How to place beams over beams

[sythlord632673]

I have a roof construction with trusses, and I want to place purlins (C1) on top of the trusses, perpendicular beams (P1) on top of them and wooden sheeting over the beams. (C1 and P1 are shown on autocad screen shot).

I've tried the frame generator, but it only creates purlins and if I try to make perpendicular beams they pass through them not over them.

Any ideas ?

[klausstroehl]

I don´t use the frame generator but in general: You can "flip" your beams by turning the "baseline orientation" of the beams from top to bottom. By choosing "other" you can choose a manual baseline offset.
The command might be a bit different in your english version, hope it helps anyway...
Cheers,
-Klaus

[Craig_L]

Alternatively make a reference plane in a section along the top chord of your truss (at pitch)
When I do this, I also move the reference plane 10mm above the rafter to allow for the cleat distance (of course this may vary depending on your project but 10mm is usually the minimum)
Label your reference plane as "Bottom of Purlin - Grd 1 to 2" or something that will make it easily identifiable.
You will need to do a reference plane for each side of your roof.
Set the workplane, and choose your new workplane as "Bottom of Purlin - Grd 1 to 2"
Model you beams, make sure you choose bottom in properties for where you beams will orient.
You can space these equally, using the dimension tool, you can also use the beam system but personally I prefer to only use the beam system on arrangements modelled on a flat surface they get more complicated when trying to put them on a roof but thats a personal preference.

[AdamCP]

A little piece of advice if you decide to host beams along a raking reference plane. Reference planes are infinite, so when you move them, Revit does the only thing it can and moves hosted elements along a line perpendicular to the plane from their original location. This is fine in a lot of cases, but imagine a pitched roof with purlins. What happens if that roof height changes? When you move your plane vertically, Revit moves the hosted purlins perpendicular the the plane instead. The apparent effect is that your framing will appear to slide down the roof if you move the plane higher.

The counter this we host all our pitched framing on finite planes, in the case of purlins, we host them on the underside of roof objects. For the rafters and such below, we use a second roof object set up as frame guide that gets filtered off drawings. If you cut a section along the roof pitch, you can set up your spacing and beam systems a lot easier as it's just like working on flat framing.

This approach is not without its own issues, but it seems to work pretty well if you get frequent height changes (even pitch changes aren't that painful).

Cheers,
Adam.