I recently saw this roof beam with circular holes in an airport. What is the reason to cut out those holes? Reduce weight? Make it stiff?
Muthu
Muthu
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Holes in a roof beam. What is the purpose? 8
- Thread starter edison123
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I've seen this claim before and it's always struck me odd (2nd link above)
"Better strength and stability – their crenellated design makes castellated beams more resistant to bending and deformation."
I feel it should include the words "for the weight of the material that is used."
I recall seeing it as a way to take an I-beam from the rolling mill and convert it to a deeper beam using a trapezoidal zig-zag that is shifted and then welded along the middle at the tops of the trapezoids. It left them with hexagonal openings.
The bit with circular holes is wasting material that is cutout and discarded, but they have an interesting look and reduce installed weight, so why not?
"Better strength and stability – their crenellated design makes castellated beams more resistant to bending and deformation."
I feel it should include the words "for the weight of the material that is used."
I recall seeing it as a way to take an I-beam from the rolling mill and convert it to a deeper beam using a trapezoidal zig-zag that is shifted and then welded along the middle at the tops of the trapezoids. It left them with hexagonal openings.
The bit with circular holes is wasting material that is cutout and discarded, but they have an interesting look and reduce installed weight, so why not?
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Yes, round or hexagonal cut-outs and then anti corrosion painting the cut edges is a pita cost rider. May be resulting lighter beam reduces the column sizes and easier erection offsets the costs?
Wonder how the size and spacing of cut-outs is calculated.
Muthu
Wonder how the size and spacing of cut-outs is calculated.
Muthu
It's along the neutral axis so it has to resist the shear between the upper and lower portions.
I only did direct mechanical design, not regulated and codified structural design, so I'd ensure there was sufficient shear area and then divvy it up some interesting way. Same thing happens to main spars in aircraft wings - lots of holes. I would not be surprised if the standards have more to say on the subject.
I only did direct mechanical design, not regulated and codified structural design, so I'd ensure there was sufficient shear area and then divvy it up some interesting way. Same thing happens to main spars in aircraft wings - lots of holes. I would not be surprised if the standards have more to say on the subject.
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Retrograde
Structural
3DDave said:
Not as much wastage as you might think.
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hokie
lol, yes, us sparkies ruin the aesthetics with our works. I am planning a new 50 ft wide x 500 ft workshop and might go for this castellated beams design.
Retrograde
That seems like a lot of work driving up the cost, weld distortion etc. and finished product is not gonna be pleasing to the eyes.
Muthu
lol, yes, us sparkies ruin the aesthetics with our works. I am planning a new 50 ft wide x 500 ft workshop and might go for this castellated beams design.
Retrograde
That seems like a lot of work driving up the cost, weld distortion etc. and finished product is not gonna be pleasing to the eyes.
Muthu
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They should be stiffer than the source beam, if one ignores the holes.
There's a Best Buy in Hawai'i that has them as roof beams witha parking garage on top
Edit: its a single, it's not a garage. So an elevated parking lot that sits on a roof.
There's a Best Buy in Hawai'i that has them as roof beams with
Edit: its a single, it's not a garage. So an elevated parking lot that sits on a roof.
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lexpatrie
Do these beams sit on top of the parking garage or is the parking garage sitting on top of these beams?
Muthu
Do these beams sit on top of the parking garage or is the parking garage sitting on top of these beams?
Muthu
Only of the webbing; the flanges are where the bulk of the weight was, and is.
TTFN (ta ta for now)
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IRstuff
Yes, flanges weigh 40 to 50% of total. (Metric beam 125 to 600 depth).
Assuming 70% of the web is cut, that leaves a decent 30 to 40% weight reduction.
Muthu
Yes, flanges weigh 40 to 50% of total. (Metric beam 125 to 600 depth).
Assuming 70% of the web is cut, that leaves a decent 30 to 40% weight reduction.
Muthu
The parking isn't a garage per se it's a single level on the roof.
Edison, it's not typically done that way, they cut the beam mid depth then weld it back together to make a deeper beam with the holes in the new midline. See the figure above.
Now, that photograph above, I'm not convinced that's a standard castellated beam. that looks like what you describe, straight up cut out holes.
3ddave, I think the comment is accurate, within the context of creating a larger moment of inertia (potentially larger strength as the flanges are farther from the centroid, provided shear in the web doesn't govern), and increasing the effective stiffness for the same weight (deflection)
Edison, it's not typically done that way, they cut the beam mid depth then weld it back together to make a deeper beam with the holes in the new midline. See the figure above.
Now, that photograph above, I'm not convinced that's a standard castellated beam. that looks like what you describe, straight up cut out holes.
3ddave, I think the comment is accurate, within the context of creating a larger moment of inertia (potentially larger strength as the flanges are farther from the centroid, provided shear in the web doesn't govern), and increasing the effective stiffness for the same weight (deflection)
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Thanks lex.
The ones in my photos cellular steel beams with holes cut out. I did not see any welds.
Muthu
The ones in my photos cellular steel beams with holes cut out. I did not see any welds.
Muthu
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