KB 000692 | Definition of Minimum Longitudinal Reinforcement for Reinforced Concrete Columns

Daily tasks in reinforced concrete design also include designing compression elements subjected to biaxial bending. The following article describes the different methods according to Chapter 5.8.9, EN 1992-1-1, which can be used to design compression elements with biaxial load eccentricities by means of the nominal curvature method according to 5.8.8.

When calculating the internal forces for the buckling analysis with the method based on nominal curvature in RF‑CONCRETE Columns, the required eccentricities have to be determined.

Effective lengths for columns can be determined automatically with RF-/CONCRETE Columns. This article describes which entries are necessary and how the calculation of the effective lengths is performed.

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.

With the Concrete Design add-on, you can perform the fatigue design of members and surfaces according to EN 1992‑1‑1, Chapter 6.8.

For the fatigue design, you can optionally select two methods or design levels in the design configurations:

• Design Level 1: Simplified design according to 6.8.6 and 6.8.7(2): The simplified design is performed for frequent action combinations according to EN 1992‑1‑1, Chapter 6.8.6 (2), and EN 1990, Eq. (6.15b) with the traffic loads relevant in the serviceability state. A maximum stress range according to 6.8.6 is designed for the reinforcing steel. The concrete compressive stress is determined by means of the upper and lower allowable stress according to 6.8.7(2).
• Design Level 2: Design of damage equivalent stress acc. to 6.8.5 and 6.8.7(1) (simplified fatigue design): The design using damage equivalent stress ranges is performed for the fatigue combination according to EN 1992‑1‑1, Chapter 6.8.3, Eq. (6.69) with the specifically defined cyclic action Q_fat.

The Concrete Design add-on allows you to perform the seismic design of reinforced concrete members according to EC 8. This includes, among other things, the following functionalities:

• Seismic design configurations
• Differentiation of the ductility classes DCL, DCM, DCH
• Option to transfer the behavior factor from a dynamic analysis
• Check of the limit value for the behavior factor
• Capacity design checks of "Strong column - weak beam"
• Detailing and particular rules for curvature ductility factor
• Detailing and particular rules for local ductility