The modal relevance factor (MRF) can help you to assess to which extent specific elements participate in a specific mode shape. The calculation is based on the relative elastic deformation energy of each individual member.
The MRF can be used to distinguish between local and global mode shapes. If multiple individual members show significant MRF (for example, > 20%), the instability of the entire structure or a substructure is very likely. On the other hand, if the sum of all MRFs for an eigenmode is around 100%, a local stability phenomenon (for example, buckling of a single bar) can be expected.
Furthermore, the MRF can be used to determine critical loads and equivalent buckling lengths of certain members (for example, for stability design). Mode shapes for which a specific member has small MRF values (for example, < 20%) can be neglected in this context.
The MRF is displayed by mode shape in the result table under Stability Analysis → Results by Members → Effective Lengths and Critical Loads.
The Concrete Design add-on allows you to perform the seismic design of reinforced concrete members according to EC 8. This includes, among other things, the following functionalities:
Seismic design configurations
Differentiation of the ductility classes DCL, DCM, DCH
Option to transfer the behavior factor from a dynamic analysis
Check of the limit value for the behavior factor
Capacity design checks of "Strong column - weak beam"
Detailing and particular rules for curvature ductility factor
Detailing and particular rules for local ductility
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.
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.
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.
Compared to the RF-/DYNAM Pro - Equivalent Loads add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Response Spectrum Analysis add-on for RFEM 6 / RSTAB 9:
Response spectra of numerous standards (EN 1998, DIN 4149, IBC 2018, and so on)
User-defined response spectra or those generated from accelerograms
Direction-relative response spectrum approach
Results are stored centrally in a load case with underlying levels to ensure clarity
Accidental torsional actions can be taken into account automatically
Automatic combinations of seismic loads with the other load cases for use in an accidental design situation
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
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.
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.
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.
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.