Challenge: Demonstrate Sagging floor Trusses Pulling in Perimeter Columns

What ozeco wrote is what I was getting at in the perimeter opposite impact tending to be in tension.
Of course in reality it is not, it may have less load than orginially though. Thus any inward bowing must be initiated directly from inward pulling rather than strictly by increased loading.

In fact as I was thinking about it, JSO's description of what is causing inward bowing is simply a rewording of NIST. In both cases inward bowing occurs where it does BECAUSE of sagging/deformed floor pan/trusses while the columns are under load. Usmani says the same thing only differing with NIST in why the floor structure has deformed.
 
What do you mean they shortened over time from heating effects?

I would think the heat WEAKENED them not shortened them. Think of it conceptually as if the columns were becoming thinner and thinner and incapable of supporting the loads on them... something like the attached cartoon... load capacity was driven away by heat

No, not thinner, called creep. Seat of pants architecture inadequate for structural fire engineering. You're as embarrasing as my crazy uncle at a friend's wedding.
Heat caused trusses to buckle and sag.
Sag caused pull in forces.
Added to compressive column forces = bending, buckling, eventual failure, at first gradually then suddenly.
 
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Ozzie's drawing is 1D and does not properly represent the load redistribution because the 3D Hat Truss moment frame. It's more likely that the hat truss evenly redistributed the loads to all remaining columns it was bearing on... including the weakest ones in the center under the antenna...which were the first to let go... probably because they were directly axially aligned with the 360 ton antenna load.

The tower did not tip toward the plane would putting the south facade in tension. Looks like nonsense and a reductionist (mis)understanding of what was happening to the loads.
 
Ozzie's drawing is 1D and does not properly represent the load redistribution because the 3D Hat Truss moment frame. It's more likely that the hat truss evenly redistributed the loads to all remaining columns it was bearing on... including the weakest ones in the center under the antenna...which were the first to let go... probably because they were directly axially aligned with the 360 ton antenna load.

The tower did not tip toward the plane would putting the south facade in tension. Looks like nonsense and a reductionist (mis)understanding of what was happening to the loads.

Posted by ozeco

......Reasons can be seen from this very simplified model. It is more extreme than Twin Towers set up BUT it illustrates the principles......

In a 3D modeling do you expect that the tower would not lean and shift center of gravity?

Of course you don't, since the upper section were observed to lean and by leaning the center of gracity is no longer directly above the core columns.
When something tilts, and is restrained from continuing to tilt by a tether on the side opposite that tilting, then that tether is in tension. If you add constraints on the sides then that tether is under less tension.
 
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What do you mean they shortened over time from heating effects?

I would think the heat WEAKENED them not shortened them. Think of it conceptually as if the columns were becoming thinner and thinner and incapable of supporting the loads on them... something like the attached cartoon... load capacity was driven away by heat

Odd that you would not know the concept of creep.

It is the slow plastic deformation of metals under stress which can be accelerated by heating.
A steel column under axial load will, when heated sufficiently, lose strength and become more plastic, if the load remains axial, and heating has increased plasticity enough, it will deform fairly evenly by bulging horizontally thus causing the total length of the column to be shorter.

What you describe is more along the lines of how concrete columns can lose strength by spalling on the column's perimeter.
 
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Ozzie's drawing is 1D and does not properly represent...
Wanna bet? :)
The main conceptual and reasoning problems you face JSander are:
1) I have put before you a principle and as a principle it is correct;
2) The next step is to apply that principle to WTC Twins;
3) You ignore the point I made and dive into detailed presumptions which support your personal pre-conception;
4) You then attempt to use your preconception to rebut my explanation of a principle;
5) You fail because my principle is correct. The real conclusion therefore should be that your presumption is wrong. (or your reasoning);
5) Your argument structure is attempting to work up from pre-decided details and that approach doesn't work. And, BTW, that is is the standard process of faulty logic routinely employed by truthers. I accept that you are not one;

Let me take one or two points and explain. (Unfortunately doing this requires moving into engineering reasoning - but a step short of needing numerical analysis) :o

(At this stage ;)) :
the load redistribution because the 3D Hat Truss moment frame1. It's more likely2 that the hat truss evenly redistributed3 the loads to all remaining columns it was bearing on4... including the weakest5 ones in the center under the antenna6...which were the first to let go7... probably because they were directly axially aligned with the 360 ton antenna load8.

