that is the characterization of a quantity like collapse front coordinate by means of other generalized quantities that have non-physical interpretation yet subsume, in aggregate, many physical quantities like material strength, connection strength, collision frequency, mass shedding, and so on. I've no expectation there should be the same results unless 'the model' predicted it. I'm guessing, if enough of the parameters were known, the similarity between WTC1 and the Landmark (two entirely different static and dynamic configurations) could be predicted.
You can get buried in terms, or you can find a good fit empirically that covers the range of observations and has less degrees of freedom than the real underlying form, if it's so amenable.
QUOTE
The fact is, if you want to get a more intuitive idea of what happened, then simply make a scale tower, with scale masses, and then drop the top block ~ 9 ft onto the bottom block.
Now, see, I'm OK with that. That's valid tweaking of the conditions.
QUOTE (David B. Benson+Feb 7 2008, 11:59 PM)
Well, here is another model which ought to be buildable: Use Lego blocks to construct the outer walls (and a core if desired); there is no expectation these will collapse. Arrange for some places regularly up the tower walls to insert cardboard pegs, the sheets of lightweight corrugated cardboard being inserted across between the walls as the tower is constructed. Place weights on the cardboard, but not enough that these either kink nor sag.
Now use some dropped starting mass on the top cardboard, enough to sag or kink the cardboard so that the pegs pull out of the holes. Progressive collapse ensues.
This is what I'm talking about (though I haven't evaluated it as a strategy). I firmly believe a small resilient structure can be made to disintegrate under influence of gravity and small initial perturbations, all conditions being right.
I understand but I'm not at the yawn point. The reason is I've been living a long time in the world where theory meets reality and I have to make it all work in the end... or else. I can tell you that, regardless of field, maturity of the discipline or the discipline of the implementor, there is frequently a substantial gap between expectation and real-life performance. A frequency great enough that, if you must insist on a black and white rule, then theory never matches reality. A quick look at the WTC2 video that had einsteen wrapped up for a while (or still does) confirms for me this subject is no different. I believe CDs are a better starting point for developing generalized theories of collapse than the towers, because of the deviations from ideal conditions unconsidered by the current 1D models.
The value of the model is its predictive power, not the postdictive power.
Let's see Seffen predict the fall rate of the Landmark, before he sees any videos. I'll tell you whether he's right or not. But I can already tell you there is no well-defined 1D crushing front for WTC2, so a model which produces a single coordinate which cannot be measured for confirmation is a model which is limited in its scope and applicability to the real world, and it is wise to keep that in mind. It may give good answers, IN ADVANCE, but that remains to be seen.
Am I right that these models have only been considered after 9/11, and then have only been used for the three buildings on that date? I think it would be an excellent thing if the Z(t) of a future CD could be predicted, based on parametric input.
I understand but I'm not at the yawn point. The reason is I've been living a long time in the world where theory meets reality and I have to make it all work in the end... or else. I can tell you that, regardless of field, maturity of the discipline or the discipline of the implementor, there is frequently a substantial gap between expectation and real-life performance. A frequency great enough that, if you must insist on a black and white rule, then theory never matches reality. A quick look at the WTC2 video that had einsteen wrapped up for a while (or still does) confirms for me this subject is no different. I believe CDs are a better starting point for developing generalized theories of collapse than the towers, because of the deviations from ideal conditions unconsidered by the current 1D models.
The value of the model is its predictive power, not the postdictive power.
Let's see Seffen predict the fall rate of the Landmark, before he sees any videos. I'll tell you whether he's right or not. But I can already tell you there is no well-defined 1D crushing front for WTC2, so a model which produces a single coordinate which cannot be measured for confirmation is a model which is limited in its scope and applicability to the real world, and it is wise to keep that in mind. It may give good answers, IN ADVANCE, but that remains to be seen.
Am I right that these models have only been considered after 9/11, and then have only been used for the three buildings on that date? I think it would be an excellent thing if the Z(t) of a future CD could be predicted, based on parametric input.
The results could then be animated if desired.
Sounds like fun. I'm in.
Now use some dropped starting mass on the top cardboard, enough to sag or kink the cardboard so that the pegs pull out of the holes. Progressive collapse ensues.
This is what I'm talking about (though I haven't evaluated it as a strategy). I firmly believe a small resilient structure can be made to disintegrate under influence of gravity and small initial perturbations, all conditions being right.
QUOTE
But yawn. This is precisely what one obtains from a computer calculation using the Seffen crush-down equation.
I understand but I'm not at the yawn point. The reason is I've been living a long time in the world where theory meets reality and I have to make it all work in the end... or else. I can tell you that, regardless of field, maturity of the discipline or the discipline of the implementor, there is frequently a substantial gap between expectation and real-life performance. A frequency great enough that, if you must insist on a black and white rule, then theory never matches reality. A quick look at the WTC2 video that had einsteen wrapped up for a while (or still does) confirms for me this subject is no different. I believe CDs are a better starting point for developing generalized theories of collapse than the towers, because of the deviations from ideal conditions unconsidered by the current 1D models.
The value of the model is its predictive power, not the postdictive power.
Let's see Seffen predict the fall rate of the Landmark, before he sees any videos. I'll tell you whether he's right or not. But I can already tell you there is no well-defined 1D crushing front for WTC2, so a model which produces a single coordinate which cannot be measured for confirmation is a model which is limited in its scope and applicability to the real world, and it is wise to keep that in mind. It may give good answers, IN ADVANCE, but that remains to be seen.
Am I right that these models have only been considered after 9/11, and then have only been used for the three buildings on that date? I think it would be an excellent thing if the Z(t) of a future CD could be predicted, based on parametric input.
QUOTE (->
| QUOTE |
| But yawn. This is precisely what one obtains from a computer calculation using the Seffen crush-down equation. |
I understand but I'm not at the yawn point. The reason is I've been living a long time in the world where theory meets reality and I have to make it all work in the end... or else. I can tell you that, regardless of field, maturity of the discipline or the discipline of the implementor, there is frequently a substantial gap between expectation and real-life performance. A frequency great enough that, if you must insist on a black and white rule, then theory never matches reality. A quick look at the WTC2 video that had einsteen wrapped up for a while (or still does) confirms for me this subject is no different. I believe CDs are a better starting point for developing generalized theories of collapse than the towers, because of the deviations from ideal conditions unconsidered by the current 1D models.
The value of the model is its predictive power, not the postdictive power.
Let's see Seffen predict the fall rate of the Landmark, before he sees any videos. I'll tell you whether he's right or not. But I can already tell you there is no well-defined 1D crushing front for WTC2, so a model which produces a single coordinate which cannot be measured for confirmation is a model which is limited in its scope and applicability to the real world, and it is wise to keep that in mind. It may give good answers, IN ADVANCE, but that remains to be seen.
Am I right that these models have only been considered after 9/11, and then have only been used for the three buildings on that date? I think it would be an excellent thing if the Z(t) of a future CD could be predicted, based on parametric input.
The results could then be animated if desired.
Sounds like fun. I'm in.
QUOTE (einsteen+Jan 30 2008, 09:39 AM)
You really posted the last inline image here, it is also extension independent.
George W. knows it: “One of the great things about books is sometimes there are some fantastic pictures.”
And that is the same for a forum.
I agree, it is a bummer. I haven't quite made up my mind whether I'll wear the scarlet letter of 'User Posted Image' with pride or use a regular link. But, if I have to post only a link, I'm going to make it count. I have a partial solution in place, just no time to do much right now.
George W. knows it: “One of the great things about books is sometimes there are some fantastic pictures.”
And that is the same for a forum.
