The fatigue design according to EN 1992-1-1 must be performed for the structural components subjected to large stress ranges and/or many load changes. In this case, the design checks for the concrete and the reinforcement are performed separately. There are two alternative design methods available.
In RFEM 6, the results for the FE mesh nodes are determined using the finite element method. For the distribution of internal forces, deformations, and stresses to be continuous, these nodal values are smoothed through an interpolation process. This article will introduce and compare the different types of smoothing that you can use for this purpose.
RFEM 5 provides the option to define a smoothing area in the "Results" → "New Average Region" menu. You can choose a rectangular, circular, or elliptical shape. With this tool you can, for example, "smooth" singularities due to nodal loads in a desired averaged region.
When evaluating line support forces, implausible diagrams sometimes arise at first glance. In particular, for variable loads at locations that also have a nodal support, at division points and edge locations of supported lines, the results sometimes show unexpected support reactions. Using the function of the linear smooth distribution in Project Navigator – Display does not always lead to the expected result diagram.
When calculating a surface model, the internal forces are determined separately for each finite element. Since the element-by-element results usually represent a discontinuous distribution, RFEM performs smoothing of the internal forces that takes into account the influence of adjacent elements. The discontinuous distribution of internal forces is adjusted with this method. The result evaluation is thus clearer and easier.
The deformations of the FE nodes are always the first result of an FE calculation. It is possible to calculate strains, internal forces, and stresses based on these deformations and the stiffness of the elements.
With the SHAPE-THIN cross-section program, you can model the corner areas of cross-sections in detail: The "Smooth Corner" function fills the corner with an element and automatically connects it with a null element. For this, simply click the corner. Use the "Create Round or Angled Corner" function to round or angle the corner. To do this, specify the fillet radius and click both elements.
When evaluating results in the smooth state, you can display the average and sum values. This option is also available for parts of a line, a section, and so on. By importing the graphic into the printout report, you can document these values in the structural analysis.
In RF-CONCRETE Surfaces, the reinforcement areas of the mesh reinforcement for basic and additional reinforcement are not entered manually, but you can select them in the library. Therefore, various product ranges are available (for example, from Germany, Austria, and the United States).
Just as in the RFEM Display Navigator, you can set the distribution of internal forces in surfaces in RF‑STEEL Surfaces. Since deformations are always the result of the FEM calculation, the corresponding forces will be recalculated. This means that the internal forces on an FEM element are calculated depending on the composition (triangular or square) in three or four places. In order to obtain continuous internal forces and thus a smoothed distribution, these internal forces have to be interpolated. Interpolation is done by selecting the "Distribution of internal forces" option in the surfaces.