Revit doesn't do structural analysis itself - it allows you to build the model in Revit and then transfer to a structural software package like RISA-3D.
When the structural model is created in Revit, what happens at the nodes? Does Revit make adjustments to the lengths of the beams to fit outside the column flanges or webs? Or is it like STAAD where the member lengths are node-to-node? Does the engineer have to zoom into the beam-column connection and actually draw the beam offset from the column flange, draw the connection plate/angles, draw the bolts...? Or are the connections detailed automatically based on the attributes (bolted connection, welded connection, moment connection, beam to column web or flange) assigned to both the beam and column similar to how Descon details connections?
Im using Revit Structure 2008 right now. I have drawn the structures in Revit and then exported them to both RAM and ETABS. Once the analysis is complete, you can reimport the designed sizes back into Revit. As said above, Revit doesnt do the analysis.
Revit automatically produces a setback that can be changed. The node is actually at the workpoint of the connection. When you go to cut the section Revit generates the 2D column and a beam. That's it. Very bland. So you have to DRAW IN BY HAND IN 2D all the bolts, clip angles, welds, text, EVERYTHING. And if you update the beam size, your hand drawn stuff DOESN'T update with it. It sucks. Everyone I know hates it. Have been to the 3 day training course and even the trainer says they a lot of people are let down when they get into it because a lot of the sales pitches are deceptive. It's so much more work for nothing gained. The company hasn't been profitable on any Revit jobs. It doesnt help coordination issues like they claim. Beware
Thanks for comments Atomic and JAE. For the coordination with other consultants like the architect and MEP, are you integrating their Revit models into yours?
JAE, if you currently draw every section with EXACTLY the correct beam sizes, then you wouldn't be bothered by this. But, there are many times where the exact member sizes really don't make a difference in what you're trying to convey. It forces you to be exact where you don't really need to be, and I just don't think our fee reflects that amount of detail.
We have architects and MEP in house, so yes we have integrated models and its easier because we're all on the same network. Coordination seems to be something everyone's interested in. BUT there's a big but. The way its set up, (which is the way autodesk recommends) Architectural has a model. Then structural makes a model and links the architectural model in. It's essentially the same thing as Xrefing a base drawing in autocad. Their 3D model shows up as a block and you draw all the structure over that block. You "freeze" out layers you dont want to see. It will not catch coordination issues like drawing a column over a wall. The only coordination feature is a thing called "copy monitor". You designate certain elements in the architectural link with copy monitor, and then if architectural moves them, it pops up a general window saying "Do a coordination review".
Having several people working on the same file makes things a bit more complicated....too complicated to type here. I recommend if you're genuinely interested you look on
My firm is just starting to jump on the "BIM" wagon. The firm I previously worked for used Revit, so that is the only software I have experience with. Does anyone have any other recommendations? What about AudoCAD 3D?
We have everything in house here...architecture, structural, mechanical, electrical, civil...etc. Is there a good base program to use for all of these disciplines?
That's the same question I have, UcfSE. I work with several architects, all outside my office, that make changes and issue new CAD bases at least once a week. Often, more often than that. We are left on our own to determine where the changes were made because they refuse to spend time either writing a revision summary or clouding the areas that were revised.
When the notice "do a coordination review" pops up, is it easy to determine what changed?
We have been using Revit and the Bently 3D package.
UcfSE asked about architects making changes. This practice will not stop, in fact it may get worse. You see, when something is modeled in 3D it APPEARS more finished than it really is. The architects mass model in a wall. Said wall appears on the 3D image but the architect doesn't work out the details of the wall section until much much later. Thing is, you need the wall section NOW to set the building grid and to see how complicated areas are going to fit together. People think the architects are getting close to complete because some semi-defined mass wall element has been placed.
Placing an object in 3D also gives the false impression that it has been thought through. Just because somebody placed the element doesn't mean it's right. Things get placed to take up space rather than placed for a specific design purpose.
Don't get me wrong - I see 3D as a very useful tool, especially for owners to "see" what they are getting beforehand. Beyond that, it seems to permit the designers to "show" more with less real design work. Design work that eventually must be performed and used to be performed sooner rather than later!
So, is 3-D modeling even worth it for a firm to invest in right now? I haven't heard much positive feedback about it. Even with all of its quirks, in your opinions, is it still better than 2-D modeling?
For those of you using Revit, are you giving the model to the contractor to be used for cost take-offs and detailing? How much data is in the Revit model with regards to member sizes, connection info, etc? A contractor that we work with on alot of projects called to see if we were using any BIM software. He wanted to know if he could get the 3D model and get everything he needed to know about materials from the model without having to do the same cost estimating effort he's always done. Also, he wanted to know how much detailing the 3D model contained and if his steel fabricators could use it to cut out some of the steel detailing lead time. Since we don't use BIM or Revit, we couldn't answer his question.
My firm uses Bently Structural (Triforma). Our drafters have been using it for quite a few years and I can't speak for how the transition worked. At this point, it only takes slightly longer for us to model something than draw it 2D, but the benefits outweigh the extra time.
It works really slick now. Probably 90% of the jobs we do are modeled. My drafters pick up conflicts all the time. They don't use a conflict detection module, but it's pretty easy to see any conflicts (duct through a beam, etc).
One thing to think about is the order of how drawings are delivered. The structural efort is big up front because everyone wants to tack something onto your structure. Something to think about during scheduling.
Bently's aquisition of RAM and STAAD creates a promising situation.
You need to evaluate the pros and cons to make a companywide investment decision.
No, we dont give the models to contractors or fabricators. Nobody has asked for it yet. Even if they did, I'm sure we'd ask a fee to cover our increased liability.