I agree, it is a bummer. I haven't quite made up my mind whether I'll wear the scarlet letter of 'User Posted Image' with pride or use a regular link. But, if I have to post only a link, I'm going to make it count. I have a partial solution in place, just no time to do much right now.
QUOTE (OneWhiteEye+Feb 8 2008, 12:57 AM)
Let's see Seffen predict the fall rate of the Landmark, before he sees any videos.
I know his equation is crush-down and the Landmark is either crush-up or crush-everywhere, but the point is still there in a twisted way. Are there any other examples of structural failures that are crush-down besides the twin towers and a house of cards on You Tube ????
So pretend an abundance of crush-downs have occurred, such that any size, shape, or construction style could be examined for its dynamics. If vertical avalanche, or any other dissipative form turns out to be the best solution for the tower collapse fronts, what might be the result of fitting these other instances for comparison?
The devil is in the details, and the details are the coefficients obtained when the best fit for a chosen hypothesis is found. This ignores how many instances are used to choose the hypothesis. For a collection of different collapses, one gets a collection of coefficients which represent the expression of the complex kinematics of each instance in the simple form of a few scalars. One is best, but that's probably the low grade only.
Viscosity of a fluid, coefficient of friction, these are magic numbers of statistical mechanics! Measure these, then systems are classified by their magic number instead of understanding all of the underlying kinematics. How does one get these for crush-down/crush-up solutions? What becomes comparable between instances, if anything?
OnEdit: Let's see Seffen predict the Z(t) of the Lego tower after I build it to DBB's specification. Then I'll instrument it, and bring it down. What pre-test measurements of the materials should I perform to supply parametric input for the equations?
OnSubsequentEdit: What? The theory isn't to that stage yet? Then, for me, it's definitely not a yawn. But, even if it is to that stage, it still wouldn't be a yawn because I'd love to do the animation - except I need those coefficients in advance.
I know his equation is crush-down and the Landmark is either crush-up or crush-everywhere, but the point is still there in a twisted way. Are there any other examples of structural failures that are crush-down besides the twin towers and a house of cards on You Tube ????
So pretend an abundance of crush-downs have occurred, such that any size, shape, or construction style could be examined for its dynamics. If vertical avalanche, or any other dissipative form turns out to be the best solution for the tower collapse fronts, what might be the result of fitting these other instances for comparison?
The devil is in the details, and the details are the coefficients obtained when the best fit for a chosen hypothesis is found. This ignores how many instances are used to choose the hypothesis. For a collection of different collapses, one gets a collection of coefficients which represent the expression of the complex kinematics of each instance in the simple form of a few scalars. One is best, but that's probably the low grade only.
Viscosity of a fluid, coefficient of friction, these are magic numbers of statistical mechanics! Measure these, then systems are classified by their magic number instead of understanding all of the underlying kinematics. How does one get these for crush-down/crush-up solutions? What becomes comparable between instances, if anything?
OnEdit: Let's see Seffen predict the Z(t) of the Lego tower after I build it to DBB's specification. Then I'll instrument it, and bring it down. What pre-test measurements of the materials should I perform to supply parametric input for the equations?
OnSubsequentEdit: What? The theory isn't to that stage yet? Then, for me, it's definitely not a yawn. But, even if it is to that stage, it still wouldn't be a yawn because I'd love to do the animation - except I need those coefficients in advance.
.
Hi everyone!
I propose using MAGNETIC ATTRACTION to 'mimic' the gravity gradient, acceleration and 'weight' effect on the steel/iron members.
The same inverse-square strength/accelerative effects can be obtained from a strong magnetic 'bed' on which the scale model tower would rest/be fixed.
Of course, the magnetic force 'starting' strength would have to be chosen so that it COMPLEMENTS, whatever the model's own gravity/weight parameters already are. so as to bring the model's TOTAL gravity/magnetic DOWNWARD FORCES to 'proper scale'.
If an ELECROMAGNET bed is used, this should be easy to 'calibrate/set' at start....AND ALSO will allow for the attraction to be CHANGED AS NECESSARY during the 'collapse' progression to 'mimic' any 'impact' forces between floors/structural elements.
The whole model may be made more 'homogenous' by also using IRON POWDER in the 'modeled concrete' floor membrane, drywall, office fixtures and contents, plane debris etc etc etc etc....each type of material having the necessary iron content to provide the necessary 'gravity mimicking' magnetic attraction forces for THOSE normally non-ferrous building components/contents.
That's my proposed 'modeling system' for situations where non-scalable gravity' is the sticking point! hehehe.
What do you think of my (All Rights Reserved!) idea, guys?
Back tomorrow. Cheers all!
RC.
.
Hi everyone!
I propose using MAGNETIC ATTRACTION to 'mimic' the gravity gradient, acceleration and 'weight' effect on the steel/iron members.
The same inverse-square strength/accelerative effects can be obtained from a strong magnetic 'bed' on which the scale model tower would rest/be fixed.
Of course, the magnetic force 'starting' strength would have to be chosen so that it COMPLEMENTS, whatever the model's own gravity/weight parameters already are. so as to bring the model's TOTAL gravity/magnetic DOWNWARD FORCES to 'proper scale'.
If an ELECROMAGNET bed is used, this should be easy to 'calibrate/set' at start....AND ALSO will allow for the attraction to be CHANGED AS NECESSARY during the 'collapse' progression to 'mimic' any 'impact' forces between floors/structural elements.
The whole model may be made more 'homogenous' by also using IRON POWDER in the 'modeled concrete' floor membrane, drywall, office fixtures and contents, plane debris etc etc etc etc....each type of material having the necessary iron content to provide the necessary 'gravity mimicking' magnetic attraction forces for THOSE normally non-ferrous building components/contents.
That's my proposed 'modeling system' for situations where non-scalable gravity' is the sticking point! hehehe.
What do you think of my (All Rights Reserved!) idea, guys?
Back tomorrow. Cheers all!
RC.
.
einsteen and one white eye.....
i've been tagging along. just wanted you to know.
okay, scale models.
the house of cards was best, because it most closely resembled the collapse in terms of a self propagating cascade of the structure. the actual energy calculations are way out of my league, BUT, the theory behind them is not.
gravity won't scale?
for every halving of size, halve the strength of the connections.
use the actual distance to drop your 'hammer'. this is also a good experiment to make you realise, "what the heck happened to everything between the 'hammer' and the 'anvil'?". (i like using hammer and anvil, because it is closer to the truth than hammer and nail. ...... 'wickerwork basket' and 'wickerwork basket' would be best. steel wickerwork, even, if that wickers, er, works)
i want to see models of things that are built to take their own mass plus a huge load of dead weight added without being structurally compromised, AND be able to stand immense horizontal forces as well WHILE holding their own mass plus a huge load of dead weight, ....collapse by crushing themselves.
the house of cards is 'best' so far, because IT ACTUALLY CRUSHED ITSELF(although, i notice none of the cards were 'dustified').
however, a slight breeze would have knocked it over, too, so it obviously was not as structurally robust(scale-wisely) as the twin towers.
i think a wickerwork model would be good. and don't scale the drop distance, but scale the strength of connections and structural components.
i've been tagging along. just wanted you to know.
okay, scale models.
the house of cards was best, because it most closely resembled the collapse in terms of a self propagating cascade of the structure. the actual energy calculations are way out of my league, BUT, the theory behind them is not.
gravity won't scale?
for every halving of size, halve the strength of the connections.
use the actual distance to drop your 'hammer'. this is also a good experiment to make you realise, "what the heck happened to everything between the 'hammer' and the 'anvil'?". (i like using hammer and anvil, because it is closer to the truth than hammer and nail. ...... 'wickerwork basket' and 'wickerwork basket' would be best. steel wickerwork, even, if that wickers, er, works)
i want to see models of things that are built to take their own mass plus a huge load of dead weight added without being structurally compromised, AND be able to stand immense horizontal forces as well WHILE holding their own mass plus a huge load of dead weight, ....collapse by crushing themselves.
the house of cards is 'best' so far, because IT ACTUALLY CRUSHED ITSELF(although, i notice none of the cards were 'dustified').
however, a slight breeze would have knocked it over, too, so it obviously was not as structurally robust(scale-wisely) as the twin towers.
i think a wickerwork model would be good. and don't scale the drop distance, but scale the strength of connections and structural components.
