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2.6.2 Principal Internal Forces
Principal Internal Forces
If the first principal internal force is negative, uncracked concrete is assumed in the area of the analyzed surface element. For walls, only the magnitude of the concrete compression stress is checked in such a case. For plates, no serviceability limit state design is carried out, at least on this surface side.
For a wall, if the first principal axial force is a tension force, the provided concrete tensile stress is determined according to the following equation.
For a plate, if the first principal moment is a positive moment, the provided concrete tensile stress is determined as follows.
If this linear-elastically determined stress σc,I is greater than the mean value of the axial tensile strength fctm, cracked concrete is assumed. Only then does RF-CONCRETE Surfaces determine the design internal forces for the individual directions of reinforcement and perform the serviceability limit state designs mentioned at the beginning of chapter 2.6.