The 9/11 Forum

I was reading today from the Karl Koch III book Men of Steel: The Story of the Family that Built the World Trade Center where on page 337 is a modification not found in the NIST report... to my knowledge.

Wherever they could, they [the Port Authority] threw us extra work. The Fuji Bank, which would be occupying floors 79 through 82, wanted to install a 10,000-pound safe. It was too heavy to put in without extra load-bearing support, so we welded plates onto both sides of columns in the core, all the way down to the basement. We also were given extra work installing dampers....

Searching for more, I did find mention of this by Shyam Sunder in a public question/answer session here:
http://www.nist.gov/el/disasterstudies/wtc/upload/Public-Transcript-021204-Final1_withlinks.pdf
From that:

Elizabeth Madsen: Good afternoon. My name is Elizabeth Madsen. My husband Bob was in
Tower Two on the – his office was on 96. He was at Fiduciary Trust Company. I just wonder – I
know that both towers had considerable financial institutions in them. All of those financial institutions had safes, and those safes had to be reinforced for many floors below them with extra concrete. Do they have anything if one of those let loose, did they – did that have anything to do with some of those towers, either one of them, collapsing? I’ve not read anything about that.
Dr. Sunder: Thank you for your question. As we are building our models, we are reviewing the actual modifications that were made to the buildings after they were initially designed. And we have come up with three or four significant modifications, one of which was when Fuji Bank wanted to install a safe. I believe it was in Tower Two. I may be wrong, but it was high up in the building, and was supposed to be a 10,000 pound safe. And they did strengthen columns that supported the safe, and the strengthening went for 30 or 40 stories below where the safe was to be kept. So I do know that there was reinforcement done for that one example.
E. Madsen: If that 10,000 pound vault let go, could that have pulled the towers with them, or helped to?
Dr. Sunder: My sense is, probably a 10,000 – remember, there were 200,000 tons of steel in the building.
E. Madsen: Yes.
Dr Sunder: So the 10,000 pounds is important when it comes to a single floor, but when it comes to a collection of floors, 10, 20, 30 floors, 10,000 becomes a small fraction of the total load. But it is something that is part of our model, and we will include it as we analyze the collapse.
E. Madsen: Thank you.
Dr. Hill: Okay, thank you all for your questions. Let me review what’s going to take place for the
rest of the afternoon.

Sadly we don't know what floor the safe was on, but we do know that on floor 81 there was more than one reinforcement done to two-way trusses for UPS batteries.


NCSTAR 1-1C also another reinforcement from 1991

I think the reinforcements were done in the NE corner where the UAL175 engine tore through, as evidenced by volatile fire centered there.


NCSTAR 1-5F -- revised floor plan provided by building occupant


NCSTAR 1-5F

I found it suspicious that the 1971 (?) structural reinforcement was not included in the NIST report.

The question is how would the concentrated load be distributed to the structure. The floors were designed to support a uniform live load of 58#/SF and a relatively small safe weighing 5 tons would far exceed the design capacity of the floor. This would require reinforcing the floor to be able to support that load. One can't place a column beneath it because the column would bear and be and even more concentrated load on a similar slab below.

The engineers designed a stronger and heavier slab in the region of the safe. But the this of course would then transfer this additional load to the beams (reinforced) and columns which supported the slab's loads.

If, for example, a single beam was designed to support the 5 ton load it would then be spanning between two columns which would each see an additional 2.5 tons. If 2 beams were supporting the load, each end would see an additional 1.25 tons.

So what WAS the original design load or the floor beams (trusses) on a typical floor and how much would the safe add to this? But more important perhaps is what was the approach to reinforcing the columns which would see the additional load.

If the load was applied by two trusses separated by 80" it would add load to perhaps a single core column and one or two of the facade assemblies. Lets look at how much floor load these were carrying on about the 81st floor. there were 29 floors above it and the roof... let's call it 30 floors which included the mech floors at 108-109. The area supported by the facade truss would be 120" wide (80+20+20) by half the span distance. Let assume the long span opposite the core.. so it would be 30' 10'x30' = 300 SF x 58# LL = 1,740# and the weight of the slab 300 x 100# x .33 (slab thickness) = 9,900# Total live and dead load = 1,740+9900 = 11,640# Then multiple this by 28 tenant floors = 325,920# plus 2 mech floor loads at 2x the tenant floor (assumed) = 23,280.... = 22,280+325,920 = 349,200# are the floor loads supported by the columns connected to the two floor trusses (or reinforced beams). Add in the weight of the columns themselves, perhaps some of weight of the hat truss... Let's call it 400,000 #. Now consider what percentage increase half the 10,000# safe adds... 5,000/400,000 = this is 1.25% load increase. Now consider that the facade were part of a vierendeel truss structural membrane which distributed the axial loads to via the spandrels to throughout the membrane.

This is well within the reserve strength (factor of safety) of the facade and core columns and would require little if any column reinforcement except some local web stiffening.

But if the safe DID collapse the floor upon which it rested it likely WOULD crash right down through every floor below it like a wrecking ball and cut a hole of destruction right to the lobby... Perhaps the mech floor below was strong enough to arrest this. Hard to know. This could not collapse the tower... but it would be a helluva repair project.

Fls 81 and 82 play a central role in collapse initiation. The pull-in of the east face occur along the 81, 82nd fl spandrels (green lines).




These are the floor slabs that undergo the famous floor sagging upon which the NIST explanation of the collapse depends.


