RFC Article on core load capacity and load distribution in WTC1

Just a quick observation as I'm reading through, in Section 6 you say "AISC
sideways inhibited" I believe you mean "AISC sidesway inhibited."

Respectfully,
Myriad
 
Myriad said:
Just a quick observation as I'm reading through, in Section 6 you say "AISC
sideways inhibited" I believe you mean "AISC sidesway inhibited."

Respectfully,
Myriad
Click to expand...

Thanks, I didn't realize that was the correct term. I thought it was a typo.
 
GregoryUrich said:
Thanks, I didn't realize that was the correct term. I thought it was a typo.
Click to expand...


Yeah, I only knew that because I stumbled over it a few months ago, in the course of the discussion of Heiwa's article. It's one of the risks of book l'arnin' -- those who learned the concepts from oral lectures might get to snicker at us a bit, but it's no matter.

I'm not sure the inclusion of the argument for a shorter effective length is a worthwhile inclusion in your paper, even as a brief aside that you correctly reject. As far as I can tell there is no rational argument for any part of the tower structures above ground level being considered sidesway inhibited in determining the effective length factors. The correct term makes this clearer, in that what is being inhibited in a sidesway inhibited connection is not just any sideways movement of the individual members, but rather horizontal (side) swaying of whole portions of the structure, or of the entire structure. Only connections anchored to the ground, or to structures built to be rigid against sidesway (e.g. by diagonal members and/or solid rigid structures like concrete walls) qualify.

Have to run -- my overall impression of the paper is that it's pretty solid; I'll try to add more meaningful criticism later.

Respectfully,
Myriad
 
With the caveat that I have not checked your calculations (which are of course the bulk of the work in the paper) I have only one other comment so far. In the Discussion section you cite assertions that the primary function of the hat truss was to support the TV antenna. But only one tower had a TV mast of significant size, and both had hat trusses.

I think you've made a good case that the hat trusses would not have transferred large amounts of load under normal static loading conditions, but the more general statement of evidence "counter-indicative of load transfer under normal loading conditions" applies only if you do not regard wind loads as included in "normal loading conditions." Perhaps you could clarify this point.

My understanding, which may be faulty in which case I welcome correction, is that the hat trusses were important in distributing wind loads. (In any case you don't appear to be challenging the claim that the hat trusses had a strong influence on load redistribution in the buildings' damaged condition post-collision, correct?)

Respectfully,
Myriad
 
Update: I haven't been able to find any reliable references for the hat trusses being important in handling wind loads, and I've been advised that initial design plans allowed for the possibilities of large antennas (of various types) on both towers. So, pretty much all the points in my previous post are falsified, and withdrawn. I apologize for the errors.

Respectfully,
Myriad
 
Thanks for your comments! I am discussing the sidesway issue with Tony and will probably change that part in accord with your criticism.
 
Newtons Bit said:
AISC is pretty clear about the definition.
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Unfortunately, I'm not able to motivate one interpretation or the other on my own. Would you be willing to write a quick blurb motivating effective length factor of 1.0 and why the sidesway monongraph doesn't apply to this case and include a nice little reference? I think I understand why, but I don't want to just rely on my interpretation. Otherwise it might end up sideways.:D
 
GregoryUrich said:
Unfortunately, I'm not able to motivate one interpretation or the other on my own. Would you be willing to write a quick blurb motivating effective length factor of 1.0 and why the sidesway monongraph doesn't apply to this case and include a nice little reference? I think I understand why, but I don't want to just rely on my interpretation. Otherwise it might end up sideways.:D
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I'm not sure you mean "motivate" there.

I'll scan a couple pages of my steel structures textbook to show you. They do a pretty good job of explaining it. As I recall, however, Tony Szamboti's position that the frames are sidesway unihibited is based on his idea that the slab braces the frame against sway. I'm not sure if this discussion would change his opinion on that.
 
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Newtons Bit said:
I'm not sure you mean "motivate" there.

I'll scan a couple pages of my steel structures textbook to show you. They do a pretty good job of explaining it. As I recall, however, Tony Szamboti's position that the frames are sidesway unihibited is based on his idea that the slab braces the frame against sway. I'm not sure if this discussion would change his opinion on that.
Click to expand...

I don't need to change Tony's opinion, but I do want to back up mine.
 
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