Beam Going Crazy!

[barrie.sharp]

I don't end up using beams very often but when I do, I find their behaviour odd. Like everything in Revit they will be acting logically but I don't know the logic!

I have been wanting to use beams for roof rafters and get varrying success. Issues I have are the connection points and beam geometry seem to have different constraints. Geometry can over extend where two beams meet at an apex. I edit the join but the choice is the beam going too far or falling short - Why don't they just mitre?

I tried throwing together my own beam from the template and added cut angles to make the ends plumb (See attached). This was just a quick test family because I know now from experience that things don't run smoothly first time on a new category. Didn't think it would be too complicated but the ref planes in the template don't have obvious constraints so I went by their labels for guidance. When I loaded the family and added it to a level, the beam appears offest by -134mm from the connection points. I locked the 'elevation center' to the ref level to attempt a fix but no.

I don't seem to get beam families.

Additionally, I have tried using beam systems as rafters. I host them on a ref plane for changing angle but I can't constrain the sketch to a footprint. It wants to align to a perpendicular ref. Is this one of the draw backs for this method?

[cliff collins]

A couple of tricks with beams:

Use a reference plane and Cut Geometry to "trim" beam ends, etc.

Use a Beam System on a sloped reference plane to control joists/rafters
which will allow the entire system to remain locked to the ref. plane, so if you
change the slope/pitch, the beam system adjusts automatically.

see this thread:

http://forums.autodesk.com/t5/Autodesk-Revit-Architecture/slope-reference-plane/td-p/2693645

Use the new Coping Tools for more precise joins. There should be properties in the beam family for controlling the "offset" spacing from end of beam to adjoining members.

cheers

[Alfredo Medina]

I was able to use your beam family on one side of a gable roof, only. In the other side, the cut angles were upside down. Therefore, I had to mirror the beam system and half of the roof, to make it work. Your idea is good, you just have to find a way to make it work on both sides. Maybe two family types for each case of angle? One with the angle going forward, and one going backwards?

I don't know why beams are so difficult in Revit. Sometimes, nothing one tries works, in trying to join or cut beams properly. It can get very frustrating, after one tries Cut Geometry, Join Geometry, Trim with a reference plane, Beam joins, etc. and all of them fail, and finally discover that the only tool that works is Opening by face, which is kind of intended for other uses. But then, it works only on one rafter at a time, since the beam system is not a grouped array. Arggg... Strange. There is definitely room for improvement in this topic of beams in Revit

[Alfredo Medina]

A couple of tricks with beams:

Use a reference plane and Cut Geometry to "trim" beam ends, etc.


Oh, I forgot that combination of Cut Geometry + Reference plane. Thanks, Cliff. That one works, too! (2011, only)

(By the way, thank you for recommending that post of mine in the Adesk forum)

[cliff collins]

Alfredo,

Yes--your posts are always very helpful, thanks.

The beam system method works really well.

BTW,
The trim w/ ref. plane and cut geometry works in 2010 as well.

cheers

[Alfredo Medina]

BTW,
The trim w/ ref. plane and cut geometry works in 2010 as well.

cheers

Not in Revit Architecture 2010. The feature has been present in Revit Structure, since previous releases, but in Revit Architecture it was introduced in 2011.

[cliff collins]

Alfredo,

Just did it in RAC 2010.

I do have the Subscription Adv.Pack / Extensions installed, maybe it's part of that?

see attached.

cheers.

[Alfredo Medina]

Alfredo,

Just did it in RAC 2010.

I do have the Subscription Adv.Pack / Extensions installed, maybe it's part of that?

see attached.

cheers.

Cliff, yes, that is probably the reason, the advantage package. That's why it is called an advantage, isn't? :)

[TheViking]

Have you tried the beam/column join editor? Beams are mainly structural and we typically do not miter beams, because it is costly. That is typically reserved for architecturally exposed structural steel. With the beam/column editor you can create the miter join as long as the beams are the same type. For the "cranked" beams you show in the roof plan the miter should be the default condition.

Erik

[Alfredo Medina]

Have you tried the beam/column join editor? ... With the beam/column editor you can create the miter join as long as the beams are the same type. ...Erik

Well, in that exercise, the beams were of the same type, on both sides of the gable, and I tried to use the beam/column join tool, and nope.. it just didn't let me do anything.

[barrie.sharp]

I was able to use your beam family on one side of a gable roof, only. In the other side, the cut angles were upside down.
The top has to be the start of the beam. I was drawing them from the ridge out.

Cutting to ref planes makes that whole family concept fairly redundant although it would save setting up the ref planes and cutting each beam.

I tried demonstrating my issues by creating the conditions on a blank project and it seems they behave fine now!

Still one issue though. The rafter I created doesn't physically sit on the connection line. I have attached a jpg to show how it floats. If I increase the beams height, it gets closer. The geometry center seems to be offset from the beam