QUOTE (newton+Feb 7 2008, 11:53 PM)
gravity won't scale?
for every halving of size, halve the strength of the connections.
use the actual distance to drop your 'hammer'.
This might work for evaluating the effect of the initial drop on the first floor that is impacted, but you would quickly notice that in halving the size of everything, but keeping the vertical distances the same, that the columns between the first floor hit and the floor below it would be way to slender and would buckle far easier than the real structure.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
for every halving of size, halve the strength of the connections.
use the actual distance to drop your 'hammer'.
This might work for evaluating the effect of the initial drop on the first floor that is impacted, but you would quickly notice that in halving the size of everything, but keeping the vertical distances the same, that the columns between the first floor hit and the floor below it would be way to slender and would buckle far easier than the real structure.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
QUOTE (adoucette to newton+Feb 8 2008, 05:18 AM)
This might work for evaluating the effect of the initial drop on the first floor that is impacted, but you would quickly notice that in halving the size of everything, but keeping the vertical distances the same, that the columns between the first floor hit and the floor below it would be way to slender and would buckle far easier than the real structure.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
Hi adoucette, everyone.
I just dropped in again to say that anyone is free to use my idea to set up all sorts of 'gravity scaled' collapse/distortion/strain etc tests/experiments....and I would appreciate it if "RealityCheck" of the "PhysorgForums Community" is attributed with this idea (unless of course some ealier reference to this gravity-mimicking/scaling 'technique' is found?).
Cheers!
RC.
.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
Hi adoucette, everyone.
I just dropped in again to say that anyone is free to use my idea to set up all sorts of 'gravity scaled' collapse/distortion/strain etc tests/experiments....and I would appreciate it if "RealityCheck" of the "PhysorgForums Community" is attributed with this idea (unless of course some ealier reference to this gravity-mimicking/scaling 'technique' is found?).
Cheers!
RC.
.
I don't know. I think I need to stay out of the business of scaled simulations. I concede that a drop of greater distance is best, but...
QUOTE (newton+Feb 8 2008, 04:53 AM)
this is also a good experiment to make you realise, "what the heck happened to everything between the 'hammer' and the 'anvil'?"
...at no point did the towers fall freely (I've seen it with my own lying eyes), so the distance would not be the actual height of a floor. If you plan on dropping the upper block, which is easier than launching it downward (maybe employing the WTC7 cantilevered inverted catapult beam), it's the height that corresponds to the actual velocity at the point of impact, as measured.
Counting on it.
...at no point did the towers fall freely (I've seen it with my own lying eyes), so the distance would not be the actual height of a floor. If you plan on dropping the upper block, which is easier than launching it downward (maybe employing the WTC7 cantilevered inverted catapult beam), it's the height that corresponds to the actual velocity at the point of impact, as measured.
QUOTE
i've been tagging along. just wanted you to know.
Counting on it.
I finally read Seffen's paper. Or should I say made a first pass? I appreciate the 'tidying up' he did, made the whole thing flow much easier. As usual, I should have read first, commented later, if at all. Didn't that bite me recently?
If I get it right, DBB, you are looking for a form for p* and c, more or less?
If I get it right, DBB, you are looking for a form for p* and c, more or less?
QUOTE (adoucette+Feb 8 2008, 05:18 AM)
This might work for evaluating the effect of the initial drop on the first floor that is impacted, but you would quickly notice that in halving the size of everything, but keeping the vertical distances the same, that the columns between the first floor hit and the floor below it would be way to slender and would buckle far easier than the real structure.
so, it would collapse more easily than the real structure. because of the slenderness of the columns. so, SCALE THAT factor, ie, thicken them. that's what "scale models" are all about, isn't it?
i just want to see a bunch of these imperfect scale models crush themselves.
so far, we have one house of cards that are a known "not-demolition with sequenced explosives" structure that crushed itself after having some vertical support removed by lateral impacts.
oh yeah, and, "gravity doesn't scale", but, "engineers DO!".
in other words, when discussing the scaling of gravity, it must be noted that the engineers who calculated the strength of the towers originally, had to mathematically scale 'upwards' for gravity effects.
in other words, it i KNOWN what the expectant forces imposed are through KNOWN masses and dimensions.
in other words, when these CLOWNS and/or scientists do experiments to 'prove' their point about cascade collapses, the experiment is not WORTHLESS or WORTHY dependent on the OBSERVER! the data speaks for itself, and not everyone has eyes to hear or smell its taste.
i'm kinda drunk, in other words.
cheers.
so, it would collapse more easily than the real structure. because of the slenderness of the columns. so, SCALE THAT factor, ie, thicken them. that's what "scale models" are all about, isn't it?
i just want to see a bunch of these imperfect scale models crush themselves.
so far, we have one house of cards that are a known "not-demolition with sequenced explosives" structure that crushed itself after having some vertical support removed by lateral impacts.
oh yeah, and, "gravity doesn't scale", but, "engineers DO!".
in other words, when discussing the scaling of gravity, it must be noted that the engineers who calculated the strength of the towers originally, had to mathematically scale 'upwards' for gravity effects.
in other words, it i KNOWN what the expectant forces imposed are through KNOWN masses and dimensions.
in other words, when these CLOWNS and/or scientists do experiments to 'prove' their point about cascade collapses, the experiment is not WORTHLESS or WORTHY dependent on the OBSERVER! the data speaks for itself, and not everyone has eyes to hear or smell its taste.
i'm kinda drunk, in other words.
cheers.
QUOTE (adoucette+Feb 8 2008, 05:18 AM)
This might work for evaluating the effect of the initial drop on the first floor that is impacted, but you would quickly notice that in halving the size of everything, but keeping the vertical distances the same, that the columns between the first floor hit and the floor below it would be way to slender and would buckle far easier than the real structure.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
And how do you scale up gravity in a scale model? A centrifuge.
I think Reality Check is on the right path, to make a scale model work for a collapse analysis you really have to scale UP the gravitational force as you scale down the size of the structure.
And how do you scale up gravity in a scale model? A centrifuge.
QUOTE (Capracus+Feb 8 2008, 05:00 AM)
And how do you scale up gravity in a scale model? A centrifuge.
Yes, you can scale in one direction, but you still have gravity acting perpendicular to your structure as well, which then makes collapse modeling problematic, particularly for a tall structure like a model of the towers.
Arthur
Yes, you can scale in one direction, but you still have gravity acting perpendicular to your structure as well, which then makes collapse modeling problematic, particularly for a tall structure like a model of the towers.
Arthur
QUOTE (OneWhiteEye+Feb 8 2008, 01:55 AM)
I don't know. I think I need to stay out of the business of scaled simulations. I concede that a drop of greater distance is best, but...
...at no point did the towers fall freely (I've seen it with my own lying eyes), so the distance would not be the actual height of a floor.
That's why I always mention dropping it ~ 9 ft to accomodate that slightly slower fall through that first story.
Arthur
...at no point did the towers fall freely (I've seen it with my own lying eyes), so the distance would not be the actual height of a floor.
That's why I always mention dropping it ~ 9 ft to accomodate that slightly slower fall through that first story.
