Hello,

I'm having some problems on results obtained from the RF-CONCRETE Columns module, in particular the Eurocode 2 shear check according to formula 6.9 (using RFEM5).

Let's consider a short concrete column (square section 100x100cm, Length=100cm), restrained at the base. On the free node I applied two kinds of loads: the first produces an uniaxial bending and the second a biaxial bending, as per following figure

The combined shear on both load cases is the same (2500 kN).

Moreover there is a traction load 2000 kN.

For the uniaxial load case, the check for struts in compression limit state (VRd,max Eurocode formula 6.9), is verified for an angle 21.8° with an usage factor 0.7769.

For the biaxial case, the check is NOT fullfilled, even considering the favourable effect of having compression struts inclined at 45°.

The biaxial check with struts at 21.8° (like those adopted for the uniaxial case) is the following.

In conclusion: if we consider two load cases that lead to exacly the same resultant shear (2500 kN), the concrete struts' resistance (inclination 21.8°) calculated by the RF-CONCRETE Columns module (VRd,max Eurocode formula 6.9)

If I compute the same case with another software, there is not such a huge difference in struts' resistance (VRd,max Eurocode formula 6.9): the reduction is 22%

In particular I notice great difference in the calculation of resistant section dimension (z and bw). The calculation base for the bi-axial shear on this alternative software may be found here: https://help.geostru.eu/rcsec/en/ver..._biassiale.htm

I suspect the formulas used in the RF-CONCRETE Columns may be too conservative.

Any comment is appreciated.

Thanks in advance,

Doug

I'm having some problems on results obtained from the RF-CONCRETE Columns module, in particular the Eurocode 2 shear check according to formula 6.9 (using RFEM5).

Let's consider a short concrete column (square section 100x100cm, Length=100cm), restrained at the base. On the free node I applied two kinds of loads: the first produces an uniaxial bending and the second a biaxial bending, as per following figure

The combined shear on both load cases is the same (2500 kN).

Moreover there is a traction load 2000 kN.

For the uniaxial load case, the check for struts in compression limit state (VRd,max Eurocode formula 6.9), is verified for an angle 21.8° with an usage factor 0.7769.

For the biaxial case, the check is NOT fullfilled, even considering the favourable effect of having compression struts inclined at 45°.

The biaxial check with struts at 21.8° (like those adopted for the uniaxial case) is the following.

In conclusion: if we consider two load cases that lead to exacly the same resultant shear (2500 kN), the concrete struts' resistance (inclination 21.8°) calculated by the RF-CONCRETE Columns module (VRd,max Eurocode formula 6.9)

- uniaxial load struts resistance 3218 kN
- biaxial load struts resistance 1450 kN

__According to these results the column is too small and should be redesigned with much larger section dimensions__, just for the biaxial case.If I compute the same case with another software, there is not such a huge difference in struts' resistance (VRd,max Eurocode formula 6.9): the reduction is 22%

In particular I notice great difference in the calculation of resistant section dimension (z and bw). The calculation base for the bi-axial shear on this alternative software may be found here: https://help.geostru.eu/rcsec/en/ver..._biassiale.htm

I suspect the formulas used in the RF-CONCRETE Columns may be too conservative.

Any comment is appreciated.

Thanks in advance,

Doug

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