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.
- 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.
- 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.
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‑/TIMBER Pro add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Timber Design add-on for RFEM 6 / RSTAB 9:
- In addition to Eurocode 5, other international standards are integrated (SIA 265, ANSI/AWC NDS, CSA O86, GB 50005)
- Design of compression perpendicular to grain (support pressure)
- Implementation of eigenvalue solver for determining the critical moment for lateral-torsional buckling (EC 5 only)
- Definition of different effective lengths for design at normal temperature and fire resistance design
- Evaluation of stresses via unit stresses (FEA)
- Optimized stability analyses for tapered members
- Unification of the materials for all national annexes (only one "EN" standard is now available in the material library for a better overview)
- Display of cross-section weakenings directly in the rendering
- Output of the used design check formulas (including a reference to the used equation from the standard)
Building stone on stone has a long tradition in construction. 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 DDMaS - Digitizing the Design of Masonry Structures. Here, the material model represents the nonlinear behavior of the brick-mortar combination in the form of macro-modeling. Do you want to find out more?
- Calculation of deflections and comparison with the normative or manually adjusted limit values
- Consideration of a precamber for the deflection analysis
- Different limit values are possible, depending on the design situation type
- Manual adjustment of reference lengths and segmentation by direction
- Calculation of deflections related to the initial structure or to the deformed structure
- Automatic consideration of time-dependent deformations by increasing the load with the creep factor (can also be user-defined on the stiffness side)
- Simplified vibration design
- Graphical result display integrated in RFEM/RSTAB; for example, the design ratio of a limit value, the deformation, or the sag
- Complete integration of the results into the RFEM/RSTAB printout report
Your RFEM/RSTAB program is responsible for generating and calculating the load and result combinations required for the serviceability limit state. Select the design situations for the deflection analysis in the Timber Design add-on. The calculated deformation values are then determined at each location of a member, depending on the specified precamber and the reference system, and then compared to the limit values.
You can specify the deformation limit value individually for each structural component in Serviceability Configuration. In this case, the maximum deformation should not exceed the permissible limit value, depending on the reference length. When defining design supports, you can segment the components. This allows you to determine the corresponding reference length automatically for each design direction.
Based on the position of the assigned design supports, the program automatically determines the difference between beams and cantilevers. Thus, you can be sure that the limit value is determined accordingly.
You find the serviceability limit state design fully integrated in the result tables of the Timber Design add-on. If yuo want to check the design results, you can open the program and display the results with all the details at each location of the designed members. Furthermore, graphics are available for you with the result diagrams of the design ratios.
A special thing is that All result tables and graphics can be integrated into the global printout report of RFEM/RSTAB as a part of the timber design results. You can also display and document the deformations of the entire structure as a part of the RFEM/RSTAB functionality. This function is independent of the add-on.
- A wide range of cross-sections, such as rectangular sections, square sections, T‑sections, circular sections, built-up cross-sections, irregular parametric cross-sections, and many others (suitability for design depends on the selected standard)
- Design of cross-laminated timber (CLT)
- Design of timber-based materials and laminated veneer lumber according to EC 5
- Design of tapered and curved members (design method according to 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
- Consideration of a notch
- Design of compression perpendicular to the grain on the end and intermediate supports with (EC 5) and without reinforcement elements (fully threaded screws)
- Optional shear force reduction at the support (see the Product Feature)
- Design of curved and tapered members
- Consideration of higher strengths for similar components that are close together (factor ksys according to EN 1995‑1‑1, 6.6(1)-(3))
- Option to increase shear resistance for softwood timber according to DIN EN 1995‑1‑1:NA NDP to 6.1.7(2)
- 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
- Determination of the equivalent member lengths for tapered members
- Consideration of Lateral-Torsional Bracing Position
- 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)
- Arbitrary definition of the charring time
- Option to calculate with or without adhesion of the layer for surface structures (cross-laminated timber)
- Free user-defined specification of the fire parameters
- Consideration of Different Effective Lengths in Fire Resistance Design
- Optional design "Compression perpendicular to grain"
- Graphical result display integrated in RFEM/RSTAB, such as a design ratio
- Complete integration of the results into the RFEM/RSTAB printout report
RFEM/RSTAB also provides a range of functions for the case of a fire. The program allows for the automatic generation of load and result combinations for the accidental design situation of fire design. The members to be designed with the corresponding internal forces are imported directly from RFEM/RSTAB. Also, all information about the material and cross-section is stored. You don't need to do anything else.
You only define the parameters relevant for the fire resistance design by assigning a fire resistance configuration to the members and surfaces to be designed. Moreover, you can also make further detailed settings, such as the definition of the fire exposure on one side up to all sides.
