Openings in a DOME 1

[Steel Inspector]

Hello,
I have a RC dome that have around 36 openings. these openings are located at three levels, 12 openings at each level.

my concern is that these openings will cut some of the reinforcement steel. it will cut one-third of the reinforcement at the first level ( closest to support ), and will cut half at the third level ( closest to dome tip ).

any thoughts?
also if you can sketch an approximate bending moment and shear diagrams to help me define the most critical area of the dome where failure will most likely occur.

( attached are dome architectural and structural drawings

 

[Steel Inspector]

human 909,
you got me

 

[human909]

human 909,
you got me

I like this guessing game.

Back to the original question. While it looks kinda 'ok'. I don't think anybody here has done enough analysis that they would stake their career or the life of others on it. And you don't seem to be in the position to perform the suitable assessment. You had some good advice from others above.

The best you can do is keep pushing the questions up the chain. If you don't get adequate answers then you need to either watch it get done and hold your breath that nothing happens or walk away and distance yourself from the job and the responsibility.

Being the person asking the questions nobody wants asked isn't always the best career move. In some organisation that sort of behaviour is going to get you pushed aside, in others you'll get noticed and promoted. Best not to be in organisation like the former unless you are a sheep; [URL unfurl="true"]https://engineervsheep.com/engineer/[/url]

 

[dhengr]

Steel Inspector:
It looks to me like this should really be six (6) separate arches, arched ribs at 30° intervals, starting at a tension ring at the base, the top of the walls, and going up through a compression ring at the top. That is, 12 half arch ribs starting at the tension ring and going up to a compression ring at the top. You may want to eliminate half the top ring of openings, or size and offset them in some way to allow the arch ribs to be sufficiently sized up near the top. Maybe the compression ring should be below this top ring of holes. The rest, including the framing and reinforcing around the openings is more or less just a thin conc. shell infill. The openings are not made by just randomly cutting uniformly spaced rebars in the conc. shell. Someone knowledgeable in conc. arches and domes should study, analyze, and design this structure. So far, that does not seem to have been done. There are way too many people running around in this world pretending to be engineers, who could not engineer their way out a paper bag which was open at both ends. Some of this crap could fail and hurt a bunch of people. Structural Engineering is not just a matter of throwing things up and hoping for the best.

 

[Brad805]

Do we know the radius of the dome?

 

[human909]

Structural Engineering is not just a matter of throwing things up and hoping for the best.

Sadly sometimes it is just that.... [flush]

You get a pink star for starting to flesh out an analysis approach.

 

[BAretired]

Looks like the inside diameter is about 156/70 * 180 = 400 units (assumed to be cm) or 4m or 13'-2" (not a very big dome).

BA

 

[IFRs]

My concern would be the knowledge that failure is not limited to uniform compression but rather more likely to be from bending under unbalanced loads, in which case the rebar might be needed to resist local tension. It would help to know if this dome approximates a thin shell and if it is sensitive to local buckling or high concentrated loads.

 

[dik]

what's a cubit?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BAretired]

cubit, unit of linear measure used by many ancient and medieval peoples. It may have originated in Egypt about 3000 bc; it thereafter became ubiquitous in the ancient world. The cubit, generally taken as equal to 18 inches (457 mm), was based on the length of the arm from the elbow to the tip of the middle finger and was considered the equivalent of 6 palms or 2 spans. In some ancient cultures it was as long as 21 inches (531 mm).

BA

 

[Brad805]

Using those dimensions it seems the space between the top holes is roughly 240mm. I think dhengr is on the right path. The dome appears to weigh around 28,000lb.

 

[BAretired]

Looks to be much thicker than it needs to be. Could be about half, or even a third the thickness shown. And I don't think the openings are any problem at all. The tension ring could be hidden within the supporting wall.

Might have made more sense to continue the dome down to roof level. Then the tension ring would be completely surrounded by roof slab.

BA

 

[dik]

Thanks, BART... I knew that before I asked the question.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BAretired]

Yes dik, I figured as much!

BA

 

[dik]

BART, your lines could have gone from the tangent of the top hole to the tangent of the bottom hole, with a fixed large circular rigid mass at the top.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

For climate change, I was thinking of building an ark last summer...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

JSteven and WARose:

I tried to upload a file, but it was too large... approx 100MB. The title is "Hagia Sophia-Istanbul's Ancient Mystery" or "Hagia_Sophia-Istanbul's_Ancient_Mystery". It's an excellent documentary on Hagia Sophia, well worth watching.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

I gave a link to the NOVA docu in this thread:

https://www.eng-tips.com/viewthread.cfm?qid=476279