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Frequently Asked Questions (FAQ)
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Yes, it is possible. For this, open Window 1.5.
If there are too few nodes selected for design, so that the program cannot determine the dimensions lx or ly automatically according to DIN EN 1992‑1‑1, 6.4.5 (NA6), Figure NA 6.22.1, a message appears, saying that the conditions for determining the minimum bending moments are not fulfilled.
The program requires at least 4 nodes to determine the span lengths in the x- and y‑direction.
In this case, you can define the minimum bending moments manually.
This is possible in RFEM in an indirect way.The soil pressure, from which the bending moment is determined for the design by using the integration, can be applied as an "external load" in the RFEM initial model.Distribution of Compressive Stress in RF-/FOUNDATION ProThis compressive stress can be applied as a "Free Surface Load" to an equivalent structural system in RFEM.In this case, the equivalent structural system is a rigid surface. The size of the surface depends on the position of the design section set in RF‑/FOUNDATION Pro. In this case, it is necessary to set "In Column Center."With this equivalent structure, it is possible to recalculate the "moment from the distribution of compression stress" determined in RF‑/FOUNDATION Pro.You can download the example described above using the link below and open it in RFEM 5.
If the beam and the surface are in the same plane, they are firmly connected to each other.
Although the member end has a member hinge, it is already connected rigidly to the surface in the next FE element and shares the load transfer with the surface by means of bending. To avoid restraining moments, the surface must also have a line hinge.
If the line hinge has been defined correctly, the problem may be in the incorrect support definition.Although the structural system (see Figure 01) would seem to be the same, there is a moment in the mid-span resulting from the determination of internal forces on the surface.In the present case, the cause can already be derived from the error message after the load case calculation.There are very large deformations resulting in the bottom structure, so that this already indicates an incorrect support of the surface.When checking the line supports, it becomes clear that the bottom structure is rotated about the global Y-axis due to the missing restraint. In the end, this leads to the non-meaningful distribution of internal forces in the basic internal force m-x.If you adjusted the line support, you will get the expected result.
AnswerThe reason for the occurrence of a bending moment in the oblique and straight bar is that the middle post has a certain flexibility due to its finite rigidity. Thus, compression takes place at the middle support, so that the deformation of the middle support also affects the right-hand latch. Because the right-hand latch is additionally held on a movable support, a forced moment arises at this point.One recognizes it above all by the respective deformations. See alsoThe calculation by means of RFEM results in minimum bending moments, which however are not taken into account in the manual calculation.
Designs in our module RF-/JOINTS Steel - Rigid are based on the assumptions and regulations of the standard EN 1993‑1‑8. Here, bending from the main beam plane is not considered.
In RFEM, it is possible to model any rigid joint. All internal forces can then be taken into account.
In the case of unsymmetric cross-sections (angles, Z sections), the main axes are inclined. The angle α describes the position of the principal axes u and v in relation to the standard axis system: This is the angle between the member axis y and the "strong" cross-section axis u. It is defined as positive if clockwise.
The resulting bending moments of an unsymmetrical cross-section are displayed in relation to the principal axes by default. Therefore, the descriptions Mu and Mv appear in the graphic and in the table. If you want to display the values of the moments related to the member axes y or z, the corresponding setting must be made in the Results navigator (see Figure 01). The internal forces My and Mz are then displayed in the graphic and in the table.
The display of the principal axes can be activated in the Display navigator by selecting "Member Axis Systems x,u,v" (see Figure 02).
The bending moment My is positive if tensile stresses occur at the positive member face (in the direction of the z axis). Mz is positive if compressive stresses occur at the positive member face (in the direction of the y axis).
The sign definition for torsional moments, axial forces, and shear forces conforms to the usual conventions: the internal forces are positive if they act in the positive direction at the positive face.
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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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