AE911 Truth's WTC7 Evaluation Computer Modelling Project

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Oystein

Senior Member
The real techno-babble is what you are mentioning here. They [NIST] can't even get ...
(Snipped commentary that is 100% off-topic and also fails completely to address what I actually communicated).

Tony, you did not understand what I posted. Or you ignored it.
I was not discussing the right and wrong of NIST's inputs and outputs.
I merely explained, to those who still have not understood (there are active posters here who evidently have not understood! And Leroy Hulsey evidently has not understood!) NIST's modelling approach, and the connections between subsequent but different models. Perhaps you have understood NIST's modelling approach and can help me help those fellow posters who have not? That would be great. However, I have a hunch that you haven't understood NIST's modelling approach yourself, as becomes evident whenever you post something from Chapter 8 when the discussion is actually about content from Chapter 10, 11 or 12.

As I have shown earlier, Hulsey for example erroneously misrepresents inputs for the Chapter 11 ANSYS model and, additionally, conflates them erroneously with inputs for the Chapter 12 LS-DYNA model. If you have understood this, I think you would be eager to inform Hulsey personally of his mistakes (have you? If not, why not?). They can be found on slides 19 to 24.
 

benthamitemetric

Senior Member
In which analysis ?
You need to be clear about that. You just stated that the results were divergent without (apparently) knowing that Dr Hulsey ran different analyses, despite him making that VERY clear in the presentation.
So which of Dr Hulsey's analyses, that you were not aware of 5 minutes ago, are you asking about now ?
The analysis in which column 79 moved 2" relative to the center of stiffness (or its original position--you choose). Is that not clear enough for you to give me the corresponding figure for the movement of A2001 relative to column 79? Please cite exactly where you got that figure from Hulsey's presentation (time stamp or slide). Thanks.
 

gerrycan

Banned
Banned
The analysis in which column 79 moved 2" relative to the center of stiffness (or its original position--you choose). Is that not clear enough for you to give me the corresponding figure for the movement of A2001 relative to column 79? Please cite exactly where you got that figure from Hulsey's presentation (time stamp or slide). Thanks.
So this is the analysis where the column moves 2" to the East, and we spoke at length about the local displacement of the connection elements being zero, and Deirdre clearly told you the displacement was Zero 10 minutes ago.
If the connection does not fail. the bolts have not broken.
you tell me how far it moved, you've been told enough times.
 

gerrycan

Banned
Banned
Maybe that's what gerrycan wants to argue. But I didn't see the figure specified in Hulsey's presentation, so I want to understand exactly how he has divined it.
MICK stated that. And i don't disagree.
If the bolts do not break, how can the girder move relative to the element it is bolted to ???
 

Oystein

Senior Member
... the statement has exactly the same weight, in fact more weight than NIST's. ...
The two statements you just made there are contradictory - at least one of them MUST be completely FALSE.
Can you please clarify, and justify your reasons?

(Hint: All orthogonal coordinate systems convey exactly the same information. Every orthogonal coordinate system can be translated losslessly into any other orthogonal coordinate system. For example, Hulsey's CoS-centered orthogonal coordinate system can be losslessly converted into a local orthogonal coordinate system centered on Col79. Another example: NIST's orthogonal coordinate system that was centered on Col79 can be losslessly converted into a local orthogonal coordinate system centered on CoS. So mathematically, neithe system is better or worse than the other. One may be more practically useful, given the problem that you want to solve. If you want to solve the question whether or not a girder end moves x inches relative to Col79 to walk off its seat, a local orthogonal coordinate system centered on Col79 is a very good, practical choice. If you want to analyse the states of torsion that the 3D structure experiences due to a global lateral force acting on the building's Center of Mass, a CoS-centered orthogonal coordinate system would be a superior choice.
Now, since Hulsey wants to assess the situation at Col79, and since he does not analys torion at all, centering his orthogonal coordinate system on CoS would be an unpractical, useless choice.
However since Hulsey in fact does NOT identify the Center of Stiffness (<- read this slowly, perhaps read it several times, let it sink in! It's an important bit to know and understand in context! Hulsey saying he is measurung relative to CoS is not the same as Hulsey actually doing that!) and instead measures either relative to the fixed ground (this assumes he does model the building as pinned to the ground, which of course he should, but it's not clear to me) or relative to Center of Thermal Expansion - which is indeed a thing different from CoS, even though Hulsey says, erroneously, that they are the same.
 

