Stress limitation check

The check is based on general assumptions, where two states of the cross-section are resolved: the uncracked section (the tensile strength of the concrete is not ignored) and the fully cracked section (the tensile strength of the concrete is ignored). The solution with ignored concrete tensile strength is considered under the assumptions of Article 7.1 (2) EN 1992-1-1.

When calculating the stress and deflections it is considered as an uncracked section, if the tensile stress in bending does not exceed f_ct, eff. The value of f_ct, eff can be considered as f_ctm or f_ctm,fl. The f_ctm value is used when calculating the crack width and tensile stiffening.

As part of this check, we deal with four basic cases in terms of stress limit.

• 7.2 (2) Compressive stress in members exposed to environments of exposure classes XD, XF and XS should be limited:

$$\left| {{s}_{c}} \right|\le {{k}_{1}}{{f}_{ck}}$$

$${{k}_{1}}=0,6$$

• 7.2 (3) The stress in the concrete under the quasi-permanent loads is limited:

$$\left| {{s}_{c}} \right|\le {{k}_{2}}{{f}_{ck}}$$

$${{k}_{2}}=0,45$$

• 7.2 (5) Tensile stresses in the reinforcement under the characteristic combination of loads shall be limited:

$$\left| {{s}_{s}} \right|\le {{k}_{3}}{{f}_{yk}}$$

$${{k}_{3}}=0,8$$

• 7.2 (5) Where the stress is caused by an imposed deformation, the tensile stress should not exceed:

$$\left| {{s}_{s}} \right|\le {{k}_{4}}{{f}_{yk}}$$

$${{k}_{4}}=1$$

Where values k₁, k₂, k₃, k₄ for use in a Country may be found in its National Annex. The recommended values are 0,8; 1 and 0,75 respectively, characteristic yield stress of the reinforcement, f_ck characteristic cylinder strength f_ck determined at 28 days.