Can you explain this video? (An I-beam cut in half, springs apart, curved)

In summary, the video demonstrates the structural behavior of an I-beam when cut in half. As the beam is severed, it springs apart and curves due to the internal stresses that were previously balanced. This visual illustrates the concept of stored elastic energy and how structural integrity can change dramatically when a component is compromised.
  • #1
Flint1234
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A gas cutting-torch was used to split an I-beam lengthwise. When the last inch was cut, the two halves flew apart, with a great energy release. The halves are then seen to be curved where they were straight. The workman was unsurprised but the cameraman was thankful for a warning given seconds in advance.

Is this just a result of thermal expansion caused by the cutting torch? I thought most of the torch heat went with the molten iron blown away.
It was apparently cut by hand, slowly, I expect. The heat would have had time to conduct through the steel, diminishing the expansion.

Is there some technology that lets one build an iron I-beam with the flanges (flat sides) in tension? Something akin to automotive-window safety glass? I'm thinking one could cold-roll the center web lengthwise which would normally make it longer. Since it's locked to the flanges, that would put the web under compression and the flanges in tension.

You could put a LOT of energy into a spring that way and you wouldn't have to strike while the iron is hot.

Is that right? What's the roller machine called? Is there videos or literature?
Thanks.

My searches were all poisoned by steel cables used to pre-stress concrete or steel sheet cold-rolled into lightweight studs (or worst, steel cables used to pre-stress lightweight studs made by cold-rolling sheet steel)
 
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  • #2
I would guess residual stress from when the beam was manufactured.
 
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  • #3
It is simple to explain. Chinese steel is rolled to meet external dimensions at the lowest cost. No annealing or controlled cooling is done, so the stress of the last rolling and cooling remains in the beam. The web was thinnest, so it cooled and set first, then the thicker flanges cooled, contracting and compressing the web axially.
That is why I prefer to work with well-behaved Australian steel.

It is unusual to split an I-beam lengthwise, unless you are fabricating a castellated steel beam, but then you would not cut it straight, and you would not use cheap Chinese steel.
 
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  • #4
A pity the link to the video seem to have been removed.
 
  • #5
DaveC426913 said:
A pity the link to the video seem to have been removed.
The video is still there for me.
 
  • #6
Baluncore said:
The video is still there for me.
Huh. This is what I get:

1707524695510.png


Anyway, thanks for posting the video.
 

FAQ: Can you explain this video? (An I-beam cut in half, springs apart, curved)

Why does the I-beam spring apart when cut in half?

The I-beam springs apart due to the release of internal stresses that were previously balanced within the material. These stresses are often introduced during the manufacturing process, such as rolling or welding, and cutting the beam disrupts this equilibrium, causing it to deform.

What causes the internal stresses in an I-beam?

Internal stresses in an I-beam can be caused by various factors including uneven cooling after rolling or welding, mechanical loads applied during handling and transportation, or residual stresses from manufacturing processes. These stresses remain locked within the material until they are released by cutting or other means.

Is it dangerous to cut an I-beam in half?

Yes, cutting an I-beam can be dangerous if proper precautions are not taken. The sudden release of internal stresses can cause the beam to move unpredictably, potentially causing injury or damage. It is important to secure the beam properly and use appropriate cutting techniques to minimize risks.

Can the springing apart of an I-beam be predicted?

While it is difficult to predict the exact behavior of an I-beam when cut, engineers can estimate the potential deformation by analyzing the stress distribution within the beam. Advanced modeling techniques and simulations can help in understanding how the beam might react when cut.

What are the practical implications of this phenomenon in construction?

Understanding the behavior of I-beams when cut is crucial in construction and demolition. It ensures the safety of workers and the structural integrity of the remaining parts of the structure. Engineers must account for these stresses when designing modifications or dismantling structures to prevent accidents and ensure stability.

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