RF-CONCRETE Members – Online Manual Version 5

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RF-CONCRETE Members – Online Manual Version 5

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3.6.6 Standard


The parameters in this tab depend on the standard set in window 1.1 General Data (see Figure 3.2). Here, you can specify standard-specific reinforcement data, which is described in the following for EN 1992-1-1.

Use the [Default] button in the bottom right corner of this tab to restore the initial values of the selected standard.

Figure 3.39 Window 1.6 Reinforcement, EN 1992-1-1 tab
Percentages of Reinforcement

The input field controls the general maximum percentage of reinforcement for the beam. EN 1992-1-1, (3) recommends a value of As,max = 0.04 Ac for tension or compression reinforcement and refers to country-specific regulations. The National Annex for Germany defines the maximum value of the sum resulting from tension and compression reinforcement with As,max = 0.08 Ac, which must not be exceeded, even in zones of overlapping joints.


If the concrete compression area is no longer able to absorb compression forces, a compression reinforcement is required. This occurs if the bending moment is exceeded, which results from the concrete edge's compression strain of −3.50 ‰ and the strain εyd when reaching the yield strength of the reinforcing steel. For rebars of the material type 500, a related neutral axis depth of x/d = 0.617 ensues. In case of continuous beams, horizontal beams of non-sway frames, and structural components mainly stressed by bending, you should not use this limiting bending moment to its full capacity in order to ensure a sufficient ability for rotation.

With the check box you can limit the depth of the compression area according to EN 1992-1-1, 5.6.3 (2). In this case, the maximum ratio is xd/d = 0.45 for concrete up to strength class C50/60 and xd/d = 0.35 for concrete starting from strength class C55/67.

Shear Reinforcement

The two input fields define the allowable range of the compression strut inclination. If there are user-defined angles beyond the allowed limits of the standard, a corresponding error message appears.

EN 1992-1-1 provides an integrated model for calculating the shear force resistance. For structural components with shear reinforcement perpendicular to the component's axis (α= 90°), the following applies:

VRd,s = Asws · z · fywd · cot θ

Equation 3.2 Shear resistance according to EN 1992-1-1, Eq. (6.8)


Table 3.1


cross-sectional area of shear reinforcement


spacing of links


design yield strength of shear reinforcement


lever arm of internal forces (assumed as 0.9 ⋅ d)


inclination of concrete compression strut

The inclination of the concrete compression strut θ may be selected within certain limits depending on the loading. This way, the equation can take into account the fact that a part of the shear force is resisted by crack friction and the virtual truss is thus less stressed. These limits are recommended in EN 1992-1-1, Eq. (6.7N) as follows:

1  cot θ  2.5  

Equation 3.3 Compression strut inclination

The compression strut inclination θ can vary between these values:

Table 3.2 Limits for compression strut inclination
Minimum inclination Maximum inclination




cot θ



The National Annex for Germany allows for a flatter compression strut inclination of 18.4°.

1.0  cot θ  1.2 + 1.4 · σcdfcd1 - VRd,ccVEd  3.0  

Equation 3.4 Compression strut inclination NA Germany

A flatter concrete compression strut results in reduced tension forces within the shear reinforcement and thus in a reduced required area of reinforcement.


The upper input fields control the Partial safety factors according to for concrete γc and reinforcing steel γs. The values according to EN 1992-1-1, Table 2.1N are preset for the load-bearing capacity. In the same way, the recommended values are preset for the serviceability. They can be adjusted as needed.

The Reduction factor α for considering long-term effects on the concrete strength can be specified separately for compression and tension loads. Again, a differentiation by design situations is possible. The values recommended in EN 1992-1-1, 3.1.6 are preset.

According to the National Annex for Germany, the reduction factor for the concrete compressive strength to be applied is αcc = 0.85, the one for the concrete tensile strength is also αct = 0.85. According to EN 1992-1-1, remark to 3.1.7 (3), the value η ⋅ fcd must additionally be reduced by 10 % if the width of the compression area decreases towards the compressed edge of the cross-section. If this condition is given, RF-CONCRETE Members will perform the reduction automatically.