Answer:
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.
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.
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