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RF-IMP 4.xx

Pre-deformed Initial Structures
and Equivalent Imperfections
for Non-linear Calculation 
The add-on module RF-IMP is used to create automatically imperfections for the geometrically non-linear calculation. 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.
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
  
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.

Equivalent imperfections are particularly used for frame structures. Then, RF-IMP shows an additional table where you can assign inclinations and precambers to the members and sets of members. They can be either generated automatically according to standards or defined manually. The following codes can be selected:
  • EN 1992:2004
  • EN 1993:2005
  •  DIN 18800:1990-11
  •  DIN 1045-1:2001-07
  •  DIN 1052:2004-08
Only the imperfection resulting appropriately to the initial deformation on the relevant member is applied. Furthermore, you can take into account the reduction factors. In this way, it is possible to apply the imperfection efficiently.
Standards for equivalent imperfections
 
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 wells as in the graphic.
Pre-deformed FE-mesh
 
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.
Data import from RF-IMP
 
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.
Imperfection included in load group
 

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Note

You can find more information about RF-IMP here:

list image Manual (PDF / 2.01 MB)
list image Hotline
list image Training

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Price Information

Net prices in €
1st license
RF-IMP 850.00
Additional license
RF-IMP 382.50
list image Pricelist
1.1 General Data
1.1 General Data
1.2 Imperfections
1.2 Imperfections
2.1 Pre-deformed Initial Structure
2.1 Pre-deformed Initial Structure