As you probably know, the design checks for the selected members are carried out, taking into account the defined charring time. All necessary reduction factors and coefficients are stored accordingly in the program and are taken into account when determining the load-bearing capacity. That saves you a lot of work.
The effective lengths for the equivalent member design are taken directly from the strength entries. You do not have to enter them again.
After completing the design, the program presents the fire resistance design checks clearly and with all result details. This allows you to follow the results completely transparently. The results also contain all the required parameters, so you can determine the component temperature at the design time.
In addition to all these features, the program allows you to integrate all result tables and graphics, including the ultimate and serviceability limit state results,into the global printout report of RFEM/RSTAB as a part of the steel design results.
For the design according to Eurocode 5, the parameters of the National Annexes (NA) are integrated for the following countries:
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DIN EN 1995-1-1/NA:2014-07 (Germany)
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ÖNORM EN 1995-1-1/NA:2019-06 (Austria)
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SN EN 1995-1-1/NA:2015-03 (Switzerland)
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BDS EN 1995-1-1/NA:20157-06 (Bulgaria)
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BS EN 1995-1-1/NA:2019-09 (United Kingdom)
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CEN EN 1995-1-1/2014-05 (European Union)
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CYS EN 1995-1-1/NA:2019-06 (Cyprus)
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CZE EN 1995-1-1/NA:2015-05 (Czech Republic)
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DS EN 1995-1-1/NA:2019-09 (Denmark)
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ELOT EN 1995-1-1/NA:2010-01 (Greece)
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EVS EN 1995-1-1/NA:2015-11 (Estonia)
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HRN EN 1995-1-1/NA:2015-03 (Croatia)
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I S. EN 1995-1-1/NA:2014-05 (Ireland)
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ILNAS EN 1995-1-1/NA:2020-3 (Luxembourg)
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IST EN 1995-1-1/NA:2014-09 (Iceland)
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LST EN 1995-1-1/NA:2014-06 (Lithuania)
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LVS EN 1995-1-1/NA:2014-12 (Latvia)
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MSZ EN 1995-1-1/NA:2015-06 (Hungary)
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NBN EN 1995-1-1/NA:2014-06 (Belgium)
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NEN EN 1995-1-1/NA:2014-06 (Netherlands)
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NF EN 1995-1-1/NA:2020-04 (France)
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NP EN 1995-1-1/NA:2014-09 (Portugal)
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NS EN 1995-1-1/NA:2014-08 (Norway)
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PN EN 1995-1-1/NA:2014-07 (Poland)
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SFS EN 1995-1-1/NA:2016-12 (Finland)
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SIST EN 1995-1-1/NA:2018-01 (Slovenia)
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SR EN 1995-1-1/NA:2014-12 (Romania)
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SS EN 1995-1-1/NA:2018-02 (Singapore)
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SS EN 1995-1-1/NA:2014-05 (Sweden)
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STN EN 1995-1-1/NA:2019-12 (Slovakia)
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TKP EN 1995-1-1/NA:2019-09 (Belarus)
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UNE EN 1995-1-1/NA:2016-04 (Spain)
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UNI EN 1995-1-1/NA:2016-11 (Italy)
Your options in timber design are diverse. You can consider cut-to-grain angles, transverse tension stresses, and volume-dependent radii of curvature for tapered and curved members. To design the area of the grain cut, the strength is adjusted accordingly in the case of bending tension or bending pressure. In order to also allow you to perform a stability analysis with the equivalent member method, the height to determine the effective and lateral-torsional buckling lengths is set at a distance of 0.65 × h to the actual design point.
Here you have a free choice. You can perform the support pressure design at any point for the loading in the y- and z-directions of a cross-section. You are free to differentiate between inner and outer supports. A factor kc,90 for the pressure perpendicular to the grain can be user-defined (for example, 1.75 for glued-laminated timber). If allowed, the support length is increased automatically according to the standard specifications. This allows you to achieve a more efficient design with minimum effort.
There is often no fire resistance design for the lateral supports of a structure. Would you like to handle this differently in your project? In order to consider this in the calculation, you can define other equivalent member lengths for the fire situation.
What happens when there is a downwind? The topside lateral-torsional bracing is not applied to reduce the effective lengths and lateral-torsional buckling lengths.
Dlubal Software just makes everything a little easier. The performed design checks of the design standard are displayed in a clear way. A design criterion is determined for each design check. Furthermore, the program deliver the design details displayed in a structured way, including the initial values, the intermediate results, and the final results. An information window in the design details shows you the calculation process with the applied formulas, standard sources, and results in great detail.
Are you still looking for the design? The design checks are available in tabular form in the Timber Design add-on. Moreover, the program can also show you the distribution of the design ratios graphically. Extensive filter options are available for you in the table as well as in the graphical output, and you can use them to display the desired design checks by limit state or design type.