FAQ 004321 | In RF‑CONCRETE Surfaces, I get non-designable situations with a note saying that the...

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Adrian Langhammer

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In RF‑CONCRETE Surfaces, I get non-designable situations with a note saying that the shear resistance cannot be checked (cross-section entirely cracked). What is the reason for this message?


A non-designable situation like this is displayed if the shear resistance without shear reinforcement VRd,c is arithmetically smaller than zero.

The value for VRd,c of less than zero is caused by large tensile axial forces. In this context, the cross-section is completely under tension or completely cracked, and no shear force resistance can be created.

For coated cross-sections with planned shear reinforcement, the following situation results:
If VRd,c < 0, no further shear design is performed in RF‑CONCRETE Surfaces, and Note 13) is displayed. This approach is conservative.

In this context, there was a request (194) for the interpretation of the standard, which allows the truss model to be used even with a completely cracked cross-section.

If a shear reinforcement is designed as planned, you can ignore the message about the non-designable situation in the program. In this case, you should ensure that VEd is smaller than VRd,max and VRd,s.


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  • Updated 06/03/2020

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