RWIND 2 and RFEM 6 can now be used to calculate wind loads from experimentally measured wind pressures on surfaces. Basically, two interpolation methods are available to distribute pressures measured in isolated points across the surfaces. The desired pressure distribution can be achieved using the appropriate method and parameter settings.
Using an example of a steel fiber-reinforced concrete slab, this article describes how the use of different integration methods and of a different number of integration points affects the calculation result.
A new capability within RFEM 6 when designing concrete columns is being able to generate the moment interaction diagram according to the ACI 318-19 [1]. When designing reinforced concrete members, the moment interaction diagram is an essential tool. The moment interaction diagram represents the relationship between the bending moment and axial force at any given point along a reinforced member. Valuable information is shown visually like strength and how the concrete behaves under different loading conditions.
Modal analysis is the starting point for the dynamic analysis of structural systems. You can use it to determine natural vibration values such as natural frequencies, mode shapes, modal masses, and effective modal mass factors. This outcome can be used for vibration design, and it can be used for further dynamic analyses (for example, loading by a response spectrum).
In RFEM, you can create screw lines using the "Trajectory" type line. To do this, you need a center line/guide line around which the line can be modeled, as well as a start and end point. Then, you can create a "Trajectory" type line between the start and end points; this initially appears as a straight line.
Occasionally, the question arises how to determine the correct load application point of the positive transverse loads in RF-/STEEL EC3 and RF-/STEEL AISC.
In RFEM 5 and RSTAB 8, it is possible to assign nonlinearities to member hinges. In addition to the nonlinearities "Fixed if" and "Partial activity", you can select "Diagram". If you select the "Diagram" option, you have to specify the according settings for the activity of the member hinge. For the individual definition points, it is necessary to specify the abscissa and ordinate values (deformations or rotations and the according internal forces) that define the hinge.
Until now, if you wanted to determine the centroid of a rectangle, it was necessary to define a line from one corner point to the diagonally opposite point. You obtained the centroid by dividing this line. In RFEM 5 and RSTAB 8, you now have the possibility to create a node between two points. Thus, it is sufficient to select the corner points; then you can determine the distance in absolute or relative values.
The RF-/STEEL EC3 add‑on module allows for the fire protection design of structural steel components. The simplified analysis is performed by determining the steel temperature iteratively for a particular point of time.
In RFEM 5 and RSTAB 8, you can now create a work plane by simply selecting three points. It is no longer necessary to create a user-defined coordinate system.
The stresses in the cross‑section of the member are calculated in the stress points. These points are set at locations in the cross‑section where extreme values for the stresses due to the loading types can occur in the material.
When modeling frame structures, RFEM and RSTAB provide various options for controlling the transfer of internal forces and moments at the connection points of members. You can use the member types to determine whether only forces act on the connected members, or whether moments act on them as well. In addition, you can use hinges to exclude specific internal forces from the transfer. One special form is scissor hinges, which allow for realistic modeling of roof structures, for example.
Pay particular attention to the connection points of members and surfaces when you deal with mixed systems, because not all internal forces can always be transferred without difficulty at the coupling location.
The design of cold-rolled steel products is defined in EN 1993-1-3. Typical cross-section shapes are channel, C, Z, top hat, and sigma sections. These are cold-rolled steel products made of thin-walled sheet metal that has been cold-formed by roll-forming or bending methods. When designing the ultimate limit states, it is also necessary to ensure that local transverse forces do not lead to compression, crippling of the web, or local buckling in the web of the sections. These effects can be caused by local transverse forces by the flange into the web, as well as by support forces at the supported points. Section 6.1.7 of EN 1993-1-3 specifies in detail how to determine the resistance of the web Rw,Rd under local transverse forces.
If you read out the results of a surface by means of the COM interface, you get a one-dimensional field with all results at the FE nodes or grid points. To get the results on the edge of a surface or along a line within the surfaces, you have to filter out the results in the area of the line. The following article describes a function for this step.
In RF-PUNCH Pro, enlarged column heads can be arranged at point-supported punching shear points, thus increasing the shear force resistance of a reinforced concrete floor. In the following article, we will show the punching shear design with the optional application of an enlarged column head.
When evaluating line support forces, implausible diagrams sometimes arise at first glance. In particular, for variable loads at locations that also have a nodal support, at division points and edge locations of supported lines, the results sometimes show unexpected support reactions. Using the function of the linear smooth distribution in Project Navigator – Display does not always lead to the expected result diagram.
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.
Especially if the adjacent area of connection points is to be analyzed, if the geometry and load of the connection do not correspond to the standard specifications, and/or if a model is to be analyzed using an FE model (for example, in plant engineering), the connections must also be evaluated in detail on the FE model.
The RF-PUNCH Pro add-on module allows you to perform punching shear designs according to EN 1992‑1‑1 [1]. In addition to the design checks of single columns, wall ends and wall corners can be analyzed in RF‑PUNCH Pro. At this point, I would also like to reference a previous article about RF‑PUNCH Pro, which explains how to determine punching load on wall ends and wall corners.
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.
The insulating glass pane design places a special requirement on the load application point of the loading. For example, wind loads and loads due to fall protection may appear. For this, the wind load should be applied on the external glass side and the handrail load should act on the internal glass pane.
In RFEM and RSTAB, you can add user‑defined dimension lines to a structural model. When creating these dimension lines, click the objects (for example, end nodes of a line, members, and so on) that represent the reference points of the dimension. If you want to add a dimension line free from the structure previously defined in the model, you have to create an additional free "help node" that acts as a reference object for the new dimension.
As mentioned in Part 1, according to the current standard DIN 18008-3, it is allowed in glass construction to represent point supports for glass components by means of FEM in order to design the adequate ultimate limit state. The rules are described in Annex B of the standard [1].
Nodal supports are usually defined with regard to the global axis system. However, it is sometimes necessary to rotate the nodal support. For example, for a floor slab with a pile foundation. For geological reasons, the piles do not rest in the ground vertically, but in an inclined position. Each end point of the piles has a nodal support that can only absorb forces along the pile foundation direction. Therefore, rotating the nodal support is required. Various options for this are described in previous posts.
If you want to connect members tangentially to a curved member or a curved surface in RFEM, it is necessary to define the member rotation of the connected members. In order to avoid manual determination, you can display the center point of the curved line and place a node on it. Then, you can select the "Member Rotation via Help node" option and specify the relevant help nodes. Thus, the members are rotated automatically in the defined plane (x-z in our example) and the top edge of the rotated cross-section is parallel to the tangent of the curved line.
The transparency of the glass material should not be missing in any building. In addition to the typical application areas such as windows, this building material is increasingly being used for facades, canopies, or even as bracing of stairways. Of course, the planning architects often set a very high standard of transparency on fixation of the glass panes. This requires special glass fittings that couple the glass panes.
In the DYNAM Pro add‑on module for RSTAB, you can now neglect masses that may have a negative effect on the equivalent mass factor when calculating eigenvalues. To do this, you can disable the masses under [Details]. These include primarily mass points located in the support of the structures.