Oystein

Senior Member
He used the CoS as a datum..
No.
This is FALSE.
Hulsey did NOT use the CoS at all.
He errs about that.

Guys, you all should terminate all discussion of CoS immediately until you have taken time to review the arguments why Hulsey does in fact NOT determine, or measure from, CoS at any given time.
 

Mick West

Administrator
Staff member
Bottom line Bentham, and back to the issue - NIST's model says 6.25 West. Dr Hulsey's says almost 2" East.
The comparison is valid regardless of where and what the fixed point of reference is providing both values are taken wrt the original position of the column.
Gerry I'm very disappointed that you posted this, as it's the exact thing that has been identified as a problem days ago. Those are measurements of different things, so you cannot compare them.

This thread is going round in circles now. I suggest you take a break.
 

gerrycan

Banned
Banned
Gerry I'm very disappointed that you posted this, as it's the exact thing that has been identified as a problem days ago. Those are measurements of different things, so you cannot compare them.

This thread is going round in circles now. I suggest you take a break.
Do you think that Dr Hulsey is expressing movement in the girder wrt it's original position Mick ?

i am fine. If I need a break I will take one. Thanks.
 

deirdre

Moderator
Staff member
To clarify this point:

bentham - This is the claim from Mick that is in dispute,
"The study makes incorrect displacement comparisons. In both 2016 and 2017 Dr. Hulsey made much of a difference in the displacement at column 79 (5.5" west vs. 2" east). But he appears to be comparing the wrong values — global instead of local displacements"
Hulsey said :
at 1 hour "here are the fires at 6pm. ....
(UAF abacus model, this is the model we're talking about)...
This is the column 79 at floor 13. 1.85" to the right. that means east, it doesnt mean west. so this whole thing moved.
1:01:47 "so you can begin to see the displacements..


so then he goes on to compare his numbers (1.85 abacus, 1.92 SAP) with NISTS (5.5/6.2)
yy.JPG


This is wrong because the real comparison to NIST 5.5 (6.2) is SAP 0, Abacus 0.
SAP and Abacus do not move east in the comparison to NIST. They don't move at all.


It is a faulty comparison. The corrected comparison is still different because of Hulseys inputs and lack of modeling the fire event.







Source: https://www.youtube.com/watch?v=RYV33LKDY8k
 

Oystein

Senior Member
...
the fact remains that the column moved East by about 2" in his analysis. ...
You claim that "the fact remains that the column moved East by about 2" in his analysis" - relative to a point that itself moved from where it originated by an unknown distance in an unknown direction relative to the ground and also by unknown, but different, distance and direction relative to the point on the floor slab where it originated prior to heating. So if your (and Hulsey's) claim were correct, than this measurement from an unknown and elusive, variable origin would be foolish.

However, this is (hopefully) the lucky day on which you will find out that Hulsey did NOT, in fact, ever measure anything relative to CoS! He most likely measure relative to the fixed ground. There is an outside chance that he measured from Center of Thermal Expansion (a concept that suffers the same problem as CoS: it moves relative to the ground and relative to the point on the slab where it started out as soon structural damage occurs anywhere in the structure).
 

benthamitemetric

Senior Member
So this is the analysis where the column moves 2" to the East, and we spoke at length about the local displacement of the connection elements being zero, and Deirdre clearly told you the displacement was Zero 10 minutes ago.
If the connection does not fail. the bolts have not broken.
you tell me how far it moved, you've been told enough times.
Where does Hulsey say local displacement was exactly zero? How does this mesh with his other models where he doesn't increase the coefficient of thermal expansion and still sees movement (e.g., trapping) of A2001, but not failure?
 

