RF-CONCRETE Surfaces Version 5

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RF-CONCRETE Surfaces Version 5

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Analytical Method

The analytical method for the serviceability limit state design is described in detail in chapter 2.6.

If you use RF-CONCRETE Deflect, this window provides additional tabs and columns. They are described in chapter 3.3.2 Nonlinear Method.

Figure 3.18 Window 1.3 Surfaces for analytical check method, Limit of Crack Widths tab
Material No.

The numbers of the materials are displayed according to window 1.2 Materials for each surface.


You can design constant and linearly variable thickness types. For orthotropic properties, the designs are limited to the ultimate limit state.


This column shows the surface thicknesses defined RFEM. The values can be changed for the design.

If the surface thicknesses are modified, the internal forces of RFEM, which result from the stiffnesses of the RFEM surface thicknesses, are used for the design. In a statically indeterminate system, the surface thicknesses modified in RF-CONCRETE Surfaces must also be adjusted in RFEM: In this way, the distribution of internal forces is correctly considered in the design.

The other column descriptions depend on the settings in the tabs below. These tabs can be controlled in the Settings dialog box (see Figure 3.10) where you can specify whether you want to design stresses and/or cracks.

The values in the columns are taken from the entries in the tabs below. These specifications apply to all surfaces by default. It is also possible to only assign the current settings to specific surfaces: Clear the All check box. Then, enter the numbers of the relevant surfaces or select them graphically in the RFEM work window with . With you assign the current settings to these surfaces. However, the assignment is applicable only for the active tab, for example Stress Check.

The following two parameters need to be defined in the Stress Check tab (see Figure 3.19).


This column shows the value of the maximum (negative) concrete stress for limiting the concrete compressive stresses (see chapter According to EN 1992-1-1, the following applies to

  • quasi-permanent action combinations, if serviceability, ultimate limit state, or durability are considerably affected by creeping:
Table 3.2

σc ≤ 0.45 ⋅ fck

7.2 (3)

  • rare (= characteristic) action combinations in exposure classes XD1 to XD3, XF1 to XF4, XS1 to XS3:
Table 3.2

σc ≤ 0.60 ⋅ fck

7.2 (2)


This value represents the maximum reinforcing steel stress for the limitation of the reinforcement's tensile stresses (see chapter According to EN 1992-1-1, the following applies to

  • rare action combinations:
Table 3.2

σs ≤ 0.80 ⋅ fyk

7.2 (5)

  • pure effects due to restraint:
Table 3.2

σs ≤ 1.00 ⋅ fyk

7.2 (5)

The remaining parameters have to be defined in the Limit of Crack Widths tab (see Figure 3.18).


The value of the effective concrete tensile strength is required for the check of crack width according to EN 1992-1-1, clause 7.3.4 (see chapter


This column manages the concrete's effective tensile strength that is to be applied for the determination of the minimum reinforcement to resist restraint according to EN 1992-1-1, clause 7.3.2 (see chapter The concrete tensile strength depends on the time of the initial crack formation.

wk,-z (top) / wk,+z (bottom)

These parameters are the allowable crack widths at the top and bottom sides of the surfaces (see chapter

Effects due to Restraint

If there are effects due to restraint, they must be considered when determining the minimum reinforcement for limiting the crack width (see chapter

In the Limit of Crack Widths tab, you can use the [Edit] button to specify the minimum reinforcement to resist effects due to restraint (see Figure 2.97).


In column I or with the check box in the Limitation of Crack Widths tab, you can configure if there are effects due to restraint.


In the Limitation of Crack Widths tab, you can specify whether there are internal or external effects due to restraint. This influences the factor k for considering nonlinearly distributed concrete tensile stresses (see Equation 2.71).


This factor takes account of the stress distribution in the tension zone (see Equation 2.71).


This column shows remarks in the form of footnotes described in detail in the status bar.


These input fields can be used to enter user-defined comments.