Buckling Analysis

[phansophea]

Hi

I have question on effective length's calculation of column of a RC structure, and the verification if the structure is sway or non sway by buckling analysis.

case 1: if the RC structure is braced by a shear wall, do we need to put all braced columns' end as pinned before taking buckling analysis in order to find global stability in order to conform to EC2 (H.2) & (H.3).

case 2: if the RC structure is not braced, what we can do to check if that structure is sway or non sway? can we do the buckling analysis the same as braced structure?Regards,

[teixeiranh]

Regarding case 1, I do not think that you need to make all the end of the columns pinned…

Regarding case 2, you may make a buckling analysis in RSAP, and evaluate if there is any global buckling mode in which xcrt is less than 10.

Buckling analysis:

http://youtu.be/M38GCsgFxb8;

[StefanoPasquini6790]

Hi,

Very nice answer teixeiranh, I should reach the goal of xcrt to 10 for linear buckling analysis and 15 for non linear buckling analysis. Take care to create your own manual load combination to check with buckling analysis.
Please, no base pinned restrained column for rc structure

Greetings

[phansophea]

teixeiranh,
case1: if we don't pinne the columns, those columns will participate in buckling. Then the column shall be calculated by EC2 (5.16). Is it right?
Case2: so there is no difference between between bracing and non bracing structure in buckling analysis.
Thanks for the reply.

[phansophea]

StefanoPasquini6790,
Of course, there is no pinned column in real structure. But in conceptual model, we can consider column as pinne, can't we?
What i want to ask is the taking to account or not the rigidity of column in buckling analysis? In EC 5.8.3.3, only rigidity of bracing structure (shear wall for example) is taken to verify global stability (bucking analysis),
What will be your reply?

[teixeiranh]

Taking into account or not the columns depends on the relative stiffness. I am not too familiar with EC2 (my work is primarily intended for steel structures).

I guess that EC2 only makes you use shear walls in the verification because they have a flexural stiffness much higher than the one of the columns. Besides that, the verification of EC2 that you are talking about is hand calculation. Isn't it? 

I really think that you may consider the stiffness of the columns in the verification.

You may also compare the results, letting the columns participate, and do not let the columns participate...

If the results differ more than you think that they should differ, then we have got a problem.