Oystein

Senior Member
...If he wanted a fixed point, he could have just used the as-built location of column 79
I hope you are clear that the "as-built location of column 79" is tied to the ground, right? So as for x- and y-coordinates, you are talking about a point on the ground exactly vertically below where C79 was on the 13th floor before heating began.

So, a coordinate system that is at rest relative to the ground.
Which, I am so certain that I offered a bet of a 20-pack of beer, is what Hulsey actually did. His confused talk of the "thermal centroid" (which isn't even a thing; should be "center of thermal expansion") and "stiffness center" (which he conflates with the former, implying they are the same, which they are most empathically not) obviously had us all confused for days.

It's time to clear up the confusion: Hulsey neither determined not measured from CoS - period.
 

Oystein

Senior Member
Are you not looking at what I am posting Oystein ?I am saying that he is expressing the movement in the column wrt it's original position.
Apparantly you are not looking what you are posting, or you don't understand what you are posting.

My last post last night contained several points of clarification that I wrote for all active participants who are still confused about a few issues. I believe that includes you.

You are in fact NOT claiming that Hulsey expressed "the movement in the column wrt it's original position". You are claiming the opposite: That Hulsey expressed movement wrt to a point that itself moves wrt to the columns (i.e. the entire building's original position, i.e. the ground). You just have not understood that this is what you are claiming, because you obviously do not understand what CoS is (a variable position as material properties and topography of the structure change with heat being applied), and what it is useful for, and what it is not useful for.
 

Mick West

Administrator
Staff member
I've removed Gerry from this thread.

The point here is a very simple one. Movement of the girder relative to the column and the seat is what causes the failure of the seated connection. So the relative motion is what is important. NIST says that the connection failed in one analysis, which means that the relative motion of the girder was >6.25" in a direction perpendicular to its long axis (i.e. sideways).

They don't specify absolute position of parts, or how much the parts moved with respect to their original positions, because that's irrelevant. All that matters is that (in that particular analysis) the relative position changed.

Hulsey models of the floor don't show any relative motion, he says it all "moves together", column AND girder just moving 2" to the east from it's original position. All other connections appear to have moved "together", with the building simply expanding in an asymmetric yet smooth manner.

It that is correct, then the building could not have possibly have collapsed from fire, case closed from Hulsey, everything else is irrelevant. However it seems highly unlikely to be correct.

Hulsey however, make a comparison of NIST's 6.25" relative motion, and his own 2" absolute motion. This comparison is meaningless as you can't simply compare relative motion to absolute motion. It's also utterly pointless if his model shows ZERO relative motion. Why not just announce THAT?

Gerry continued for several pages to argue that NIST was not accurate because it was not reporting absolute positions and motions. This was irrelevant, and was explained several times to him, and yet he continued, which simply cluttered up the thread.
 

Oystein

Senior Member
Consider slide 78:

Hulsey (2017) - Page 78.jpg

It shows the entire floor diaphragm - which is the floor slab plus ???.

Suppose Hulsey's model run had resulted in actual discontinuities within the floor system - such as beams moving relative to the floor slab, or floor slab being crushed where the slab to one side of the crush zone moves more in the east-west direction than the slab on the other side.

Would this figure show such discontinuities? How?
I think this sort of graphic simply is incapable of showing whether, or where, discontinuities between slab and steel frame arise, for this would mean that within one and the same pixel, there are two distinct travel distances to be mapped: One for the concrete, one for the steel. Which one does the Figure in fact show?

I think it should be clear that this sort of map can only map the floor slab. Not the steel.
So either we cannot determine at all from this Figure if and how any internal column, girder or beam moved; or the map is ambiguous, such that we can only guess what it perhaps shows.

