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 practice, an engineer often faces the task of representing the support conditions as close to the reality as possible in order to be able to analyze the deformations and internal forces of the structure subjected to their influence and to enable construction that is as cost efficient as possible. RFEM and RSTAB provide numerous options for defining nonlinear nodal supports. This second part describes the options for creating a nonlinear support for a restraint and provides a simple example. For a better understanding, the result is always compared to a linearly defined support.
This example describes a definition of a planar surface by four nodes that have been imported and seem to lie in a common plane. In reality, they are not exactly in one plane due to (for example) a previous modeling error of a few millimeters. When trying to create a planar surface, the error message "Error in the surface definition! The nodes do not lie in a common plane." appears.
If you have imported a DXF file in RFEM or you need to add a membrane to an existing member structure, you can use the function "Tools" → "Generate Model - Surfaces" → "Surfaces from Cells", and thus quickly create planar surfaces.
Modeling planar structural components such as glass panes is generally possible only in RFEM. If it is necessary to define the stiffening effect of a pane in a particular case, it can also be simulated in RSTAB.
In RFEM, surfaces are automatically connected if they have common boundary lines. If the definition line of a surface is lying in another surface, the line is automatically integrated into the surface, provided that it is a planar surface. For quadrangle surfaces, however, automatic object detection would be relatively time-consuming. For this reason, the corresponding function is deactivated. The integrated objects must be specified manually.
RFEM and RSTAB provide numerous options for nonlinear definitions of nodal supports. With regard to an earlier article, further possibilities of the nonlinear support design for a movable support are shown in a simple example in this article. For a better understanding, the result is always compared to a linearly defined support.
In practice, an engineer often faces the task of representing the support conditions as close to the reality as possible in order to be able to analyze the deformations and internal forces of the structure subjected to their influence, and to enable construction that is as cost-effective as possible. RFEM and RSTAB provide numerous options for defining nonlinear nodal supports. The first section of my article describes the options for creating a nonlinear free support and provides a simple example. For a better understanding, the result is always compared to a linearly defined support.
A member's boundary conditions decisively influence the elastic critical moment for lateral-torsional buckling Mcr. The program uses a planar model with four degrees of freedom for its determination. The corresponding coefficients kz and kw can be defined individually for standard-compliant cross-sections. This allows you to describe the degrees of freedom available at both member ends due to the support conditions.
Based on the technical article about the ultimate limit state design of rail welds, the following explanation refers to the process of fatigue design of rail welds. In particular, this article explains in detail the effects of considering an eccentric wheel load of 1/4 of the rail head width.