Static analysis buckling

Although a SPACE GASS non-linear static analysis does not perform a full buckling analysis, it does include some buckling checks as described below. For details of the capabilities of a full buckling analysis, refer to Buckling analysis.

The SPACE GASS non-linear static analysis includes a simple buckling check on individual members that is intended to alert you if a member is being removed from the model due to its Euler buckling load being exceeded. However, it is not a full buckling check that considers groups of members or the structure as a whole.

A common misconception appears to be that if the static analysis passes this simple single member buckling check then buckling is not a problem. Another misconception is that if the simple buckling check fails, you can just subdivide the buckled member until the error goes away and everything will be Ok. Clearly, this doesn't fix the problem, it just transfers the buckling from a single member mode to a multi-member mode that is no longer detected by the single member buckling check. The only way to be sure that buckling is not a problem is to perform a full buckling analysis.
If a member fails the single member buckling check then it is removed from the model for that load case in all further iterations, even if its axial load reduces to within its buckling capacity in later iterations. This is different to tension-only and compression-only members which can be disabled in a particular iteration and then restored in a later iteration if the sign of their axial force reverses.
The SPACE GASS non-linear static analysis also includes a buckling check for the entire model (except for any "BC" linear plates) that simply alerts you if the structure's buckling capacity has been exceeded. This will allow you to determine if the static analysis results are reliable or not, and nothing more. It will not calculate member effective lengths or the buckling load factor, and hence will not be able to alert you if buckling is close to happening. Consequently, a full buckling analysis will still be required for most structures.

It is very important to note that the results of a static analysis will be incorrect if the structure's buckling capacity has been exceeded, and hence one of the key roles of a buckling analysis is to ratify the static analysis results.

Although most practical structures do not come close to reaching their buckling load, unless you know that your model has not reached its buckling load, you should perform a buckling analysis.