Good Evening All,
I have two questions for you today.
I know this has come up in the past with regards ISM data exchange between RAM Concept and Autodesk Revit but I have not heard any updates from Bentley or any other sources since so I figure it is worth asking again. I know that currently, ISM can import reinforcement from Revit only but reinforcement designed and detailed in RAM Concept cannot be exported to Revit for final documentation which seems to be a tragic waste of what is a pretty detailed reinforcement model. It may not be 100% what will be documented for construction but it is pretty dam close and would cut out a hell of a lot of duplication if ISM supported this.
Secondly, I am wondering if anyone else would find it useful if RAM Concept supported some additional bar shapes? The ones I am most interested in are 'U'-bars, 'Z'-bars and cranked bars. I am specifically looking for these shapes because current Architectural trends in Australia is resulting in slabs with increasing complex geometry in order to achieve the desired architectural form and this is often achieved by introducing slab folds, steps and setdowns which we would normally achieve using either 'Z'-bars or cranked bars in order to ensure continuity of reinforcement through setdowns/steps/folds. Secondly, I find that in thin slabs specially, it is difficult to achieve the required development lengths using the 90 degree hook option and i must therefore design using the fully anchored option which means that I have to detail these in RAM Concept for both top and bottom mats which results in duplication. My preferred end detail for slabs is and always has been to provide a full 'U'-bar connecting the top and bottom mats together (see attached photo noting that the top mat is not installed but you can see from the 'U'-bar where it will be located). This way, I achieve the full development length for top and bottom mats and I also find it works well on site as it temporarily supports the ends of the top reinforcement (saves bar chairs and is good for OH&S) and it reduces number of bars thus saving on handling and tying.
The challenge we faced when implementing rebar import into ProConcrete and Tekla was that the ISM formulation of rebar groups didn't always fit nicely into the format used by the detailing programs. Thus, a group of rebar in the design application for a beam, column, wall or slab was often broken up into individual bars in the detailing application. At that point the individual bars can be a real pain to modify in the detailing application and since the design program rebar geometry is never quite right for detailing purposes it was of little use to a detailer.
Thus we have been hesitant to invest a lot of time into Revit - Rebar import until we have some confidence that users will like it and use it.
If you have any examples you are willing to share please send them over (via Secure File Upload link below left or private message). Potentially we could have a meeting with you and other users who are interested in this topic along with some of our product managers to plot a road map forward.
Seth,
Thanks for your reply. Traditionally, in Australia, structural engineers typically provide only basic 2D CAD plans and elevations showing the main rebar with general notes covering secondary distribution steel for fire, crack control, minimum bending capacity and so forth but typically do not provide any dimensions or scheduling capabilities. However, in Ireland where I trained, the structural engineer provides substantially more information traditionally in the form of 2D plans and elevations but with everything drawn to be dimensionally correct in the correct locations and scheduled so that all reinforcement gets cut and bent to the exact specification of the structural engineer.
Fee structures in Australia make it incredibly difficult to provide detailed reinforcement drawings which could be used to schedule, fabricate and install reinforcement on site. The schedules and drawings are typically prepared by a third-party shop detailed similar to the process used for steel or precast structures. However, with reinforcement shop drawings, we typically do not get engaged to review the shop drawings before reinforcement fabrication and installation on site and therefore we encounter a lot of mistakes on site (e.g. missing bars, insufficient cover, incorrect shapes, clashes) which can often be difficult to rectify and have resulted in concrete pour cancellations in the past. Add to this the fact that slab geometries we encounter are becoming increasingly complicated and the requirements of AS 3600 with regards secondary steel, tying details, development lengths are becoming more stringent which all require more input from an engineer, it is hard to see how this traditional approach is sustainable long term.
At our office, we are hoping to be able to provide fully dimensionally correct 3D reinforcement models that we can schedule and are suitable for reinforcement fabrication and installation on site. We hope to take advantage of the BIM process to assist us with this. We and most other architectural and structures consulting firms currently use Revit for 3D BIM documentation. We hope to provide dual option of a 3D IFC model that we can pass on to shop detailers or provide traditional 2D plans with matching bar schedules, both of which could be used to fabricate and install reinforcement on site in a way that matches all requirements of AS 3600, matches that used in our design and fits properly within formwork. However, to do this at a cost that won't cripple us, we need better data sharing between RAM Concept and Revit.