Arthur
QUOTE (newton+Feb 8 2008, 04:13 AM)
so, it would collapse more easily than the real structure. because of the slenderness of the columns. so, SCALE THAT factor, ie, thicken them. that's what "scale models" are all about, isn't it?
But when you "thicken" them, you increase the mass so much that your corresponding 'scale' attributes (like the weight of the floors) no longer are in the right proportion, so you have to scale them up as well, as you do so your model structure starts to look like the real tower.
Engineers designing the structure for gravity loads were dealing with STATIC loads on the structures, they don't consider the forces generated when the top 30 floors accelerate downward.
Arthur
But when you "thicken" them, you increase the mass so much that your corresponding 'scale' attributes (like the weight of the floors) no longer are in the right proportion, so you have to scale them up as well, as you do so your model structure starts to look like the real tower.
QUOTE
oh yeah, and, "gravity doesn't scale", but, "engineers DO!".
in other words, when discussing the scaling of gravity, it must be noted that the engineers who calculated the strength of the towers originally, had to mathematically scale 'upwards' for gravity effects.
in other words, it i KNOWN what the expectant forces imposed are through KNOWN masses and dimensions.
in other words, when discussing the scaling of gravity, it must be noted that the engineers who calculated the strength of the towers originally, had to mathematically scale 'upwards' for gravity effects.
in other words, it i KNOWN what the expectant forces imposed are through KNOWN masses and dimensions.
Engineers designing the structure for gravity loads were dealing with STATIC loads on the structures, they don't consider the forces generated when the top 30 floors accelerate downward.
Arthur
QUOTE (OneWhiteEye+Feb 8 2008, 02:02 AM)
If I get it right, DBB, you are looking for a form for p* and c, more or less?
Rather more than less, except I use the notations from the B & V paper.
For WTC 2 the 1d equation works fine for the first 4 seconds. For the rest of the collapse some adjustments, such as having the top portion fall apart and away from the vertical, would be necessary. The 1d equation is actually quite robust.
AFAIK, nobody has used the crush-down equation except on the WTC towers, with WTC 1 being the simpler case (all I specialize in). For the leg-n-cardboard model, I see no way to predict in advance the form nor coefficients of the resistive force, except that probably the vertical avalanche term needs to be replaced by an air resistance term.
Dropping the top portion from an extra height should not be necessary for the Lego-n-cardboard model, provided the Lego bricks do not impact squarely on the Lego bricks below. The idea is that the cardboard tabs are so weak that such pull out as the cardboard 'floor' sags or kinks.
Rather more than less, except I use the notations from the B & V paper.
For WTC 2 the 1d equation works fine for the first 4 seconds. For the rest of the collapse some adjustments, such as having the top portion fall apart and away from the vertical, would be necessary. The 1d equation is actually quite robust.
AFAIK, nobody has used the crush-down equation except on the WTC towers, with WTC 1 being the simpler case (all I specialize in). For the leg-n-cardboard model, I see no way to predict in advance the form nor coefficients of the resistive force, except that probably the vertical avalanche term needs to be replaced by an air resistance term.
Dropping the top portion from an extra height should not be necessary for the Lego-n-cardboard model, provided the Lego bricks do not impact squarely on the Lego bricks below. The idea is that the cardboard tabs are so weak that such pull out as the cardboard 'floor' sags or kinks.
QUOTE (David B. Benson+Feb 8 2008, 06:21 PM)
Rather more than less, except I use the notations from the B & V paper.
OK, good, I'm getting on track. Seffen's paper was a good read. Master hand-waver, and I mean that as a compliment. There are a few things I didn't get, such as the justification for the application of the Maxwell Construction in this instance, but I'll go over it again and see if things are clearer. Another issue is t0 and initial velocity, but I'll get back to that.
I always have left open the possibility that 1D methods can give good results, despite simplifying assumptions. Now I wonder how one goes about verifying against the real thing, where there is not always a visible or well-defined crushing front. Checking the integral against total time (determined by audio, yes?) is necessary and good but, in my opinion, insufficient to validate. That's why I appreciate what you're doing.
I always have left open the possibility that 1D methods can give good results, despite simplifying assumptions. Now I wonder how one goes about verifying against the real thing, where there is not always a visible or well-defined crushing front. Checking the integral against total time (determined by audio, yes?) is necessary and good but, in my opinion, insufficient to validate. That's why I appreciate what you're doing.
AFAIK, nobody has used the crush-down equation except on the WTC towers, with WTC 1 being the simpler case (all I specialize in).
Circumstance may have dictated it be this way up to this point, but I humbly suggest this specialized sub-field will benefit from consideration of a broader collection of actual instances. Even if they need to be made in the lab.
Ahh, then we can't make a realistic animation simulation before building and collapsing the Lego tower. So maybe not a yawn, after all.
Ahh, then we can't make a realistic animation simulation before building and collapsing the Lego tower. So maybe not a yawn, after all.
...except that probably the vertical avalanche term needs to be replaced by an air resistance term.
For all velocities? I must return to the idea of regimes of applicability for recurring forms.
I think your model is quite brilliant, and would probably work even if it needed ad-hoc tweaks. What's most interesting is it defeats the necessity of developing sufficient proportional kinetic energy in order crush members below. Instead, the (considerably smaller) existing energy is applied to cleverly take the structure apart. I realized yesterday after a frame by frame review of the house of cards that the same phenomena is at work there. In fact, the collapse is virtually arrested twice, but continues after a pause due to induced instability. No cards buckle, none are crushed, obviously. It seems the Lego tower would likewise collapse due to lateral instabilities and not crushing. Hmmm...
Both Seffen and the Bazant, et al, series are not framed in this context. Best I can tell, Seffen's math does not care what the origins of resistive force is, but at least his narrative pays lip service to the notion of buckling and crushing, going as far as to outline three regimes. I suppose this is how he came to the range of values used with the Maxwell Construction.
Because the papers focus on crushing, I think when people say they'd like to see a scale model, they'd like to see it crush itself, not just disassemble itself.
OK, good, I'm getting on track. Seffen's paper was a good read. Master hand-waver, and I mean that as a compliment. There are a few things I didn't get, such as the justification for the application of the Maxwell Construction in this instance, but I'll go over it again and see if things are clearer. Another issue is t0 and initial velocity, but I'll get back to that.
QUOTE
For WTC 2 the 1d equation works fine for the first 4 seconds. For the rest of the collapse some adjustments, such as having the top portion fall apart and away from the vertical, would be necessary. The 1d equation is actually quite robust.
I always have left open the possibility that 1D methods can give good results, despite simplifying assumptions. Now I wonder how one goes about verifying against the real thing, where there is not always a visible or well-defined crushing front. Checking the integral against total time (determined by audio, yes?) is necessary and good but, in my opinion, insufficient to validate. That's why I appreciate what you're doing.
QUOTE (->
| QUOTE |
| For WTC 2 the 1d equation works fine for the first 4 seconds. For the rest of the collapse some adjustments, such as having the top portion fall apart and away from the vertical, would be necessary. The 1d equation is actually quite robust. |
I always have left open the possibility that 1D methods can give good results, despite simplifying assumptions. Now I wonder how one goes about verifying against the real thing, where there is not always a visible or well-defined crushing front. Checking the integral against total time (determined by audio, yes?) is necessary and good but, in my opinion, insufficient to validate. That's why I appreciate what you're doing.
AFAIK, nobody has used the crush-down equation except on the WTC towers, with WTC 1 being the simpler case (all I specialize in).
Circumstance may have dictated it be this way up to this point, but I humbly suggest this specialized sub-field will benefit from consideration of a broader collection of actual instances. Even if they need to be made in the lab.
