WTC: A Question about joints in the verticle beams

[BigAl]

Someone just asked me "where are the 1300 ft long beams on the pile if something didn't cut them during the collapse?"

I know that man-made explosives weren't used on 9/11 but I don't have a clear idea how those beams came apart, either. I recall that during construction, the beams were bolted together as they were lifted into place. Were they welded afterwards? In either case, were these joints where beams came apart, due to off-axis loads during the collapse or did they just torque off at random lengths?

I've been in a materials lab when steel was tested to destruction. I have no problem believing that cascading bolt failures explains the "pop pop pop " that twoofers cite as evidence of man-made explosives.

 

[Gravy]

The columns were shipped from the foundries and fabricators in lengths that would fit on trucks, mostly 30-40 feet. The exterior columns were bolted together and the core columns were welded. They mostly separated at those connections - their weakest points – as can be seen in a few thousand photographs.

 

[defaultdotxbe]

additionally the core was not designed to withstand any (or withstand very little) horizontal load, so it couldnt stand on its own (as many truthers claim it shoudl have) plus it sustained an unknown amount of damage as half a million tons of skyscraper collapsed around it

 

[Architect]

From a professional perspective, Gravy's description is exactly what we'd expect.

 

[The Almond]

Someone just asked me "where are the 1300 ft long beams on the pile if something didn't cut them during the collapse?"

I was once asked this exact question on another forum. My response was, "How does a truck carrying a 1300 foot column make a left turn?" Everything that goes to a site is carried there in standard flat bed trucks and assembled on site. The truther in question suggested that they simply carried the raw materials to the site and pressed a 1300 foot beam, then erected it. Were the stundies invented at the time, that little jewel would have taken the cake.

 

[BenBurch]

defaultdotxbe, You can actually see in some video the core columns standing momentarily after the walls and floors have fallen away, and then succumbing to that very lack of ability to handle lateral loads.

The Almond, You know I can just barely imagine a way to do continuous casting on site in which you have your casting equipment start at the bottom and rise to the top while being fed raw materials hoisted from below. NuCor has been very successful at continuous casting operations. I just can't imagine why you would WANT to. And in any case we have many photos of the construction.

 

[gumboot]

I was once asked this exact question on another forum. My response was, "How does a truck carrying a 1300 foot column make a left turn?" Everything that goes to a site is carried there in standard flat bed trucks and assembled on site. The truther in question suggested that they simply carried the raw materials to the site and pressed a 1300 foot beam, then erected it. Were the stundies invented at the time, that little jewel would have taken the cake.

I feel sorry for the poor construction worker who had to hold it steady while the concrete set.

-Gumboot

 

[GregoryUrich]

additionally the core was not designed to withstand any (or withstand very little) horizontal load, so it couldnt stand on its own (as many truthers claim it shoudl have) plus it sustained an unknown amount of damage as half a million tons of skyscraper collapsed around it

This is a completely unbased claim. All of the horizontal beams in the core acted to some extent as Vierendeel trusses. Withstand high winds, maybe not. Stand on it's own most probably.

 

[e^n]

This is a completely unbased claim. All of the horizontal beams in the core acted to some extent as Vierendeel trusses. Withstand high winds, maybe not. Stand on it's own most probably.

I was under the impression that the core columns to beam connections were very simple and not designed to work as any sort of moment frame. I am no engineer but it seems unlikely such a huge and slender structure could survive without any sort of diagonal or moment bracing. Perhaps in a perfect world but you seem to be implying they would stand 'in real life' as it were?

 

[BenBurch]

This is a completely unbased claim. All of the horizontal beams in the core acted to some extent as Vierendeel trusses. Withstand high winds, maybe not. Stand on it's own most probably.

My understanding is that it was extensively braced during construction precisely because it could not take lateral loads well without the walls and floor.

 

[Newtons Bit]

This is a completely unbased claim. All of the horizontal beams in the core acted to some extent as Vierendeel trusses. Withstand high winds, maybe not. Stand on it's own most probably.

They won't, Greg. The trusses that connect to the columns are just pinned connections. They won't act as a frame. Anything more than the slightest breeze or eccentric loading would cause it to topple.

 

[defaultdotxbe]

This is a completely unbased claim.

The dense array of columns along the building perimeter was to resist the lateral load due to hurricane force-force winds, while also sharing the gravity loads about equally with the core columns.

The floors supported their own weight, along with live loads, provided lateral stability to the exterior wals and distributed wind loads equally among exterior walls.

In the framed-tube concept, the exterior frame system resists the force of the wind.

