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RF-/DYNAM Pro - Forced Vibrations Add-on Module for RFEM/RSTAB
Extension of RF-DYNAM Pro - Natural Vibrations for Time History Analysis and Multi-Modal Response Spectrum Analysis
Customer Projects
The RF-/DYNAM Pro - Forced Vibrations add‑on module provides a tool for dynamic analysis of mechanical structures to external excitations. Various excitation functions can be defined in a tabular form, as harmonic loads or as a function of time. The time history analysis is performed either with the modal analysis or with the linear implicit Newmark analysis.
Using the multi‑modal and multi‑point response spectrum analyses, it is possible to perform seismic analyses. The required spectra can be created in compliance with the standards or user‑defined. The add‑on module contains an extensive library of accelerograms from earthquake zones, which can be used to generate response spectra.
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Features of Time History Analysis
- Combination of user-defined time diagrams with load cases or combinations (nodal, member and surface loads as well as free and generated loads can be combined with functions varying over time)
- Combination of several independent excitation functions
- Extensive library of seismic events (accelerograms)
- Linear implicit Newmark analysis or modal analysis in time history
- Structural damping using Raleigh damping coefficients or Lehr's damping
- Direct import of initial deformations from a load case or combination
- Graphical display of results in a time history diagram
- Export of results in user-defined time steps or as an envelope
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Features of Multi-Modal Response Spectrum Analysis
- Response spectra of numerous standards (ASCE 7-16, NBC 2015, etc.)
- User-defined response spectra or generated from accelerograms
- Direction-relative response spectra approach
- Manual or automatic selection of the relevant mode shapes of response spectra (5 % rule of EC 8 applicable)
- Result combinations by modal superimposition (SRSS or CQC rule) and by direction superimposition (SRSS or 100 % / 30 % rule)
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Input
It is necessary to enter the required response spectra, accelerations, or time diagrams. Dynamic load cases define the location and direction of response spectra effects as well as acceleration time, or force-time excitations.
Time diagrams can be combined with static load cases which provide great flexibility. For the time history analysis, you can import the initial deformation from any load case or load combination.
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Calculation
The time history analysis is performed with the modal analysis or the linear implicit Newmark analysis. The time history analysis in this add‑on module is restricted to linear systems. Although the modal analysis represents a fast algorithm, it is necessary to use a certain number of eigenvalues to ensure the required accuracy of results.
The implicit Newmark analysis is a very precise method, independent of the number of eigenvalues used, but requires sufficient small time steps for calculation. For the response spectra analysis, equivalent static loads are calculated internally. A linear static analysis is performed subsequently.
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Results
Due to the integration of RF‑/DYNAM Pro in RFEM / RSTAB, you can incorporate numeric and graphic results from RF‑/DYNAM Pro – Forced Vibrations to the global printout report. Also, all RFEM options are available for a graphical visualization.
The results of the time history analysis are displayed in a time course monitor. All results are plotted versus time. You can export the numeric values to MS Excel.
In the case of a time history analysis, you can export results of the individual time steps or filter most unfavourable results of all time steps.
The response spectrum analysis generates result combinations. Mode and load force combinations due to the components of earthquake action are used internally.
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Simplified Blast Design According to AISC Steel Design Guide 26
Blast loads from high energy explosives, either accidental or intentional, are rare but may be a structural design requirement.

Considering the Stiffness of Gas Solids in Nonlinear Time History Analysis
The stiffness of gas given by the ideal gas law pV = nRT can be considered in the nonlinear dynamic analysis.
The calculation of gas is available for accelerograms and time diagrams for both the explicit analysis and the nonlinear implicit Newmark analysis. To determine the gas behaviour correctly, at least two FE layers for gas solids should be defined.
- RF‑/DYNAM Pro - Forced Vibrations and RF‑/DYNAM Pro - Equivalent Loads perform the multi-modal response spectrum analysis. What are the differences?
- There are two different add-on modules for a response spectrum analysis in RF‑/DYNAM Pro. What can be the reasons for the different results of both add-on modules?
- What is the meaning of the superposition according to the CQC rule in a dynamic analysis??
- How can I display the results of the RF‑/DYNAM Pro add-on module in the printout report?
- Rayleigh damping is available in RF‑/DYNAM Pro. How do I determine and use these factors?
- Two solving methods for a linear time history analysis are available in the RF‑/DYNAM Pro add-on module. What is the difference between them?
- In RF‑/DYNAM Pro, the "From self-weight of structure" option is available in a mass case. Is it always necessary to activate this option in order to consider the dead load of the structure?
- I have used the RF‑/DYNAM Pro add-on module to generate the governing result combinations of seismic loads. What is the next procedure to perform the design of the individual structural components?
- Why do I only obtain the seismic loads calculated in one direction in the case of design with RF‑/DYNAM Pro?
- During the check in RF‑/DYNAM Pro, I get the message "No natural vibration case or dynamic load case has been selected for the calculation." Why?
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