1) My explanation clearly referred to the whole top structure - initially treating it as rigid then, stage two recognising flexibility. The hat truss is part of that top section structure. So what part it plays does not change what I said. Drop it out of your thinking until we or you reach the stage where you can legitimately bring it into consideration. We are not at that point. Yet.

2) Personal prejudgement which you use to support the following bit of reasoning. Both are wrong.

3) Nothing evenly redistributed AND nothing was evenly redistributed. That is the central point of my explanatory model. Which you have seen before. So step one is to accept/reason/understand why that explanatory simplified model is correct. Because it is a building block of reasoned understanding. And WTC 9/11 Real collapse needs a lot of those building blocks assembled into one explanation.

4) We are not discussing what the hat truss was bearing on. We are discussing the interface between the Top Block and the impact zone>>lower tower. Your presumption about the Hat Truss is leading you off the line of reasoning.

5) "Weakest" is an undefined concept. Irrelevant to my explanatory model. But, worse, it is not defined for WTC real 9/11. Whether or not you are right about "weakest" what are you saying is weakest? Are you talking about "weakest" applying to a single column? Several columns? The whole of the core?"

6) Yes there were columns "in the centre" which positioned them "under the antenna" BUT any inference beyond that fact is not supported at this stage of either my explanation or your implied claim.

7) I am aware of strong evidence from reliable measures that core collapsed first. That aspect is not relevant to my explanation at this stage. If you need it to build a robust claim I would accept it as a legitimate element of a reasoned claim - subject to verification if the claim relied on it AND was faced by a counter claim.

8) A very dubious assumption. BUT the key flaw is that your own claim rebuts it. You cannot have the hat truss "evenly redistributing" AND "antenna loads directly on core" in the same argument. Those two are mutually incompatible.

...The tower did not tip toward the plane would putting the south façade in tension....
Somewhat unclear to put it mildly. BUT you started your post by disagreeing with my explanation of a principle. Yuo seem to have swapped horses. At this stage my explanation has not progressed to full consideration of the real 9/11 event. And we don't have a coherent overall explanation from you. So whatever your point is it is moot.

...Looks like nonsense and a reductionist (mis)understanding of what was happening to the loads.
I take that to mean "It looks to me, JSanderO, like nonsense..etc.."

Great. We need to build your understanding. The only disappointment being that so far you have not taken my first stage explanation on board.

Meanwhile, for any other members who may be thinking 'Ozeco has posted "nonsense and a reductionist (mis)understanding"' don't get too excited. It is a long time since I made a fundamental error at this basic level of engineering. HOWEVER that only applies to what I actually post. Not what people misrepresent me as posting. ;)

And thanks to JSanderO - opportunities to work through real engineering issues are rare these days.
thumbup.gif


:D
 
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BTW...did we ever get Mr. JSanderO's technical background/education...just wondering!

I will say his posts are better than our favorite poster M_T, who remains technically clueless IMHO.

Also, Mr. Gage is coming to Denver, this coming June, I cannot wait!
 
Wanna bet? :)
The main conceptual and reasoning problems you face JSander are:
1) I have put before you a principle and as a principle it is correct;
2) The next step is to apply that principle to WTC Twins;
3) You ignore the point I made and dive into detailed presumptions which support your personal pre-conception;
4) You then attempt to use your preconception to rebut my explanation of a principle;
5) You fail because my principle is correct. The real conclusion therefore should be that your presumption is wrong. (or your reasoning);
5) Your argument structure is attempting to work up from pre-decided details and that approach doesn't work. And, BTW, that is is the standard process of faulty logic routinely employed by truthers. I accept that you are not one;

Ozzie,

Your cartoon is fine. But to me it is a simplification and does not depict the complexity of the load redistribution.