The building core, generally designed to be part of the vertical gravity load-carrying system of the structure, need not be part of the lateral load-carrying system of the structure. In this case, the structural engineer may have preferred the use of partition walls rather than structural walls in the core area to reduce building weight. In the case of the WTC towers, the core had 2 hour fire-rated, gypsum partition walls with little structural integrity, and the core framing was required to carry only gravity loads.

pay attention to that one ^

The WTC floor system was essential to the stability of the building as a whole since it provided lateral stability to the columns and diaphragm action to distribute wind loads to the columns of the frame-tube system.

http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf

 

[Tony Szamboti]

This is a completely unbased claim. All of the horizontal beams in the core acted to some extent as Vierendeel trusses. Withstand high winds, maybe not. Stand on it's own most probably.

The welds would have maintained most of the moment of inertia of the columns since they were on the outside. The weld planes would thus have had nearly the same bending strength as the column itself. This would have allowed the central core to be self supporting.

However, if their welds did not have the complete cross section of the columns in the core then they would not have maintained the same resistance to shear at the weld planes.

Where would shear forces have come from to break the columns at their weld planes?

 

[beachnut]

The welds would have maintained most of the moment of inertia of the columns since they were on the outside. The weld planes would thus have had nearly the same bending strength as the column itself. This would have allowed the central core to be self supporting.

However, if their welds did not have the complete cross section of the columns in the core then they would not have maintained the same resistance to shear at the weld planes.

Where would shear forces have come from to break the columns at their weld planes?

The core could not stand on it's own. No lateral strength. This is your failure, to understand the WTC. The shell was the lateral load, the core the gravity load, the floors connect them.

The central core would fall in a slight breeze.

I will define the slight breeze, and I have lived in OKC.

Next you 9/11 truth "experts" will be saying the floors could stand on their own. The key to the whole thing, and you have no clue. Just a real bad paper with false information. 600 mph, real stupid!

This post will be my last here on the subject.

And I was hoping 9/11!

 

[Tony Szamboti]

The core could not stand on it's own. No lateral strength. This is your failure, to understand the WTC. The shell was the lateral load, the core the gravity load, the floors connect them.

The central core would fall in a slight breeze.

I will define the slight breeze, and I have lived in OKC.

Next you 9/11 truth "experts" will be saying the floors could stand on their own. The key to the whole thing, and you have no clue. Just a real bad paper with false information. 600 mph, real stupid!

And I was hoping 9/11!

It is you who obviously doesn't know what he is talking about. Do you know anything about antenna tower design, both self supporting and guyed? You probably don't even know what the term moment of inertia means.

You are a joke Beachnut and a real nuisance.

 

[Gravy]

The welds would have maintained most of the moment of inertia of the columns since they were on the outside. The weld planes would thus have had nearly the same bending strength as the column itself. This would have allowed the central core to be self supporting.

However, if their welds did not have the complete cross section of the columns in the core then they would not have maintained the same resistance to shear at the weld planes.

How could relatively superficial welds have the nearly same bending strength as the columns? Am I missing something?

 

[Architect]

DO Truthers know nothing about structural design?!?!?!

 

[GregoryUrich]

How could relatively superficial welds have the nearly same bending strength as the columns? Am I missing something?

Check out Major Tom's site for pictures of the steel at GZ. If I remember correctly, most horizontal members are broken not at the joints, but somewhere in the element. Look at the columns, I think most have portions of horizontal members still connected.

 

[Gravy]

Check out Major Tom's site for pictures of the steel at GZ. If I remember correctly, most horizontal members are broken not at the joints, but somewhere in the element. Look at the columns, I think most have portions of horizontal members still connected.

We're just talking about the column joints, I believe.

 

[Newtons Bit]

The welds would have maintained most of the moment of inertia of the columns since they were on the outside. The weld planes would thus have had nearly the same bending strength as the column itself. This would have allowed the central core to be self supporting.

However, if their welds did not have the complete cross section of the columns in the core then they would not have maintained the same resistance to shear at the weld planes.

Where would shear forces have come from to break the columns at their weld planes?

If I had the laughing dog picture, I'd be using it, you clearly have no clue.

1) No one measures a weld by a moment of inertia, we use the elastic section modulus (typically referred to as s, measured by in^3). This is because it's pointless to calculate the moment of inertia, since you never calculate the stiffness of a weld.

For the welds to "maintain most of the moment of inertia of the columns", they would need to be the same length and width as the column, as well as the same THICKNESS. Are you trying to tell me that they put in full-penetration welds that are over 2" thick?

2) No one would ever make a column splice in a gravity column that would develop the full strength of the column. In the 60's and 70's, there wasn't even any imperative to develop the strength of the column in the weld, just be strong enough to resist the forces applied to it.

The splices only need to be strong enough to resist the minor bending moments in the columns due to eccentric loads and minor p-delta affects and to stand up during construction. This isn't much.

In modern construction, the only time when an engineer would use a weld that would develop the full strength of a column is in the lateral system that is specifically designed to resist seismic forces (R>3). Other than that, the engineer would only design the weld to resist the forces that it would reasonably see (rarely the strength of the column).