VE 0017 | Plastic Bending - Continuous Load

The three types of moment frames (Ordinary, Intermediate, Special) are available in the Steel Design add-on of RFEM 6. The seismic design result according to AISC 341-22 is categorized into two sections: member requirements and connection requirements.

To evaluate whether it is also necessary to consider the second-order analysis in a dynamic calculation, the sensitivity coefficient of interstory drift θ is provided in EN 1998‑1, Sections 2.2.2 and 4.4.2.2. It can be calculated and analyzed using RFEM 6 and RSTAB 9.
The coefficient θ is calculated as follows:$$\mathrm\theta\;=\;\frac{\displaystyle{\mathrm P}_\mathrm{tot}\;\cdot\;{\mathrm d}_\mathrm r}{{\mathrm V}_\mathrm{tot}\;\cdot\;\mathrm h}\;$$

The Steel Design add-on in RFEM 6 now offers the ability to perform seismic design according to AISC 341-16 and AISC 341-22. Five types of seismic force-resisting systems (SFRS) are currently available.

The building model is calculated in two phases:

• Global 3D calculation of the global model, where the slabs are modeled as a rigid plane (diaphragm) or as a bending plate
• Local 2D calculation of the individual floors

After the calculation, the results of the columns and walls from the 3D calculation and the results of the slabs from the 2D calculation are combined in a single model. This means that there is no need to switch between the 3D model and the individual 2D models of the slabs. The user only works with one model, saves valuable time, and avoids possible errors in the manual data exchange between the 3D model and the individual 2D ceiling models.

The vertical surfaces in the model can be divided into shear walls and opening lintels. The program automatically generates internal result members from these wall objects, so they can be designed as members according to any standard in the Concrete Design add-on.

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.