You could get the beam curve, or what I like to call "the blue wire", from your Revit Beams using the OOTB "StructuralFraming.Location" node.
You would expect (as I did) that the beam curve or "work line" of the beam would be located at the TOP CENTER of the beam. However, if your beam's "Z" Offset Value is NON ZERO then the beam curve or "work line" is not at the top center of the physical beam.
You have two options to correct this. You could get the true geometric top center of the beam by doing an analysis of the beam geometry using dynamo. This method is a bit complicated....... or you could use the method below.
Also to avoid this from happening you could choose to NEVER use the "Z" offset value to move your beams in the Z direction and instead change their "Z" direction location via the "end level offset" values. For me... I use both.
Also note that this method shown above will not work if your beam reference work plane is not horizontal. In that case you would need to change the vector input from "z" to another vector that is perpendicular to your work plane but this case is not that common.
Good luck finding those Revit Beam worklines!