A few days ago I received some thoughts from Ben Osborne at McVeigh & Mangum Engineering in Atlanta on modeling post tension structures in Revit. Or, more precisely, the post-tension reinforcing bars. We had some discussions back and forth around Adaptive Components (AC’s) and Flex Pipes, and I decided to pursue the AC solution.
First, a couple of pre-requirements. The bars need to be able to shift between variable number of “ups and downs”. Because Adaptive Components have a fixed set of Adaptive Points, that means one family for each set of these.
I also need to be able to control tangent angel for each point. This seems difficult as I can find no other way of doing so than adding additional Reference Points very close to the geometry points. I’m sure the angle these form with the geometry points can be parameterized somehow, but in this example I’ve settled for horizontal tangents.
Last, the geometry of the bars should never exceed the concrete cover, meaning the “ups” and the “downs” needs to be offset by one radius from the original Adaptive Point.
Based on the Adaptive Point I add new Reference Points, hosted as a chain so that if I move the Adaptive Point all the other (4 in the example above) move with it.
The distances between the points are length parameters associated with the Offset parameter of the Reference Points. In order to make this work both ways (the different high and low extremes have both positive and negative offset values) you want to set up inverted duplicates of all length parameters.
When all points are in place I host the nice face-based anchor family that Ben has produced to the end points, and voila; Fully parametric post tension bar, flexible in all imaginable directions and pretty easy to model.
How would you add those extra “ups and downs”? Could you upload another version of your family with a couple more “ups and downs”?
Thanks
Yea, it’s pretty easy. You just copy the middle point around, and rehost the new reference points (some lose their host references when they are copied). Then you produce a new reference spline by points and redo the circle and sweep. I’ve uploaded a new file with 5 points – 3 ups and 2 downs. It’s in the Content section.
Thanks, Håvard
Hi, Håvard. PT rebars modeling via adaptive components is a good idea. But for this purpose I usually use PT tendons family based on structural framing template . It not only creates the tendons, but also sends an analytical model with all loads from post tension in RSA for further analysis. You can read more on my blog: Perfect Project
Yes, I can see how that can be useful Max. However, I love the way I can control the curves with points, and also the possibilities opened by surface, patterns and path hosting.
And being able to use the Repeater feature in 2013.
Max, the link to your blog says the page does not exist! Interested in how you are using structural framing template with PT and RSA. Are you revising the page?
Hi, Steve! You can read this: http://goo.gl/bRl8Q Also on YouTube: http://youtu.be/i5mnLPIdXwE
Revit do not have a PT tendons family OTB in the structural framing template.
Yes, you are right! But we can create it
Hi Max,
The download content doesn’t seem to work. I am working on a project where we need to model all the PT anchors so I wanted to use what you created already.
Also, I had a question about model size, a couple years ago I worked on a project where we modeled the PT tendons and the revit file quickly went from 70MB to 500MB just by adding about 20 tendons. I used a generic model in place using a sweep along a spline, I’m sure this isn’t the most efficient way, but it was the quickest way I knew at the time.
Cheers.
I’ve updated the link to point to my content section. It should work now. Thanks for letting me know.
Please feel free to use whatever you need, but be aware the families still need some tweaking. I’m no post tension expert and still receive feedback on how these can work even better.
I do not see any big impact on file size while using Adaptive Components.
Hi Håvard,
Very interesting subject with PTE modelling.
Du you have any pointers, on how to handle PTE modelling around slab openings?.
My experience with PT modeling is limited to these Adaptive Component tests unfortunately. But if you could provide an illustration..?
Sure: http://www.gratisimage.dk/image-F82E_518200F5.jpg
I’m very interested in an easy way to make annotation on the placement of the tendons. Perhaps a macro is the way to go?
I’m not sure exactly how that would be built, but you can model a void family and cut out the opening outlines from the PT’s in question. That will obviously not automatically produce new anchors – you’d have to model those additions manually.
Regarding annotation, you can use Spot Elevation on the Reference Points in the project environment. As long as you annotate the high’s and low’s I think you’re in the clear.