Online Training | Eurocode 2 | Reinforced Concrete Design - Serviceability

The RF-CONCRETE Members and CONCRETE add-on modules provide the option for "Dimensioning of Longitudinal Reinforcement for Serviceability Limit State". You can select the design criteria for the calculation of the longitudinal reinforcement.

When designing reinforced concrete components according to EN 1992‑1‑1 [1], nonlinear methods of determining internal forces for the ultimate and serviceability limit states are possible. In this case, the internal forces and deformations are determined with respect to their nonlinear behaviour. The analysis of stresses and strains in cracked state usually provides the deflections, which clearly exceed the linearly determined values.

The fatigue design according to EN 1992-1-1 must be performed for the structural components subjected to large stress ranges and/or many load changes. In this case, the design checks for the concrete and the reinforcement are performed separately. There are two alternative design methods available.

The deformation analysis according to the approximation method defined in standards (for example, deformation analysis according to EN 1992‑1‑1, 7.4.3) applies to the calculation of "effective stiffnesses" in the finite elements in accordance with the existing limit state of the concrete with or without cracks. These stiffnesses are used to determine the surface deformation by repeated FEM calculation.

The effective stiffness calculation of finite elements takes into account a reinforced concrete cross-section. Based on the internal forces determined for the serviceability limit state in RFEM, the program classifies the reinforced concrete cross-section as 'cracked' or 'uncracked'. If the tension stiffening at a section should be considered as well, a distribution coefficient (according to EN 1992-1-1, Eq. 7.19, for example) is used. The material behavior for the concrete is assumed to be linear-elastic in the compression and tension zone until the concrete tensile strength is reached. This is reached exactly in the serviceability limit state.

When determining the effective stiffnesses, creep and shrinkage are taken into account at the "cross-section level". The influence of shrinkage and creep in statically indeterminate systems is not taken into account in this approximation method (for example, tensile forces from shrinkage strain in systems restrained on all sides are not determined and must be considered separately). In summary, RF-CONCRETE Deflect calculates deformations in two steps:

1. Calculation of effective stiffnesses of the reinforced concrete cross-section assuming linear-elastic conditions
2. Calculation of the deformation using the effective stiffnesses with FEM

Do you have individual column sections and angled wall geometries, and need punching shear design for them?

No problem. In RFEM 6, you can perform punching shear design not only for rectangular and circular sections, but for any cross-section shape.

The Concrete Design add-on provides you with the option to perform the simplified fire resistance design according to EN 1992‑1‑2 for columns (Section 5.3.2) and beams (Section 5.6).

The following design checks are available for the simplified fire resistance design:

• Columns: Minimum cross-sectional dimensions for rectangular and circular sections according to Table 5.2a as well as Equation 5.7 for calculating time of fire exposure
• Beams: Minimum dimensions and center distances according to Table 5.5 and Table 5.6

You can determine the internal forces for the fire resistance design according to two methods.

• 1 Here, the internal forces of the accidental design situation are included directly into the design.
• 2 The internal forces of the design at normal temperature are reduced by the factor Eta,fi (ηfi), then used in the fire resistance design.

Furthermore, it is possible to modify the axis distance according to Eq. 5.5.