QUOTE
For the leg-n-cardboard model, I see no way to predict in advance the form nor coefficients of the resistive force, ...
Ahh, then we can't make a realistic animation simulation before building and collapsing the Lego tower. So maybe not a yawn, after all.
QUOTE (->
| QUOTE |
| For the leg-n-cardboard model, I see no way to predict in advance the form nor coefficients of the resistive force, ... |
Ahh, then we can't make a realistic animation simulation before building and collapsing the Lego tower. So maybe not a yawn, after all.
...except that probably the vertical avalanche term needs to be replaced by an air resistance term.
For all velocities? I must return to the idea of regimes of applicability for recurring forms.
QUOTE
Dropping the top portion from an extra height should not be necessary for the Lego-n-cardboard model, provided the Lego bricks do not impact squarely on the Lego bricks below. The idea is that the cardboard tabs are so weak that such pull out as the cardboard 'floor' sags or kinks.
I think your model is quite brilliant, and would probably work even if it needed ad-hoc tweaks. What's most interesting is it defeats the necessity of developing sufficient proportional kinetic energy in order crush members below. Instead, the (considerably smaller) existing energy is applied to cleverly take the structure apart. I realized yesterday after a frame by frame review of the house of cards that the same phenomena is at work there. In fact, the collapse is virtually arrested twice, but continues after a pause due to induced instability. No cards buckle, none are crushed, obviously. It seems the Lego tower would likewise collapse due to lateral instabilities and not crushing. Hmmm...
Both Seffen and the Bazant, et al, series are not framed in this context. Best I can tell, Seffen's math does not care what the origins of resistive force is, but at least his narrative pays lip service to the notion of buckling and crushing, going as far as to outline three regimes. I suppose this is how he came to the range of values used with the Maxwell Construction.
Because the papers focus on crushing, I think when people say they'd like to see a scale model, they'd like to see it crush itself, not just disassemble itself.
QUOTE (OneWhiteEye+Feb 8 2008, 02:12 PM)
For all velocities? I must return to the idea of regimes of applicability for recurring forms.
Because the papers focus on crushing, I think when people say they'd like to see a scale model, they'd like to see it crush itself, not just disassemble itself.
All reasonable starting values just above 0, yes. The reason is that the cardboard 'floors' do not continually keep being re-crushed. The 'floors' simply move all the air out of the way to come in contact with the one below. So the vertical avalanche dissipation do not occur, but the air resistance is still there.
Depends upon what 'crushing' is to mean. For the Lego-n-cardboard model, crushing is the same as 'pancaking' all the cardboard 'floors' together. I repeat that I expect the Lego walls to largely remain standing; this is not a complete simulation.
Because the papers focus on crushing, I think when people say they'd like to see a scale model, they'd like to see it crush itself, not just disassemble itself.
All reasonable starting values just above 0, yes. The reason is that the cardboard 'floors' do not continually keep being re-crushed. The 'floors' simply move all the air out of the way to come in contact with the one below. So the vertical avalanche dissipation do not occur, but the air resistance is still there.
Depends upon what 'crushing' is to mean. For the Lego-n-cardboard model, crushing is the same as 'pancaking' all the cardboard 'floors' together. I repeat that I expect the Lego walls to largely remain standing; this is not a complete simulation.
QUOTE (David B. Benson+Feb 8 2008, 09:57 PM)
All reasonable starting values just above 0, yes. The reason is that the cardboard 'floors' do not continually keep being re-crushed. The 'floors' simply move all the air out of the way to come in contact with the one below. So the vertical avalanche dissipation do not occur, but the air resistance is still there.
Thank you, that makes perfect sense. The form of the air resistance, in this case, is that of forcing air through an orifice. If the cardboard were replaced with glass sheets and also pegged with glass, the air resistance would matter less, and crushing more. With proper materials and construction, I think it would be possible to fade between the regimes (as I've been calling them, for lack of a better term) almost continuously, in an incremental fashion.
Crushing of cardboard floors => zero compaction.
Thank you, that makes perfect sense. The form of the air resistance, in this case, is that of forcing air through an orifice. If the cardboard were replaced with glass sheets and also pegged with glass, the air resistance would matter less, and crushing more. With proper materials and construction, I think it would be possible to fade between the regimes (as I've been calling them, for lack of a better term) almost continuously, in an incremental fashion.
QUOTE
Depends upon what 'crushing' is to mean. For the Lego-n-cardboard model, crushing is the same as 'pancaking' all the cardboard 'floors' together. I repeat that I expect the Lego walls to largely remain standing; this is not a complete simulation.
Crushing of cardboard floors => zero compaction.
QUOTE (OneWhiteEye+Feb 8 2008, 03:48 PM)
Crushing of cardboard floors => zero compaction.
Have to define terms carefully.
Suppose the cardboard 'floors' are 1 cm apart and are 2 mm thick. Then the stretch (inverse compaction ratio) is 0.2, since 1 cm becomes 2 mm, assuming no actually crushing for the corrugated cardboard.
(This model does have the advantage that the stretch is nearly constant and can be determined in advance.)
Have to define terms carefully.
Suppose the cardboard 'floors' are 1 cm apart and are 2 mm thick. Then the stretch (inverse compaction ratio) is 0.2, since 1 cm becomes 2 mm, assuming no actually crushing for the corrugated cardboard.
(This model does have the advantage that the stretch is nearly constant and can be determined in advance.)
QUOTE (David B. Benson+Feb 8 2008, 11:26 PM)
Have to define terms carefully.
Suppose the cardboard 'floors' are 1 cm apart and are 2 mm thick. Then the stretch (inverse compaction ratio) is 0.2, since 1 cm becomes 2 mm, assuming no actually crushing for the corrugated cardboard.
(This model does have the advantage that the stretch is nearly constant and can be determined in advance.)
Oh, I should have got the distinction. Change in all volume. Cardboard floors => much compaction.
Suppose the cardboard 'floors' are 1 cm apart and are 2 mm thick. Then the stretch (inverse compaction ratio) is 0.2, since 1 cm becomes 2 mm, assuming no actually crushing for the corrugated cardboard.
(This model does have the advantage that the stretch is nearly constant and can be determined in advance.)
Oh, I should have got the distinction. Change in all volume. Cardboard floors => much compaction.
QUOTE (OneWhiteEye+Feb 8 2008, 04:31 PM)
Cardboard floors => much compaction.
Assuming nothing is placed on the cardboard 'floors' to simulate the truss height, ceiling systems and office furnishings and contents. I'd leave all this out, myself.
By the way, a value for the stretch of about 0.2 is used in the B&V and BLGB papers.
Assuming nothing is placed on the cardboard 'floors' to simulate the truss height, ceiling systems and office furnishings and contents. I'd leave all this out, myself.
By the way, a value for the stretch of about 0.2 is used in the B&V and BLGB papers.
QUOTE (NEU-FONZE+Jan 29 2008, 03:13 PM)
Since you appear to be a statistics aficionado...
Funny you should say that, I don't self-identify that way, but it is beginning to look like it.
Perhaps this could help you decide, perhaps not:
http://kjafnjnhk.myfastforum.org/sutra6.php#6
To be fair, I'm going to do the reverse in a bit. Edit: oh, I guess that's not necessary.
Funny you should say that, I don't self-identify that way, but it is beginning to look like it.
QUOTE
Does Arthur always post soon after I post, or is that just my imagination?
Perhaps this could help you decide, perhaps not:
http://kjafnjnhk.myfastforum.org/sutra6.php#6
To be fair, I'm going to do the reverse in a bit. Edit: oh, I guess that's not necessary.
Little SILLY, don't you think?
