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).
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.
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 yet for the design standard ADM 2020).
Design of cross-sections of Class 4 with effective cross-section properties according to EN 1993‑1‑5 (licenses for RSECTION and Effective Sections are required for the RSECTION cross-sections)
Shear buckling check with consideration of transverse stiffeners
Stability analyses for flexural buckling, torsional buckling, and flexural-torsional buckling under compression
Lateral-torsional buckling analysis of the structural components subjected to moment loading
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
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 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)
Have you activated the Time-Dependent Analysis (TDA) add-on? Very well, now you can add time data to load cases. After you have defined the start and end of the load, the influence of creep at the end of the load is taken into account. The program allows you to model creep effects for frame and truss structures made of reinforced concrete.
In this case, the calculation is performed nonlinearly according to the rheological model (Kelvin and Maxwell model).
Was the calculation successful? You can now display the determined internal forces in tables and graphics, and consider them in the design.
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)
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
Compared to the RF‑/ALUMINUM add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Aluminum Design add-on for RFEM 6 / RSTAB 9:
In addition to Eurocode 9, the US standard ADM 2020 is integrated.
Consideration of the stabilizing effect of purlins and sheets by rotational restraints and shear panels
Graphical display of the results in the gross section
Output of the used design check formulas (including a reference to the used equation from the standard)
For each load case, the deformations can be displayed at the end time.
These results are also documented for you in the printout report of RFEM and RSTAB. You can select the report contents and extent specifically for the individual design checks.
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?
Do you have great respect for the ravages of time? After all, it eventually gnaws at your construction projects. Use the Time-Dependent Analysis (TDA) add-on to consider the time-dependent material behavior of members. Long-term effects, such as creep, shrinkage, and aging, can influence the distribution of internal forces, depending on the structure. Prepare for this optimally with this add-on.
Did you know that To calculate masonry structures, a nonlinear material model has been implemented in RFEM. It is based on the approach of Lourenco, a composite yield surface according to Rankine and Hill. This model allows you to describe and model the structural behavior of masonry and the different failure mechanisms.
The limit parameters were selected in such a way that the design curves used correspond to a normative design curve.
RFEM allows you to use a special line hinge to model the special properties of the connection between the reinforced concrete slab and masonry wall. This limits the transferable forces of the connection depending on the specified geometry. You guess right: This means that the material cannot be overloaded.
The program develops interaction diagrams that are applied automatically. They represent the various geometric situations and you can use them to determine the correct stiffness.
The calculation of masonry is carried out in compliance with the nonlinear-plastic material law. If the load at any point is higher than the possible load to be resisted, redistribution takes place within the system. This have the simple purpose of restoring the equilibrium of forces. With the successful completion of the calculation, the stability analysis is provided.
The program does a lot of work for you. For example, the load or result combinations required for the serviceability limit state are generated and calculated in RFEM/RSTAB. You can select these design situations for the deflection analysis in the Aluminum Design add-on. Depending on the specified precamber and reference system, the program determines the deformation values at each location of a member. They are then compared to the limit values.
You can specify the deformation limit value individually for each structural component in Serviceability Configuration. In this case, you define the maximum deformation depending on the reference length as the allowable limit value. By defining design supports, you can segment the components. In this way, you can determine the corresponding reference length automatically for each design direction.
And that's not all. Based on the position of the assigned design supports, the program allows you to automatically determine the distinction between beams and cantilevers. The limit value is thus determined accordingly.
You can find the serviceability limit state design checks in the result tables of the Aluminum Design add-on. They are already fully integrated there. You have the option to display the design results with all the details at each location of the designed members. You can also use graphics with the result diagrams of the design ratios.
You can integrate all result tables and graphics into the global printout report of RFEM/RSTAB as a part of the aluminum design results. RFEM/RSTAB also allows you to display and document the deformations of the entire structure independently of the add-on.
Do you prefer it clear? So do we! That's why all performed design checks for the design standard are displayed for you in a clear way. You determine a design criterion for each design check. You get design details, which include the initial values, intermediate results, and final results, arranged in a structured way for each design check. You can find the calculation process with the applied formulas, standard sources, and results in great detail in an information window in the design details.
You can find the design checks displayed in tables in the Aluminum Design add-on. Moreover, you can display the distribution of the design ratios graphically. Extensive filter options are available for you both in the table as well as in the graphical output. You can thus specifically display the desired design checks by limit state or design type in the program.
When calculating the deflection limit, you have to consider certain reference lengths. You can define these reference lengths and the segments to be checked independently of each other, depending on the direction. For this, define design supports at the intermediate nodes of a member and assign them to the respective direction for the deformation analysis. Thus, the segments are created where you can define a precamber for each direction and segment.
Note that the definition of the effective lengths in the Aluminum Design add-on is an essential requirement for the stability analysis. For this, define the nodal supports and effective length factors in the input dialog box. Do you want to clearly document the nodal supports and the resulting segments with the associated effective length factors? To check the input data, it is best for you to use the graphic display in the RFEM/RSTAB work window. Thus, you can comprehend the design at any time with minimum effort.
As usual, you enter the structural system and calculate the internal forces in the programs RFEM and RSTAB. You have unlimited access to the extensive material and cross-section libraries. Did you know that you can create general cross-sections using the RSECTION program? That saves you a lot of work.
Don't be afraid of additional windows and input chaos! Aluminum Design is completely integrated into the main programs and automatically takes into account the structure and the available calculation results. You can directly assign further entries for the aluminum design, such as effective lengths, cross-section reductions, or design parameters, to the objects to be designed. You can simply and efficiently select the elements graphically using the [Select] function.
Was your design successful? Very good, now comes the relaxed part. Because the program gives you the performed design checks in a table. You can display all result details in detail here. The clearly presented design formulas ensure that you will be able to understand the results without any problems. There is no black-box effect with Dlubal Software.
The design checks are carried out at all governing locations of the members and displayed graphically as a result diagram. You can find more detailed graphics in the result output. This includes the stress distribution on the cross-section or the governing mode shape, for example.
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.
The Aluminum Design add-on provides you with further options. Here you can also design general cross-sections that are not predefined in the cross-section library. For example, create a cross-section in the RSECTION program and then import it into RFEM/RSTAB. Depending on the design standard used, you can select from various design formats. This includes, for example, the equivalent stress analysis.
With a license for RSECTION and Effective Sections, you can also perform the design checks while taking into account the effective cross-section properties according to EN 1993‑1‑5.