Friday, April 15, 2016

Band Aid BIM–Surface Subgrade

Autodesk continues to push Band Aid BIM through blogs and advertising. Now I’d prefer to have actual BIM instead of Band Aid BIM. Band Aid BIM is the worst kind of BIM there is. It pretends to be something it isn’t. One big sign Civil 3D is Band Aid BIM is there is no concept of existing pavements. Does Autodesk not believe that the sea of black and white stuff doesn’t exist in the world. Autodesk sometimes sites the amount of infrastructure the US and the World will need to do in the coming years, but doesn’t create tools to process it?

One common task done is to remove existing pavement. Well since there isn’t any existing pavement objects in Civil 3D we have to employ Band Aid BIM to model this. The first thing we have to do is create a polyline that encompasses the areas of existing pavement. Then in order to simulate an existing pavement we need to create a new surface. I called mine XPaveArea. Then paste in the existing ground surface and then add in the pavement areas as boundaries. Now lower the XPaveArea surface the desired distance that represents the pavement sections. So I created a cross section to show the surfaces at this point.


Now I need to create an existing subgrade surface that represents surface the contractor is expected to build from, in my case called XGND-Datum. After all we don’t want to pay the contractor twice for the same work (removing the pavement and then calculating the cut/fill from the top of pavement).


Now in the resulting picture we can see we are screwed. Most pavement has vertical or near vertical edges. Civil 3D has decided to drop the surface down and then triangulate to another triangle a far distance away from our surface. In the area of landscaping what happened to our surface? Shouldn’t it jump up to the XGND surface? This means more work in this Band Aid BIM situation. We have to create another surface to fill in the gap for the median. See pasting surfaces pastes in holes as nothingness rather than the surface as it should do.

So to fix this we now have to add in information to the XGND surface. So create a surface with the XGND surface and then add the holes for the XPaveArea as boundaries. Then paste that into the XGND-Datum Surface. This is the result:


Well that sucks the triangulation doesn’t work. So now we need to create offsets of the boundaries at a small amount, say 0.001 units and then apply the boundaries in the correct order. This will let Civil 3D know how the vertical data should be handled at this location.


So looking better. To fix the outer edges of the pavement we need to add in a breakline to the XGND-Datum surface that represents the existing ground surface a small distance away from the boundary, say 0.001 units. Don’t forget about this command:


Once we do that we finally get a half assed, Band Aid BIM solution to the problem.


So how to fix this tragedy? I guess ask for Civil BIM first. If Autodesk refuses, like they currently are doing despite marketing BIM, I guess we can settle for these ideas on the Idea Station:

Pasted surface interaction with abutting surfaces

Pasted surface interaction when the top surface has more than one boundary

Surface Thickness

Band Aid BIM Improvement - Paste Surface Options


Anonymous said...

Have you tried Revit Site Designer? I'm curious if that's in a usable condition yet. Also I noticed that Autodesk in their release today is calling Civil 3D for "legacy workflows" and Infraworks as their "BIM solution". Can you actually do design and documentation in Infraworks now? Either way, as expected, Civil 3D is slowly dying...

Christopher Fugitt said...

Revit Site Designer, the last time I heard is dead.

No, Infraworks doesn't do design or documentation on an engineering level. Its still a crappy preliminary design tool. Not sure if you can take a program that does crap and turn it into accurate program.


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