As of 2/10/08
Of the 9,171 replies in this thread, David has 1,422, I have 1,132, wcelliot has 539 and einsteen has 512
So the chance of replying after a Neu post seems to relate pretty much to just how often we reply.
Paranoia, don't you just love it.
Arthur
As of 2/10/08
Of the 9,171 replies in this thread, David has 1,422, I have 1,132, wcelliot has 539 and einsteen has 512
So the chance of replying after a Neu post seems to relate pretty much to just how often we reply.
Paranoia, don't you just love it.
Arthur
QUOTE (adoucette+Feb 11 2008, 04:20 AM)
Little SILLY, don't you think?
Lot silly. If it weren't for my obsessive/compulsive disorder...
I agree, very much. I'd be tempted to think significant deviations from the distribution of individual post totals might mean - something.
I agree, very much. I'd be tempted to think significant deviations from the distribution of individual post totals might mean - something.
Paranoia, don't you just love it.
Then this may interest you:
http://kjafnjnhk.myfastforum.org/sutra7.php#7
By the reasoning above, certain people stand out as having a deviant probability of posting soon after you... and one of them is NEU-FONZE...
Lot silly. If it weren't for my obsessive/compulsive disorder...
QUOTE
Of the 9,171 replies in this thread, David has 1,422, I have 1,132, wcelliot has 539 and einsteen has 512
So the chance of replying after a Neu post seems to relate pretty much to just how often we reply.
So the chance of replying after a Neu post seems to relate pretty much to just how often we reply.
I agree, very much. I'd be tempted to think significant deviations from the distribution of individual post totals might mean - something.
QUOTE (->
| QUOTE |
| Of the 9,171 replies in this thread, David has 1,422, I have 1,132, wcelliot has 539 and einsteen has 512 So the chance of replying after a Neu post seems to relate pretty much to just how often we reply. |
I agree, very much. I'd be tempted to think significant deviations from the distribution of individual post totals might mean - something.
Paranoia, don't you just love it.
Then this may interest you:
http://kjafnjnhk.myfastforum.org/sutra7.php#7
By the reasoning above, certain people stand out as having a deviant probability of posting soon after you... and one of them is NEU-FONZE...
QUOTE (OneWhiteEye+Feb 10 2008, 11:48 PM)
By the reasoning above, certain people stand out as having a deviant probability of posting soon after you... and one of them is NEU-FONZE...
But actually, I'd put that down to the natural nature of this forum.
A number of us have had "side discussions" about an issue that really only interested one or two of us.
Neu and I have had several of these.
Arthur
But actually, I'd put that down to the natural nature of this forum.
A number of us have had "side discussions" about an issue that really only interested one or two of us.
Neu and I have had several of these.
Arthur
OneWhiteEye:
Since Arthur just posted, I am now contributing to the statistic of my responding whenever Arthur posts. However, if Arthur posts next he will only add to his proven tendency to post after I post.
Yes!
Looks like I've found a way to keep Arthur from posting!
Is this a bad thing?
Since Arthur just posted, I am now contributing to the statistic of my responding whenever Arthur posts. However, if Arthur posts next he will only add to his proven tendency to post after I post.
Yes!
Looks like I've found a way to keep Arthur from posting!
Is this a bad thing?
QUOTE (adoucette+Feb 8 2008, 12:09 AM)
That's my point though.
We've seen a number of these various attempts to "model" the towers, and in every case they scale the towers down AND then they scale the drop distance.
Then they say, SEE, it doesn't collapse (like in the video that einsteen posted)
The fact is, if you want to get a more intuitive idea of what happened, then simply make a scale tower, with scale masses, and then drop the top block ~ 9 ft onto the bottom block.
I can assure you when the velocity goes back up to what it should be, the top block WILL crush the bottom portion.
Arthur
I guess that in that case the mini-tower breaks in parts like a piece of spaghetti.
The card-house is a nice example of progressive collapse, a complete one and a fast one, but this house is not a one that will last for long in wind or a small earthquake. In general when you compare a real car with a toy car then the latter is also much stronger, for a crash leading to damage you really have to move it very fast, but an interesting thing is that a large structure like the wtc could swing in the wind which means that the strength has been corrected for. A mini-tower with the same construction as the wtc and the same behavior is hard or maybe not doable even not in a centrifuge.
We've seen a number of these various attempts to "model" the towers, and in every case they scale the towers down AND then they scale the drop distance.
Then they say, SEE, it doesn't collapse (like in the video that einsteen posted)
The fact is, if you want to get a more intuitive idea of what happened, then simply make a scale tower, with scale masses, and then drop the top block ~ 9 ft onto the bottom block.
I can assure you when the velocity goes back up to what it should be, the top block WILL crush the bottom portion.
Arthur
I guess that in that case the mini-tower breaks in parts like a piece of spaghetti.
The card-house is a nice example of progressive collapse, a complete one and a fast one, but this house is not a one that will last for long in wind or a small earthquake. In general when you compare a real car with a toy car then the latter is also much stronger, for a crash leading to damage you really have to move it very fast, but an interesting thing is that a large structure like the wtc could swing in the wind which means that the strength has been corrected for. A mini-tower with the same construction as the wtc and the same behavior is hard or maybe not doable even not in a centrifuge.
QUOTE (OneWhiteEye+Feb 8 2008, 01:42 AM)
I agree, it is a bummer. I haven't quite made up my mind whether I'll wear the scarlet letter of 'User Posted Image' with pride or use a regular link. But, if I have to post only a link, I'm going to make it count. I have a partial solution in place, just no time to do much right now.
Sometimes I also wonder whether there is a good alternative to move, setting up a new one is not much work but maintaining it is a major job. The other bad thing is that subtopics are needed, I have the feeling that physorg thinks one of them is enough...
Sometimes I also wonder whether there is a good alternative to move, setting up a new one is not much work but maintaining it is a major job. The other bad thing is that subtopics are needed, I have the feeling that physorg thinks one of them is enough...
QUOTE (newton+Feb 8 2008, 04:53 AM)
the house of cards is 'best' so far, because IT ACTUALLY CRUSHED ITSELF(although, i notice none of the cards were 'dustified').
I think it could not really be compared with the twin towers because it is no tube in tube design, nothing can funnel or wedge (although I'm no funneler or wedger) and I think if you make this house cards higher the collapse will obtain a constant velocity, a kind of terminal velocity because it doesn't look like the cards are collected in a stack, but it is a progressive collapse. The only progressive top-down progressive collapse that I know before 9/11 was a couple of balconies at a corner of a building.
I think it could not really be compared with the twin towers because it is no tube in tube design, nothing can funnel or wedge (although I'm no funneler or wedger) and I think if you make this house cards higher the collapse will obtain a constant velocity, a kind of terminal velocity because it doesn't look like the cards are collected in a stack, but it is a progressive collapse. The only progressive top-down progressive collapse that I know before 9/11 was a couple of balconies at a corner of a building.
QUOTE (NEU-FONZE+Feb 11 2008, 11:39 AM)
Looks like I've found a way to keep Arthur from posting!
Hahahaha...
Only if you believe in the magic of the numbers.
Hahahaha...
Only if you believe in the magic of the numbers.
I'm ill now and not able to think (that's normal for a CT'er of course) or calculate and have to sleep but last week I took a part of the antenna and a part of the roof and found these two smear-o-grams, synced in time
Compare Drop Antenna With Drop Edge Of Roof
Could the difference between those distances (corrected for distance 32 meter behind the roof , camera angle etc) account for the point where the drop starts, if yes then case solved, if no then the antenna indeed drops first. Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
Compare Drop Antenna With Drop Edge Of Roof
Could the difference between those distances (corrected for distance 32 meter behind the roof , camera angle etc) account for the point where the drop starts, if yes then case solved, if no then the antenna indeed drops first. Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
QUOTE (einsteen+Feb 11 2008, 01:10 PM)
Sometimes I also wonder whether there is a good alternative to move, setting up a new one is not much work but maintaining it is a major job. The other bad thing is that subtopics are needed, I have the feeling that physorg thinks one of them is enough...
