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Useful Program Features
The Knowledge Base includes technical articles on a wide array of structural analysis and design topics.
These articles are intended to help you navigate through the Dlubal programs, learn efficient tips and tricks, and provide further insight into the program features.
Why Dlubal Software?
Iterative RFEM Calculation with Load Increments
The calculation in RFEM is usually carried out in several calculation steps, the so-called iterations. It is then possible to consider particular characteristics of the model such as objects with nonlinear functions. In addition, by using the iterative calculation, nonlinear effects are taken into account which result from changes in deformation and internal forces in case of the second-order analysis or when considering large deformations (cable theory). In case of complex models, geometric linear calculations are usually not sufficient.
Differences of Calculation Methods in Structural Analysis
For structural dimensioning according to the valid rules, there are often several options or calculation methods to determine the internal forces. It is up to the engineer to decide which theory is suitable to design the structure.
Setting National Annex as Default
If you want to design structural components in an RFEM or RSTAB add‑on module, there are several National Annexes available in some add‑on modules. In the case of structures, which are to be analysed mainly according to a specific National Annex, the add‑on modules provide the option to set a default value. Thus, it is not necessary to select the NA again for each new model.
Keeping Local Iteration Conditions
If there are nonlinearities used in a model, for example contact solids, an error message may appear at the end of the calculation due to the locally unfulfilled convergence criteria. The reason for this is that the convergence of the global iteration conditions is governing in the calculation.
To record and display a relation between various calculation results, it is possible to use the calculation diagrams. You can create and display them using the ‘Calculation Parameters’ dialog box available under ‘Calculation’ → ‘Calculation Parameters’.
Batch Processing of Multiple Files
In RFEM and RSTAB, files can be automatically computed in a sequence of calculation, so the models can be processed overnight, for example.
Shear Area Types and Their Meaning
If you look at the cross‑section properties of the metal category, you can see that there are three types of shear area, whose meaning and calculation are described here.
Critical Load Factor
RSTAB can calculate a critical load factor for each load case LC and each load combination CO in compliance with the second‑order analysis. The critical load factor indicates the number by which the load must be multiplied so that the model under the associated load becomes unstable (buckling).
Alternative to Gamma Method: Semi-Rigid Composite Beam as Framework Model 2
As already mentioned in the first part of the article, the flexural stiffness of a stiffness beam is determined to consider the shear stiffness of the fasteners.
Deactivation of Nonlinear Effects
If there are nonlinear effects used in a model, for example ineffective supports/foundations, member nonlinearities or contact solids, then it is possible to deactivate these effects in the Global Calculation Parameters (see Figure).
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