Time for an update on our Revit-RAM process!
First, some successes: We’ve been doing a lot of one-way transfers, Revit to RAM, with pretty good success. It helps that Bentley released a 64-bit version of the ISM link, reducing model export times by a LOT. One engineer in my office modeled up a steel-framed building (with something like 2000 columns) in Revit, exported it to RAM Structural System, and ran an analysis in about 2 hours. I did the same thing with a 53-story concrete building in about 4 hours. And for that building, we also brought the new column and wall sizes back into Revit! I hope it is the first of many round-trips.
It hasn’t been an unqualified success. RAM still doesn’t read the analytical location of structural elements, which can lead to some quirks when importing and exporting elements. For example, steel columns are almost always centrally aligned, but concrete columns are often aligned by face. Same thing with walls; sometimes the centers line up, sometimes the hold point is one edge or another. Not all the walls came back from RAM with the correct hold line, but I can’t be positive I modeled them correctly in the first place, so I’ll have to try again another time. Face-aligned concrete columns are at least a little easier to tweak if necessary.
Concrete floors on metal deck still don’t transfer very well, and we’re still doing all our load assignments in RAM because we aren’t trying to use multiple analytical packages on the same model. But the biggest disappointment so far has been rebar. RAM SS will design rebar, of course, and it can export it back to Revit…as 3D rebar. Which we’re not using yet. So I haven’t been able to find a way to automate the population of the column schedule with the appropriate rebar. Maybe by the time I write “third thoughts” we’ll have made some progress…
But honestly, I think there will always be one major deal-breaker when it comes to a true 2-way transfer of information: engineering judgment. Engineering analysis and design does not always require the same precision that a set of construction documents does. It just doesn’t, and it never will. Tweaks to a slab edge condition that require changes to every floor plan and section cut in Revit may not have any effect on the structural design at all — so what do you do? Stop sending the floors back and forth? Send them back and update the design model? Break the link entirely? All potentially valid options depending on how big the discrepancy is and how far along you are in the design process.
Even with the drawbacks, though, the process is constantly improving and evolving. Here’s to progress!