You see my 'solution' was to appropriate another forum for spillover. I like to post a lot of images since it draws attention away from my empty words. When they can't be inlined, I'm ******!
Something about this doesn't flow right:
"And, at external links 37 and 38, you will see another pretty picture that conclusively proves I'm not hitting on all 8 cylinders..."
If I've got to post a link then, like I say, it should count. Besides, I can inline full size images over there, as well as:
- edit whenever I want (unlimited edit time for all levels of user)
- delete whenever I want
- go off topic at will
- categorize and archive in a central location
- keep my hosted images active with less effort
- adhere to my own forum rules, which are void
I know, that's called a blog. The word has such ugliness as it tries to wriggle through my neurons, I couldn't do anything like that.
"Oh yeah, we had dinner at Sal Minella's Seafood and Pasta Tuesday, and I was up all night blogging"
You see my 'solution' was to appropriate another forum for spillover. I like to post a lot of images since it draws attention away from my empty words. When they can't be inlined, I'm ******!
Something about this doesn't flow right:
"And, at external links 37 and 38, you will see another pretty picture that conclusively proves I'm not hitting on all 8 cylinders..."
If I've got to post a link then, like I say, it should count. Besides, I can inline full size images over there, as well as:
- edit whenever I want (unlimited edit time for all levels of user)
- delete whenever I want
- go off topic at will
- categorize and archive in a central location
- keep my hosted images active with less effort
- adhere to my own forum rules, which are void
I know, that's called a blog. The word has such ugliness as it tries to wriggle through my neurons, I couldn't do anything like that.
"Oh yeah, we had dinner at Sal Minella's Seafood and Pasta Tuesday, and I was up all night blogging"
QUOTE (einsteen+Feb 11 2008, 05:55 PM)
I'm ill now...
Sorry to hear that. Rest and replace your electrolytes, if you've had episodes of blogging.
hahaha
hahaha
last week I took a part of the antenna and a part of the roof and found these two smear-o-grams, synced in time
Compare Drop Antenna With Drop Edge Of Roof
Could the difference between those distances (corrected for distance 32 meter behind the roof , camera angle etc) account for the point where the drop starts, if yes then case solved, if no then the antenna indeed drops first. Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
An interesting idea, yes. There have been discussions of differential displacements, no real work yet in that direction of which I'm aware. I have impressions about this which I need to get together but, essentially, everything hinges (geometrically, pun intended) on whether there is a proper hinge, and the location. The close-up video of tower 2 you posted a while back appears to negate my naive ideas about what is possible and likely for hinge action.
I say 'appears' because I have to watch a video frame by frame hundreds of times and take measurements before I feel anywhere close to proclaiming something as a fact. By the point of proclamation, though, I feel no hesitation.
Sorry to hear that. Rest and replace your electrolytes, if you've had episodes of blogging.
QUOTE
and not able to think (that's normal for a CT'er of course)
hahaha
QUOTE (->
| QUOTE |
| and not able to think (that's normal for a CT'er of course) |
hahaha
last week I took a part of the antenna and a part of the roof and found these two smear-o-grams, synced in time
Compare Drop Antenna With Drop Edge Of Roof
Could the difference between those distances (corrected for distance 32 meter behind the roof , camera angle etc) account for the point where the drop starts, if yes then case solved, if no then the antenna indeed drops first. Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
An interesting idea, yes. There have been discussions of differential displacements, no real work yet in that direction of which I'm aware. I have impressions about this which I need to get together but, essentially, everything hinges (geometrically, pun intended) on whether there is a proper hinge, and the location. The close-up video of tower 2 you posted a while back appears to negate my naive ideas about what is possible and likely for hinge action.
I say 'appears' because I have to watch a video frame by frame hundreds of times and take measurements before I feel anywhere close to proclaiming something as a fact. By the point of proclamation, though, I feel no hesitation.
QUOTE (einsteen+Feb 11 2008, 10:55 AM)
Compare Drop Antenna With Drop Edge Of Roof
Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
Neat. What I suspected.
Yes, but no work has been done yet.
Perhaps this has been discussed in the OneWhiteEye-DBB discussions but I'm not sure...
Neat. What I suspected.
Yes, but no work has been done yet.
For the Lego block-n-cardboard model, I hypothesis a resistive force function of the form
k0 + k1(Z')^2
the first term due to inelastic behavior and sliding friction, the second due to air resistance.
k0 + k1(Z')^2
the first term due to inelastic behavior and sliding friction, the second due to air resistance.
Einsteen:
Could you provide a little more explanation of what we are seeing in those smear-o-grams...
Why the need for two separate images?
Could you not display the antenna and the roof line motion on the same smear-o-gram?
One thing I see in some of the WTC 1 collapse videos is that the antenna shows a distinct "wobble" just before it disappears into the smoke clouds. This suggests that the antenna was disconnected from the upper block by this stage of the collapse.....
Could you provide a little more explanation of what we are seeing in those smear-o-grams...
Why the need for two separate images?
Could you not display the antenna and the roof line motion on the same smear-o-gram?
One thing I see in some of the WTC 1 collapse videos is that the antenna shows a distinct "wobble" just before it disappears into the smoke clouds. This suggests that the antenna was disconnected from the upper block by this stage of the collapse.....
QUOTE (NEU-FONZE+Feb 11 2008, 03:18 PM)
One thing I see in some of the WTC 1 collapse videos is that the antenna shows a distinct "wobble" just before it disappears into the smoke clouds. This suggests that the antenna was disconnected from the upper block by this stage of the collapse.....
Or that the antenna tower and the hat truss together act as a mass-spring system to produce oscillations, finally growing large enough to be easily seen...
Or that the antenna tower and the hat truss together act as a mass-spring system to produce oscillations, finally growing large enough to be easily seen...
DBB:
What excites the oscillations of the antenna/hat truss assembly?
What excites the oscillations of the antenna/hat truss assembly?
QUOTE (NEU-FONZE+Feb 11 2008, 05:02 PM)
What excites the oscillations of the antenna/hat truss assembly?
Tipping?
I should think that suffices.
Tipping?
I should think that suffices.
QUOTE (David B. Benson+Feb 12 2008, 12:34 AM)
Tipping?
I should think that suffices.
Compression energy being released do to weld failure would be more likely.
PS. I bet I can get Arthur to post 9/11 was an inside Job and now I can prove it.
I should think that suffices.
Compression energy being released do to weld failure would be more likely.
PS. I bet I can get Arthur to post 9/11 was an inside Job and now I can prove it.
Neu-Fonze,
That was not possible because the roof below the antenna is covered by smoke, the following image will explain that
Picture Showing That The Roof Of The First Smearogram Is Covered By Smoke
But you gave me a good idea, I've cropped the antenna to 16x200 and the right part of the building to 16x140, see these two images:
Part Of Antenna Cropped
Part Of Roof Cropped
The time interval is unchanged of course.
I've created a new video 16x340 and that raw (resulting) video is available here:
http://rapidshare.com/files/91193001/together.avi.html
and you see that the antenna also topples a small fraction to the left, one should correct for that.
I've created a smear-o-gram from a part of this, resulting in
Smearogram With At Top The Antenna And Down The Right Corner Of The Building's Roof
I'm not going to draw lines now, anyone should do his own analysis.
