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, 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.
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.
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.
If nonlinearities are used in a model (for example, contact solids), an error message may appear at the end of the calculation due to the locally unfulfilled convergence criteria. The reason for this is that the convergence of the global iteration conditions governs in the calculation.
Contact solids can be created between two flat surfaces or between two cylindrical shells. However, if the area of the contact problem is a little more complicated, it is necessary either to simplify the system so that the requirements of a contact solid can be met, or go back to the "old" modeling style using a rod model.
If a model should contain members with elastic foundations, the contact forces and moments are displayed in numerical form in the result windows. The graphical display of results is specified by the "Members" entry in the Results Navigator.
The shear resistance design value of a joint depends mainly on the formation or the roughness of the connection. When determining the ultimate limit state, this is considered by the factors µ (friction) and c (adhesion percentage of the contact area of the composite concrete).
You can define nonlinear supports in RFEM and RSTAB. In RFEM, these are represented by nodal, line, and surface supports. Many customers contact us because of nonlinearities that are apparently not acting as desired. For example, there is a failing line support in a model. Since the structure is statically determined as supported, a linear nodal support is usually added. If the nodal support rests at the start or the end of a nonlinearly supported line, there is no clear definition of the degrees of freedom, so the nonlinearity cannot be considered properly. In this case, RFEM displays a warning message.