The most benign assumptiom here is that this Figure does not inform us about the movement of the beams and girders at all.
 

deirdre

Moderator
Staff member
(which isn't even a thing; should be "center of thermal expansion") and "stiffness center" (which he conflates with the former, implying they are the same, which they are most empathically not)
this is probably irrelevant but I'd like to sort it out for myself. In a regular building with no fires.. the "center of thermal expansion" would be the same as the CoS, right? Because say we are in a heat wave (75F vs 98F outside temperature), then the building would expand thermally from the CoS. ??

obviously in a fire situation the pieces would expand where the fire is.
 

Mick West

Administrator
Staff member
this is probably irrelevant but I'd like to sort it out for myself. In a regular building with no fires.. the "center of thermal expansion" would be the same as the CoS, right? Because say we are in a heat wave (75F vs 98F outside temperature), then the building would expand thermally from the CoS. ??
I presume Hulsey was referring to the "Thermal center":
https://en.wikipedia.org/wiki/Thermal_center
However:
Since it's not solid, nor does it have homogenous thermal properties (concret not the same as steel), nor was there a single thermal variation applied to the whole body, then I don't think that a thermal centroid applies to the building, and probably not even just under hot day conditions. And probably it's not at the CoS.

(I'm not clear what "Isostatically constrained" means in this context, the link goes to "statically indeterminate", so I think it means something like all the connections are elastic, like spring systems. Since there is possible/likely plastic deformation (of steel) and fracturing (of concrete) then I don't think the system is isostatically constrained either)

I suspect Hulsey was simply referring to absolute displacement (i.e. relative to the ground) then when talking about areas with zero displacement he used the term "thermal centroid" and then "center of stiffness" as they were probably round about there too. However it's not really clear. Nor is it particularly relevant how the building expanded if there were not local relative movements (like of a girder relative to the column it was attached to)
 

Mick West

Administrator
Staff member
well it's relevant to him because he is, in all likelihood, trying to prove CD. :)
Not really, expand or not expand, expand left, expand right, it makes no difference if there is JUST this smooth expansion.
And I don't think it's fair to say he's trying to prove CD. I'd reserve judgement on that.
 

Oystein

Senior Member
this is probably irrelevant but I'd like to sort it out for myself. In a regular building with no fires.. the "center of thermal expansion" would be the same as the CoS, right? Because say we are in a heat wave (75F vs 98F outside temperature), then the building would expand thermally from the CoS. ??

obviously in a fire situation the pieces would expand where the fire is.
No. CoS and CoTE are distinct and different concepts.

The building would expand around the Center of Thermal Expansion when exposed to thermal loading - hence the word. The best way to think of CoTE is probably to picture the structure floating freely in space: It expands to all directions, like a balloon when you inflate it, and somewhere there is a center that doesn't go any direction. The structure experiences no total angular momentum here.

The Center of Stiffness is a concept that looks at torsion in a pinned structure: Suppose the ground underneath the building accelerates laterally due to a seismic event. This is a lateral force that acts on all mass points equally (equal acceleration), so you can think of the force as acting on its Center of Mass. Now, most structures are not uniformly or symmetrically stiff: Let's say the left side is build relatively stiff, and the right side is built relatively elastic. Then the entire structure responds laterally to the seismic event, but the elastic side more so than the stiff side, such that the elastic side moves farther. This means: The structure actually rotates a bit - or since it is pinned to the ground, the structure experiences torsion (what's the verb for "torsion"? The action of going into torsion?). The Center of Stiffness now is the point around which the upper level that you are looking at (an upper floor, the roof...) rotates, its pivot, and you find it by subtracting the translation of that plane relative to the ground.

If the Center of Stiffness happens to be the same as the Center of Mass, then no torsion occurs. Also, if they are not the same, but the force vector, emenating from CoM, points directly at or away from CoS, not torsion occurs.