That was not possible because the roof below the antenna is covered by smoke, the following image will explain that
Picture Showing That The Roof Of The First Smearogram Is Covered By Smoke
But you gave me a good idea, I've cropped the antenna to 16x200 and the right part of the building to 16x140, see these two images:
Part Of Antenna Cropped
Part Of Roof Cropped
The time interval is unchanged of course.
I've created a new video 16x340 and that raw (resulting) video is available here:
http://rapidshare.com/files/91193001/together.avi.html
and you see that the antenna also topples a small fraction to the left, one should correct for that.
I've created a smear-o-gram from a part of this, resulting in
Smearogram With At Top The Antenna And Down The Right Corner Of The Building's Roof
I'm not going to draw lines now, anyone should do his own analysis.
Einsteen:
That helps a lot! Especially your first explanatory image showing how a particular object on WTC 1 relates to a line or band on your smear-o-gram!
Nice work!
That helps a lot! Especially your first explanatory image showing how a particular object on WTC 1 relates to a line or band on your smear-o-gram!
Nice work!
I'm absolutely not sure what can be seen from it, but the functions f(t) from the parts of the antenna and the roof should be plotted with maple for example and the points where f(t) becomes negative should be compared. In the videos we are limited to the resolution of a pixel, if a line jumps from 0 to -1 it doesn't mean that that is also the point where the theoretical functions match. It's not that easy. When I first saw this movie (more than a year ago) I also though that the antenna really dropped first, I gave it no longer attention when I saw the toppling from an other video, but if I look at the video frame by frame it still looks a little bit like that the inner part drops down and the perimeter fails after it, but that is no hard conclusion at the moment, enough gibberish for now.
Indeed, great work, einsteen.
David B. Benson, two questions. Could you post your latest measured and calculated (best hypothesis) data series, as well as the resultant coefficients? If so, I'll make you an animation of the results, at least one. And, would you be willing to apply your process to other datasets over time in an effort to get a generalized model of structural crush-down?
David B. Benson, two questions. Could you post your latest measured and calculated (best hypothesis) data series, as well as the resultant coefficients? If so, I'll make you an animation of the results, at least one. And, would you be willing to apply your process to other datasets over time in an effort to get a generalized model of structural crush-down?
Einsteen:
YOU ARE THE MAN!
I have taken your WTC 1 smearogram and derived two plots, one for the roof line curve and one for the curve formed by the dark band near the top of the antenna.
(I did this by enlarging your smearogram on a xerox machine about 3 times and marking it up with grid lines.)
I have now also done a quick calibration to convert the data to time in seconds and drop in meters.
I get an excellent fit (R^2 = 0.9996 !!!) for each set of data to two simple parabolic equations:
drop (roof) = 2.6362 t^2 - 1.5223 t
drop (antenna) = 3.0305 t^2 - 0.8544 t
Now comes the good part!
By setting the drop equal to zero for each equation I get an effective collapse initiation time:
For the roof line: t (zero) = 0.5775 seconds
For the antenna: t (zero) = 0.2819 seconds
Hence Delta t = 0.5775 - 0.2819 = 0.2956 seconds
In other words:
THE ANTENNA STARTS TO DROP ~ 0.3 SECONDS BEFORE THE ROOF LINE!
YOU ARE THE MAN!
I have taken your WTC 1 smearogram and derived two plots, one for the roof line curve and one for the curve formed by the dark band near the top of the antenna.
(I did this by enlarging your smearogram on a xerox machine about 3 times and marking it up with grid lines.)
I have now also done a quick calibration to convert the data to time in seconds and drop in meters.
I get an excellent fit (R^2 = 0.9996 !!!) for each set of data to two simple parabolic equations:
drop (roof) = 2.6362 t^2 - 1.5223 t
drop (antenna) = 3.0305 t^2 - 0.8544 t
Now comes the good part!
By setting the drop equal to zero for each equation I get an effective collapse initiation time:
For the roof line: t (zero) = 0.5775 seconds
For the antenna: t (zero) = 0.2819 seconds
Hence Delta t = 0.5775 - 0.2819 = 0.2956 seconds
In other words:
THE ANTENNA STARTS TO DROP ~ 0.3 SECONDS BEFORE THE ROOF LINE!
QUOTE (NEU-FONZE+Feb 12 2008, 11:56 AM)
THE ANTENNA STARTS TO DROP ~ 0.3 SECONDS BEFORE THE ROOF LINE!
This, I believe, is to be expected: south wall buckles, followed by the east and west walls; antenna tower begins tilting; north wall buckles and begins to tilt to the south, hinged on the buckled part.
This, I believe, is to be expected: south wall buckles, followed by the east and west walls; antenna tower begins tilting; north wall buckles and begins to tilt to the south, hinged on the buckled part.
QUOTE (OneWhiteEye+Feb 12 2008, 11:04 AM)
Indeed, great work, einsteen.
David B. Benson, two questions. Could you post your latest measured and calculated (best hypothesis) data series, as well as the resultant coefficients? If so, I'll make you an animation of the results, at least one. And, would you be willing to apply your process to other datasets over time in an effort to get a generalized model of structural crush-down?
Second that!
Yes, but be patient. We are still recovering from the most significant snow fall in an least twelve years. Worse, we had an unscheduled power outage over the weekend (for 4 hours), and I'm still working to bring up my four machines.
If, in the future, there is additional crush-down data (say, from models), I'd be happy to analyze it.
David B. Benson, two questions. Could you post your latest measured and calculated (best hypothesis) data series, as well as the resultant coefficients? If so, I'll make you an animation of the results, at least one. And, would you be willing to apply your process to other datasets over time in an effort to get a generalized model of structural crush-down?
Second that!
Yes, but be patient. We are still recovering from the most significant snow fall in an least twelve years. Worse, we had an unscheduled power outage over the weekend (for 4 hours), and I'm still working to bring up my four machines.
If, in the future, there is additional crush-down data (say, from models), I'd be happy to analyze it.
Wow, Neu-Fonze, 0.3 seconds, your sure ? Sounds like a lot. I'll look at your analysis later, I had to save the virtualdub settings but I'm sure you believe me and everyone can use the original video to review. The latter smearogram isn't the same as the first one btw, I had to repeat the procedure to create the screen dumps.
einsteen --- Does not sound like a lot to me. The hat truss surely could not transfer loads any faster than that. Specially loads which take about that length of time to reach maximum.
Einsteen and DBB:
If you look at the two equations I gave in my last post they approximate:
s (roof line) ~ 2.64 t^2
s (antenna) ~ 3.03 t^2
Now for free fall under a constant force, s = 1/2 a t^2, we see an acceleration of about 5.3 m/s^2 for the roof line and 6.06 m/s^2 for the antenna, which sounds quite reasonable!
Anyway, in a third of a second the antenna would drop 27 cm which would be hardly noticable from the ground, (but very significant for the building!)
However, after 2 seconds the antenna would have dropped {0.27 + 4x (3.03 - 2.64)} or almost 2 meters more than the roof.....
My next step is to include the effects of tipping, but I think this is a small effect for the first couple of seconds.
If you look at the two equations I gave in my last post they approximate:
s (roof line) ~ 2.64 t^2
s (antenna) ~ 3.03 t^2
Now for free fall under a constant force, s = 1/2 a t^2, we see an acceleration of about 5.3 m/s^2 for the roof line and 6.06 m/s^2 for the antenna, which sounds quite reasonable!
Anyway, in a third of a second the antenna would drop 27 cm which would be hardly noticable from the ground, (but very significant for the building!)
However, after 2 seconds the antenna would have dropped {0.27 + 4x (3.03 - 2.64)} or almost 2 meters more than the roof.....
My next step is to include the effects of tipping, but I think this is a small effect for the first couple of seconds.
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