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!

A large part of my role as Digital Design Manager is getting multiple software platforms to play nicely together. Frankly, getting one at a time to behave is often a challenge, but I thought I’d share a few thoughts on the compatibility of two programs that see a lot of use around here: Revit and RAM.

Revit to RAM

The first time we tried to link the two systems, we started in Revit. This was an existing structure, steel framed, that we were modeling for seismic analysis purposes. The goal was to start in Revit (so we’d have a documentation model ready to go for a later design phase) and then export to RAM Elements.

Unfortunately, it turned into a complete mess. We discovered (too late) that the ISM translator only pulls the physical model from Revit and ignores the analytical elements. This meant that our steel joist roof didn’t connect to the beams it was supported by, columns missed their connections to beams, etc. It was a real disappointment, after all the work we’d put in to making sure our analytical nodes were connected.

We eventually were able to get the model to run, but it was a real headache.

HOWEVER, I have not given up! This was only our first attempt, and involved RAM Elements instead of RAM Structural System. I hope to find a good test project soon for Round 2.

RAM to Revit

Our next experiment went the other way — from RAM Structural System to Revit. This was another steel-framed structure, and when documentation started the engineer had already built a RAM model for some schematic design calcs. It seemed silly to start from scratch in Revit when we could at least try the import.

And this one worked beautifully.

All the elements came into Revit right where they should be. The beams had physical and analytical components. (I haven’t figured out that quirk of ISM yet.) Anything that looked off, like a grid line that stopped halfway up the building, could be traced back to the RAM model element’s definition, not the import process. I estimate that it saved us at least 3 solid days of drafting/modeling time, if not more.

The catch with this second project is that it’s historic steel, not modern. So the RAM model had lots of substitutions for archaic shapes, which had to be swapped out in Revit to be properly displayed & tagged. So I don’t know yet if we’ll be able to round-trip the model. There might be some tweaks we can make to the mapping file to accommodate the historic shapes, but my research hasn’t gotten that far yet.

It’s a good start, though…onward and upward!