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How does RFEM effectively determine the shape of a curved plate structure (compression shell) subjected to compression only?

Answer

The effectiveness of a tensile structure subjected to compression depends on its shape. For each load distribution, there is an associated optimal shape that transfers the loads to the foundations by using as little material as possible.

Figure 01 - Form-finding of a compression-loaded tensile structure

Since the use of a structural system usually specifies several load states, it is recommended to align the optimal shape with the main load (permanent load) of the model for purely strategic reasons.

The RFEM program helps you to find these model shapes in conjunction with the RF-FORM-FINDING add-on module. The underlying form-finding process shifts the position of the FE mesh nodes in space on the basis of a specified load so that the new position of the elements transfers the load mainly via the membrane's load-bearing capacity. The explicit use of the normal force resistance of members and the membrane force resistance of the surface elements results in constant stress states in the cross-sections. This stress-free state makes optimal use of the cross-sections and allows for a very effective structure with minimum material input.

This process can be applied both for the usual cable and membrane structures consisting of limp elements under tension as well as for pressure-loaded rigid beams and shell structures.

To develop an optimal pressure plate shape in RFEM, proceed as follows:


  1. Activation of the RF-FORM-FINDING module in the "General Data" under the "Options" tab
    Figure 02 - Activation of form-finding options

  2. Specification of form-finding settings for the structural elements
    Figure 03 - Form-finding setting for beam
    Figure 04 - Form-finding setting for surface element

  3. Defining the main loading for the shaping
    Figure 05 - Defining the external form-finding loading

  4. Form-Finding Analysis
The finally developed shape can then be used in RFEM for the structural analysis with regard to the further variable loads.

Keywords

FF Eggshell form-finding Vault Material usage

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RFEM Main Program
RFEM 5.xx

Main Program

Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

Price of First License
3,540.00 USD
RFEM Tensile Membrane Structures
RF-FORM-FINDING 5.xx

Add-on Module

Form-finding of tensile membrane and cable structures

Price of First License
1,750.00 USD