Now, combine the two concepts:
When you heat a building that is pinned to the ground, it is not free to expand (assuming that the ground remains cool and does not expand). This induces internal stress in the structure similar, but not same, to the way a lateral seismic force induces lateral, and by way of differential stiffness, torsional stress.

I think, analogous to the CoM/CoS relationship, the following is true about the CoTE/CoS relationship:
If the Center of Thermal Expansion is the same as the Center of Stiffness, then thermal expansion will not result in torsion. Otherwise, some torsion will occur.

It would, in general, be quite an amazing coincidence if CoS and CoET were the same in a complex and asymmetric structure as the WTC7 building. So Hulsey is almost certainly wrong to insinuate that the two can be used equivalently in his model.

On account of heating, whether in Hulsey's model or NIST's, or in reality, the building experiences some torsion. I think this is apparent in Hulsey's slide 77, where, on the east side, the borders between two colors run roughly north-south, and in the SW corner, they run roughly perpendicular to that (although I couldn't tell from this where the pivot point might be, i.e. the CoS). In addition, the floor expands in general, in all directions, and again, it would be difficult to tell where the center of that is, which would be the CoTE.

Hulsey (2017) - Page 77.jpg

Obviously, Hulsey's map does indicate displacement relative to something. Since deformation due to Thermal Expansion is modulated by torsion through diffential Stiffness, it would probably require a very complex mathematical analysis to disentangle CoS and CoTE, which is why I bet a 20-pack of beer that Hulsey determined, nor measured from, neither, and instead measured everything relative to the ground. And in his talk, he merely SPECULATES that the area that moves least relative to the ground is where the CoS, or the CoTE, might be found if he looked for it. It's probably not completely wrong to start looking in that region, but he is, with good reason, very vague about the precise location of that center - and goes on to invalidly conflate the two different centers.

I think he wants to direct the audience's attention to a rather trivial point: That the espanding slab moves a greater distance the farther away it is from some center. And then went on to confuse himself that measurements are actually relative to the center.

But neither the CoS, nor the CoM, nor the CoTE, are points that fixed relative to the ground as the building is heated.
 

Oystein

Senior Member
Or the column.
Well, where there is a column, there is not slab, and vice versa. So technically speaking, the Figure would be able to map both slab and columns, for they don't overlap.
If Hulsey doesn't address this explicitly, I guess we can only guess whether the map shows columns or not.
 

Mick West

Administrator
Staff member
Well, where there is a column, there is not slab, and vice versa. So technically speaking, the Figure would be able to map both slab and columns, for they don't overlap.
If Hulsey doesn't address this explicitly, I guess we can only guess whether the map shows columns or not.
They actually do overlap in that the columns fit through a hole in the slab. The beams and girders are underneath. This diagram shows a single surface with holes for elevators. Presumably it could also show holes for columns, but they would be very small. However you can tell it does not, as there's no meshing around the holes. It appears to just show a homogenous slab that either includes the columns as part of that slab, or ignores them.
 

Oystein

Senior Member
They actually do overlap in that the columns fit through a hole in the slab. The beams and girders are underneath. This diagram shows a single surface with holes for elevators. Presumably it could also show holes for columns, but they would be very small. However you can tell it does not, as there's no meshing around the holes. It appears to just show a homogenous slab that either includes the columns as part of that slab, or ignores them.
Yes, that's exactly how I see it.

ETA: The grid in slide 78 has about 33 cells between A2001 and the east wall, and the length of the beams spanning that distance is what ... 52 feet? Don't trust my memory, and I am too lazy to look it up, but that is reasonably close I think. So each cell is about 1.5 feet x 1.5 feet. That is on the order of magnitude of the cross-section of the internal columns.
Then again, the borders between two colors cut freely at any angles through the cells, so I am not sure what the relevance of the grid is.
 
