L'add-on Analisi tensioni-deformazioni è disponibile per l'attivazione nei Dati base del modello (fig. 1). Una volta attivato l'add-on, il navigatore, le tabelle e le finestre di dialogo vengono estese con nuove voci che sono completamente integrate nell'interfaccia utente di RFEM/RSTAB.
Questo articolo mostrerà un esempio pratico di come gestire i dati di input per le configurazioni di aste e superfici ed eseguire l'Analisi tensioni-deformazioni in RFEM 6. L'analisi tensioni-deformazioni sarà eseguita per un segmento della copertura di uno stadio fatta di membrane, mostrato nell'immagine 2. This way, you can check whether its elements (which were modeled in the program beforehand) meet the design requirements, or whether their properties must be revised (for example, regarding cross-section, material, thickness, and so on).
As already mentioned, the objects of the Stress-Strain Analysis category are available both in the navigator and in the table to define the input data for the design. Hence, you can check the objects to be designed as well as their materials and cross-sections. Depending on the selected object, specific configurations where you can specify limit values and other design options can be defined as well.
Given that this model consists of members and surfaces, specific tables for each of these object types are available in the stress-strain analysis settings. The configuration settings can be accessed via the "Open editing dialog box" icon (Image 3) where you can create different types for each design configuration and assign the appropriate configuration to each object.
First, you can create a new member configuration based on the default values of the selected design standard. To do so, you can use the "New" button positioned below the list, which shows all configurations of this limit state available in the model. Since no configuration has been defined yet, this list is empty (Image 4).
You can start defining the design configuration in the "Main" tab of the dialog box by selecting the stresses to be calculated and specifying the limit stresses for comparison. For instance, you can choose between limiting normal, shear, or equivalent stress, as well as specifying a user-defined limit stress. In this example, the equivalent von Mises stress will be selected for calculation, and you can see the associated formula in the right part of the dialog box.
Other design-relevant options can be found in the "Special Options" tab shown in Image 5. Hence, you can modify the weighting of the normal and shear stresses in the Mises equivalent stress by specifying the kσx, and kτ factors, respectively.
If transverse loads are applied to the upper chord of beams, it is also possible to consider the eccentrically acting transverse loads by a simplified method for I-sections with which the bending moment Mz is completely applied to the top flange for each rolled or parametric symmetric I-section of the design case.
Once the configuration is defined, you can assign it to the respective objects via the "Select Individually" button in the dialog box at the top right, or directly in the input table of the stress-strain calculation for the corresponding configuration (Image 6). Inoltre, è possibile creare più configurazioni e assegnarle a oggetti diversi.
Le specifiche all'interno di una configurazione si applicano a tutti gli oggetti a cui è assegnata questa configurazione. If no configuration is assigned to an object to be designed, no designs are performed for this object.
The design configurations are also included in the edit dialog box of the individual members, as shown in Image 7. The assignment can be done in the Design Configurations tab of the dialog box, where you can select an existing configuration from the list, use the "New" button to create a new configuration, or use the "Multiple Selection" button to graphically select another object from which the respective configuration is imported. The edit menu of the selected configuration can be opened via the "Edit" button.
Allo stesso modo, è possibile definire le configurazioni della superficie tramite la tabella di analisi tensioni-deformazioni o la finestra di dialogo di modifica delle superfici specifiche. You can select the stresses to be calculated and specify the limit stresses as shown in Image 8. To specify a user-defined limit stress, select the limit stress type "User". This activates the "User-Defined Limit Stress" where you can define the values of interest.
Altre impostazioni per l'analisi tensioni-deformazioni saranno definite nei prossimi articoli della Knowledge Base. However, if you perform the analysis with the above-defined member and surface configurations, you will obtain the results as shown in Image 9.
The results are available in both graphical and tabular form. È possibile selezionare i risultati specifici da visualizzare nel navigatore Risultato, mentre i risultati dettagliati per le aste e le superfici si possono trovare nella tabella Analisi tensioni-deformazioni. This way, you can check whether the elements meet the design verifications or whether they need to be edited in terms of cross-section, material, thickness, and so on.
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