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Another Question for Heiwa : Amazing Fireproof Steel
- Thread starter Architect
- Start date
Belz...
Fiend God
Heiwa, perhaps picture will help you:
A
X
B
Remove X. See what happens ? B held A before X was removed bu now it doesn't. A comes crashing down on B.
That is in fact what happens if all columns fail. If you take a stress-strain diagram, the static load is a point on the linear function in the beginning, if it is disconnected it in fact jumps to (0,0) and some elastic energy is released. I understand Heiwa's point. One of his points was that the energy to break the initial columns needs to be subtracted from the released potential energy. But the more important point is the collapse initiation. You first need an initial velocity to overcome the remaining elastic and plastic energy. That's also the reason that we will never see a building collapse like the twin towers and wtc7 after 9/11 and before 9/11, because the kinetic energy in a small movement is always very low and easily absorbed, if not elastic then plastic. I would say that on 9/11 the columns couldn't handle te static load at a certain time.
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Newtons Bit
Penultimate Amazing
- Joined
- Apr 12, 2007
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- 10,049
It would actually move up about 10cm, and then start oscillating for awhile. It's not critically damped.
rwguinn
Penultimate Amazing
Just from the nature of the beast (molecular structure,whatever)--internal friction in the crystal structure of the material gives welded steel is about 2.5% damping.
Bolted/riveted, around 4-5%, depending on how far/where/how well...
Free fall? The 260+ columns are still between upper A and lower B. Try my simple model test http://heiwaco.tripod.com/nist1.htm#6 .
Does the water tank, A, (representing the upper block) suddenly drop free fall?
You have not read my article! There, as an example, the upper block A (rigid/stiff) free falls over 3.7 m and is assumed impacting at infinite time (like a billiard ball) with the lower structure B. But B is not another billiard ball. It is a spring or actually more like a wall on a billiard table. Thus ball A (dynamic load) bounces against billiard table wall B ... and bounces back ... somewhere.
The static load of wall B before impact was 0. During impact it was higher but after impact it is 0 again.
When you play billiards a ball A hitting the table wall B does not globally collapse the whole billiard saloon, n'est pas?
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Vous etes fous, n'est pas?
THe lower structure is not designed to accommodate the collapsing load of the upper structure. It is not strong enough to stand and hence allow the upper part to "bounce back".
Really, did you learn structures (cough) playing pool or something?
peteweaver
Graduate Poster
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- Mar 1, 2007
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Heiwa, the upper block weighed more than a tad heavier than a billiard ball.
The downward momentum was such that it kept going.
The downward momentum was such that it kept going.
X
Slide Rulez 4 Life
- Joined
- Oct 17, 2007
- Messages
- 4,127
Who said anything about freefall?
All I said was that given the structural damage and effects of heat, the steel will eventuall fail.
When that happens, the upper part is coming down. I don't care how many desks are underneath it, it's not going to stop until it hits something very solid. Like the Earth.
It's fairly simple. The upper part weighs a certain amount. This weight is supported by the framework beneath it. When the framework is heated, it loses it's strength (being hit by heavy things doesn't help much). When this happens, the framework no longer has the strength to support the load.
At this point, the load is going to fall. And if it's a heavy enough load, the building is not going to be able to stop it.
I've bolded the part you seem to be having difficulty with.
No, the load will not fall down or impact something suddenly! The load compressing the framework will move slowly downwards and every centimeter of compression is due to gravity and thus consumed as compression. No sudden free falls, no impacts! That's what my model test is all about. Easy to see and understand. One reason being buckling stress > yield stress at increased temperatures, when yield starts. The column will only yield (compress), not buckle.
But you do not see anything like that of any videos of the WTC1 collapse. There the 'load' (the upper block) breaks up even before anything happens at the initiation zone and the lower block below.
Only fools believe that all 280+ columns in the initiation zone 'disappeared' simultaneosuly allowing upper block A to free fall on lower block B.
But if you believe that you can invent all sorts of theories like Bazant and Seffen but then you have also to assume that the upper block is rigid/stiff, etc.
A lot of fools also believe that the upper block is rigid/stiff while the lower block is just the opposite.
Most amazing is that many fools believe that the upper block floated on an 'intermediate zone' of crushed material during the 'gravity' collapses, i.e. from top:
upper block (rigid/stiff dropping down, weighs something), intermediate zone (broken material in 1000's pieces being compressed), 'crush front' (where everything is crushed only due to gravity, like a meat grinder), intact structure (very weak structure ready to get crushed).
funk de fino
Dreaming of unicorns
As long as Heiwa the welder is comparing the Twin Towers to children using a bed as a trampoline you are all wasting your time even more than he has wasted his.
Kirkmanesque.......
Kirkmanesque.......
You really do not believe that, are you? Collapsing load (of the upper structure)! I like the invention of this new CD method.
Just initiate a collapsing load (of an upper structure) ... and everything collapses.
Is your 'collapsing load' equivalent to the Nist 'release of potential energy above'?
And what has this to to with the strain energy of the structure below?
The lower structure is not designed to accommodate the collapsing load of the upper structure. So what was the lower structure designed to accommodate? Only the weight of the upper structure? Yes- fantastic! And the safety factor? 3 - 5! Good.
