20091125

Calculating Pour Volumes


I'm sort of a feral child, and people ask me questions to which there might already be perfectly good answers. This time, the question was "In Revit, is there a way for me to analyze large concrete pours for irregular concrete elements?" I never heard back if it was useful, so you can be the judge.
Lets say you have a large irregularly shaped concrete element, like one of these:


or these:


You need to model and schedule it not only as a single monolithic element, but also as a series of pours that will happen in stages. What to do?


First, make your irregular shape in an external family of whatever category makes sense for your use. Here I'm doing it as a generic model (you can start this way and change it to, say, structural foundation if you need).


Next, take the whole complex chunk and slice it up at regular horizontal intervals. To do this, go to an elevation view and make 2 reference lines with parameterized dimensions (label them "top" and "bottom") to the reference level. Make void geometry on the horizontal workplane of each ref line, one going up on the "top" ref line, the other going down on the "bottom" ref line. These voids should each be large enough to completely cut the base form.



Now cut the complex geometry with your voids.




You now have a basic rig to move this slice of your solid geometry up and down the form.

Make as many types as you will have pours. For this example I have only 6 ridiculously deep pours of 20 feet each: 6 types, called pour 1 to pour 6, you may require more, shallower slices. Pour 1 is going to be the slice starting at 0' and ending at 20'. So bottom dimension is set to 0' and top is 20'. Progress up through each pour at 20' intervals.




Also make yourself a type "whole", with bottom set at 0' and top set over the top of the form. This will give you one type that shows the whole form for you to continue making design changes.



Load the family into the project environment and place 6 copies of the family in the same location. Set each instance of the family as a different type so that you have an instance of each slice and so make a reconstituted whole.


In this way the entire monolithic element can be instantiated as a series of pours by a single loaded family with many types, and each pour can be scheduled independently.
The nice part about this is that you get your schedulable volumes that are still fully integrated with your original form. To make changes, simple go back to your loaded family and make alteration to the "whole" type and reload it into the project for updates.


Bonus exploration for those who are interested: REBAR! I have no idea how this would work with rebar, I don't do much in Revit Structure, but I suspect that it would work nicely.

9 comments:

  1. I hate be a buzzkill, but I think there's a much easier way. If you just make your crazy object out of a mass, then you can slice it up with mass floors (at levels). Then you just make a mass floor schedule and oila! You've got volumes at each floor. Am I missing something specific to calculating volume for concrete pours?
    -Chico

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  2. Hi Chico,
    Yes, that would be WAY easier, but there are a few major drawbacks to that approach. First, you are stuck with your element in Mass category, and this can have bad results setting visibility in different views, especially if you have other massing elements that you really want to function as Masses. Second, the accuracy of volumes for overhanging situations will not be great, as Mass floor volume calculations determine the volume by projecting up from the floor. Lastly, you have to add additional levels to your project, as the exisiting levels will not coincide with what your pour volumes need to be. The mass floor method is great for fast and rough estimates, but I think has some problems maintaining the basic BIM-ness of the model, especially in a situation where you want to model large chuncks of material and not use the mass as a rig to skin with walls, floors, and roofs.

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  3. And besides, did you SEE how cool it looks to be able to isolate indiidual slices?

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  4. And you should never underestimate the value of "coolness."

    Great post BTW.

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  5. Many times I need to create lofted shape columns and also use the mass family for that. You will indeed lose the BIM-ness, but since Autodesk hasn't provided us with the proper tools, we don't have a choice.

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  6. Patrick,
    What kind of form are you looking to do in the column category?

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  7. On many projects, I needed columns and beams that are compiled through multi profiles along a path. Prior to Revit 2010 I've the loft tool in Rhino for this and imported it in Revit. Now, some of the shapes can be created in Revit, but I'll have to keep it as a mass and give it a new subcategory or i'll have to export it as a dwg and re-import it back into Revit. If these tool massing tools where available in the other families or if Revit had the ability to change the massing category to something else, the BIM-ness and parametrics can be maintained.

    In other cases, the columns are create trough subdivision surface modeling.

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  8. Interesting, what kind of work are you doing that regularly needs such fancy columns? Elements made with extensive sub-d modeling are pretty much out of the range of Revit, but most geometry that is a little bit "rational" can be made in the regular family (not conceptual) editor after a little post-rationalizing.

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  9. I've been working since 2007 in Denmark and the architecture in Europe is very different from in the states. Where in the US a client would request a Victorian style hotel, in Europe clients want a Zaha Hadid replica. That's also the reason why Revit hasn't really broken through here yet. Rhino and Maya in combiantions with Autocad is pretty much the standard here.

    On occasion we may use Revit for documentation, if the geometry is simple and not too large. However, I've been doing some testing on much more complex structures. Colomns and beams for the most part can be rationalized in a later stage of the design process. A simple loft tool in these families would be very useful. For now, multiple swept blends will do.

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