Unbraced, Slender RC Column Design PLEASE HELP ASAP!

[Struct_Dre]

Hello All!

I am a relatively new engineer and I'm really stuck on a project trying to design an unbraced, slender reinforced concrete column. I have read through my RC concrete design textbooks and I am extremely confused. My conclusion from reading is that it is very difficult to do these calculations by hand and they should instead be done with some kind of engineering software. TEDDS does not allow the design of an unbraced, slender column, but I do have access to RISA-3D.

I would like to know how to apply loading to the column in RISA. I think I would break it down into a concentric axial load and a moment, but I'm not sure what the moment would be. Please see the screenshot of my column (plan view) I have beams on two sides of the column.

Please help. I am so confused, my project is due, and I have been reading about this all day with no answer. Some info on my column:

18"x18" RC with L=18.5' and e=9

 

[WARose]

Is it just a single column and you know the controlling load case/forces (as per the applicable load combinations)?

 

[r13]

Does your office have CRSI design manual? Or check older reinforced concrete textbook for column interaction diagrams. You need at least know P, then get M by multiply P with code specified minimum eccentricity. Don't be afraid of asking help from your seniors.

 

[BAretired]

What do you mean "my project is due"? Is this a homework assignment? What textbooks have you been reading? Have you searched the internet?

Have you come across this article? It includes an example with a 20"x20" column with 28'-0" height, more slender than yours.

http://by.genie.uottawa.ca/~murat/CHAPTER 4 - SLENDER COLUMNS - SP17 - 09-07.pdf

My conclusion from reading is that it is very difficult to do these calculations by hand and they should instead be done with some kind of engineering software.

Engineers have been designing columns long before computers were available. A slender column can be analyzed using Newmark's Numerical Procedures, a hand method. Your column is not particularly slender and you have not described the loading or the boundary conditions.

Provide a sketch showing the load applied and the end conditions.

BA

 

[MIStructE_IRE]

When you say unbraced, is this a cantilevered column resisting lateral load?

What’s on top of the beams? If you have an RC slab can it be detailed to offer restraint to the column...assuming the slab is actually tied to something which offers lateral stability?

 

[WARose]

Engineers have been designing columns long before computers were available. A slender column can be analyzed using Newmark's Numerical Procedures, a hand method. Your column is not particularly slender and you have not described the loading or the boundary conditions.

In addition, in the back of a lot of concrete texts, there are interaction diagrams that allow one to select % of steel based on the loads.

 

[r13]

BA,

The deadline is approaching, but solution is not insight. A little too late to learn then. The seniors, or the boss should be consulted/notified. I guess the office has solution on hand already, who will let junior engineer sitting in dark without pre-task chat/instruction.