If there is a load case or load combination in the program, the stability calculation is activated. You can define another load case in order to consider initial prestress, for example.
For this, you need to specify whether to perform a linear or nonlinear analysis. Depending on the case of application, you can select a direct calculation method, such as the Lanczos method or the ICG iteration method. Members not integrated in surfaces are usually displayed as member elements with two FE nodes. With such elements, the program cannot determine the local buckling of single members. That's why you have the option to divide members automatically.
You can select several methods that are available for the eigenvalue analysis:
- Direct Methods
- The direct methods (Lanczos [RFEM], roots of characteristic polynomial [RFEM], subspace iteration method [RFEM/RSTAB], and shifted inverse iteration [RSTAB]) are suitable for small to medium-sized models. You should only use these fast solver methods if your computer has a larger amount of memory (RAM).
- ICG Iteration Method (Incomplete Conjugate Gradient [RFEM])
- In contrast, this method only requires a small amount of memory. Eigenvalues are determined one after the other. It can be used to calculate large structural systems with few eigenvalues.
Use the Structure Stability add-on to perform a nonlinear stability analysis using the incremental method. This analysis delivers close-to-reality results also for nonlinear structures. The critical load factor is determined by gradually increasing the loads of the underlying load case until the instability is reached. The load increment takes into account nonlinearities such as failing members, supports and foundations, and material nonlinearities. After increasing the load, you can optionally perform a linear stability analysis on the last stable state in order to determine the stability mode.
As the first results, the program presents you with the critical load factors. You can then perform an evaluation of stability risks. For member models, the resulting effective lengths and critical loads of the members are displayed to you in tables.
Use the next result window to check the normalized eigenvalues sorted by node, member, and surface. The eigenvalue graphic allows you to evaluate the buckling behavior. This makes it easier for you to take countermeasures.
- Calculation of models consisting of member, shell, and solid elements
- Nonlinear stability analysis
- Optional consideration of axial forces from initial prestress
- Four equation solvers for an efficient calculation of various structural models
- Optional consideration of stiffness modifications in RFEM/RSTAB
- Determination of a stability mode greater than the user-defined load increment factor (Shift method)
- Optional determination of the mode shapes of unstable models (to identify the cause of instability)
- Visualization of the stability mode
- Basis for determining imperfection
- Consideration of 7 local deformation directions (ux, uy, uz, φx, φy, φz, ω) or 8 internal forces (N, Vu, Vv, Mt,pri, Mt,sec, Mu, Mv, Mω) when calculating member elements
- Usable in combination with a structural analysis according to linear static, second-order, and large deformation analysis (imperfections can also be taken into account)
- In combination with the Stability Analysis add-on, allows you to determine critical load factors and mode shapes of stability problems such as torsional buckling and lateral-torsional buckling
- Consideration of end plates and transverse stiffeners as warping springs when calculating I-sections with automatic determination and graphical display of the warping spring stiffness
- Graphical display of the cross-section warping of members in the deformation
- Full integration with RFEM and RSTAB
You can perform the calculation of the warping torsion on the entire system. Thus, you consider the additional 7th degree of freedom in the member calculation. The stiffnesses of the connected structural elements are automatically taken into account. It means, you don't need to define equivalent spring stiffnesses or support conditions for a detached system.
You can then use the internal forces from the calculation with warping torsion in the add-ons for the design. Consider the warping bimoment and the secondary torsional moment, depending on the material and the selected standard. A typical application is the stability analysis according to the second-order theory with imperfections in steel structures.
Did you know that The application is not limited to thin-walled steel cross-sections. Thus, it is possible for you, for example, to perform the calculation of the ideal overturning moment of beams with solid timber cross-sections.
