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Thread: Truss Family vs. Generic Model

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    Truss Family vs. Generic Model

    I need a roof truss for a building I am modeling that does not need to be flexible at all (i.e. there is only one truss type in the building. I may need to change the truss as the design is refined, but all trusses will be the same). I am having a bear of a time creating a truss family that gives me the results I need.

    Do I lose any functionality by using a generic model instead? If I assign materials to my generic model can it still be used for structural modeling (not sure if this is actually necessary at this point)? I'm also not sure if having a truss family somehow will make placing the roof on top easier...

    Thank you!

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    Member Andres Franco's Avatar
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    Hi sleeknub,

    Well I think is always a good idea to model objects in the right category that will let you to have control all the aspects related to trusses and structural elements, maybe that will be more difficult at the begining but sure at the end you'll have much more better results and all the stuff related like quantities and so on.

    But in some specific cases if you are having a lot of issues and you are newbie in Revit I know by my own experience that this will be frustrating, so, a generic model can help you save time if your project but to the other side that will give you some headaches, so be careful

    To respond your question abut functionality: I guess that apart of losing the posibility of making structural analisys and quantification with your generic model and some visibility controls related to specific categories, create your truss within will no suposse a big deal, but it's just my opinion.

    Regards
    cganiere likes this.

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    I agree that you should first try the intended family type. That being said, we found it could not meet our needs at this time for wood trusses so we create them with an assembly of structural framing members and connectors. To do this manually in Revit, create your truss with the framing members as needed. Then make an assembly out of them. Since all your trusses are the same, one change will apply to all and you can generate a shop drawing of it if needed.

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    The problems I am running into are the end conditions on the top chord, which overhangs the bottom chord and needs to be squared off to accept the fascia, and the junction between the top and bottom chord (the bottom chord overlaps the top chord, but needs to be "coped" to it or shaped in a specific way). I am not aware of a way to modify these end conditions...only how to automatically cope the chords, which doesn't quite get me to where I want to be.

    Here are a couple photos of a similar roof truss that will help illustrate what I'm talking about. I'm guessing this is something simple...I just can't figure it out.
    Attached Thumbnails Attached Thumbnails Truss Family vs. Generic Model-2017-06-01-14.11.28.jpg   Truss Family vs. Generic Model-2017-06-01-14.12.12.jpg  

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    Yea, you have to make your own Top Cord Family for that.

    Quote Originally Posted by sleeknub View Post
    The problems I am running into are the end conditions on the top chord, which overhangs the bottom chord and needs to be squared off to accept the fascia, and the junction between the top and bottom chord (the bottom chord overlaps the top chord, but needs to be "coped" to it or shaped in a specific way). I am not aware of a way to modify these end conditions...only how to automatically cope the chords, which doesn't quite get me to where I want to be.

    Here are a couple photos of a similar roof truss that will help illustrate what I'm talking about. I'm guessing this is something simple...I just can't figure it out.


    Yea, you have to make your own Top Cord Family for that. I use a Rafter family I made that works for both top cord and rafters. If you flip it upside down it will work for half a bottom cord too. Then mirror it for the other half of your bottom cord. I know I could do a much better family but I work for one of the largest truss plate manufactures in the world and we have software that creates trusses on the fly in Revit so I don't really need to bother with manually creating them anymore.

    Enjoy, I hope it helps out.
    Attached Thumbnails Attached Thumbnails Truss Family vs. Generic Model-cut_rafter_tailsettings.png   Truss Family vs. Generic Model-cutrafterridgeoffset.png  
    Attached Files Attached Files

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    Thanks SBabin. Are you using that as part of a generic model, or an actual Revit truss? As far as I can tell Revit just, in effect, takes an extrusion and extrudes it along the length of the chord, so you can't define an end condition. Are you able to model out that rafter and have Revit use it as the top chord in a truss (as opposed to a generic model)?

    I'm attaching a couple examples of what I was able to achieve using a generic model and using a truss family. I would like to get the truss family to look like the generic model, if possible.
    Attached Thumbnails Attached Thumbnails Truss Family vs. Generic Model-generic.png   Truss Family vs. Generic Model-truss.png  

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