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Mick West

Administrator
Staff member
Then again, the borders between two colors cut freely at any angles through the cells, so I am not sure what the relevance of the grid is.
That's a good point, it's almost like it represents an AVERAGE displacement, like it's a smoothed simplification of the various individual displacements at different nodes, and not any actual data.

Here's what's under that C79 dot. You can extract it from the PDF. Drag the slide to compare.
20170919-111428-0gyus.jpg 20170919-111437-wuy2g.jpg


20170919-111316-6x4bl.jpg 20170919-111334-losx3.jpg
 

benthamitemetric

Senior Member
Does this seems like a good visual representation of the 6.25" vs. 2" that Hulsey is making?

View attachment 29019
It does at a high level of approximation but I think the caveat is that we don't really know the full range of motion of the individual elements in either model. For example, if you look back at the actual temperature model NIST used for floor 13, you will note that they modeled the fire as coming from the south and then crossing northwest across and around column 79. Though NIST doesn't give an exact play by play of how things shifted in that time frame, one can imagine the series of very complicated, interdependent, and somewhat overlapping reactions that may have occurred, e.g., (1) girder A2002 heats up and pushes column 79 north, (2) the eastmost beams heat up and push girder A2001 west, (3) girder A2002 begins to cool, pulling column 79 south as girder A2001 heats up and pushes column 79 south, (4) the girder to the west of column 79 begins to heat up, pushing column 79 east just as girder 79 and the eastmost beams begin to cool, pulling girder A2001 back east as the girder shrinks again lengthwise. At the end of this chain, we know NIST found that girder A2001 slipped off the seat to the west, as your graphic indicates, but we do not know exactly where the column was relative to the girder in the y axis at that moment, nor do we know that the aggregate lateral movement was truly just a clean walk to the west. I think it was probably something more of a circular dance between the column and the girder that ended up with the net westward movement of the girder as being the slippage point given the heat progression (which, again, it is worth pointing out, Hulsey did not model).
 

deirdre

Moderator
Staff member
Yeah, I was ignoring the y movement of column and girder there on the NIST side,
uh oh :) that's the movement that would make the girder allegedly stick on the side plate.

your y movement is bigger than your x in the hulsey model. and the NIST model.. because the column moves a bit (which is semi-realistic) sort of confuses the issue of the relative-motion definition.

probably need to add some text that state "rough approximation of general movements", since we don't know how much NISTs moved east or north. and as @benthamitemetric stated, 'when' they moved or moved back.
 

James Ice

New Member
It's irrelevant, because it's the relative motion that's important.

Do you understand what I mean by relative motion? For two points A and B it's the change in A-B. (i.e. (A'-B') - (A-B) )
So if the column is A and the end of the girder is B, then any absolute movement of A and/or B is incorporated into the relative motion of A-B
Mick, you keep saying this site is to help people make sense of stuff that can seem confusing to non experts, but I wish you would take a bit more care to express things more clearly. Asimov, for instance, it would be great to think how he might have tried to explain what you are trying to explain here.
 

Structural Muse

New Member
Critical Issues that Dr. Hulsey fails to point out in his presentation

· All steel frame buildings are susceptible to collapse from fire. That why steel members are protected with fireproofing, and sprinkler systems are installed.

· Building 7 was poorly designed. I’m sure it met the building codes of the time, but the building had a general lack of ductility and redundancy.

· WTC 7 was heavily damaged by the collapsed of the North WTC tower. Seven of the critical exterior load bearing columns were completely severed. This, in the end, would help to accelerate the collapse of structure.

· The relative movement of girder on the bearing seat connection of column 79 is not important. Hulsey neglects the presence of the four high structural bolts connecting the girder to the column. These bolts must fail first, ripping thru the flanges of the girder and the horizontal bearing/connections plates. This whole connection t will come apart like a small bomb. Relative movement, not even a consideration.
 

