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.
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.
The dynamic analysis in RFEM 6 and RSTAB 9 is divided into several add-ons. The Modal Analysis add-on is a prerequisite for all other dynamic add-ons, since it performs the natural vibration analysis for member, surface, and solid models.
The Construction Stages Analysis (CSA) add-on allows for the design of member, surface, and solid structures in RFEM 6 considering the specific construction stages associated with the construction process. This is important since buildings are not constructed all at once, but by gradually combining individual structural parts. The single steps in which structural elements, as well as loads, are added to the building are called construction stages, whereas the process itself is called a construction process.
Thus, the final state of the structure is available upon completion of the construction process; that is, all the construction stages. For some structures, the influence of the construction process (that is, all the individual construction stages) might be significant and it should be considered so that errors in the calculation are avoided. A general overview of the CSA add-on is given in the Knowledge Base article titled “Consideration of Construction Stages in RFEM 6”.
In order to create a surface model with failing supports close to reality, an option called "Failure if contact perpendicular to surfaces failed" is available in RFEM 5 for contact solids under "Contact Parallel to Surfaces".
In RFEM and RSTAB, there are various options to renumber the individual structural elements, such as nodes, lines, members, surfaces, or solids. Two options are available for renumbering: singly and automatically.
In RFEM, you can display the contact properties between two surfaces by means of contact solids. Among other things, you should ensure that both contact surfaces of a contact solid have the same integrated objects. Therefore, when modeling the contact surfaces, we recommend using the copy function in order to create the second contact surface.
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.
For designing glass in the RF‑GLASS add‑on module, you can use one of two calculation methods: a 2D or a 3D calculation. The main difference between these design options is the automatic modeling of the layers in a temporary model. In a 2D calculation, each layer is generated as a surface element (plate theory); in a 3D calculation, it is generated as a solid. Depending on the selected layer composition, you can either select an option or find it preselected by the program.
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.
The transparency intensity of various graphic elements in the Solid Transparent Display Mode can be edited individually in the Program Options dialog box under the Graphic tab to improve the overview.
With RFEM, you can generate member, surface, or solid loads resulting from motions. Thus, for example, braking or acceleration forces can be generated automatically from linear movements or from rotational movements on a structural system.
If nonlinear effects - such as failing supports, foundations, member nonlinearities, or contact solids - are used in the model, you can deactivate them in the global calculation parameters.
With the orthotropic elastic-plastic material model, you can calculate solids with plastic material properties in RFEM 5 and evaluate them according to the Tsai‑Wu failure criterion. The Tsai-Wu criterion is named for Stephen W. Tsai and Edward M. Wu, who published it in 1971 for plane stress states.
The elastic‑plastic material model in RFEM 5 allows you to calculate surfaces and solids with plastic material properties and to carry out a stress evaluation. This material model is based on the classic von Mises plasticity.
With the nonlinear elastic material model in RFEM 5, you can calculate and carry out a stress analysis of surfaces and solids with nonlinear material properties.
Prestressed concrete slabs consist of composite, uniaxially stressed hollow plates with a width of about 1.20 m. These elements are prestressed with pre-tension in a precast concrete plant. The precasting is usually done with slipformers. Due to the lesser self‑weight of the non‑solid slab and the existing prestress, these precast prestressed hollow core slabs show a lower deflection than loosely reinforced slabs made of solid concrete.
The beam is resting on the column, and the beam ends at the outer edge of the column. These requirements can be fulfilled easily in an architectural model with solids. In member analysis, simplified line models are used in which center lines meet in a common node. In this article, the influence of member eccentricities on the determination of internal forces is shown on three simple models.
This article describes how to determine the contact force between two objects behaving like walls that are diagonally inclined at a certain angle on top of each other. Define a nodal release to determine this contact force. Since a nodal release requires certain conditions, this article shows two examples.
The definition of the non-linear contact problem plays an important role for more detailed investigations of shear/hole bearing connections or their immediate environment. This article uses a solid model to search for comparable and simplified surface models.
From time to time, two intersecting beams overlap at a short distance. Such a structure raises the question, with regard to the modeling, of how it is possible to consider a contact with force transmission under compression between the two beams, while the contact under tension (for example, in case of a lifting top beam) should fail.
For the serviceability limit state design according to Section 6.6 of Eurocode EN 1997‑1, settlement has to be calculated for spread foundations. RF-/FOUNDATION Pro allows you to perform the settlement calculation for a single foundation. For this, you can chose between an elastic and a solid foundation. By defining a soil profile, it is possible to consider several soil layers under the foundation base. The results of the settlement, foundation tilting, and vertical soil contact stress distribution are displayed graphically and in tables to provide a quick and clear overview of the calculation performed. In addition to the design of the foundation settlement in RF-/FOUNDATION Pro, the structural analysis determines the representative spring constants for the support and can be exported to the structural model of RFEM or RSTAB.
The "Result Beam" member type has been available since the release of RFEM 5. The result beam is a virtual member that does not have any stiffness nor require any support. It can be used in various situations in order to integrate the results from members, surfaces, and solids, and to display them as member internal forces.
Silos are used as large containers for storage of bulk materials such as agricultural products or source materials as well as intermediates of industrial production. The structural engineering of such structures requires a precise knowledge of the stresses due to particulate solids in the building structure. The standard EN 1991‑4 "Actions on Silos and Tanks" [1] provides the general principles and requirements for determining these actions.