The NIST did not notice the pull-in of a portion of the north wall at the same time shown below:




The north wall pull-in, ignored by the NIST, occurs across from the 1000 row core columns at the same time as the east wall pull-in.

For a person that doesn't ignore this information, it seems from the geometry of inward bowing and pull-in that the 1000 row core columns were dropping to cause the inward bowing, not the sagging of the long span trusses as the NIST claims.


Once again, we see that people don't seem to care what was actually observed when dreaming up a collapse initiation model for WTC2.



In general, we have found that people don't seem to care about observable evidence at all.

Another indication that the east side of the core failed first, rather than the east wall as the NIST claims, is in the kink along the roofline a few moments later:





Concave roofline deformation and the pull-in of the north wall as the east wall is also pulled inward indicate the initial failure and drop was through the east side of the core, not from a failure of the east wall as the NIST claims.

The 2 observables shown above are consistent with core column failure along the row of spices a few feet above the 80th floor slab.

In fact, all observables I have seen are consistent with the upper 1000 row of core columns falling out of their splices (or "saddles") between the 80th and 81st floor slabs. So any information about the 80th to 82nd floor slabs and the interconnections between core columns in this region, like in the OP, is important and appreciated.

.............................

Here is the inward bowing starting to form.



The MER panels form an extra-rigid band around the building, and it was just above this rigid band that the inward bowing (IB) forms. The most extreme portion of the IB are the 81st and 82nd floor slabs.



......


There is strong interconnected belt around the MER floors shown as the green pattern on the left.

The pull-in of the east wall occurs along the 81, 82nd floor, which are the 2 spandrels directly above the green belt (with the exception of 2 panels which remained attached from just above the green belt. The wall breaks along the upper edge of the green belt and tucks inside the lower wall.

The clean tuck inside can be seen as further indication that the east side of the core fell before the east perimeter, pulling the whole upper sheet inward.



.................................

when was this done? just before 9/11 or way before 9/11? was it 71?

Dan can you be more specific in what you are asking?

What does *this* refer to?

Is 71 1971?... floor 71... July 1?

Tom,

Excellent work.. clearly presented... Brilliant analysis...

Question... the core columns were typically 36' tall... and their bottom was about 4' above the floor and ended 8 feet or so above 3 floors up. We can see this in the construction photos and in the debris where the bracing was attached to the beam stubs.

Do we presume the the columns from 73-75 punched through the MER floors the same 4' or so and there were MER columns which the wickdot page shows as MUCH larger and then these heavier MER punched through and were 4 feet into the 77th floor where they were reduced in cross section? The MER facade had definitely stiffer columns.. wider than at the tenant floors... and the core columns on those floors were likewise *beefed up*. So the entire MER part of the building was markedly more rigid that what was above or below them.. including the floor construction. This would obviously be a place for the structure to *fracture*... the region/boundary between the weaker and the stronger parts. And this can be related to WTC 2 very well.

WTC 2 had lost columns on the column 1001 corner of the core from the plane strike if I am not mistaken. It is not unreasonable to assume that that entire corner lost bearing connection and the columns above that corner had no support... and could drop a bit... they were being held in place from the hat truss above and their column to column connections were now in tension - not compression ...and the unaffected bracing above. It's not unreasonable if the above is true that the slight drop of the columns on that corner of the core would cause the entire corner of the floor to be pulled toward the dropping or missing corner. There was a transfer truss or girder from each of the four corners of the core to the facade which supported one side of the floors of the corner... drop the column... girder goes with it and it pulls all the trusses framed into it.

I've always had a strong suspicion that the collapses started at the big cahunas - the four corner columns of the core... those 4 supported 30% of the entire floor loads!... while the 8 columns on the short side supported 20% and the 12 on the long side supported the remaining 50% of the floor loads.

The corners were the crossing point and one of the main bearing points for the hat truss as well which has 8 main trusses 4 in each direction.

This analysis seems rather obvious... so why is NIST so blind to it? They didn't even attempt to rule it out?

I suppose we need to develop a theory for how further weakening caused the core to let got which was telegraphed by the core pulling the corner section inward. Any thoughts?

We can safely bet that the reinforced columns were on the east side because of access and apparent rentable space within the core, and not the 1001 or 1008 because of their maxed-out responsibility. So probably 902 and 1002. Koch did say columns plural.

It will be interesting to search photos of Ground Zero and scrapyards for columns with welded plates. P.S. Did everybody see the new NIST image database? Pretty much all the recent FOIA releases are on the NIST site now.

http://wtcdata.nist.gov/gallery2/v/NIST%20Materials%20and%20Data/Collected+Steel/

whoops! sorry about that. Was it 1971?

Got it... almost... what was WHAT done? with reference to those dates??? If you are referring to the omission of the 1971 structural reinforcement associated with a safe.. I suspect they considered it of little import on the failure of the frame. I would tend to agree... adding 5 tone concentrated load and some reinforcement to some columns amounts to nothing in the big picture for those structures.

What was the significance?

There was some modifications made and it should be noted. Matt, do you think the modification weakened or strengthened the structure? Do you think it would .. the Fujibank modification play a role in resisting the collapse or promoting it or neither?

Please explain.

The added support may have helped the structure during plane impact. Of course the reinforcement may have only been on floors 80 and below, only under the severed columns.

My main concern was with the history. I wanted to ask if anybody had seen this in the NIST report. No details on this matter is frustrating.

PS Check out this new WTC2 video.

Not having seen what this reinforcement was.. and assuming it was on the NE side I would guess it played no role in resisting or promoting the collapse. It's just a interesting bit of information...leading no where.