Thus, it is possible to assign the relevant load cases or load combinations to a mass case, then include them in a mass combination together with partial safety factors.
Transfer of Loads as Masses
In RF-/DYNAM Pro - Natural Vibrations, it is possible to transfer complete load cases/load combinations as masses. To do this, you can simply save the load case or the load combination to be considered as a mass case in the add‑on module.
Author
Mr. Frenzel is responsible for developing products for dynamic analysis. He also provides technical support for customers of Dlubal Software.
Links
Do you have any questions?
Length: 00:01:26 min
Length: 01:01:38 min
Length: 00:01:15 min
Knowledge Base
Length: 00:01:15 min
Length: 00:00:53 min
Knowledge Base
Length: 00:03:05 min
Knowledge Base
Length: 00:02:25 min
Length: 01:01:16 min
Blast loads from high-energy explosives, either accidental or intentional, are rare but may be a structural design requirement. These dynamic loads differ from standard static loads due to their large magnitude and very short duration. A blast scenario can be carried out directly in an FEA program as a time history analysis to minimize loss of life and evaluate varying levels of structural damage.
In RFEM, you can modify stiffnesses for materials, cross-sections, members, load cases, and load combinations in many places. There are two options in RF‑DYNAM Pro for considering these modifications when determining the natural frequencies.
RF-/DYNAM Pro - Equivalent Loads allows you to determine the loads due to equivalent seismic loads according to the multi‑modal response spectrum method. In the example shown here, this was done for a multi‑mass oscillator.
In this article, representations of a blast scenario of a remote detonation performed in RF-DYNAM Pro - Forced Vibrations are shown, and the effects are compared in the linear time history analysis.
![Reduction of Building to Cantilever Structure: The individual mass points represent the floors. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces [2].](/en/webimage/009762/2420261/01-en-png-12-png.png?mw=350&hash=dd36dc43123116724231958668ad6cdcb13a0169)
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 behavior correctly, at least two FE layers for gas solids should be defined.
- Automatic consideration of masses from self-weight
- Direct import of masses from load cases or load combinations
- Optional definition of additional masses (nodal, linear, surface masses, as well as inertia masses)
- Combination of masses in different mass cases and mass combinations
- Preset combination coefficients according to EC 8
- Optional import of normal force distributions (in order to consider prestress, for example)
- Stiffness modification (for example, deactivated members or stiffnesses can be imported from RF-/CONCRETE)
- Consideration of failed supports or members
- Definition of several natural vibration cases (for example, to analyze different masses or stiffness modifications)
- Results of eigenvalue, angular frequency, natural frequency, and period
- Determination of mode shapes and masses in nodes or FE mesh points
- Results of modal masses, effective modal masses, and modal mass factors
- Visualization and animation of mode shapes
- Various scaling options for mode shapes
- Documentation of numerical and graphical results in the printout report
After the calculation, the eigenvalues, natural frequencies, and natural periods are listed. These result windows are integrated in the main program RFEM/RSTAB. The mode shapes of the structure are included in tables and can be displayed graphically or as an animation.
All result tables and graphics are part of the RFEM/RSTAB printout report. This way, clearly arranged documentation is ensured. Furthermore, it is possible to export the tables to MS Excel.
The RF-DYNAM Pro - Natural Vibrations module of RFEM provides four powerful eigenvalue solvers:*Root of characteristic polynomial
- Method by Lanczos
- Subspace Iteration
- ICG iteration method (Incomplete Conjugate Gradient)
The DYNAM Pro - Natural Vibrations module for RSTAB provides two eigenvalue solvers:
- Subspace Iteration
- Shifted inverse power method
The selection of the eigenvalue solver depends primarily on the size of the model.
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?
Why can I only calculate seismic loads in one direction when using 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?
Is it possible to display natural frequencies separately for each direction?
What is the approach for seismic design in RFEM or RSTAB 8?
What is the meaning of the symbols in the graphical display of mode shapes of the RF‑/DYNAM Pro add-on module?
Recommended Products for You
RFEM 6 | Main Program RFEM 6
Main Program
The new generation of 3D FEA software is used for the structural analysis of members, surfaces, and solids.