Some have said that the membrane nature of the facade enabled all the loads to be moved around the missing columns and if true... why would any load redistribute to any of the other sides? Do you think the floors of the twin towers would redistribute axial loads of the facade to the core?

I don't think any rows inside of the core perimeter would be seeing much load increase from the facade damage in any case... if any only row 500. And that lost some columns from the plane hit.

So are we to believe that the floor sagging was on the south side? All sides?

What seems to make sense to me is that the core was losing strength from heat. if the strength dropped below the service loads the floors above the plane strike zone had no axial support... and they were still connected to the hat truss and the floors from 98 to the roof. That entire "block" was not being supported by what was left of the facade... and the hat truss. But the hat truss no longer had any support from core which has lost its yield strength... so ALL the hat truss (tried) distributed all the loads to the facade.

The core connections were not designed as hangers... and so the core separated from the hat truss... and dropped into the plane crash zone.

As it did the center of the core then saw the concentrated load of the antenna which began to collapse the center of the hat truss. What was left of the floors from 98 to the roof were hanging from the inside of the facade. The buckled columns in the plane strike zone pulled the floors down and this was an inward force on the perimeter... which provided the direction to the facade as it buckled...unable to support the floors without help from the buckled core.

Color me imaginative....
 
Odd that you would not know the concept of creep.

No... I would have thought that the heat weakened columns would buckle... go out of column or separate at the splices which were unrestrained and 3' above the floor level.

Don't forget the horseshoe column(s) which all originated in the core. Those babies were severely buckled and looks like they were the last men standing with enormous loads...

Weren't there columns which were folded from so much load?

As the loads were not increasing... the columns were dropping out from heat weakening and the redistributed load shot up just at the moment of release... and a few columns were left to hold up the entire mass of 12 floors and failed.
 
Ozzie,

Your cartoon is fine. But to me it is a simplification and does not depict the complexity of the load redistribution.
Thanks. I said it was a simplification of a principle. That principle one of the building blocks to comprehend the overall WTC load redistribution..

OK you don't want to follow my explanation or discuss with me as I build up to a full explanation.

Great. Your alternate choice is build your own. And I have already cautioned about starting of with presumptive guesses as to what you want the conclusion to be.

Nothing more I can do at this stage.

Unless some other member wants to discuss how the principles build up to a coherent hypothesis. And I never said it would be either simple or easy.

Cheers.

Some parting comments:
...Some have said that the membrane nature of the facade enabled all the loads to be moved around the missing columns and if true... why would any load redistribute to any of the other sides? Do you think the floors of the twin towers would redistribute axial loads of the facade to the core?
I am not musing on what some have said. My focus has been explain for you and a couple of others - jdh and DGM for examples and any other members reading these posts - the basic principles of load re-distribution and cascading failure so we can more legitimately explore the initiation of WTC1 and 2 collapse.
 
I am not musing on what some have said. My focus has been explain for you and a couple of others - jdh and DGM for examples and any other members reading these posts - the basic principles of load re-distribution and cascading failure so we can more legitimately explore the initiation of WTC1 and 2 collapse.

Good discussion... Let me go back and try to follow your line of reasoning.
 
Evenly distributing is clearly a poor choice of words. Spank me.

How do you see the loads being redistributed?

Assume facade damage and say 4 columns in row 500 and perhaps a couple in 600 in the center...and a section of the floors between collapsed locally.

over...

We're talking wtc 1
 
So why would it be unusual for the extra weight of the aircraft and heat from the fires to cause the trusses to sag and pull the perimeter columns inward.

What am I missing ?
 
So why would it be unusual for the extra weight of the aircraft and heat from the fires to cause the trusses to sag and pull the perimeter columns inward.

What am I missing ?
The FEA or hand calculations. Are you participating?
 
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