BIM: IFC odi et amo [ENG]

bimdesign.pro (47)in #english • 7 years ago

Hello everybody!
I already told you what the IFC format is and what it is for.
Let's deepen the subject ...

Why is the IFC so important and who requests it?

Each BIM software saves in the proprietary format, and who have the license can connect it in their BIM model. This is a huge limitation for the BIM philosophy: trying to involve all disciplines and stakeholders in an integrated design.
The data must be the center of the information exchange.

Imagine, for example, a race: Architects use Archicad, structurers use Tekla and plant engineers use Revit. These groups have already acquired licenses and trained personnel.
How could they work on a single BIM model and how could they communicate informations to each other?

The IFC format is born from this requirement: it is necessary to receive and send the data from and to all the stakeholders.
On the other hand, the client may not have any of the proprietary software mentioned above, and of course, he must be able to open the BIM model.
Another limitation is the regulatory aspect (at least the Italian one): It is not possible to request a proprietary format, but only standard formats, in a public tender.
Here the role of the IFC assumes a central importance in the exchanging process of data and informations.
It's everytime so easy?
Look carefully, sometimes not. There are (as in many exports from one format to another) translation errors, butthey are improved from year to year through the research for BuildingSmart.

How big are these "translation errors"? Why do they exist? What do they do?

Here I can answer you by referring to my personal experience. In BIM there are different methods for modeling the same object. The geometric result is the same, what change are the informations that can be associated to the element.
Sometimes there is the need to model in one way rather than another in order to "extract data" or to associate different construction phases.
Let's take a practical example, I bring you the program I use the most, that is Revit.
The simple operation of "creating a wall with a void" can be done in n ways:

Architectural wall + a void family (generic model) that cuts it
Wall in place + a void in place (always discouraged, except in special cases)
Architectural wall + empty window family
Architectural wall with edited profile (also not recommended)
Mass surface wall + surface-based void family

... The list could go on, and I just wanted to make a hole in the wall! Then, if my wall belongs to the actual state and the "hole" is the project, some of the methods mentioned above are not feasible.

By exporting all these "holes in the wall" in IFC, the results at the opening of the file may surprise you:
The puncture may not have been translated, and you will find the whole wall!
Or again: you could open the IFC again with a BIM software and not see the puncture, while opening the same IFC with another BIM software you would see it correctly.
These geometric errors depend on the modeling technique used, which is sometimes not "well translated" by the format during export. Other times they depend on the software that "misread" IFC. If the thing is desired or not by the softwarehouse I leave it to you ...
To avoid these errors, I recommend to always do some tests during the work in progress, as well as assigning the right IFC classes already from the native file.

It is enough to export from the native software in IFC and open the new file with the free viewer of the software that will read your work.

All the major BIM software, in fact, have a free version with the purpose of displaying the BIM model.
You can not save or make changes, but they are very useful tools to check IFC export and reading.
Do you want me to mention someone? Naviswork freedom, solvers viewer, inventor view, A360 view ...
An error in the exchanging data, such as not representing a hole, could be a structural problem (the calculations are not true) or computational (no costs are considered because the quantity is incorrect).

Due to this reasons we should take great care to how the BIM model is exported to IFC, always check it and if you find technological problems report them to the collaborators and the client.

See you at the next post!

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