estimate soncrete coloumn size for ETABS?

[nimaoy]

Hi
Is there any experiment for estimate initial section size of column for modeling concrete structure in ETABS?

 

[LGARG]

Hi,

im not too familiar with the ACI code. i used to calculate with the din code (Germany). In this code you use a stress for Concrete considering let say 1.2% of reinforcement and a 2.1 safety factor. Then you divide the total load per column by this stress and you get the requiered area of concrete. I hope that this could be usefull.

LG

 

[Mixtli]

You have to guess a section to start with, actually you did it before performing the analysis, right; well to that section assign between 1 and 4% of rebar, choose a distribution for it,, and voila. After that you have to rerun the design software to see if the columns pass and the safety factor on them.

Regards

 

[ash060]

This was a rule of thumb I picked up in school for the ACI code. 1.6P/0.5f'c = Ag of the column. Just take the axial load of the column and divide by half the concrete stress to get an estimate.

 

[nimaoy]

thank you...but I want to know how can I estimate column size before input the model in ETABS?

 

[hokie66]

nimaoy,

With all due respect, the answer ash060 gave you is appropriate. So you just need to be able to estimate your column loads to get a start. If you don't know how to do that, you should not be using a complex program like ETABS.

 

[nimaoy]

as you know we should first of all estimate column size and after that we can analysis and calculate force and moment, so my question is : first of all and before analysis how we can estimate column size for modeling and analysis in ETABS- for example 30*30 or 40*40 or....?

 

[LGARG]

hi nimaoy

You should follow the ash060 suggestion. You have to calculate the Ag(total area).So if you want a square column the side B will be = (Ag)1/2.


LG

 

[nimaoy]

so, how can I guess P (axial force) before analysis ?

 

[WillisV]

Ummm...a column load take down by hand calcs based on tributary areas? If you can't estimate a column load by hand then you shouldn't be analyzing the column in a program.

 

[LGARG]

You calc the tributary areas per the dead load and live load for gravity columns, and if you have seismic you could take a lower value of stress or lets say1.6P/ 0.35f´c in ACI code for lateral resistant columns to take into account the seismic forces. This is like a fist approach. So when you create your model, you will have elements with more certain rigidities.


LG