Unfortunately, there are two different interfaces with the same file extension - the .stp interface of the German Steel Construction Association (Deutcher STahlbau-Verband, DSTV) on one hand, and the STEP interface (STandard for the Exchange of Product model data) on the other hand, which is defined in the standard ISO 10303.
While the DSTV interface refers to the system axes of members - that is, to the structural model - the STEP interface refers to the model geometry in the form of boundary lines, surfaces, and simple solids. In the latter case, the models can be imported either as RFEM objects (nodes, lines, surfaces, solids) or as background layers so that the nodes can be set manually. The STEP interface does not usually transfer any system lines, but only the outer contours of structural components, so it is necessary to manually create system planes afterwards. You can do this in RFEM and RSTAB, for example, using a CAD/BIM model.
If you get the error message shown in Image 01, you have tried to import an .stp file based on STEP using the DSTV interface. As described above, these formats are not compatible with each other.
In this case, select the STEP format for the import, as shown in Image 02. If a message shown in Image 03 appears, it is because this interface requires the RF-LINK add-on module.
![Spans Based on Figure 5.2 from [1]](/en/webimage/039540/3493372/01_Abmessungen_EN.png?mw=512&hash=3cc425f1463bd5981b358d5889e3109e07ae1233)
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