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
- 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.
- A wide range of available sections, such as rolled I-sections; channel sections; T-sections; angles; rectangular and circular hollow sections; round bars; symmetrical and asymmetrical, parametric I-, T-, and angle sections; built-up cross-sections (suitability for design depends on the selected standard)
- Design of general RSECTION cross-sections (depending on the design formats available in the respective standard); for example, equivalent stress design
- Design of tapered members (design method depending on the standard)
- Adjustment of the essential design factors and standard parameters is possible
- Flexibility due to detailed setting options for basis and extent of calculations
- Fast and clear results output for an immediate overview of the result distribution after the design
- Detailed output of the design results and essential formulas (comprehensible and verifiable result path)
- Numerical results clearly arranged in tables and graphical display of the results in the model
- Integration of the output into the RFEM/RSTAB printout report
- Design of tension, compression, bending, shear, torsion, and combined internal forces
- Tension design with consideration of a reduced section area (for example, hole weakening)
- Automatic classification of cross-sections to check local buckling
- Internal forces from the calculation with Torsional Warping (7 DOF) are taken into account by means of the equivalent stress check (currently not for the design standards AISC 360‑16 and GB 50017).
- Design of cross-sections of Class 4 with effective cross-section properties according to EN 1993‑1‑3 (licenses for RSECTION and Effective Sections are required for the RSECTION cross-sections)
- Shear buckling check according to EN 1993‑1‑5 with consideration of transverse stiffeners
- Design of stainless steel components according to EN 1993‑1‑4
- Stability analyses for flexural buckling, torsional buckling, and flexural-torsional buckling under compression
- Import of the effective lengths from the calculation using the Structure Stability add-on
- Graphical input and check of the defined nodal supports and effective lengths for stability analysis
- Lateral-torsional buckling analysis of the structural components subjected to moment loading
- Depending on the standard, a choice between user-defined input of Mcr, analytical method from the standard, and use of internal eigenvalue solver
- Consideration of a shear panel and a rotational restraint when using the eigenvalue solver
- Graphical display of a mode shape if the eigenvalue solver was used
- Stability analysis of structural components with the combined compression and bending stress, depending on the design standard
- Comprehensible calculation of all necessary coefficients, such as the factors for considering moment distribution or interaction factors
- Alternative consideration of all effects for the stability analysis when determining internal forces in RFEM/RSTAB (second-order analysis, imperfections, stiffness reduction, possibly in combination with the Torsional Warping (7 DOF) add-on)
You enter the structural system and calculate the internal forces in the programs RFEM and RSTAB. You have full access to the extensive material and cross-section libraries. Did you know? You can also use the RSECTION program to create general cross-sections.
You find Steel Design fully integrated in the main programs. They automatically take into account the structure and the available calculation results. You can assign further entries for the aluminum design, such as effective lengths, cross-section reductions, or design parameters, to the objects to be designed. At many places of the program, you can easily select the elements graphically using the [Select] function.
