Points 1.1 and 1.2 do not follow from point 1 and cannot be considered more than idle speculation unless supported by evidence.
The claim of the absence of peer review is unsupported, and appears to be contradicted by the publication of the paper and its addenda in a peer-reviewed journal. The quality of a paper is usually assessed based on number of cites (reflecting, generally, the importance of the paper) and on whether (and under what circumstances) its major findings are overturned (reflecting the correctness of the paper). Conclusions about the quality of a paper based on concerns other than its importance and correctness, such as the amount of time the authors spent writing it or the amount of dialog it generates in response, are unjustified. One might as well judge a paper by what typeface it's printed in.
Analysis using simplifications and approximations of the system being analyzed are not at all unusual in science. The implicit claim is that the simplifcations and approximations do not substantially affect the conclusions. The way to challenge this claim is to make a case that the simplifications and approximations do in fact invalidate the authors' conclusions. Simply pointing out that the analysis is simplified and approximate, which is clearly acknowledged by the authors and understood by the editor, peer reviewers, and every reasonable reader, is not a worthwhile point of critique. The engineering community has had, and continues to have, ample time and opportunity to publish peer-reviewed papers challenging Bazant and Zhou's assumptions, approximations, and conclusions.
The last sentence, even if it were true, is a criticism of NIST, not of Bazant and Zhou.
It is fairly well established that fires significantly increase the temperature of their surroundings. Do you demand a time vs. luminance curve when the weatherman says "it's sunny outside?" If you wish to challenge the claim that heating would occur as a result of large building fires, then provide a rationale for such a claim (as in, "this fire was different from all other fires because...[fill in the blank]").
Your assemblage of quoted phrases misstates the paper's claim. The actual claim is that "Once more than about a half of the columns in the critical floor that is heated most suffer buckling (stage 3), the weight of the upper part of the structure above this floor can no longer be supported." Most of the body of the paper shows, step by step, why global collapse must ensue from this.
It is true that they do not explain why the weight of the upper part of the structure cannot be supported by less than about half the columns. This is a technical paper in a technical journal. You should not expect it to explain or cite information that is common knowledge among its intended readership.
Have you asked any engineers about this point? Are you making the contrary claim that half the columns on a floor should be able to support the load of buildings in general, or of the WTC towers in particular?
Buckled columns retain an insignificant fraction of their load carrying capacity. Again, this is a technical paper in a technical journal. It is not necessary or expected that it will repeat basic facts that are already common knowledge among its intended readership.
Not specifying which columns buckled is among the "simplifications and assumptions" that the paper acknoweldges. To challenge this, show how which specific columns buckled would make a difference in the paper's conclusions.
Curves of temperature of steel versus strength are commonly available throughout the literature. Are you making a contrary claim that heating does not lower the yield strength, or are you just faulting them for not including more Engineering 101 information in the paper for your convenience?
If you think this point invalidates their conclusions, then provide your own numerical estimates of the columns' yield strength, and show that they falsify Bazant and Zhou's scenario.
There's that "fail to explain" basic facts again. Gee, you'd think they were writing a technical paper in a technical journal for a technical audience, rather than an introductory textbook. Oh, wait...
If they'd claimed to show an exact probability of their scenario, or to have determined the only possible failure scenario, or even to have determined the most likely possible failure scenario, then you'd have a point here. As it is, you've just pointed out that the claim they did make is completely consistent with the content of the paper.
I just heated a piece of uninsulated steel over my gas stove for a few minutes, and it became orange-hot, which shows that it reached a temperature well over 360° C. Therefore your claim that "actual tests of uninsulated steel show temperatures never exceed 360°C" is falsified.
None of the other NIST findings that you report are evidence that steel in the critical floor did not reach 800°C. Only that some of the columns they tested did not, and that the tests available to them were unable, by the nature of the test, to distinguish temperatures above 600°C.
The actual statement in the paper is this: "The heating is probably accelerated by a loss of the protective thermal insulation of steel during the initial blast." Note "probably," and that no mention is made of what portion.
Nonetheless this is indeed a point of contention. Some engineers believe that dislocation of insulation was not a significant factor, because the steel would have heated to failure anyhow, and/or because the insulation was already damaged or inadequate before the impact.
Or are you making a contrary claim that dislocation of insulation would not have occurred? If so, what protected the insulation from dislocation?
Perhaps because the temperature reached by a fire is not particularly sensitive to the amount of air flow. Even a fire in a sealed room, zero air flow, can reach 800°C. But the exhausting of smoke shows that the air flow in the WTC tower fires was greater than zero.
There's no contradiction with the observed behavior, if the fractures occurred primarily near the top floors of the "many floors" whose columns were buckling at any given time. There is no claim that the fractures themselves would occur many floors at a time.
Most of the column failures were at the welds/connections. Bazant and Zhou may not have been aware of this detail at the time, but it doesn't affect their conclusions. The plastic deformations they hypothesize would have absorbed more energy than elastic deformation followed by weld failure, so their assumption is conservative against progressive collapse.
Perhaps they felt that the causal connection between the columns fracturing and the loads supported by those columns falling down did not need to be explained to an educated audience.
Tipping is addressed in appendix II.
Actually they do consider one likely mechanism for this:
"...and the upper part possibly getting wedged inside an emptied lower part of the framed tube..."
Actually they do. "Buckling" of a column implies lateral displacement of a portion of the column. The load on a buckled column would likely result in lateral movement. Though they don't explain it explicitly, "ejected" debris is an obvious expected consequence of their scenario.
So, then, that would be one of the "simplifications" they openly acknowledge exist in their scenario. They state that "errors by a factor of two would not be surprising" but would not affect their conclusions." Can you show that inclusion of concrete pulverization in their scenario would affect their calculations by more than a factor of 2?
Not within the scope of this paper, though they do describe the general characteristics of such interactions:
"For example, the upper part of one tower is tilting as it begins to fall (see Appendix II); the distribution of impact forces among the underlying columns of the framed tube and the core, and between the columns and the floor-supporting trusses, is highly nonuniform..."
"For our purpose, we may assume that all the impact forces go into the columns and are distributed among them equally. Unlikely though such a distribution may be, it is nevertheless the most optimistic hypothesis to make because the resistance of the building to the impact is, for such a distribution, the highest. If the building is found to fail under a uniform distribution of the impact forces, it would fail under any other distribution."
If you would like to perform an analysis or simulation of exactly how all the parts of the collapsing structure would interact with each other, floor by floor, for the entire collapse, I'd be eager to see the results.
Respectfully,
Myriad
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