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STEP format application protocol (AP230)

Mohamed Lotfy's picture

Hi all,

I'm using OpenCASCADE to export STEP files which are needed to be imported on Tekla-structures(X-Steel), a steel Building Information Modeling BIM s/w.
The problem is, OpenCASCADE handles STEP AP214 and AP203. Tekla handles STEP AP230 which is related to steel structures. Whenever I import a step file exported from Tekla in OpenCascade I get an error message and vise versa.
Does anyone have a solution to the different Application Protocol(AP) mismatch?

thank you in advance!
Best regards

Roman Lygin's picture


As you point out, OCC does only support AP214 and AP203. Obviously you cannot read in AP230 entities as OCC translator won't recognize them (and there are no classes that would describe them in memory in run-time). You could extend OCC API by adding C++ classes for those entities and/or translating only geometric (and other OCC-supported) data, e.g. using so called selections (read STEP's Data Exchange User's Guide p.16).

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Mohamed Lotfy's picture

Hi Roman,

Thank you for your reply. In fact, what you said is what I dream three weeks ago. For the time being, I ONLY want to export the GEOMETRIC(SOLID) model from OpenCascade in a STEP file and import it in Tekla which read AP230. In other words, if I modeled a simple solid box on OpenCascade, Couldn't I view it as a geometry on any other CAD s/w that support STEP regardless the other data that is related to manufacturing, design, tolerances, material, colors, etc...
I have read "2.4. Mapping STEP entities to Open CASCADE shapes" pp. 17 in
"Data Exchange STEP Import/Export User’s Guide" but I didn't find a clear answer to my question. Could you guide me more?

Thanks in advance
Best regards

Roman Lygin's picture

During export, the OCC translator will create a hierarchy of meta-entities (in addition to geometric ones that are AP-invariant). Some of them will be AP-specific. Have you tried to import such a file into your Tekla software ? Does it fail to recover geometric information ?
My comment was rather relevant if you tried to import Tekla data into OCC. The latter allows you to skip meta-entities and read only geometric data. Of course, I have no idea if you software provides similar things.


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Mohamed Lotfy's picture

I tried to export a simple flange(solid box) from tekla. It is not read by OCC. I did the opposite operation and the same result I got.
According to your last comment. OCC allows us to skip meta-entities and read only geometric data. Though I don't know how, the question now is, could OCC export only the geometric data and discard the meta-entities? if yes, tekla will find nothing to read but geometric entities and the reading process will succeed as I guess. If yes, please guid me to the article in the manual that enable me to export only the geometric data from OCC to STEP file.

thanks in advance
Best regards

Dmitry's picture

Some month ago i have read a lot of article about step. This subject is very complex, if you want to undestand everythink. You need some knowledge base in theory....

My advise:
1.Try to find in which format is written the geometrical part of the STEP AP230: STEP AP214 or AP203.
2.Try to separate this part of the data and create a new file in the geometrical format (STEP AP214 or AP203).

Make it per hand.

Andrey BETENEV's picture

In general, STEP format is oriented to representation of product structure (called meta-data here) as a major point; shape geometry is considered to be just an attribute describing some aspects of the product. STEP file can contain many geometric data only some of which do really represent the shape. At least, this is true for AP203 and AP214, and I suspect (even if do not know for sure) that AP230 is also product-based.

Thus for correct reading of STEP file it is unavoidable to analyse product data in it.

As well, most probably Tekla reader needs product data to be present in the STEP file, and will not read anything if it is not present. This can be checked by exporting some simple model from Tekla and manually editing STEP file to see which product entities are critical for reading the file back and which are not.

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