- General stress analysis
- Automatic import of internal forces from RFEM/RSTAB
- Graphical and numerical output of stresses, strains, clearance, and design ratios fully integrated in RFEM/RSTAB
- User-defined specification of the limit stress
- Summary of similar structural components for the design
- Wide range of customization options for graphical output
- Clearly arranged result tables for a quick overview after the design
- Simple traceability of the results due to the complete documentation of the calculation method including all formulas
- High productivity due to the minimal amount of input data required
- Flexibility due to detailed setting options for basis and extent of calculations
- Gray zone display for unimportant value ranges (see Product Feature)
- Cross-section optimization
- Transfer of optimized sections to RFEM/RSTAB
- Design of any thin-walled section from RSECTION
- Representation of a stress diagram on a section
- Determination of normal, shear, and equivalent stresses
- Output of stress components for the individual member internal force types
- Detailed representation of stresses in all stress points
- Determination of the largest Δσ for each stress point (for example, for fatigue design)
- Colored display of stresses and design ratios for a quick overview of the critical or oversized zones
- Output of parts lists
- Determination of principal and basic stresses, membrane and shear stresses, as well as equivalent stresses and equivalent membrane stresses
- Stress analysis for structural surfaces including simple or complex shapes
- Equivalent stresses calculated according to different approaches:
- Shape modification hypothesis (von Mises)
- Shear stress hypothesis (Tresca)
- Normal stress hypothesis (Rankine)
- Principal strain hypothesis (Bach)
- Optional optimization of surface thicknesses and data transfer to RFEM
- Output of strains
- Detailed results of individual stress components and ratios in tables and graphics
- Filter function for solids, surfaces, lines, and nodes in tables
- Transversal shear stresses according to Mindlin, Kirchhoff, or user-defined specifications
- Stress evaluation for welds at connection lines between surfaces (see the Product Feature)
After you have completed the design, the program takes care of clearly arranged results. Thus, the program shows you the resulting maximum stresses and stress ratios sorted by section, member/surface, solid, member set, x-location, and so on. In addition to the tabular result values, the add-on shows you the corresponding cross-section graphic with stress points, stress diagram, and values as well. You can relate the design ratio to any kind of stress type. The current location is highlighted in the RFEM/RSTAB model.
In addition to the tabular evaluation, the program offers you even more. You can also graphically check the stresses and design ratios on the RFEM/RSTAB model. It is possible for you to adjust the colors and values individually.
The display of result diagrams of a member or set of members enables you a targeted evaluation. For each design location, you can open the respective dialog box to check the design-relevant section properties and stress components of any stress point. Finally, you have the option of printing the corresponding graphic, including all design details.
- You can activate or deactivate the use of torsional warping in the Add-ons tab of the model's Base Data.
- After activating the add-on, the user interface in RFEM is extended by some new entries in the navigator, tables, and dialog boxes.
The parameters of the National Annexes (NA) to Eurocode 3 of the following countries are integrated:
-
DIN EN 1993-1-1/NA:2016-04 (Germany)
-
ÖNORM EN 1993-1-1/NA:2015-12 (Austria)
-
SN EN 1993-1-1/NA:2016-07 (Switzerland)
-
BDS EN 1993-1-1/NA:2015-10 (Bulgaria)
-
BS EN 1993-1-1/NA:2016-07 (United Kingdom)
-
CEN EN 1993-1-1/2015-06 (European Union)
-
CYS EN 1993-1-1/NA:2015-07 (Cyprus)
-
CSN EN 1993-1-1/NA:2016-06 (Czech Republic)
-
DS EN 1993-1-1/NA:2015-07 (Denmark)
-
ELOT EN 1993-1-1/NA:2017-01 (Greece)
-
EVS EN 1993-1-1/NA:2015-08 (Estonia)
-
HRN EN 1993-1-1/NA:2016-03 (Croatia)
-
I S. EN 1993-1-1/NA:2016-03 (Ireland)
-
ILNAS EN 1993-1-1/NA:2015-06 (Luxembourg)
-
IST EN 1993-1-1/NA:2015-11 (Iceland)
-
LST EN 1993-1-1/NA:2017-01 (Lithuania)
-
LVS EN 1993-1-1/NA:2015-10 (Latvia)
-
MS EN 1993-1-1/NA:2010-01 (Malaysia)
-
MSZ EN 1993-1-1/NA:2015-11 (Hungary)
-
NBN EN 1993-1-1/NA:2015-07 (Belgium)
-
NEN EN 1993-1-1/NA:2016-12 (Netherlands)
-
NF EN 1993-1-1/NA:2016-02 (France)
-
NP EN 1993-1-1/NA:2009-03 (Portugal)
-
NS EN 1993-1-1/NA:2015-09 (Norway)
-
PN EN 1993-1-1/NA:2015-08 (Poland)
-
SFS EN 1993-1-1/NA:2015-08 (Finland)
-
SIST EN 1993-1-1/NA:2016-09 (Slovenia)
-
SR EN 1993-1-1/NA:2016-04 (Romania)
-
SS EN 1993-1-1/NA:2019-05 (Singapore)
-
SS EN 1993-1-1/NA:2015-06 (Sweden)
-
STN EN 1993-1-1/NA:2015-10 (Slovakia)
-
TKP EN 1993-1-1/NA:2015-04 (Belarus)
-
UNE EN 1993-1-1/NA:2016-02 (Spain)
-
UNI EN 1993-1-1/NA:2015-08 (Italy)
- Realistic representation of interaction between a building and soil
- Realistic representation of the influences of the foundation components on each other
- Extensible library of soil properties
- Consideration of several soil samples (probes) at different locations, even outside the building
- Determination of settlements and stress diagrams as well as their graphical and tabular display
Entering soil layers for soil samples is performed in a clearly arranged dialog box. A corresponding graphical representation supports clarity and makes checking the input user-friendly.
