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Thread: Variable Sloping Concrete Slab

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    All AUGI, all the time ford347's Avatar
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    Question Variable Sloping Concrete Slab

    I am a Revit Architecture user since 6 or 7 and have recently downloaded the 2013 suite to try out. I am playing around with structure because an Engineer has approached me about modeling one of their buildings structurally for the contractors in the field. I have a concrete roof to model. The roof slopes to two valley lines longitudinally for drainage. This will not be warped. I see only floor and slab foundation options on the structure tab, both of which do not give me the option to modify sub-elements, but do allow me to place reinforcement. I get the modify sub elements with an architectural roof but cannot place reinforcement. I'm not sure what to do from here and have not found anything in the help documents.

    Can someone explain how I am suppose to get the variable slopes I need (flat on bottom) AND get the option to add reinforcement to the roof slap?

    I also have concrete roof beams that run perpendicular to the valley lines and those will need to taper as well. I assume I model those in place?

    Thanks,
    Josh

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    Super Moderator david_peterson's Avatar
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    Default Re: Variable Sloping Concrete Slab

    Are you modeling in RA or in RS?
    When I model I "Floor" object, (not a slab, the slab tool is for foundation slabs, the floor tool is for everything else.
    Floors work just fine inf RS 2013 for me.
    As for modeling the rebar, good luck with that.
    Dave Peterson

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    "The more you know, the less you know, because the more you know you don't know". --M. Lin

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    All AUGI, all the time ford347's Avatar
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    Default Re: Variable Sloping Concrete Slab

    I used the floor tool, works fine. I thought I tried that, but obviously I did not. Thank you!

    As for the rebar, that sounds like a warning? Is the rebar difficult to model or do you experience problems by doing so?

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    Super Moderator david_peterson's Avatar
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    Default Re: Variable Sloping Concrete Slab

    The problem is 2 fold.
    1 - Depending on slab thickness, you may need to reference cover from the bottom face or the top face, and I'm not sure how well that will work.
    2 - It's going to increase your model size by a lot if you start modeling all the bars.
    3 - In my experience, it's never going to get placed exactly where you want it anyway.
    4 - It's usually a better idea to draw structural details 2d since they are there to show design intent and if you model it and start to model the section cut, you'll be chasing your tail fixing it.
    5 - 2d detail components for rebar simply work better for most things IMHO.
    Dave Peterson

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    All AUGI, all the time ford347's Avatar
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    Default Re: Variable Sloping Concrete Slab

    I see the logic and would choose to do it the same way if I were issuing construction docs. I am converting the Engineer's AutoCad model to Revit structure so they can pass it along to the MEP contractors who are using Revit MEP. I asked if they wanted to see the rebar modeled for any MEP penetrations and they said they would like to see it, but if it were a pain then they would create an allowable schedule for their penetrations. Sounds like I may want to suggest the schedule route if this becomes too tedious.

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    All AUGI, all the time ford347's Avatar
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    Default Re: Variable Sloping Concrete Slab

    taperedbeam.png
    As far as my concrete beams, as you can see in the pic, the bottom of the beam is level and the top follows the roof slope. I created an in place and will probably copy that into multiple positions. Would this be the best way or is there another way to accomplish this?

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    Super Moderator david_peterson's Avatar
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    Default Re: Variable Sloping Concrete Slab

    Quote Originally Posted by ford347 View Post
    taperedbeam.png
    As far as my concrete beams, as you can see in the pic, the bottom of the beam is level and the top follows the roof slope. I created an in place and will probably copy that into multiple positions. Would this be the best way or is there another way to accomplish this?
    In my opinion No. It depends on what drives your concrete beam schedule.
    In reality, most contractors would pour the slab and beams flat on top to finish the structural slab and then add a topping slab to create the pitch. I have yet to see a contractor actually get these slopes all correct in one shot. Also if you were to construct it in this manor your beam ties would all be a different height to match the top of beam (part of the reason why they are usually done in 2 pours). Again if this is just so the mep guys have something to go off of, they what you have is fine.
    Again I would have used typical beams and slab, then add a topping slab over it for the slopes. Easier and you don't have to create in-place families. Plus if the future when the slope changes, you wouldn't have to fix your beams, only the topping slab would be affected
    Dave Peterson

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    "The more you know, the less you know, because the more you know you don't know". --M. Lin

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    All AUGI, all the time ford347's Avatar
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    Default Re: Variable Sloping Concrete Slab

    Good point. I am a wood framer, so I'm unfamiliar with the workflow on these building types.
    I ended up just making a quick family for that beam to include a void shape for the top slope. It has worked fine so far and is better than creating them in place. In the future, I'll know to go the route you suggested. At this point, I'm not sure it's worth changing given the function of the model. I'll have to think about it.

    Thanks for the info! Very helpful.
    Josh

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