So the 'collapsing load' of the upper structure exceeded that? Halleluja. This is actually the message of this new sect. Well, you can believe whatever.
[sigh]
There are so many basic errors in your argument that it is hard to know where to begin. What I find especially disappointing is that no qualified structural engineer would ever make these mistakes.
Let's start at the beginning, since Structures 1.1 seems to have strangely passed you by.
Buildings are designed for credible loads, principally as set out in building regulations/codes/standards plus any additional site or project specific issues. These will include a safety margin which will vary by element and load but is nevertheless finite.
Perhaps more importantly, the elements of such a design will be sized in order to meet their indvidual loading capacity. So, for example, a floor will not necessarily be able to carry or transmit a vertical loading such as might be expected of a column.
This is particularly relevant to the collapse of the WTC becauseof two things. Firstly, the imposed load arising from the collapse of the upper portion onto the lower part is going to clearly - and massively - exceed the design capacity of the surviving structure. There can be absolutely no doubt about this, given the sheer mass of material. Secondly, even those elements which are still standing will be subject to wildly varying moments, load paths, as the whole thing starts to go which will result in further destabilisation.
You might like to suggest that this is opinion, but you are wrong. This is fact. This is what really happens to buildings.
Now, what you also seem to be suggesting is that the collapse pattern would be gradual. The reasons for this seem to be unclear, and you have failed to provide a technical analysis of sufficient depth to support such a proposition, however if I can make some general comments.
The structure of the towers was essentially composite in nature. Contrary to your oft-stated views on this site, neither the envelop of the core were capable of surviving to their full height as free standing structures but rather relied on the bracing action of the floors and the hat trusses.
Again this is not a matter of opinion, but is fact. Saying that it is a birdcage will not make it so, and you need to grasp this reality with both hands if you are to be taken seriously.
Secondly there is absolutely no doubt that steel can, and does, fail in fire conditions. This is recognised in the authoritive sources set out in my OP and includes, by way of example, building regulations and fire testing data that is beyond reproach.
Evidence, in particular photographic material, strongly supports the NIST proposition that failure of the trussed girder beams lead to deflection of the external envelop to the point of failure. Once loadbearing capacity was exceeded (or rather dropped to the point of failure) then collapse was unavoidable.
You seem to be assuming a gradual plastic collapse, however you have wholly failed to substantiate this. In comparison, experience and study of other buildings tells us that major structural failure is usually very rapid as the transfer of loads from the failed members results in overload and progressive failure of the adjacent elements.
Again, this is not a matter of opinion. This is accepted fact across the engineering and architectural communities.
I note in passing that you have also failed to respond to the Ronan Point reference which unfortunately lends the lie to your assertion that a rapid, progressive, elemental collapse is physically impossible.
Likewise you have sought to claim that there is no such thing as a structural engineer, which is patently untrue, and ignored my link to the IStructE. If you do look at their site, I suggest you note the number of members they have and qualifications required for entry.
Against this background I have to ask what you think you're achieving here. Your paper has been torn to shreds by a number of posters, and you have been wholly unable to respond with meaningful analysis. Not a single member of the Truth Movement, bar Terry, has supported your incredible (litterally) arguments. Instead you respond with evasion and occasional hyperbole.
Why do you persist with this madness?
Dave Rogers
Bandaged ice that stampedes inexpensively through
There's your problem, right there. The problem is that buckling was observed, therefore a theory based on the assumption that it can't happen is an unrealistic one.
Three questions for you, Heiwa:
(1) What were the temperatures of all the columns that failed?
(2) What were the yield stresses for each of those columns?
(3) What were the buckling stresses for each of those columns?
You can't actually answer any of those questions, I suspect. Without those answers, your entire analysis is yet another Unevaluated Inequality Fallacy.
Dave
You forgot to clarify the difference between the static load (weight) of a non-rigid block above and the 'collapse load' of the same block, non-rigid of course above.
Is the 'collapse load' some dynamic load? Free fall? Of what? A non-rigid block above? Why would it free fall? All the 260+ or 280+ support columns fail completely simultaneously? Any evidence for that? Or progressively? Completely? How? Buckle? Buckle bend, buckle twist, buckle compress?
I haven't seen any buckled columns of any kind from the so called initiation zones. So how could a 'collapse load' be imposed? A hammer hitting it? Where did it come from?
And evidently the perimeter wall columns assembly and the core columns assembly could could stand by themselves without any floors hanging on them. Basic! Reason for that? Well the stresses in the assemblies are then <5% of yield and only caused by their own weights (no floors adding any loads) and the assemblies are well supported by horizontal spandrels and beams. Add the floors and the supporting structure (the columns) are stressed <30% of yield. Such structures do not globally collapse due to some local failures due to e.g. heat.
Madness is just to accept all nonsense suggested by FEMA, NIST, Bazant, Seffen & Co. Luckily NIST has abandoned the 'hammer hit' theory but unfortunately suggests something else - floors dropping down? 700 bolted connections/floor suddenly, simultaneously or progressively sheared off.
But I haven't seen any evidence for that either. What I see on all videos is the upper block of WTC1 (not heated at all but full of smoke from the fire below) breaking up before any collapse below even starts. Madness to ignore such obvious observations.
Belz...
Fiend God
Why not ? How much of that force do you think B can handle ? Remember, A isn't falling by 12 pixels, in reality.