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Compression-Bending interaction curves for circular columns 6

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mte12

Structural
Mar 1, 2022
141
Has anyone come across N-M interaction curves for circular columns?
Tabulated for different diameters/grade/% steel.
In metric units.

As for attached which is for square columns.

Untitled_ibmafv.png
 
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The CRSI Handbook used to have tables (not graphs) that had all the inflection points (0% fy; 25% fy, etc.) necessary to create these graphs. The bad news is that the copy I have is dated 1992. Maybe some of the others have better references, but in my experience, these kind of books have went the way of the dodo. Since you can run a computer program (does PCACOL still exist?) and punch one of these out in seconds, the hard copy volumes are obsolete.
I still find them useful, but I'm a dinosaur.
 
A long time back RCC had concrete design spreadsheets on their website, and I downloaded the collection. There were 39 of them. RCC 54 is one that deals with circular columns, but is likely based on code of 'yesteryear'. The sheet is editable so you should be able to update it, easily. There are likely others out there that are similar. [ponder]

In addition to the disclaimer, they have this note:

Clipboard01_mzza9y.jpg


[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1658759729/tips/RCC54_Circular_Column_Charting_e3ehki.xls[/url]

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik
 
Here's a link:
MNL-17(21): ACI Reinforced Concrete Design Handbook Design Aids

ACI Reinforced Concrete Design Handbook - Volume 3: Design Aids
Appendix D - Column Interaction Diagrams
p. 25
b_acgm6v.jpg


Starting p. 69
s_ouyx3u.jpg


CRSI also has several design checklists (with included Excel sheets), one of which is for columns, including circular columns, for $12. It's not metric but you could convert units. I have some of these checklists/spreadsheets, and they're great. CRSI Column Design Checklist Link
 
I forgot to add, I had to use an Excel 'crack' to access the earlier spreadsheets... I don't know if I still have the crack...

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik
 
Thanks to all for providing spreadsheets/graphs/links. This will definitely help.
 
Thanks, these are very helpful.
 
You can also program (in e.g., excel or python) a solution for the five key points on the M-N graph; only slightly more effort is required to create a full interaction diagram. Use strain compatibility, bernoulli hypothesis (strain varies linearly in section) and some material model (maybe parabolic compressive for concrete and bilinear perfectly plastic for rebar), choose the values of strain (for five points on M-N graph or more) and calculate stresses, forces, centroids of forces and bending moments about some axis of your choice. The idea should be clear by reviewing a reinforced concrete design book explaining the procedure for column and doubly reinforced beam design.

I would prefer to do it this way instead of relying on nomograms, unless of course you do a few spot checks on each and every nomogram you choose to use - it can be quite difficult to spot possible errors in them otherwise.
 
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