How to link revit parameter to ifc parameter?

[roquealfonso]

Hi,

I'm to trying to export a structural model with rebar to IFC (IFC 4 - Structural Reference Exchange), however, there are some parameters that Revit doesn't automatically fill to their corresponding IFC parameter even though they are named almost identical and refer to the same information. 

Revit parameters (for rebar) ---> (IFC 4) corresponding IFC parameter 
Total Bar Length   ------> BarLength
Bar Diameter / Model Bar Diameter -----> Nominal Diameter
Spacing   -----> BarSpacing
Shape -----> BendingShapeCode

I don't understand why these parameters are not filled after doing the export to IFC even though they refer to the same info, they are named almost the same, and Revit internally does provide this info. So why it doesn't fill that info to the corresponding IFC parameter?

I also thought of individually adding the IFC parameter to Revit by using the shared parameter txt that lists all ifc parameters, but I don't know how to tell Revit to associate or fill me in these new project parameters with the already existing revit paramater.

[L.Maas · Accepted solution]

First, HERE a manual relating to IFC and Revit. It is a good source to get you familiar with Revit and IFC.

What you want is mapping a parameter to an IFC class of a common property set.

IFC has defined common property sets for many classes (doors, windows etc).

A lot of these are exported by Revit. Sometimes not all common properties are exported.

In this case you want map Revit parameters to IFC classes.

In this case you can do this by assigning a parameter mapping table in the IFC settings (green hereunder)

You can create a parameter mapping table with something like notepad. It should be a standard .txt file

In here you write which Revit parameter to map which IFC common property set

It looks like this:

Green are comments and not important.

You see here that a Revit parameter "Fire Rating Type" is mapped to an IFC FireRating class.

Some Notes:

-Important is that FireRating belongs to the assigned IFC common property set.

-That the common property set exist in the IFC schema.

-Names are spelled correctly.

-If the value in the Revit parameter is empty than it will not be exported to IFC.

HERE a Youtube video explaining this further

If you want build your own property sets than you can do this with "user defined property sets" (in yellow in screenshot)

It works similarly, but syntax is bit different.