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.
In computational fluid dynamics (CFD), complex surfaces that are not completely solid can be modeled using porous or permeability media. In the actual world, examples of such things include windbreak fabric structures, wire meshes, perforated facades and claddings, louvers, tube banks (stacks of horizontal cylinders), and so on.
An FE mesh quality display is available in RFEM as a tool for structural analyses of two-dimensional components. It leads to the execution of an internal check of the generated finite elements for defined criteria.
RFEM and RSTAB save the input data, the FE mesh, the results, the printout reports, and the 3D gITF model preview, including all visual objects, in one file.
For solids, there is another option for the FE mesh setting. You can arrange a layered FE mesh in addition to a holistic FE mesh refinement. For this option, you can perform a defined division of the solid with finite elements between two parallel surfaces. This option is particularly suitable for very large solid geometries with a low height.
Often in RFEM, only part of a surface must be loaded, not an entire surface. A typical case of this is soil pressure. For this purpose, there is the option of defining free surface loads. They are surface-independent and are displayed in defined coordinate dimensions in the graphic.
Supports can be copied and moved using drag & drop, even if the "Move/Copy" function is not available in the shortcut menu. This applies to all kinds of supports: nodal supports, line supports, and surface supports. These can easily be assigned to further nodes, lines, or surfaces.
The "Mapped Mesh Preferred" option has an influence on the mesh generation of surfaces with curved and folded outlines. The program tries to align the FE mesh with the boundary lines of the surfaces.
Concrete on its own is characterized by its compressive strength. An important part of reinforced concrete is reinforcing steel, which contributes to both the compressive and the tension resistance of the concrete. Welded wire fabric is generally located in the tension areas of the beams or surface elements (hollow core ceiling, wall, shell) to transfer the tensile forces induced by external loading.
In RF‑CONCRETE Surfaces, the design of the surface reinforcement is done by means of a freely definable reinforcement mesh. In RF‑CONCRETE Surfaces, you can display the reinforcement direction by activating the reinforcement arrow that represents it.
The name of the project/model from the General Data is shown in the header of the printout report by default. In RFEM 5 and RSTAB 8, the model name can be changed manually in the printout report independently of the actual name.
This article describes how a flat slab is generated as a 2D model in RFEM and the loading is applied according to Eurocode 1. The load cases are combined according to Eurocode 0 and calculated linearly. In the RF-CONCRETE Surfaces add-on module, the bending design of the slab is performed while taking into account the standard requirements of Eurocode 2. The reinforcement is complemented by a rebar reinforcement for areas that are not covered by the mesh basic reinforcement.
The secondary reinforcement according to DIN EN 1992-1-1 9.2.1 is used to ensure the desired structural behavior. It should avoid failure without prior notification. The minimum reinforcement has to be arranged independently of the size of the actual loading.
As of the program version X.11, the filter options of small compression forces or moments for stability analysis in RF‑/STEEL EC3 have been revised. The revision of these filter options in the "Stability" tab of the "Details" dialog box allows you to work in the module transparently, since they are now independent of the design.
In RFEM, structures can be modeled and analyzed in a spatial environment. The permanent 3D visualization helps you to better understand complex models and to represent the force flux. However, you can switch from a spatial mode to a planar sheet mode in the documentation of a calculation. To do this, you have to describe the spatial calculation of the structure with all the necessary properties on "flat" paper pages for an independent reader. Usually, you try to display the load actions and the corresponding results by using an orthogonal view of the substructure of the entire structure. Obviously, the load symbols depicted in the 3D mode in a view perpendicular to the load become unrecognizable due the missing expansion. In order to still be able to create a clear representation of all information, the corresponding adjustments are available in RFEM.
In RFEM, you can generate surfaces from members (for example, to perform an accurate FE simulation on a member). Specific parameters such as automatic FE mesh refinement or rigid surfaces can be defined prior to the generation.
If intersections created in RFEM 4 are opened in an RFEM 5 file, the file management of intersections remains in the old format for compatibility reasons. Thus, the individual partial surfaces of the intersection can be activated or deactivated using only the "Integrated/Components" tab, all partial surfaces can only have the same thickness, and it is impossible to use the separate FE mesh refinement for the individual surface components.
The DXF interface in RFEM now exports a 3DFACE element in the DXF file for each FE mesh cell of the exported structure. The 3DFACE element is detected by AutoCAD during import, for example, and can be displayed as a surface in the graphic. Different visual styles help display the 3DFACE surfaces in a desired view.
The form-finding process in RF-FORM-FINDING displaces the corner nodes of FE elements of a membrane surface in space until the defined surface stress is in equilibrium with the boundary conditions. This displacement is independent of the element geometry. In the case of elements with four corner nodes, the free displacement may cause spatial drilling in the element plane and thus exceed the validity limits of the calculation; therefore, triangular elements are generally recommended for form‑finding systems. Triangular elements remain independent of the corner node displacement and stay within the calculation limitations.
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).
In RFEM, there are a file‑based and a direct DXF interface. The file-based DXF interface allows you to export the data in a DXF file that is transferred directly into an open AutoCAD file. In the interface dialog box, you can select which data are to be exported (results as isolines, result values, or finite element mesh with boundary and integration lines).
In RFEM, you can use the export function to export the generated FE mesh in DXF as a result. To do this, open the export dialog box in the program and select "ASCII Format - Results". In addition to a result (for example, isolines), you can select the FE Mesh in the "Results - Isolines (.dxf)" tab. After the export, the mesh in DXF is available in the DL‑FE‑MESH layer.
You can document the results of RF‑CONCRETE Surfaces graphically in the printout report. To do this, the "Values on Surfaces" setting is often selected in the Results Navigator of RF‑CONCRETE Surfaces. A text bubble including a result value is displayed, and depending on the settings in the Results Navigator, it can be displayed on the surface grid points, manually defined points, or in FE mesh points.
In RF-CONCRETE Surfaces, you can use the "Filter Points" function when evaluating results by points. This filter function allows for a user-defined group of points that can be defined in the result window. You can select the filter in Window 2.3 Required Reinforcement by Points, among others.
It is often necessary to adjust the FE mesh of surface elements to the geometric structure. RFEM provides various options for this. For example, the FE axis can be rotated around a point, aligned in the direction of a point, or oriented to a user-defined coordinate system. Another option is the direction parallel to a line, and in this case in particular, it is possible to enter or select several lines.
During the cooperation between the structural and design engineers, the DXF format is often used if there is no direct interface. However, the geometrical data of these DXF files are not always accurate. For example, an inaccuracy in the third decimal place is not noticeable, but it can lead to numerical problems when generating the FE mesh in RFEM.
"Distribution of load" represents a load actually applied to the system of FE mesh points or FE surfaces. The FE mesh size plays an important role in the loading in the case of line loads and free loads in particular.