Geometrical Imperfections

Open the Geometrical Imperfections dialog, using either method:

• Click Geometry menu > Additional Attributes > Geometrical Imperfections.
• Click .

This dialog lets you define initial geometrical imperfections. Geometrical imperfections can be assigned to single bars or to a group of coolinear bars (so-called superbars). Imperfections do not cause initial forces or structure stresses. Imperfections only change the structure geometry.

When using geometrical imperfections, remember:

• Imperfections are assigned only to bar elements
• Imperfections are assigned at the midpoint in the length of a single bar or coolinear bar group
• Imperfections change the geometry of a bar or a bar group; the change of geometry is modeled by a created chain of calculation elements that represent a deformed shape
• All results from structure calculations are displayed on a deformed structure (that is, the structure with geometrical imperfections considered). Nodal displacements are determined in relation to the initial geometry you defined.

Note: When defining geometrical imperfections a bar can be further divided into calculation elements. Use the Analysis Types dialog - Structure Model tab tab in theAnalysis Type dialog to define these divisions.

The dialog has 3 parts:

• At the top, there are several buttons:
  • - Adds a new type of geometrical imperfection (Definition of a new imperfection type).
  • - Deletes a type of imperfection from the list.
  • , , , and - Displays the list of active imperfections as: large icons, small icons, short list, and long list.
  • - Deletes from the list, all types of imperfections that are not in the designed structure.
  • - Opens the Label Manager dialog.
• A field that lists the active imperfection types
• At the bottom, the current selection field and standard buttons.

Similar to the dialog that defines other structure attributes, the process of defining a geometrical imperfection in a structure has 2 steps:

1. Defining a geometrical imperfection type

   If the list of imperfections is empty, or a new imperfection type is to be added to the list, click Definition of a new imperfection type:

   • If none of the imperfection types is selected, clicking opens the dialog to define a new imperfection type. The fields are filled with the last imperfection definition (except for the LABEL field) or the default parameters are set.
   • If an imperfection type is highlighted, clicking opens the dialog to define a new imperfecton type. All fields (except for the LABEL field) are filled using the highlighted type.

   Also, you can open the dialog for defining a new imperfection type by double-clicking an element in the list of imperfections. The Imperfection definition dialog opens with all fields filled according to the imperfection type selected.

2. Assigning imperfections to structure bars.

To delete an imperfection from the structure:

1. Click on the active imperfection list,
2. Select an object in the structure that you want to delete the imperfection from.

You cannot modify this type of imperfection; it is assigned the same way as the imperfection properties are to a structure element.

After an imperfection is assigned, its symbol is drawn on the graphical screen.

See also:

Calculation of initial deflection for imperfections according to Eurocode 3