Modal Analysis
Glossary Term
The modal analysis is the basis for further dynamic analysis, such as for loading by a response spectrum or a time diagram. This is a completely linear method; the nonlinearities existing in the system are not taken into account.
Modal Analysis in RF-/DYNAM Pro
It is possible to perform the modal analysis in RFEM or RSTAB by using the RF-/DYNAM Pro add-on module. In addition to the results of modal parameters in tables, the natural vibration modes are also available graphically for the evaluation.
Furthermore, the modal analysis represents a method for solving time history. In this case, the determined eigenvalues and mode shapes of the model are directly used.
Keywords
Eigenvalue analysis Eigenvalue problem Dynamics Natural vibration Natural frequency Mode shape Modal mass Modal mass factor
Bibliography
Links
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Determination of equivalent loads in RFEM and RSTAB
With RF-/DYNAM Pro Equivalent Loads, it is possible to perform an equivalent load calculation using the multimodal response spectrum method. In the example shown here, this was done for a multi‑mass oscillator.
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.
- 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?
- How can I consider prestressed cables in RF‑/DYNAM Pro?
- After calculating the add -on module RF-/DYNAM Pro - Equivalent Loads, the size of my file has increased significantly. The performance has deteriorated enormously. What could be the reason for this?
- I would like to calculate and design "temporary structures." What do I need for this?
- Which programs can I use to calculate and design power plants?
- I noticed deviations from the map of DIN EN 1998‑1 or DIN 4149 in the online service "<a href="https://www.dlubal.com/en/solutions/online-services/snow-load-wind-speed-and-seismic-load-maps" target="_blank">Geo-Zone Tool: Snow, Wind, and Seismic Zone Maps</a>." Can you tell me which map is current and thus governing?
- How do you distinguish between the response spectra with equivalent loads and the response spectra without equivalent loads in RFEM and RSTAB?
- I would like to design an aluminum or lightweight structure. Is it possible to use RFEM or RSTAB for this?
- Why do I only obtain the seismic loads calculated in one direction in the case of design with RF‑/DYNAM Pro?
- Are the models and presentations from Info Day 2020 freely available, and can you send them to me?
Associated Products
Main Program
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements
3,540.00 USD
Main Program
The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions
2,550.00 USD
Add-on Module
Dynamic analysis of natural frequencies and mode shapes of member models
850.00 USD
Add-on Module
Dynamic analysis of natural frequencies and mode shapes of member, surface, and solid models
1,030.00 USD
Add-on Module
Dynamic and seismic analysis including time history analysis and multi-modal response spectrum analysis
1,120.00 USD
