Understanding Concrete Beam Joins

A few weeks back I was asked how Revit Structure handles concrete beam joins and how to control and manage how beams are connected and processed at the junctions. In older releases of Revit the beams would always mitre which was good in some cases but in other situations really didn’t give the correct solution. I have now modelled the various configurations and created some images so you can see how the beams will join. If you do want a mitred junction which is not 90 degrees then you will need to use a precast material.

About lawrenceh

I am currently employed by Excitech, one of the largest Autodesk resellers in the UK, to provide training and other services such as implementation and project support to our clients. The main products I get involved with are Autodesk Revit Structure & Autodesk Inventor. My personal interests include aviation, engineering and walking.
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10 Responses to Understanding Concrete Beam Joins

  1. Erik Snell says:

    Do these joins meet with your expectations? I like how you tested with colors. This is the same method we used at the factory.

  2. lawrenceh says:

    Hi Eric,

    I did find this a good and easy way to test and document the beams. It does work much better than previous releases but I still would like to see the beam join tool working on concrete items and the ability to cut concrete items with reference planes ( the same as steel and precast). Sometimes you will want the beams to mitre that are not 90deg and it is a bit if a pain using precast members for this as you may want to join to other members. What does everyone else think?

    • Erik Snell says:

      In our research for cast-in-place concrete we found that miter joins were not actually “real”, at least on the construction side. When would you want a miter? Only for beams of the same size and position? Is this so there is even distribution of material? I would really like to understand your needs beyond the graphics.

  3. lawrenceh says:

    Hi Erik, If you have two beams of the same size that are meeting at say 45 degrees then I would expect a mitre to be formed. If the junction was detailed as per my image (top row, second image) then it would make the formwork more complex. I have had a number of customers asking about this and I will see if I cant get some more specific information on how these details are shuttered on site.

  4. Erik Snell says:

    Why would the formwork be more difficult? With cast-in-place concrete the 2 beams are poured at the same time (i.e. no construction joints). The formwork would be identical, miter or not. This comes down to owning the volume of concrete at this point. If they are poured at different times or different grades of concrete I would not expect a miter at all as this would be very difficult to form.

  5. lawrenceh says:

    If you use the example on the top row – second image then you have three external faces. If you have a mitre then there are only two external faces and hence less formwork. Imagine the 3rd image on the top row but cranked at an angle like the second image. You will have one less face to shutter?

  6. Harryboie says:

    You are so cool! I do not think I have read anything like that before. So great to discover someone with a few unique thoughts on this topic. Really.. many thanks for starting this up. This web site is something that’s needed on the internet, someone with a little originality!

  7. rebecca says:

    i am having an issue with 3 cast in place grade beam intersecting at a concrete column. 2 of the grade beams form a 90 degree angle and the third grade beam is at a 45 degree angle. the visual problem is the beam intersecting with the column and two other beam. It is not clean. I just tried to change them to pre-cast and still did not work.
    any ideas?

    • lawrenceh says:

      Hi Rebecca,

      It’s a little difficult to guess what Revit has done with your concrete beams but if there are any shards of beam sticking out you can cut these off by using the opening by face command. Revit will complain that this doesn’t fully cut but just ignore and this will work.

      The other option is to load in a precast beam and then use the beam join tool on the modify ribbon. I would also delete the start and end reference extensions so the members join.

  8. gerald says:

    how do i analyze a reinforced concrete L shaped beam with supports at the only the two extreme joints. i was thinking of analysing the beam a single span beam. can somebody help me pls.?

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