Price of First License
4,170.00 USD
RFEM 6 | Dynamic Analysis
Add-On
The Modal Analysis add-on allows for the calculation of eigenvalues, natural frequencies, and natural periods for member, surface, and solid models.
Price of First License
1,210.00 USD
RFEM 6 | Dynamic Analysis
Add-On
The Response Spectrum Analysis add-on performs seismic analysis using multi-modal response spectrum analysis. The spectra required for this can be created in compliance with the standards or can be user-defined. The equivalent static forces are generated from them. The add-on includes an extensive library of accelerograms from seismic zones that can be used to generate the response spectra.
Price of First License
1,390.00 USD
RFEM 6 | Dynamic Analysis
Add-On
Using the Pushover Analysis add-on, you can analyze the seismic actions on a particular building, and thus assess whether the building can withstand an earthquake.
Price of First License
1,300.00 USD
RFEM 6 | Additional Analysis
Add-On
The Time-Dependent Analysis (TDA) add-on allows you to consider the time-dependent material behavior of members. The long-term effects, such as creep, shrinkage, and aging, can influence the distribution of internal forces, depending on the structure.
Price of First License
1,030.00 USD
RFEM 6 | Design
Add-On
The Concrete Design add-on allows for various design checks according to international standards. You can design members, surfaces, and columns, as well as perform punching and deformation analyses.
Price of First License
2,550.00 USD
RFEM 6 | Design
Add-On
The Steel Design add-on performs the ultimate and serviceability limit state design checks of steel members according to various standards.
Price of First License
2,550.00 USD
RFEM 6 | Design
Add-On
The Timber Design add-on performs the ultimate, serviceability, and fire resistance limit state design checks of timber members according to various standards.
Price of First License
1,930.00 USD
RFEM 6 | Design
Add-On
The Masonry Design add-on for RFEM allows you to design masonry using the finite element method. It was developed as part of the research project titled DDMaS – Digitizing the Design of Masonry Structures. The material model represents the nonlinear behavior of the brick-mortar combination in the form of macro-modeling.
Price of First License
1,660.00 USD
RFEM 6 | Design
Add-On
The Aluminum Design add-on performs the ultimate and serviceability limit state design checks of aluminum members according to various standards.
Price of First License
1,750.00 USD
RSTAB 9 | Main Program RSTAB 9
Main Program
The modern 3D structural analysis and design program is suitable for the structural and dynamic analysis of beam structures as well as the design of concrete, steel, timber, and other materials.
Price of First License
2,910.00 USD
RSTAB 9 | Dynamic Analysis
Add-On
The Modal Analysis add-on allows for the calculation of eigenvalues, natural frequencies, and natural periods for member, surface, and solid models.
Price of First License
1,210.00 USD
RSTAB 9 | Dynamic Analysis
Add-On
The Response Spectrum Analysis add-on performs seismic analysis using the multi-modal response spectrum analysis. The spectra required for this can be created in compliance with the standards or can be user-defined. The equivalent static forces are generated from them. The add-on includes an extensive library of accelerograms from seismic zones that can be used to generate response spectra.
Price of First License
1,390.00 USD
RSTAB 9 | Dynamic Analysis
Add-On
Earthquakes may have a significant impact on the deformation behavior of buildings. A pushover analysis allows you to analyze the deformation behavior of buildings and compare them with seismic actions. Using the Pushover Analysis add-on, you can analyze the seismic actions on a particular building, and thus assess whether the building can withstand the earthquake.
Price of First License
1,300.00 USD
RSTAB 9 | Design
Add-On
Concrete Design add-on allows for various design checks of members and columns according to international standards.
Price of First License
2,550.00 USD
RSTAB 9 | Design
Add-On
The Steel Design add-on performs the ultimate and serviceability limit state design checks of steel members according to various standards.
Price of First License
2,550.00 USD
RSTAB 9 | Design
Add-On
The Timber Design add-on performs the ultimate, serviceability, and fire resistance limit state design checks of timber members according to various standards.
Price of First License
1,930.00 USD
RSTAB 9 | Design
Add-On
The Aluminum Design add-on performs the ultimate and serviceability limit state design checks of aluminum members according to various standards.
Price of First License
1,750.00 USD