I didn't BUT
mea a little bit
culpa.
I have for some time been trying to persuade Sander to approach the analysis starting from known facts rather than from speculations about unknowns and probably unknowables.
I wanted to make the points of known fact:
1) EPH fell;
2) Therefore Col 79 and related stuff holding up EPH must have failed
3) Therefore Col 79 must have bent buckled twisted corkscrewed or otherwise stopped being a straight vertical load carrying column.
Sander had been arguing for Euler buckling so I followed his lead and used Euler buckling as the preferred one to discuss because he was apparently comfortable with the idea. My bad - should have left it generic "buckling" but....
...so I said this:
..and Sander overlooked the hint in "I have said and asked for rebuttal of"..Too subtle.
I'll stick with "Col 79 failed by some sort of buckling" - it makes zero difference to what I was saying which famous name we attach to the buckling.
Ozzie,
Not accurate.
If something above 79 line comes down.. 79 has not get out of the way. You use the term "fail" But really what does that mean? Your list of fail is incomplete.
I don't think a buckled column web crippled and or flange crippled or even pretzled or twisted would produce the drop of the EPH we see. I could be wrong.
Obviously 79 line failed to hold up the EPH
What also could fall (pun intended) under the fail category is if a low down 2 story column was displaced ie pushed out of the way... ya know the truck plowing into it (didn't happen) .. or pulled out of the way. Presumably the columns above the displaced column would then have no support and drop like a lead sinker and the line has failed and what it supports drops
We need to consider the likelihood of one of the columns below 79 fl 13 buckling. These were over 1,100# / ft monsters... I am almost 100% certain that none of the saw web/flange crippling etc. The flange at flr 13 was almost 5" thick and the web 3". I am certain the plates were thicker lower down.
We can consider perhaps... multi- column buckling... ie consider a stack of columns as one and buckling could be any place in the stack and that could be the column to column joint shearing. The joint was much less robust the cross section of the column. But for that to happen it would likely have to be leveraged which is how the spire columns parted neatly into 36' segments. Fine. But the were pretty much "free standing" and swaying in the breeze. How do we get the 79 line of columns to sway?
So could the collapsing single floor pull the a column of that monster section laterally and shear the connection in the process such that the one above was free to drop straight down? Who knows? I don't think so.
I don't think col 79 line buckled because I don't see where the forces came from
I don't think col 79 buckled at flr 13 because again there were no new forces to cripple that critter
I don't think the girder would cause buckling if it walked OFF the seat. I don't think the girder could push it south.
I am certain there was no Euler buckling because the column length would have to be 271' to exceed the SR of 150.
I am left with a column down low in the line moving laterally causing the connection to the column above it to shear free for the line of 79s above to drop.
Those are the only kinds of column fails which make any sense in the real world.
If you can suggest another... please do. What NIST shows in the pretty picture seems a fantasy.
Of course it would have been handy if NIST pulled those #79 columns from the debris. They were unique and not hard to identify without stickers or painted numbers. And kid can figure out which were the 14WF7320s with 2" welded plates on each set of flanges look like.
It's also highly unlikely (are you there Seymour Butz) that a girder or all of the steel framed into one floor location could cause that monster to buckle or translate to mis align it with one above or below.. these columns had dimensions of 26x22 and weighed 1,100#/ft. Isn't it hard to imagine that a 4" slab with some rebar could move that monster enough to displace it?
My conclusion is that some very large lateral force likely PUSHED not pulled 79 causing the misalignment the FAILure of the entire line. It was a heavy member framed INTO column 79 somewhere below 13.
Does this make sense?
