Web
When you perform nonlinear analysis and you are interested to investigate the local buckling results in the web, you need to define the imperfection for web panels. The beam web is divided by vertical stiffeners that make web panels. The panels are selected individually for imperfection shape and magnitude input.
Examples of input
Global
When you perform nonlinear analysis and you are interested to investigate the global buckling results of a beam, like lateral torsional buckling, the imperfection must be defined for the zone of investigation. Here you define the buckling length zone (L), the shape, and the magnitude of imperfection.
Examples of input
From Buckling
The imperfection shape can be created based on the buckling shape that you obtained from the Linear Buckling Analysis results. In this case, after the analysis in the results panel you have to select the buckling mode (Result step), give the name to this shape, and click the ‘Set as imperfection’ button. After this, if you go to Imperfections > From buckling you will see the table row with the saved buckling shape. Then you can control the magnitude of the imperfection for the farther nonlinear analysis.
Initial Stress
Initial stresses are used to define a stress state in the structure before the application of any external loads or boundary conditions. This could be due to residual stresses from manufacturing processes, assembly processes, or previous loadings. Typically, initial stress is used for beam members to represent residual stresses that occur during manufacturing. These stresses can influence the strength and buckling capacity of the beam once external loading is applied. In this context, you can specify the pattern of the initial stress distribution for beams. Click ‘Preview’ to view the stress distribution, and click ‘Generate’ to apply the initial stress to the finite elements. Note that if the mesh with defined residual stress is updated, this data will be removed, and the initial stress must be redefined if necessary. To understand the stress-deformed state of the model after applying residual stress, perform a linear static analysis without any external loads and examine the results
