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Frequently Asked Questions (FAQ)
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AnswerIn order to display the loads correctly, it is necessary to make some adjustments. In the case of an incrementally applied load, the boundary of the area load plane may only be defined in sections (by load increment). Otherwise, the load is distributed linearly over the entire area load plane.
Only the default setting of 1 load increment can be set when a complex nonlinear material model is defined. The reason for this is because the program cannot determine the correct material stiffness for each incremental loading amount. The exact maximum load needs to be applied to the structure in order to determine the state of the material's stress/strain diagram.Figure 01 - Material Model - Nonlinear material definedThis setting can be found and changed under "Calculation Parameters" as well as under the "Calculation Parameters" in the load cases and combinations dialog box.
AnswerYou can access the results of the individual load increments by activating the "Save the results of all load increments" option in the calculation parameters of the load case or load combination (see Figure 01).
By using the "Calculation Diagrams" window in the calculation parameters, it is possible to additionally evaluate the individual results for the selected elements (see Figure 02). It is also possible to easily create several calculation diagrams.
AnswerThe "Incrementally Increasing Loading" function of load cases and load combinations can incrementally increase the assigned load level and find the equilibrium for each load increment. The reference level "Load Increment 1.0 = 100% of the defined load" is the defined loading for load cases and the combination of load cases modified with partial safety factors for load combinations. The detailed settings of the function define the initial load increment k0, the quantity of load increment Δk, the refinement of the last load increment, the break criterion, and the statical initial load situation.The initial load increment k0 defines the beginning of the process. This entry does not depend on the pure entry of load cases and load combination, and can be greater or less than 1.0. The program always displays all results on the basis of the load increment 1.0 within the regular calculation and performs the additional analysis of the possible load increments by activating "Incrementally Increasing Loading."The incrementally increasing loading is specified by the load increment Δk. With each process loop, the program increases the load to be analyzed by adding the increment to the previously analyzed load increment. The increment is constant until the break criterion is reached.Due to the constant increment size, it is not possible to determine an exact load factor according to the break criterion. Finally, the program shows the approximate load factor on the basis of the last load increment at which the equilibrium for the model can be found. After the calculation, the relevant load situation is displayed in Table "4.0 Results - Summary." By specifying the refinement of the last load increment, the initial increment Δk is divided by the refinement value after reaching the break criterion, and the process is repeated from the lastly performed load increment until a new break occurs. Due to the smaller increment, the resulting load factor is more accurate.The break criterion for the process is basically the point at which the program cannot find any equilibrium for the applied load (second-order analysis). Furthermore, you can specify the break-off by activating the maximum deformation on a specific node.In reality, certain force components remain constant with no regard to an action (for example, self-weight, prestress, and so on), so the detailed setting provides the option to assign a fixed load component for the incrementally increasing loading. The fixed load can either be a load case or a load combination. This load component is independent of the loading to be increased and is simply added to the variable component in the process.If the intermediate results of the active load increments are of interest in addition to the final load factor, it is possible to use the "Save the results of all load increments" function for load cases and load combinations in order to display the intermediate results. The corresponding options are available in the panel window and in the result tables.In RSTAB, the activation for saving the intermediate results is linked to the RSBUCK add-on module, and in RFEM, the activation of the incrementally increasing loading is linked to the RF‑STABILITY add-on module. In these cases, a license of the corresponding add-on module must be available in addition to the licensing of the main program.
AnswerYes, it is possible.In the calculation parameters of each load case or load combination, you can find the "Modify loading by factor" option.You can select it and enter a factor which multiplies the loading for the calculation of the internal forces of this load case or load combination. See Figure 01.
Yes, this is possible.In the calculation parameters of the load cases or load combinations, you can set the "Load increases" or "Load increments" and select the option where you want to save the results of the load increments (Figure 01)After the calculation, you can control the load increments resp. stages in the result display panel.See Figure 02.
Define several load cases to create a moving load. Each load case should correspond to a certain position of the moving load in the structure.
You can easily generate the load cases from the load positions on members in the add-on modules RF-MOVE (for RFEM) and RSMOVE (for RSTAB). Using RF-MOVE Surfaces, it is also possible to generate load cases from moving loads on surfaces in RFEM (see the figure).
Check if the settings for considering the favorable effect by tension forces are the same in RSTAB and RSBUCK.
RSTAB determines the critical load factor according to the nonlinear calculation method: The loading is increased gradually by the value of the load factor increment Δk until the system becomes unstable. On the other hand, RSBUCK performs a linear eigenvalue analysis. Therefore, the elements acting nonlinearly, such as failing members or supports, may have different effects in RSTAB and RSBUCK.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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