In many frame and truss structures, it is no longer sufficient to use a simple member. You often have to consider cross-section weakenings or openings in solid beams. In such cases, you can use the "Surface Model" member type. It can be integrated into the model like any other member and offers all the options of a surface model. The present technical article shows the application of such a member in an existing structural system and describes the integration of member openings.
The goal of using the RFEM 6 and Blender with the Bullet Constraints Builder add-on is to obtain a graphical representation of the collapse of a model based on real data of physical properties. RFEM 6 serves as the source of geometry and data for the simulation. This is another example of why it is important to maintain our programs as so-called BIM Open, in order to achieve collaboration across software domains.
The Steel Joist Institute (SJI) previously developed Virtual Joist tables to estimate the section properties for Open Web Steel Joists. These Virtual Joist sections are characterized as equivalent wide-flange beams which closely approximate the joist chord area, effective moment of inertia, and weight. Virtual Joists are also available in the RFEM and RSTAB cross-section database.
The dialog box for editing load or result combinations is a non-modal dialog box. This means that after you open this dialog box, you can edit the combinations outside the dialog box as well. For manually defining or editing a combination, a separate dialog box can be opened parallel to the "Edit load cases and combinations" dialog box.
Inserting holes in surfaces is very easy due to the large selection of tools. In order to insert holes or drilling in solids, it is necessary to keep in mind that an opening at the beginning and the end of a continuous hole must be created, as well as a surface that separates the hole from the solids.
Warning Regarding Connection to Project
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When opening a model immediately after opening the program, there is a message window asking if you want to create a new project for the model in the Project Manager.
In RF-/STEEL EC3, you can optimize a cross-section automatically within the design. To do this, select the corresponding cross-section in Table 1.3 or define variable parameters for a welded cross-section.
In RFEM and RSTAB, you can work with the Project Manager. It allows you to create an entire project structure and to connect it with the folders on the local hard disk.
For a clearer display of the structure, you can display it in different colors. The corresponding selection can be opened by right-clicking the work window.
In the case of open cross-sections, the torsional load is removed mainly via secondary torsion, since the St. Venant torsional stiffness is low compared to the warping stiffness. Therefore, warping stiffeners in the cross-section are particularly interesting for the lateral-torsional buckling analysis, as they can significantly reduce the rotation. For this, end plates or welded stiffeners and sections are suitable.
With the "Convert Area Loads on Openings to Line Loads" function, you can automatically take into account, for example, wind loads applied on windows or other loads applied on non‑bearing structures not represented in the model in openings. You can access this function via "Tools" → "Generate Loads" → "From Area Loads on Openings...."
In cross‑sections created in SHAPE‑THIN, the openings, such as bolt holes, can be modeled by using the elements with zero thickness. The program provides two options for calculating shear stresses in the area of such null elements.
According to Book 631 of the DAfStb (German Committee for Structural Concrete), Chapter 2.4, the structural behavior of ceilings changes if their continuous support by walls is interrupted in areas of openings. Depending on the length of the opening area and the plate thickness, measures are necessary regarding the analysis of the ceiling in the area of the opening.
The proportion of glass used when planning a building is increasing. Open, light-flooded buildings represent the modern art of architecture. However, specialized engineers have to face new challenges during planning. One such example is ceiling-high glass facades loaded by a handrail. The influence of this loading, as well as the calculation of the deformation, are shown in this article.
Since the ultimate limit state of beams in the area of openings is affected, particular attention should be paid to this. In general, small openings can be sufficiently covered by adapting the beam structure to the openings. For big openings, it is necessary to consider and model the area separately.
The Steel Joist Institute (SJI) previously developed Virtual Joist tables to estimate the section properties for Open Web Steel Joists. These Virtual Joist sections are characterized as equivalent wide-flange beams which closely approximate the joist chord area, effective moment of inertia, and weight. Virtual Joists are also available in the RFEM and RSTAB cross-section database.
This article presents a bending beam with a circular opening analyzed using the numerical method. As a reference point, there is an example of a perforated beam from [1]. In our case, the 3D model was simplified to a two-dimensional discretization.
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 first part of the article series about the COM interface described opening and creating a model in RFEM. The second part explains creating and modifying elements on an example of a member. The elements described in Part 1 will not be explained again here.
The first part of the post about the COM interface describes opening and closing RFEM. VBA programming language is used in Excel; however, the program sequence is the same as for programming with C#. First, it is necessary to add the corresponding reference in VBA to recognize the commands for the interface. The image on the left shows an example of RFEM 5.
In his bachelor's thesis, Jonas Mösch analyzes the open and closed interfaces in BIM-based structural design. The theoretical section covers the definition of the term "Building Information Modeling".
You may already be familiar with the "Center of Gravity and Info" function, which can be accessed using the shortcut menu of any element. If you want to display this information on several elements consecutively, you have to close the dialog box and open the shortcut menu of the next element over and over again.
In RFEM, you can open and further edit structures with loads and load cases that have been modeled in RSTAB. For example, this may be necessary if you realize during the model input that it is useful to include surface elements such as wall surfaces and others in the existing RSTAB model.
RFEM and RSTAB provide the export interface ("File" → "Export") to export model and load data, as well as results, to Excel or in a CSV file in one step. You can select the tables to be exported in the "Export Tables" section. The "Only selected tables" option allows you to export only a specific selection of tables. Use the [Select Load Cases and Tables for Export] button to open the corresponding dialog box.
The geometry data of an RFEM model are currently managed in 29 tables, so not all of the tabs are displayed at once. To open a particular table, we recommend using the navigation menu that you can open by right-clicking on any tab. A shortcut menu appears, where you can quickly access the desired input table.
The national parameters of EN 1992‑1‑1 for each country can be exported from RF‑/CONCRETE, RF‑/CONCRETE Columns, and RF‑/FOUNDATION Pro. To do this, there are interfaces with MS Excel, OpenOffice, and CSV. By exporting the national parameters, you can edit them in (for example) MS Excel, and display possible differences between the individual National Annexes clearly (see the image).
RF‑CONCRETE Surfaces performs the ultimate and the serviceability limit state design of slabs, plates, folded plates, and shells. In RFEM 5, the reinforcement resulting from this design can be displayed graphically on the surfaces of the structure using isolines. For the reinforcement design, it may be useful to export the results as isoline distribution in a DXF file in order to open them in a CAD application as background layers.