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Pre-Deformed Initial Structures
and Equivalent Imperfections
for Non-Linear Calculation |
The add-on module RF-IMP is used to create imperfections for the geometrically non-linear calculation automatically. Thus, in RFEM when calculating according to the second-order or the large deformation analysis, you can perform ultimate limit state designs including stability. This applies not only to framework structures, but also to structures with shell and solid elements.
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| Features
- Creation of a pre-deformed FE mesh
- Generation of equivalent imperfections for members as equivalent loads taking into account
- the reduction factors r1 and r2
- the rises of precambers depending on the buckling stress curves
- Deformation of the structure due to displacement of nodes
- Generation of imperfections in accordance with
- Equivalent imperfections on members and sets of members (for example columns consisting of several members)
- Visualization of generated imperfection modes
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Input
RF-IMP evaluates the predeformation of a load case, the eigenmodes of a stability analysis or a dynamic calculation. Due to this initial deformation, it is possible either to pre-deform the structure or to create a load case with equivalent imperfections for members.
For structural systems consisting of surface and solid elements and of members, you can take advantage of the pre-deformed initial structure. You only need to specify a maximum value to which the deformation will be scaled. Then, all the FE or structure nodes will be scaled with regard to the initial deformation.
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| Generation
When you use a pre-deformed FE mesh, RF-IMP saves the data for the displacement of each individual node in the background. If you want to create load groups, you can take advantage of the stored data. To check the generated data, the module displays the pre-deformation in tables and in the graphic.
If you want to displace the structure nodes directly, the node coordinates are modified immediately after the generation.
In case equivalent imperfections are used, RF-IMP creates a normal load case containing the member imperfections. For checking purposes, the generated imperfections are represented in tables as well as in the graphic. |
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| Using a pre-deformed FE mesh
If a pre-deformed FE mesh has been created, it can be used in load groups. Just select the corresponding RF-IMP case in the load group's calculation parameters. Then, the calculation of the internal forces will be carried out for the imperfect system. |
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| Using equivalent imperfections
For this type of generation you create a normal load case that contains the equivalent imperfections. This load case can be modified manually. Subsequently, it will be combined together with the "normal" load cases in load groups. |
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Note
You can find more information about RF-IMP here:
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1.1 General Data
1.2 Imperfections
2.1 Pre-deformed Initial Structure
EN 1992:2004
DIN 18800:1990-11
