Cross-section classes. When do buckling occur?

[Mekanikles]

Hi,

Let's ask the expertise.

In EC they divide cross-sections in classes from 1-4. I guess the classes is similiar in other standards?

My question is, how do you determine the critical stress in which buckling will occur for classes 2-4 on a specific cross-section?

 

[KootK]

It is similar in North American practice. The philosophy is to preclude local plate buckling. Something along these lines:

1) Based on the aspect ratio of individual plate element, determine if you can design to elastic, plastic, or post-plastic strain levels without risking plate buckling.

2) Employ a code specified design method appropriate to the strain level specified in step one.

3) Proceed without fear of local plate buckling.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[Mekanikles]

Thanks. For example an I-beam that would be to check the flange and web plate individually, right?

(I guess I thought there was some conservative reducing factors that you used that takes into account the width,height,material of the individual plate and the cross-section, to calculate an approximate stress level when local plate buckling will occur)

 

[KootK]

For example an I-beam that would be to check the flange and web plate individually, right?

Yes. Slenderness ratios need to be satisfied for the flange and web separately.

I guess I thought there was some conservative reducing factors that you used that takes into account the width,height,material of the individual plate and the cross-section, to calculate an approximate stress level when local plate buckling will occur

There are procedures for doing this when slenderness ratios are too high. It's not the normal design method however. The cold formed metal design specification, S136, is a good reference for those situations.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.