How to evaluate the buckling results
First of all, we have to determine the minimum force amplifier to reach the elastic critical buckling, αcr using buckling analysis. IDEA StatiCa provides the buckling factors in a result tables and the buckling shapes for each factor can be provided in a 3D view.
The limit value for global analysis can be found in EN 1993-1-1:2005 Cl. 5.2.1.
In the first example, the pressure force is applied to the beam connected by a connecting plate.
The results from the geometrically linear calculation are provided and the first factor is 8,76. According to EN 1993-1-1:2005 Cl. 5.2.1, the limit value is 15 because this joint is critical for the stability of the beam itself and the conclusion is the connection did not pass the buckling analysis. Not to mention that this one-sided connecting plate is dangerous in this bracing in the pressure configuration.
On the other hand, in case of most plates in connections, local buckling can occur and the maximum value of critical buckling factor, αcr, that requires thorough analysis is usually smaller. It has been verified that for stiffeners and column panel in shear, it is not necessary to take into account buckling if the critical buckling factor is higher than 3.
We have to determine the right limit value for each component and decide. This example shows that the first buckling mode is that of a stiffener with factor αcr = 8,76 >> 3. In this example, this first buckling mode is not dangerous.