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 initial stiffness Sj,ini is a decisive parameter for evaluating whether a connection can be characterized as rigid, non-rigid, or hinged.
In the “Steel Joints” add-on, you can calculate the initial stiffnesses Sj,ini according to Eurocode (EN 1993-1-8 Section 5.2.2) and AISC (AISC 360-16 Cl. E3.4) in relation to the internal forces N, My, and/or Mz.
The optional automatic transfer of initial stiffnesses allows for a direct transfer as member end hinge stiffnesses in RFEM. Then, the entire structure is recalculated and the resulting internal forces are automatically adopted as loads in the calculation and design of the connection models.
This automated iteration process eliminates the need for manual export and import of data, reducing the amount of work and minimizing potential sources of error.
Always keep track of your model. The model check quickly detects for you the input errors, such as overlapping members or identical nodes. You can automatically connect intersecting members during your input. Members can also be extended or divided graphically. The measure function allows you to determine lengths and angles of members and surfaces (only RFEM).
With this function, it is possible to refine the FE mesh on surfaces automatically. The mesh refinement is gradual. In each step, the FE mesh is recreated based on an error comparison of the results in the previous calculation step. The numerical error is evaluated from the results of surface elements and is based on the energy formulation of Zienkiewicz-Zhu.
The error evaluation is carried out for a linear static analysis. We select a load case (or load combination) for which the FE mesh is generated. The FE mesh is then used for all calculations.
All design results and design checks are displayed in detail and in a comprehensible manner. An error log indicates non-designable situations or failed recommendations. Due to the permanent integration in RFEM/RSTAB, subsequent modifications in the structural system and in loading are automatically taken into account for the connections to be checked.
If one of the designs could not be fulfilled, the corresponding line is highlighted in red. The output appears in a short or a long form in the global printout report of RFEM/RSTAB. Furthermore, you can easily export all result tables to MS Excel or in a CSV file. A special transfer menu defines all specifications required for the export.
Members can be extended or divided graphically. The model check quickly detects input errors such as identical nodes or duplicate members and eliminates them. When entering structural data, you can automatically connect intersecting members. The measure function allows you to determine lengths and angles of members and surfaces (only RFEM).
In RF‑/LTB, the design is usually performed according to the equivalent member method according to DIN 18800, Part 2. However, you can specify extensive detailed settings for the design in a separate dialog box:
Design according to Bird/Heil
Optionally, it is possible to apply the method according to Bird/Heil in the program
the required shear stiffness Sreq
the lateral-torsional buckling load Nki
the critical buckling moment Mki
.
This plastic-plastic calculation method is only valid for lateral and torsional restraints with simple bending with simultaneous load introduction on the upper flange. Further requirements that must be met can be found in the program manual. In case of invalid conditions (for example, biaxial bending), RF-/LTB displays the corresponding error message. In addition, the reduction factorκM for the bending moments My can be set to 1.0 if a restrained rotation axis is present.
Non-Designable Internal Forces
It is possible to neglect non-designable internal forces and thus exclude them from the design if the quotient of the internal force and the fully plastic internal force falls below a certain value. This way, you can neglect, for example, a small moment about the minor axis, thus avoiding the method for biaxial bending.
Allowance according to DIN 18800, Part 2, Element (320) and Element (323)
Automatic determination of ζ
If you want the factor for the determination of the ideal elastic critical moment Mcr to be determined automatically, you can select one of the following types:
Solving the elastic potential numerically
Comparison of moment diagrams
Australian Standard AS 4100-1990
US standard AISC LRFD
When aligning the moment distributions, you can use the library which contains more than 600 moment distributions in tables.
After the calculation, the module shows clearly arranged tables listing the results of the nonlinear calculation. All intermediate values are included in a comprehensible manner. Graphical representation of design ratios, deformations, concrete and reinforcing steel stresses, crack widths, crack depths, and crack spacing in RFEM facilitates a quick overview of critical or cracked areas.
Error messages or remarks concerning the calculation help you find design problems. Since the design results are displayed by surface or by point including all intermediate results, you can retrace all details of the calculation.
Due to the optional export of input or result tables to MS Excel, the data remain available for further use in other programs. The complete integration of results in the RFEM printout report guarantees verifiable structural design.