With regards the RAM Concept 2D reinforcement, generally when I am working in RAM Concept, I design it and lay it out as I would detail it. I generally have a good idea based on experience where I will need the reinforcement, where my splices will be located so I will start my design by laying out user designed reinforcement based on this experience and in accordance with the detailing rules from AS 3600 and the Institution of Structural Engineers Standard Method of Detailing Reinforced Concrete. Then I run a couple of RAM Concept runs with the program designed reinforcement turned off to find out where it is failing, increase/decrease the reinforcement accordingly and gradually iterate until I get it all working with used designed reinforcement. Prior to doing that, I work out all my covers, maximum bar spacing, span directions, and so forth in accordance with AS 3600 to satisfy fire, exposure, crack width requirements so that when I lay out my initial reinforcement then I no longer need to worry about these. I find that typically, bar spacings in the 150 mm to 200 mm works best for most situations. I am hesitant to rely on program designed reinforcement for construction documentation particularly with complex slab geometries as it tends to come up with bar arrangements that typically would not be very practical on site. Therefore, the 2D CAD output files I generate are generally 90% of what will appear on the final documentation with exception to the edge details and details at setdowns and folds which as stated in my introduction RAM Concept does not support the bar shapes we typically use at these locations. We get out drafty to amend these accordingly with ‘U’-bars, ‘Z’-bars and cranked bars as per our typical detail library. We detail the reinforcement in Revit by inserting the 2D CAD output as an external reference in Revit and the drafty traces over it so it matches exactly what comes out of RAM Concept bars the details discussed above. We have found this to be a very time consuming task so if we could get the 3D data from RAM Concept directly into Revit in a format that can easily be manipulated then it would massively boost our productivity even if it were say only 80% of what will be on our final documentation.
Ideally, I would like to lay out my initial educated guess of what the reinforcement layout is going to be in Revit as it is simply better at drafting than RAM Concept is, import that layout into RAM Concept, iterate it until it works and send the final bar arrangement/sizes/spacings back to Revit for final documentation. I know that ISM provides unidirectional reinforcement export from Revit which I have not tried to date but it is the next thing I want try out. I currently generate all my slab geometry in Revit and export it to RAM Concept, again because Revit is far better at this than RAM Concept and gives me a resulting RAM Concept Model on the exact same co-ordinate system as my Revit model. I can do that now with 100% reliability including slabs with highly complex geometry in the form of varying depth band beams, setdowns, steps, upstand beams and downstand beams with little or no manipulation of the analytical model in Revit or rework in RAM Concept (with exception to curved edges which RAM Concept does not cope with very well).
With regards our Revit setup, we are working though our first full 3D job involving reinforcement detailed in 3D. Our Revit rebar modelling therefore is mostly as it comes out of the box with exception to the bar calloffs which we have generated a custom family for. We are however sending our staff on the advanced Revit training course next month which covers custom families and if we see benefit on generating custom reinforcement families or Dynamo scripts to cover some of the repetitive tasks then we will develop these in house.
I have sent you some documents via the secure file upload link which include a sample 2D reinforcement drawing from a number of years ago generated in AutoCAD with an add on called CADS RC (actually reinforcement drawings matching the photo included in my original post), a sample Revit file including reinforcement designed in RAM Concept (our first attempt at this), the 2D drawings exported from RAM Concept and the matching RAM Concept files.
Thanks for all this great feedback. I've drawn it to the attention of the product managers.
Meanwhile, for tracking purposes, the official enhancement request number for getting Revit ISM plguin to import reinforcement is: 133288: ISMRL: Revit link, import ISM reinforcement (rebar)
I don't have anything specific logged for U bars yet, that would require changes in both the ISM rebar interfaces and the design applications like Ram Concept.
By the way, if you did not know this, you can save the rebar as user bars, export to ISM and then generate an i-model showing the structure transparently with rebar. This i-model can then be viewed or queried on the iPad (or phone and soon on Android devises) using Structural Navigator. That might help with on-site inspections.