Mick West

Administrator
Staff member
Mick, you keep saying this site is to help people make sense of stuff that can seem confusing to non experts, but I wish you would take a bit more care to express things more clearly. Asimov, for instance, it would be great to think how he might have tried to explain what you are trying to explain here.
Relative motion is the change in position of something (B) relative to something else (A). It's the movement of A that someone on B would observe, if he imagined he was not moving.

Let's say the reference is a train. You are on a train, you look out of the window, you see the trees flying by at 100 mph. So here the relative motion of the tree's is 100 mph backwards. But they are not actually moving.

Movement of ground = A = 0 mph,
Movement of train = B = 100 mph
Movement of ground relative to train = A-B = -100 mph

And of course the movement of the train relative to the ground is B-A = 100mph.
 

deirdre

Moderator
Staff member
Mick, you keep saying this site is to help people make sense of stuff that can seem confusing to non experts, but I wish you would take a bit more care to express things more clearly. Asimov, for instance, it would be great to think how he might have tried to explain what you are trying to explain here.
I like as an example.. you are walking on moving walkway at the airport, holding hands with your 3 year old. he let's go of your hand and runs 3 feet in front of you. Did he move 3 feet?

He moved 3 feet in relation to you. But because he and you are on a moving walkway, he probably moved 4 to 5 feet relative to his actual position in the airport.
3.jpg
 

Mick West

Administrator
Staff member
Critical Issues that Dr. Hulsey fails to point out in his presentation

· All steel frame buildings are susceptible to collapse from fire. That why steel members are protected with fireproofing, and sprinkler systems are installed.

· Building 7 was poorly designed. I’m sure it met the building codes of the time, but the building had a general lack of ductility and redundancy.

· WTC 7 was heavily damaged by the collapsed of the North WTC tower. Seven of the critical exterior load bearing columns were completely severed. This, in the end, would help to accelerate the collapse of structure.

· The relative movement of girder on the bearing seat connection of column 79 is not important. Hulsey neglects the presence of the four high structural bolts connecting the girder to the column. These bolts must fail first, ripping thru the flanges of the girder and the horizontal bearing/connections plates. This whole connection t will come apart like a small bomb. Relative movement, not even a consideration.
These are rather subjective points. This thread is getting rather long, so I'd prefer it if people focussed more on specific points about what is actually in Hulsey's study. Since it's not fully released, speculative criticism of what it does not contain is not helpful.
 

Oystein

Senior Member
· The relative movement of girder on the bearing seat connection of column 79 is not important. Hulsey neglects the presence of the four high structural bolts connecting the girder to the column. These bolts must fail first, ripping thru the flanges of the girder and the horizontal bearing/connections plates. This whole connection t will come apart like a small bomb. Relative movement, not even a consideration.
This is something I haven't given any thought before, and thus I do not remember if I read the details, or what they are.

Can you show us what the failure mode was in NIST's Chapter 11 ANSYS model that failed the lateral intergrity of that connection? Did the bolts shear, or did the girder's flange tear out, or did the seat/clip tear out,or shear? You seem to be saying that the flange tore out, causing it to lose integrity and strength.

ETA: NCSTAR 1-9, page 495:
This seems to contradict your point.
 
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James Ice

New Member
Relative motion is the change in position of something (B) relative to something else (A). It's the movement of A that someone on B would observe, if he imagined he was not moving.

Let's say the reference is a train. You are on a train, you look out of the window, you see the trees flying by at 100 mph. So here the relative motion of the tree's is 100 mph backwards. But they are not actually moving.

Movement of ground = A = 0 mph,
Movement of train = B = 100 mph
Movement of ground relative to train = A-B = -100 mph

And of course the movement of the train relative to the ground is B-A = 100mph.
I think this is great. But might I ask you attemept to put your arguments to Gerrycan in a similar way? It seems you are clear there is nothing so hard to grasp about relative motion, so why are you making out that this is such a big thing and has bearing upon Hulsey's claims?

Can you explain it to the layman?
 
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