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Frequently Asked Questions (FAQ)
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In comparison with a "normal" surface load, the free rectangular loads have the disadvantage that the load does not graphically get a "cover," and thus the load distribution is not clearly recognizable in the graphic printout.
You can use the display of load distribution in Project Navigator - Results: Thus, the 2D FE elements will be graphically colored, and the corresponding result values will be displayed in the adjacent color panel.
AnswerIn fact, this error message only appears if a member hinge that allows a rotation about the local x‑axis has been assigned to a member at both ends. Thus, the member can rotate freely about its own axis and is therefore unstable.Assign a new release to one of the member ends where the degree of freedom φx is not hinged.
You can check the load application by using Project Navigator - Results → Load Distribution. In sections, the load distribution can be displayed graphically over the perimeter and the height.
Figure 01 shows the free variable load on a cylinder along the perimeter. Figure 02 shows the free variable load over the height. The load distribution can clearly be seen by the load distribution in the horizontal and vertical section.
A free variable load allows you to apply a load on surfaces that can vary in height and perimeter.
Figure 01 shows a circular container that is only loaded by more than a half of the perimeter in the surface normal direction. To define a load varying along the perimeter, it is necessary to activate the "Varying" option" under "Along perimeter." Click the corresponding button to enter the factors for the load including the angles where they occur. Furthermore, you can define the rotation axis. The factor kα creates a reference to the load value p of the initial dialog box.
As an alternative, it is possible to split the surface into the corresponding surface components. Subsequently, you can apply a surface load to the relevant surface components.
The container shown in Figure 01 has been modeled with two partial surfaces in Figure 02. Thus, it is possible to apply the surface load to the container half that should be loaded.
AnswerIn contrast to the normal surface or nodal load, a free load is defined by the influence range and the influenced elements. By definition, free loading is only applied to the areas of the selected elements resting within this influence range.A free load is defined by the absolute coordinates, with no regard to the elements of the model. For entering data, you can easily define them by selecting the model nodes, though there will be no link to the selected nodes. For example, if the model is then moved, the free load remains in the assigned position.If using an imperfection generated by RF‑IMP as a pre‑deformed FE mesh, the free loads are applied to this deformed structure. This may be out of the influence range and absorbs no load.If the load is expected to be linked to the structure and also moved in the case of displacements and generated imperfections, it is necessary to use the standard loads. As an alternative, it is also possible to increase the influence range of the free load as required in order to stress the entire structure anyhow.A simple check of the applied load is possible by displaying the load distribution in the Project Navigator - Results.
AnswerIt is not possible to transfer free loads (such as free concentrated loads, free line loads, and so on) via the IFC interface.
The projection plane and the load direction are different parameters and independent of each other.
While the load direction represents the actual direction of the acting load, the projection plane, together with the corresponding coordinates of the load position, describes the plane from which the load's position is projected onto the surfaces subjected to the load.
In the "Edit Free Rectangular Load" dialog box, the graphic to the right is used for information purposes, see Figure 01.
In a dynamic analysis, you can only calculate as many mode shapes as the structural system has degrees of freedom. The degrees of freedom mean the number of mass points multiplied by the number of the directions in which the masses act.
A cantilever that is not split by the FE mesh has a mass point at the end. The action direction of the masses in RF‑/DYNAM Pro is limited to the X and Y direction. Thus, the system has 2 degrees of freedom, thus 2 mode shapes can only be calculated.
Please note: In this case, the selection of the method for solving eigenvalue problem is very important. In contrast to the "Root of the characteristic polynomial" method, the Lanczos method cannot calculate all eigenvalues of the system, but only n -1, which means only 1 eigenvalue in this example.
AnswerFor the design using Equivalent Member Method and General Method, there are four degrees of freedom considered in the eigenvalue solver. These are as follows:
If the RF‑/STEEL Warping Torsion add-on module is activated, there are seven degrees of freedom available:
- uY' (displacement from the plane)
- φX' (rotation about the X'-axis)
- φZ' (rotation about the Z'-axis)
- ω (warping)
- ux (displacement in x)
- uy (displacement in y)
- uz (displacement in z)
- φx (rotation about the x-axis)
- φy (rotation about the y-axis)
- φz (rotation about the z-axis)
- ω (warping)
AnswerThe add-on module is designed for pre-tensioning or post-tensioning prestress. The templates for the tendon geometry are based on parabolic diagrams. This means that the modules are not designed explicitly for the design of flat slabs.Possible Procedure:The geometric distribution for a free tendon position cannot be determined automatically by the add-on modules. However, it is possible to use a user-defined tendon distribution as a basis. Unbonded prestress could be set by adjusting friction coefficients.The deformation analysis cannot be performed in the RF‑TENDON and RF‑TENDON Design add‑on modules. However, it is possible to perform the deformation analysis by using RFEM in conjunction with RF‑CONCRETE NL or RF‑CONCRETE Deflect when applying equivalent prestress loads. The equivalent prestress loads are exported without the influence of long-term losses and would have to be reduced by a factor corresponding to these losses in RFEM.
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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