The design of cold-formed steel members according to the AISI S100-16 / CSA S136-16 is available in RFEM 6. Design can be accessed by selecting “AISC 360” or “CSA S16” as the standard in the Steel Design Add-on. “AISI S100” or “CSA S136” is then automatically selected for the cold-formed design.
RFEM applies the Direct Strength Method (DSM) to calculate the elastic buckling load of the member. The Direct Strength Method offers two types of solutions, numerical (Finite Strip Method) and analytical (Specification). The FSM signature curve and buckling shapes can be viewed under Sections.
Due to the integrated RF-/STEEL Warping Torsion module extension, it is possible to perform the design according to Design Guide 9 in RF-/STEEL AISC.
The calculation is performed with 7 degrees of freedom according to the warping torsion theory and enables a realistic stability design, including consideration of torsion.
The determination of the critical buckling moment is carried out in RF-/STEEL AISC by using the eigenvalue solver which allows an exact determination of the critical buckling load.
The eigenvalue solver shows a display window of the eigenvalue graphics, which enables checking of the boundary conditions.
In STEEL AISC, it is possible to consider lateral intermediate supports at any location. For example, it is possible to stabilize only the upper flange.
Furthermore, user-defined lateral intermediate supports can be assigned; for example, single rotational springs and translational springs at any location at the cross-section.
Due to the integration of RF‑/DYNAM Pro in RFEM or RSTAB, you can incorporate numeric and graphic results from RF‑/DYNAM Pro - Nonlinear Time History to the global printout report. Also, all RFEM and RSTAB options are available for a graphical visualization. The results of the time history analysis are displayed in a time history diagram.
The results are displayed as a function of time and the numerical values can be exported to MS Excel. Result combinations can be exported, either as a result of a single time step or the most unfavorable results of all time steps are filtered out.
Calculation in RFEM
The nonlinear time history analysis is performed with the implicit Newmark analysis or the explicit analysis. Both are direct time integration methods. The implicit analysis requires small time steps to provide precise results. The explicit analysis determines the required time step automatically to provide the stability to the solution. The explicit analysis is suitable for the analysis of short excitations, such as impulse excitation, or an explosion.
Calculation in RSTAB
The nonlinear time history analysis is performed with the explicit analysis. This is a direct time integration method and determines the required time step automatically in order to provide the solution stability.
RF-/DYNAM Pro - Nonlinear Time History is integrated in the structure of RF‑/DYNAM Pro - Forced Vibrations and extended by two nonlinear analysis methods (one nonlinear analysis in RSTAB).
Force-time diagrams can be entered as transient, periodic, or as a function of time. Dynamic load cases combine the time diagrams with the static load cases, which provides high flexibility. Furthermore, it is possible to define time steps for the calculation, structural damping, and export options in the dynamic load cases.
- Nonlinear member types, such as tension and compression members or cables
- Member nonlinearities, such as failure, tearing, yielding under tension or compression
- Support nonlinearities, such as failure, friction, diagram, and partial activity
- Release nonlinearities, such as friction, partial activity, diagram, and fixed if positive or negative internal forces
- User-defined time diagrams as a function of time, in tabular form, or as harmonic loads
- Combination of the time diagrams with RFEM/RSTAB load cases or combinations (enables definition of nodal, member, and surface loads, as well as free and generated loads varying over time)
- Combination of several independent excitation functions
- Nonlinear time history analysis with the implicit Newmark analysis (RFEM only) or the explicit analysis
- Structural damping using Rayleigh damping coefficients or Lehr's damping
- Direct import of initial deformations from a load case or combination (RFEM only)
- Stiffness modifications as initial conditions; for example, axial force effect, deactivated members (RSTAB only)
- Graphical display of results in a time history diagram
- Export of results in user-defined time steps or as an envelope