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

 

[dik]

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

-Dik

 

[Steel Inspector]

https://ibb.co/dGsXLQK

https://ibb.co/jfVz996

https://ibb.co/92NN0mj

https://ibb.co/fqXD51S

https://ibb.co/GcByprb

 

[Steel Inspector]

https://we.tl/t-F5x9AxkGj0

 

[centondollar]

You are wasting your time if you expect to be provided with structural analysis of a reinforced concrete dome (loads? axisymmetry? prestress?) with irregularities in the form of numerous openings. This is the work that the structural engineer (is that you?) is expected to do.

 

[Steel Inspector]

No i am not the structural engineer, but i don't trust my structural engineer. his instructions are to just go ahead and cut the steel as the dome is already lifting its self ( i have no idea what he means by that, may be he means that the concrete alone is enough ).

that's why i asked.

 

[centondollar]

In that case, you need to contact the superiors of the structural engineer and figure this out.

 

[Steel Inspector]

the superiors are worser. you might say that i am in the middle of people who are engineers by name only. they lack knowledge, and because of that they don't see the dangerous consequences of what they do.

so if you can be of any help, plz.

 

[dik]

The proportions of the thickness and span seem a little out of whack. It's a matter of someone doing a decent FEM (or something of that ilk) analysis. The holes, in a compression element don't look overly onerous.

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

-Dik

 

[centondollar]

The help in this case consists of the structural engineering providing proof for his claims. If he cannot use calculations (analysis results (moment, shear, normal forces) and concrete section design) to prove that the holes can be made, the holes should not be made.

 

[Steel Inspector]

mr dik,
so you believe it is not that dangerous? do you think its possible to procced without doing an analysis to consider the openings? or is it necessary to hold untill doing the analysis?

 

[Steel Inspector]

mr centondollar,
thank you very much

 

[dik]

Just dik...

Off the top it doesn't look dangerous, just based on the proportions. The openings are well distributed and symmetrical.
Analyses and design of domes is a specialty and should be undertaken by skilled people. It's a matter of doing the 'sums' to determine it's safe. The dome thickness appears to be very thick based on the span. Being thick doesn't make things easier; it can introduce secondary flexural forces due to the thickness.

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

-Dik

 

[Steel Inspector]

thank you, dik

 

[WARose]

A RC dome ain't the time for amateurs. If there is nobody around you that you trust: sub it out to someone else.

 

[JStephen]

It's a design issue, not an inspection issue.
If you do it right, you can build some pretty substantial domes without any reinforcing at all (Hagia Sophia, etc)
Whether the holes cut the reinforcing or what, would be design issues.
If you don't trust the designer to design it, the holes are not the issue.

 

[WARose]

If you do it right, you can build some pretty substantial domes without any reinforcing at all (Hagia Sophia, etc)

ACI allows unreinforced (i.e. plain) concrete where arching action puts a member into compression at all times (under any loading). But I couldn't imagine doing that with anything like a dome. (The temperature load is too much of a X-factor.) The only time I use plain concrete is for something where if it cracks/fails.....nothing too bad is going to happen. (Like a slab on grade.) A dome falling down is real bad.

 

[dik]

and the ones standing are the 'good' ones...

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

-Dik

 

[human909]

and the ones standing are the 'good' ones...

I laugh but you likely didn't say that in jest.


This is an interesting build. I am not skilled in concrete but overall the dome section seem proportionate likely over designed. The engineer probably just threw a double span slab at it and then said turn it into a dome. The sharp transition from dome to vertical will put the concrete into tension, this seems to have been catered for with hoop reinforcing. Still you would make sure that detail is right. Likewise the holes look ok except for the top ones which are a little close together for my liking to call it good without calcs to back it up.

Steel Inspector judging by this post and others I'd be guessing you are working in central asia or the middle east and you seem to be too curious for your own good. Asking questions which nobody wants asked!

 

[dik]

I've changed a lot. When I was young, I would have jumped at the opportunity of doing a dome... not so much now.

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

-Dik