- For the design according to Eurocode 3, the parameters of the National Annexes (NA) are integrated for the following countries:
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DIN EN 1993-1-1/NA:2016-04 (Germany)
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ÖNORM EN 1993-1-1/NA:2015-12 (Austria)
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SN EN 1993-1-1/NA:2016-07 (Switzerland)
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BDS EN 1993-1-1/NA:2015-10 (Bulgaria)
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BS EN 1993-1-1/NA:2016-07 (United Kingdom)
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CEN EN 1993-1-1/2015-06 (European Union)
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CYS EN 1993-1-1/NA:2015-07 (Cyprus)
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CZE EN 1993-1-1/NA:2016-06 (Czech Republic)
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DS EN 1993-1-1/NA:2015-07 (Denmark)
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ELOT EN 1993-1-1/NA:2017-01 (Greece)
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EVS EN 1993-1-1/NA:2015-08 (Estonia)
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HRN EN 1993-1-1/NA:2016-03 (Croatia)
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I S. EN 1993-1-1/NA:2016-03 (Ireland)
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ILNAS EN 1993-1-1/NA:2015-06 (Luxembourg)
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IST EN 1993-1-1/NA:2015-11 (Iceland)
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LST EN 1993-1-1/NA:2017-01 (Lithuania)
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LVS EN 1993-1-1/NA:2015-10 (Latvia)
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MS EN 1993-1-1/NA:2010-01 (Malaysia)
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MSZ EN 1993-1-1/NA:2015-11 (Hungary)
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NBN EN 1993-1-1/NA:2015-07 (Belgium)
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NEN EN 1993-1-1/NA:2016-12 (Netherlands)
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NF EN 1993-1-1/NA:2016-02 (France)
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NP EN 1993-1-1/NA:2009-03 (Portugal)
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NS EN 1993-1-1/NA:2015-09 (Norway)
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PN EN 1993-1-1/NA:2015-08 (Poland)
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SFS EN 1993-1-1/NA:2015-08 (Finland)
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SIST EN 1993-1-1/NA:2016-09 (Slovenia)
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SR EN 1993-1-1/NA:2016-04 (Romania)
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SS EN 1993-1-1/NA:2019-05 (Singapore)
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SS EN 1993-1-1/NA:2015-06 (Sweden)
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STN EN 1993-1-1/NA:2015-10 (Slovakia)
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TKP EN 1993-1-1/NA:2015-04 (Belarus)
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UNE EN 1993-1-1/NA:2016-02 (Spain)
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UNI EN 1993-1-1/NA:2015-08 (Italy)
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- The design according to US standard AISC 360 includes analysis methods according to:
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Load and Resistance Factor Design (LRFD)
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Allowable Stress Design (ASD)
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Was your design successful? Just sit back and relax. The program gives you the performed design checks in tables. All result details are displayed for you and you can easily follow them using the clearly arranged design formulas.
The design checks are carried out at all governing locations of the members. A graphical display is provided as a result diagram. Furthermore, you have access to detailed graphics, such as the stress distribution on a cross-section or the governing mode shape, available in the result output.
All input and result data are part of the RFEM/RSTAB printout report. You can select the report contents and extent specifically for the individual design checks.
- 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.
- Simple definition of construction stages in the RFEM structure including visualization
- Adding, removing, modifying, and reactivating member, surface, and solid elements and their properties (for example, member and line hinges, degrees of freedom for supports, and so on)
- Automatic and manual combinatorics with load combinations in the individual construction stages (for example, to consider mounting loads, mounting cranes, and other loads)
- Consideration of nonlinear effects such as tension member failure or nonlinear supports
- Interaction with other add-ons, such as Nonlinear Material Behavior, Structure Stability, Form-Firnding, and so on.
- Display of results numerically and graphically for individual construction stages
- Detailed printout report with documentation of all structural and load data for each construction stage
Have you created the entire structure in RFEM? Very well, now you can assign the individual structural components and load cases to the corresponding construction stages. In each construction stage, you can modify release definitions of members and supports, for example.
You can thus model structural modifications, such as those that occur when bridge girders are successively grouted or when columns are settled. Then, assign the load cases created in RFEM to the construction stages as permanent or non-permanent loads.
Did you know that The combinatorics allows you to superimpose the permanent and non-permanent loads in load combinations. In this way, it is possible for you to determine the maximum internal forces of different crane positions or to consider temporary mounting loads available in one construction stage only.
If there are geometry differences arising between the ideal and the deformed structural system from the previous construction stage, they are compared in the program. The next construction stage is built on top of the stressed system from the previous construction stage. This calculation is nonlinear.
Was the calculation successful? Now you can view the results of the individual construction stages graphically and in tables in RFEM. Moreover, RFEM allows you to consider the construction stages in the combinatorics and include it in further design.
Once you activate the Form-Finding add-on in the Base Data, a form-finding effect is assigned to the load cases with the load case category "Prestress" in conjunction with the form-finding loads from the member, surface, and solid load catalog. This is a prestress load case. It thus mutates into a form-finding analysis for the entire model with all member, surface, and solid elements defined in it. You reach the form-finding of the relevant member and membrane elements amid the overall model by using special form-finding loads and regular load definitions. These form-finding loads describe the expected state of deformation or force after the form-finding in the elements. The regular loads describe the external loading of the entire system.
