Is it possible to connect a rib member to two surfaces with different thicknesses? And where can I check the cross-section properties of this composite cross-section? In RFEM, I can only see the eccentric rectangular profile and its cross-section properties.


You can connect a rib member to a line on two surfaces with different thicknesses.

To determine the stiffness or internal forces, the eccentricity of the rectangular cross-section is determined using the mean value of both connected surfaces in RFEM.

Figure 01 - RFEM Model of Rib with Different Plate Thicknesses

For designing in RF-CONCRETE Members, the add-on module determines its cross-section, which is displayed in the input dialog box ‘1.4 Ribs’ of the add-on module.

Figure 02 - Dialog Box '1.4 Ribs' in RF-CONCRETE Members

By clicking the ‘i’ button (see Figure 02), it is possible to open an info dialog box for the generated rib cross-section, where all cross-section properties applied for the design in the module, like the position of the shear center and centroid, etc., can be viewed.

Figure 03 - Cross-Section Properties of Rib Cross-Section in RF-CONCRETE Members

If the ‘Effective Width’ is adjusted in the ‘1.4 Ribs’ dialog box (e.g. to 0.50 m) this has influences on the cross-section applied in RF-CONCRETE Members and its cross-section properties.

Figure 04 - Modified Cross-Section Properties of Rib Cross-Section

However, this does not influence the stiffness or the determination of internal forces in the 3D model in RFEM.


Rib Cross-section property Center of gravity Shear center Plate width



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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 Concrete Structures

Add-on Module

Design of reinforced concrete members and surfaces (plates, walls, planar structures, shells)

Price of First License
810.00 USD