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
![Loads [kN] Klicke auf die Grafik für eine vergrößerte Ansicht
Name: immagine_2022-02-02_101122.png
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ID: 3627](filedata/fetch?id=3627&d=1643793107)
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.
![Uniaxial case Klicke auf die Grafik für eine vergrößerte Ansicht
Name: immagine_2022-02-02_101432.png
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ID: 3628](filedata/fetch?id=3628&d=1643793283)
For the biaxial case, the check is NOT fullfilled, even considering the favourable effect of having compression struts inclined at 45°.
![Biaxial case Klicke auf die Grafik für eine vergrößerte Ansicht
Name: immagine_2022-02-02_102533.png
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ID: 3629](filedata/fetch?id=3629&d=1643793937)
The biaxial check with struts at 21.8° (like those adopted for the uniaxial case) is the following.
![biaxial check with struts at 21.8° Klicke auf die Grafik für eine vergrößerte Ansicht
Name: immagine_2022-02-02_102721.png
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ID: 3630](filedata/fetch?id=3630&d=1643794050)
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%
![shear checks Klicke auf die Grafik für eine vergrößerte Ansicht
Name: immagine_2022-02-02_103631.png
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ID: 3631](filedata/fetch?id=3631&d=1643794593)
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
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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