Do you know exactly how the form-finding is performed? First, the form-finding process of the load cases with the load case category "Prestress" shifts the initial mesh geometry to an optimally balanced position by means of iterative calculation loops. For this task, the program uses the Updated Reference Strategy (URS) method by Prof. Bletzinger and Prof. Ramm. This technology is characterized by equilibrium shapes that, after the calculation, comply almost exactly with the initially specified form-finding boundary conditions (sag, force, and prestress).
In addition to the pure description of the expected forces or sags on the elements to be formed, the integral approach of the URS also enables a consideration of regular forces. In the overall process, this allows, for example, for a description of the self-weight or a pneumatic pressure by means of corresponding element loads.
All these options give the calculation kernel the potential to calculate anticlastic and synclastic forms that are in an equilibrium of forces for planar or rotationally symmetric geometries. In order to be able to realistically implement both types individually or together in one environment, the calculation provide you with two ways to describe the form-finding force vectors:
- Tension method - description of the form-finding force vectors in space for planar geometries
- Projection method - description of the form-finding force vectors on a projection plane with fixation of the horizontal position for conical geometries
The form-finding process gives you a structural model with active forces in the "prestress load case" This load case shows the displacement from the initial input position to the form-found geometry in the deformation results. In the force or stress-based results (member and surface internal forces, solid stresses, gas pressures, and so on), it clarifies the state for maintaining the found form. For the analysis of the shape geometry, the program offers you a two-dimensional contour line plot with the output of the absolute height and an inclination plot for the visualization of the slope situation.
Now, a further calculation and structural analysis of the entire model is performed. For this purpose, the program transfers the form-found geometry including the element-wise strains into a universally applicable initial state. You can now use it in the load cases and load combinations.
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‑/STAGES add-on module (RFEM 5), the following new features have been added to the Construction Stages Analysis (CSA) add-on for RFEM 6:
- Consideration of construction stages at RFEM level
- Integration of the construction stage analysis into the combinatorics in RFEM
- Additional structural elements, such as line hinges, are supported
- Analysis of alternative construction processes in a model
- Reactivation of elements
Compared to the RF-FORM-FINDING add-on module (RFEM 5), the following new features have been added to the Form-Finding add-on for RFEM 6:
- Specification of all form-finding load boundary conditions in one load case
- Storage of form-finding results as initial state for further model analysis
- Automatic assignment of the form-finding initial state via combination wizards to all load situations of a design situation
- Additional form-finding geometry boundary conditions for members (unstressed length, maximum vertical sag, low-point vertical sag)
- Additional form-finding load boundary conditions for members (maximum force in member, minimum force in member, horizontal tension component, tension at i-end, tension at j-end, minimum tension at i-end, minimum tension at j-end)
- Material types "Fabric" and "Foil" in material library
- Parallel form-findings in one model
- Simulation of sequentially building form-finding states in connection with the Construction Stages Analysis (CSA) add-on
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
Compared to the RF‑/STEEL EC3 add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Steel Design add-on for RFEM 6 / RSTAB 9:
- In addition to Eurocode 3, other international standards are integrated (such as AISC 360, CSA S16, GB 50017, SP 16.13330)
- Consideration of hot-dip galvanizing (DASt guideline 027) in the fire protection design according to EN 1993‑1‑2
- Input option for transverse stiffeners that can be taken into account in the shear buckling analysis
- Lateral-torsional buckling can also be checked for hollow sections (for example, relevant for slender, high rectangular hollow sections)
- Automatic detection of members or member sets valid for the design (for example, automatic deactivation of members with invalid material or members already contained in a member set)
- Design settings can be adjusted individually for each member
- Graphical display of the results in the gross section or the effective section
- Output of the used design check formulas (including a reference to the used equation from the standard)
With Dlubal Software, you always have an overview, regardless of whether your projects are from the reinforced concrete, steel, timber, aluminum, or other industry. The program clearly displays the design check formulas used in your design (including a reference to the used equation from the standard). These design check formulas can also be included in the printout report.
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