An extensible database facilitates the selection of soil material properties. The Mohr-Coulomb model as well as a nonlinear model with stress and strain dependent stiffness are available for a realistic modeling of the soil material behavior.
You can define any number of soil samples and layers. The soil is generated from all entered samples using 3D solids. Assignment to the structure is carried out using coordinates.
The soil body is calculated according to the nonlinear iterative method. The calculated stresses and settlements are displayed graphically and in tables.
- Automatic consideration of masses from self-weight
- Direct import of masses from load cases or load combinations
- Optional definition of additional masses (nodal, linear, or surface masses, as well as inertia masses) directly in the load cases
- Optional neglect of masses (for example, mass of foundations)
- Combination of masses in different load cases and load combinations
- Preset combination coefficients for various standards (EC 8, SIA 261, ASCE 7,...)
- Optional import of initial states (for example, to consider prestress and imperfection)
- Structure Modification
- Consideration of failed supports or members/surfaces/solids
- Definition of several modal analyses (for example, to analyze different masses or stiffness modifications)
- Selection of mass matrix type (diagonal matrix, consistent matrix, unit matrix), including user-defined specification of translational and rotational degrees of freedom
- Methods for determining the number of mode shapes (user-defined, automatic - to reach effective modal mass factors, automatic - to reach the maximum natural frequency - only available in RSTAB)
- Determination of mode shapes and masses in nodes or FE mesh points
- Results of eigenvalue, angular frequency, natural frequency, and period
- Output of modal masses, effective modal masses, modal mass factors, and participation factors
- Masses in mesh points displayed in tables and graphics
- Visualization and animation of mode shapes
- Various scaling options for mode shapes
- Documentation of numerical and graphical results in printout report
In the modal analysis settings, you have to enter all data that are necessary for the determination of the natural frequencies. These are, for example, mass shapes and eigenvalue solvers.
The Modal Analysis add-on determines the lowest eigenvalues of the structure. Either you adjust the number of eigenvalues or let them determined automatically. Thus, you should reach either effective modal mass factors or maximum natural frequencies. Masses are imported directly from load cases and load combinations. In this case, you have the option to consider the total mass, load components in the global Z-direction, or only the load component in the direction of gravity.
You can manually define additional masses at nodes, lines, members, or surfaces. Furthermore, you can influence the stiffness matrix by importing axial forces or stiffness modifications of a load case or load combination.
In RFEM, you can use these three powerful eigenvalue solvers:
- Root of Characteristic Polynomial
- Method by Lanczos
- Subspace Iteration
RSTAB, on the other hand, provides you with these two eigenvalue solvers:
- Subspace Iteration
- Shifted inverse power method
The selection of the eigenvalue solver depends primarily on your model size.
As soon as the program has completed the calculation, the eigenvalues, natural frequencies and periods are listed. These result windows are integrated in the main program RFEM/RSTAB. You can find all mode shapes of the structure in tables and also have an option to display them graphically and to animate them.
All result tables and graphics are part of the RFEM/RSTAB printout report. In this way, you can ensure clearly arranged documentation. You can also export the tables to MS Excel.
- Automatic generation of FE analysis models: The add-on automatically creates a finite element model (FE) of the steel connection in the background.
- Consideration of all internal forces: The calculation and design checks include all internal forces (N, Vy, Vz, My, Mz, MT) and are not limited to planar loading.
- Automatic load transfer: All load combinations are automatically transferred to the FE analysis model of the connection. The loads are transferred directly from RFEM, so manual data input is not necessary.
- Efficient modeling: The add-on saves you time when modeling complex connection situations. You can also save the created FE analysis model and use it further for your own detailed analyses.
- Extensible library: An extensive and extensible library with predefined steel connection templates is available.
- Wide applicability: The add-on is suitable for connections of any type and shape, compatible with almost all rolled, welded, built-up, and thin-walled cross-sections.
- Selection of nodes in the RFEM model, automatic recognition and assignment of the members connected to the node
- Many predefined components available for easy input of typical connection situations (for example, end plates, cleats, fin plates)
- Universally applicable basic components (plates, welds, auxiliary planes) for entering complex connection situations
- No manual editing of the FE model required by the user, the essential calculation settings can be changed via the configuration settings
- Automatic adaptation of the connection geometry, even if the members are subsequently edited, due to the relative relation of the components to each other
- Parallel to the input, a plausibility check is carried out by the program to quickly detect missing input or collisions, for example
- Graphical display of the connection geometry that is updated in parallel with the input
The program supports you: It determines the bolt forces on the basis of the FE analysis model and evaluates them automatically. The add-on performs the standard-compliant design of bolt resistance for failure cases, such as tension, shear, hole bearing, and punching, and clearly displays all required coefficients.
