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.
- Consideration and display of story masses
- Listing of structural elements and their information
- Automated creation of result sections on shear walls
- Output of section resultants in global direction for determining shear forces
- Optional definition of rigid diaphragm by story (story modeling)
- Stiffness type Floor Slab - Rigid Diaphragm
- Defining floor sets,
- for example, calculation of slabs as a 2D position within the 3D model
- Shear walls: Automatic definition of result members with any cross-section
- Design of rectangular cross-sections using the Concrete Design add-on
- Definition of deep beams
- Design with the Concrete Design add-on
- Tabular output of story actions, interstory drift, and center points of mass and stiffness, as well as the forces in shear walls
- Separate result display of the floor and stiffening design
- Optional neglecting of openings of a certain size
You have two options for a building model. You can create it when you start modeling the structure, or activate it afterwards. In the building model, you can then directly define the stories and manipulate them.
When manipulating the stories, you can choose whether to modify or retain the included structural elements using various options.
RFEM does some of the work for you. For example, it automatically generates result sections, so you don't need to perform a lot of calculations.
You can display the results as usual via the Results navigator. Furthermore, the dialog box of the add-on shows you the information about the individual floors. Thus, you always have a good overview.
The Dlubal structural analysis software does a lot of work for you. The input parameters, which are relevant for the selected standards, are suggested by the program in accordance with the rules. Furthermore, you can enter response spectra manually.
Load cases of the type Response Spectrum Analysis define the direction in which response spectra act and which eigenvalues of the structure are relevant for the analysis. In the spectral analysis settings, you can define details for the combination rules, damping (if applicable), and zero-period acceleration (ZPA).
Did you know that Equivalent static loads are generated separately for each relevant eigenvalue and excitation direction. These loads are saved in a load case of the Response Spectrum Analysis type and RFEM/RSTAB performs a linear static analysis.
The load cases of the type Response Spectrum Analysis contain the generated equivalent loads. First, the modal contributions have to be superimposed with the SRSS or CQC rule. In this case, you can use the signed results based on the dominant mode shape.
Afterwards, the directional components of earthquake actions are combined with the SRSS or the 100% / 30% rule.
- 002108
- General
- Optimization & Cost / CO2 Emission Estimation for RFEM 6
- Optimization & Cost / CO2 Emission Estimation for RSTAB 9
- Artificial intelligence technology (AI): Particle swarm optimization (PSO)
- Structure optimization according to the minimum weight or deformation
- Use of any number of optimization parameters
- Specification of variable ranges
- Optimization of cross-sections and materials
- Parameter definition types
- Optimization | Ascending or Optimization | Descending
- Application of parametric models and blocks
- Code-based JavaScript parametrization of blocks
- Optimization taking into account the design results
- Tabular display of the best model mutations
- Real-time display of the model mutations in the optimization process
- Model cost estimation by specifying unit prices
- Determination of the global warming potential GWP when realizing the model by estimating the CO2 equivalent
- Specification of weight-, volume-, and area-based units (price and CO2e)
- 002109
- General
- Optimization & Cost / CO2 Emission Estimation for RFEM 6
- Optimization & Cost / CO2 Emission Estimation for RSTAB 9
Did you know? The structural optimization in the programs RFEM and RSTAB is a completion of the parametric input. It is a parallel process beside the actual model calculation with all its regular calculation and design definitions. The add-on assumes that your model or block is built with a parametric context and is controlled in its entirety by global control parameters of the "optimization" type. Therefore, these control parameters have a lower and upper limit and a step size to delimit the optimization range. If you want to find optimal values for the control parameters, you have to specify an optimization criterion (for example, minimum weight) with the selection of an optimization method (for example, particle swarm optimization).
You can already find the cost and CO2 emission estimation in the material definitions. You can activate both options individually in each material definition. The estimation is based on a unit for unit cost or unit emission for members, surfaces, and solids. In this case, you can select whether to specify the units by weight, volume, or area.
- 002110
- General
- Optimization & Cost / CO2 Emission Estimation for RFEM 6
- Optimization & Cost / CO2 Emission Estimation for RSTAB 9
There are two methods that you can use for the optimization process, with which you can find optimal parameter values according to a weight or deformation criterion.
The most efficient method with the littlest calculation time is the near-natural particle swarm optimization (PSO). Have you heard or read about it? This artificial intelligence (AI) technology has a strong analogy to the behavior of flocks of animals, looking for a resting place. In such swarms, you can find many individuals (cf. optimization solution - for example, weight) who like to stay in a group and follow the group movement. Let's assume that each individual swarm member has a need to rest at an optimal resting place (cf. best solution - for example, lowest weight). This need increases as the resting place is approached. Thus, the swarm behavior is also influenced by the properties of the space (cf. result diagram).
Why the excursion into biology? Quite simply – the PSO process in RFEM or RSTAB proceeds in a similar way. The calculation run starts with an optimization result from a random assignment of the parameters to be optimized. It repeatedly determines new optimization results with varied parameter values, which are based on the experience of the previously performed model mutations. The process continues until the specified number of possible model mutations is reached.
As an alternative to this method, the program also offers you a batch processing method. This method attempts to check all possible model mutations by randomly specifying the values for the optimization parameters until a predetermined number of possible model mutations is reached.
After calculating a model mutation, both variants also check the respective activated design results of the add-ons. Furthermore, they save the variant with the corresponding optimization result and value assignment of the optimization parameters if the utilization is < 1.
You can determine the estimated total costs and emission from the respective sums of the individual materials. The sums of the materials are composed of the weight-based, volume-based, and area-based partial sums of the member, surface, and solid elements.
- Stress determination using an elastic-plastic material model
- Design of masonry disc structures for compression and shear on the building model or single model
- Automatic determination of stiffness of a wall-slab hinge
- An extensive material database for almost all stone-mortar combinations available on the Austrian market (the product range is continuously being expanded, for other countries as well)
- Automatic determination of material values according to Eurocode 6 (ÖN EN 1996‑X)
- Option to create pushover analysis
You enter and model the structure directly in RFEM. You can combine the masonry material model with all common RFEM add-ons. This enables you to design the entire building models in connection with masonry.
The program automatically determines for you all parameters required for the calculation by using the material data that you have entered. Then, it finally generates the stress-strain curves for each FE element.
Was your design successful? Then just sit back and relax. You benefit from the numerous functions in RFEM also here. The program gives you the maximum stresses of the masonry surfaces, whereby you can display the results in detail at each FE mesh point.
Moreover, you can insert sections in order to carry out a detailed evaluation of the individual areas. Use the display of the yield areas to estimate the cracks in the masonry.
- 002161
- General
- Optimization & Cost / CO2 Emission Estimation for RFEM 6
- Optimization & Cost / CO2 Emission Estimation for RSTAB 9
Both optimization methods have one thing in common. At the end of the process, they provide you with a list of model mutations from the stored data. Here you can find the details of the controlling optimization result and the associated value assignment of the optimization parameters. This list is organized in descending order. You can find the assumed best solution shown in the first line. For this, the optimization result with its determined value assignment is closest to the optimization criterion. All add-on results have a utilization < 1. Furthermore, once the analysis is completed, the program will adjust the value assignment to that of the optimal solution for the optimization parameters in the global parameter list.
In the material dialog boxes, you can find the additional tabs "Cost Estimation" and "Estimation of CO2 Emissions". They show you the individual estimated sums of the assigned members, surfaces, and solids per unit weight, volume, and area. Furthermore, these tabs show the total cost and emission of all assigned materials. This gives you a good overview of your project.
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.