Introduction

Stress limitation (SLS) check is based on the calculation of stresses in particular component (concrete fibre, reinforcement bar) and comparison with limited values with respect of EN 1992-1-1 requirements. Based on the internal forces, concrete cross-section and reinforcement defined by the user, SCIA Engineer is able to calculate the plain of equilibrium of a member or a single cross-section and find the actual value of stresses in each component.

Generally, stress limitation from the point of the serviceability limit state is based on the verification of the following states:

• compressive stress in concrete - the high value of compressive stress in concrete could lead to appearance of longitudinal cracks, spreading of micro-cracks in concrete and higher values of creep (mainly non linear) . This effect can led to state when the structure is unusable.
• tensile stress in reinforcement - stress in reinforcement is verified due to limitation of unacceptable strain existence and thus appearance of cracks in concrete .

The method described in chapter "Theoretical background" is used for determination of the plane of the equilibrium. There are used different stress-strain diagrams towards the Capacity-response (ULS). Stress-strain diagrams based on the serviceability limit state are used for the finding of the plain of the equilibrium. This check provides the calculation of the stresses in particular components for each state of cross-section.

Generally, this check uses the iterative method for the interaction of the normal force (N) with uni-axial or bi-axial bending moments (M_y + M_z). Additionally, there is possibility to calculate stresses for short-term or long-term stiffness which is applied via modified stress-strain diagram.