Do you want to perform weld design? The welds are modeled as elastic-plastic surface elements, and their stresses are read out from the FE analysis model. The plasticity criteria is set in the way that they represent failure according to AISC J2-4, J2-5 (strength of welds), and J2-2 (strength of base metal). The design can be performed with the partial safety factors of the selected National Annex of EN 1993‑1‑8.
The plates in the connection are designed plastically by comparing the existing plastic strain to the allowable plastic strain. The default setting is 5% according to EN 1993‑1‑5, Annex C, but can be adjusted by user-defined specifications, as well as 5% for AISC 360.
You can display all essential results on the FE model. In this case, you can filter the results separately according to the respective components.
Furthemore, RFEM delivers you all design checks in a tabular form, including the display of the formulas used. If you wish, you can transfer the result tables to the RFEM printout report.
Compared to the RF‑/STABILITY (RFEM 5) and RSBUCK (RSTAB 8) add-on modules, the following new features have been added to the Structure Stability add-on for RFEM 6 / RSTAB 9:
- Activation as a property of a load case or a load combination
- Automated activation of the stability calculation via combination wizards for several load situations in one step
- Incremental load increase with user-defined termination criteria
- Modification of the mode shape normalization without recalculation
- Result tables with filter option
Compared to the RF-/STEEL Warping Torsion add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Torsional Warping (7 DOF) add-on for RFEM 6 / RSTAB 9:
- Complete integration into the environment of RFEM 6 and RSTAB 9
- 7th degree of freedom is directly taken into account in the calculation of members in RFEM/RSTAB on the entire system
- No more need to define support conditions or spring stiffnesses for calculation on the simplified equivalent system
- Combination with other add-ons is possible, for example for the calculation of critical loads for torsional buckling and lateral-torsional buckling with stability analysis
- No restriction to thin-walled steel sections (it is also possible to calculate ideal overturning moments for beams with massive timber sections, for example)
Compared to the RF‑/DYNAM Pro - Natural Vibrations add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Modal Analysis add-on for RFEM 6 / RSTAB 9:
- Preset combination coefficients for various standards (EC 8, ASCE, and so on)
- Optional neglect of masses (for example, mass of foundations)
- Methods for determining the number of mode shapes (user-defined, automatic - to reach effective modal mass factors, automatic - to reach the maximum natural frequency)
- Output of modal masses, effective modal masses, modal mass factors, and participation factors
- Masses in mesh points displayed in tables and graphics
- Various scaling options for mode shapes in the Result navigator
Compared to the RF‑SOILIN add-on module (RFEM‑5), the following new features have been added to the Geotechnical Analysis add-on for RFEM 6:
- Creation of the layered soil as a 3D model from the entirety of the defined soil samples
- Recognized material law according to Mohr-Coulomb for soil simulation
- Graphical and tabular output of stresses and strains at any depth of the soil
- Optimal consideration of the soil-structure interaction on the basis of an overall model
Compared to the RF‑/STEEL add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Stress-Strain Analysis add-on for RFEM 6 / RSTAB 9:
- Treatment of members, surfaces, solids, welds (line welded joints between two and three surfaces with subsequent stress design)
- Output of stresses, stress ratios, stress ranges, and strains
- Limit stress depending on the assigned material or a user-defined input
- Individual specification of the results to be calculated through freely assignable setting types
- Non-modal result details with prepared formula display and additional result display on the cross-section level of members
- Output of the design check formulas used
Do you work with steel connections? The Steel Joints add-on for RFEM supports you when analyzing steel connections by using an FE model. In this case, the modeling runs fully automatically in the background. Nevertheless, you can control this process via the simple and familiar input of components. You can then use the loads determined on the FE model for your design of the components according to EN 1993‑1‑8 (including National Annexes).
Reinforced concrete usually answers the question "How much can you carry?" simply with "Yes". Nevertheless, you need a three-dimensional moment-moment-axial force interaction diagram for the graphical output of the ultimate limit state of reinforced concrete cross-sections. The Dlubal structural analysis software offers you just that.
With the additional display of the load action, you can easily recognize or visualize whether the limit resistance of a reinforced concrete cross-section is exceeded. Since you can control the diagram properties, you can customize the appearance of the My-Mz-N diagram to suit your needs.
Did you know that you can also display the moment-axial force interaction diagrams (M‑N diagrams) graphically? This allows you to display the cross-section resistance in the case of an interaction of a bending moment and an axial force. In addition to the interaction diagrams related to the cross-section axes (My‑N diagram and Mz‑N diagram), you can also generate an individual moment vector to create an Mres‑N interaction diagram. You can display the section plane of the M‑N diagrams in the 3D interaction diagram. The program displays the corresponding value pairs of the ultimate limit state in a table. The table is dynamically linked to the diagram so that the selected limit point is also displayed in the diagram.