Warping Torsion
This tab allows for settings of the warping analysis for sets of members. You can access the entries if the RF-/STEEL Warping Torsion module extension is licensed.
If you want RF-/STEEL EC3 to Perform a warping analysis, select this check box. Thus, the other dialog sections become accessible. At the same time, the corresponding options for the stability analysis of sets of members will be locked in the Stability tab.
In the method with seven degrees of freedom, the stability calculation is carried out according to the second-order analysis for flexural-torsional buckling taking into account warping torsion and imperfections affine to mode shapes. The freedom degrees of the displacements and rotations in and about the three axes X', Y' and Z' as well as warping can be user-defined in Windows 1.7 and 1.8 (see Figure 2.34 and Figure 2.36). In Window 1.13, you have to define the initial rise of the precamber (see Figure 2.52).
Find a detailed description of the second-order analysis for flexural-torsional buckling in the RF-/FE-LTB manual on our website.
Find some examples describing the principles of this method in the following articles:
- https://www.dlubal.com/en-US/support-and-learning/support/knowledge-base/001298
- https://www.dlubal.com/en-US/support-and-learning/support/knowledge-base/001377
In addition to the second-order analysis, the Method of Warping Analysis can be a linear calculation. Then, the set of members will be analyzed according to linear static analysis. This way, it is possible, for example, to analyze effects of warping and to deduce consequences on the stability behavior.
The warping analysis is performed iteratively, with the stiffness matrix K changing due to already computed internal forces and deformations. The Max number of iterations prevents the calculation from entering an infinite loop when there are convergence problems.
The Load Application has an important role for the stability analysis with seven degrees of freedom. Depending on the application point, the load has a stabilizing or destabilizing effect on the stability behavior. Use the nine setting options to define the location where the load is acting on the cross-section. The current point is highlighted red in the cross-section sketch.
Determination of loading in RF-/STEEL Warping Torsion
The loadings applied for the warping analysis are based on the results from RFEM or RSTAB. The module extension uses the member deformations in order to determine the moment distributions and thus the loads. It is therefore necessary to ensure, when defining the boundary conditions in Window 1.7, that the singled out member set model corresponds to the conditions of the RFEM/RSTAB model. For example, if rotations are enabled for a horizontal beam node, which are restricted in the model by a connected column, different internal force distributions in RFEM or RSTAB and RF-/STEEL EC3 will be the result.
The following article describes how the loading is determined in RF-/STEEL Warping Torsion:
https://www.dlubal.com/en-US/support-and-learning/support/knowledge-base/001417