As before, it is possible to define additional masses on nodes, lines, members, and surfaces. However, this is only an additional option. The defined masses can be combined in mass combinations where the combination factors are preset automatically by RF‑/DYNAM Pro - Natural Vibrations in accordance with EN 1990 and EN 1998‑1, but can be adjusted depending on your needs.
Import of Masses with RF-/DYNAM Pro - Natural Vibrations
The new RF‑/DYNAM Pro - Natural Vibrations module has been available since RFEM version 5.04.xx and RSTAB version 8.04.xx were released. Masses can now be imported directly from load cases and load combinations.
Links
Do you have any questions?
Knowledge Base
Length: 00:01:15 min
Length: 00:00:53 min
Customer Project
Length: 00:00:11 min
Length: 00:01:03 min
Knowledge Base
Length: 00:01:27 min
Length: 00:00:32 min
Length: 00:02:07 min
Length: 00:02:00 min
Length: 00:00:00 min
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.
Both the determination of natural vibrations and the response spectrum analysis are always performed on a linear system. If nonlinearities exist in the system, they are linearized and thus not taken into account. Straight tension members are very often used in practice. This article will show how you can display them approximately correctly in a dynamic analysis.
When introducing and transferring horizontal loads such as wind or seismic loads, increasing difficulties arise in 3D models. To avoid such issues, some standards (for example, ASCE 7, NBC) require the simplification of the model using diaphragms that distribute the horizontal loads to structural components transferring loads, but cannot transfer bending themselves (called "Diaphragm").
![Reduction of a building to a 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=512&hash=8189361dbff525c2ff39c36a72a1ca91810208f6)
For the ultimate limit state design, EN 1998-1 Section 2.2.2 and 4.4.2.2 [1] requires the calculation considering the second-order theory (P-Δ effect). This effect may be neglected only if the interstory drift sensitivity coefficient θ is less than 0.1. The coefficient θ is defined as follows:$$\mathrm\theta\;=\;\frac{\displaystyle{\mathrm P}_\mathrm{tot}\;\cdot\;{\mathrm d}_\mathrm r }{{\mathrm V}_\mathrm{tot}\;\cdot\;\mathrm h}\;(1)$$mitθ = interstorey drift sensitivity coefficientPtot = total gravity load at and above the considered story, considered in the design situation Earthquake (see Equation 2) dr = mutual story drift determined as the difference of the horizontal displacements dS at the top and bottom of the considered story, for this, the displacements are determined using the linear design response spectrum with q = 1.0Vtot = total seismic load of the considered story by using the design linear response spectrumh = the story height
- 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.
Input windows require all data necessary for determination of natural frequencies, such as mass shapes and eigenvalue solvers.
The RF-/DYNAM Pro - Natural Vibrations add-on module determines the lowest eigenvalues of the structure. The number of eigenvalues can be adjusted. Masses are directly imported from load cases or load combinations (with optional consideration of total masses or a load component in the direction of gravity).
Additional masses can be defined manually at nodes, lines, members, or surfaces. Furthermore, it is possible to control the stiffness matrix by importing normal forces or stiffness modifications of a load case or combination.
Why can I only calculate seismic loads in one direction when using RF‑/DYNAM Pro?
What is the approach for seismic design in RFEM or RSTAB 8?
How many mode shapes do I need to consider in the dynamic analysis?
Is it possible to refer to the transverse distribution of a load in the case of the isotropic material model? | Masonry | Plastisch Einfluss zu nehmen?
What is the effect of the "Independent FE Mesh Ppreferred" option in the mesh settings?
How do I define a plastic hinge in RFEM 6?
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