Economical Column Design (Rule of Thumb) 3

[struggle67]

Hi

I am new to columns or any vertical member design. I only know some of the basic theories.

Let’s say I am free to choose whatever column size I want. May I know based on your experience, where is the most economical point (NEd, MEd) on the column-interaction diagram? Reinforcement ratio? 2%? And why?

Thanks, and Best Regards,

 

[Lomarandil]

That was my first thought too Steve, but I don't think your conversion works.

----
just call me Lo.

 

[Settingsun]

0.6 *sqrt(f'c) is for metric units, so you convert 2500psi to 17.2MPa before running the calc.

 

[Lomarandil]

Ah, right you are!

----
just call me Lo.

 

[Celt83]

I looked at taking:
Pu = PhiPn,max = 0.85*0.65*((0.85*F'c*(Ag-Ast))+(Fy*Ast))

substitute Ag = b*h and Ast = (1/100)*b*h

Determine a M,min as (0.6+0.03*h)*Pu

Then the max ratio of Secondary to First order moments is 1.4, so M = M,min/1.4

divide both sides by s = b*h*h / 6

From here I plugged in Fy = 60,000 psi, F'c = [2500,3000,4000,5000] and h = [12,18,24,36]

This results in PSI values so I divided by 145 to get Mpa. The 24 and 36 h at the lower F'c comes in near 2.5

Steveh49 likely has it, but I found some fun new math software so took it for a spin.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer