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angular constraint within flexible elements

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Message 1 of 10
kwg06516
3557 Views, 9 Replies

angular constraint within flexible elements

constrain train.PNG

 

I'm building a PEMB frame family partly to teach myself and because none of the ones I could find online match the ones I'm working with.  It's been a bumpy road but I've gotten the family to the point where there are parameters and elements for the flange, web, baseplate & girts.

 

Where I've run into a problem are the bracing flanges.  The flange at the top of the column was simple enough since it's always horizontal but the beam braces are all 90 deg to the top chord.  Any refrence plane or reference line drawn from the intersection of the bottom & column chords to the top chord does not move with the other chords when the family types are changed.  I applied a 90 deg angular dimension constraint between the top chord and the bracing flange but when I change the pitch of the top chord by increasing the Ridge Height Revit gives me a warning message that the constraint is no longer satisfied instead of rotating the flange!

 

 

 


AutoCAD 2010


AutoCAD 2015


Revit 2015

9 REPLIES 9
Message 2 of 10
kwg06516
in reply to: kwg06516

Forgot to attach a copy of the frame.

 


AutoCAD 2010


AutoCAD 2015


Revit 2015

Message 3 of 10
kwg06516
in reply to: kwg06516

Update:  I created some vertical flanges just to get something out of the office, but when I tried to create a new family type with different eave and ridge heights I get a constraint error on the flanges.  What did I do wrong?

 

  1. The reference planes are driven by the parameters.
  2. The reference lines are snapped to the planes.
  3. I tested them all before creating a single sweep or extrusion.  There were no errors.
  4. The flange is a continuous sweep constrained to the reference lines and planes.
  5. The web is an extrusion constrained to the inside edges of the sweep.
  6. The horizontal braces are two extrusions constrained to a refrence plane, the inside edges of the of the sweep and the parameter for flange thickness.
  7. I created the first family type to match the field conditions in the 24 ft bays.
  8. Then I created the vertical braces in the same manner as the horizontal braces.
  9. Then I tried to create a second family type for the 25 ft bays.  This changed the pitch and I get this constraint error!

I can't see where the conflict is, especially when Revit doesn't highlight the conflicts in the family editor the way it does in the project editor.

 

 


AutoCAD 2010


AutoCAD 2015


Revit 2015

Message 4 of 10

when you say :

"2.-The reference lines are snapped to the planes." - I presume you want to say that the start and end points of the Reference Lines are snapped to intersections of Reference Planes ?

I think you have to check again steps 1,2,3 .

If I were you , I would erase the object and check again the first three steps flexing the paramaters one by one till I am sure that there are no more problems...then I would made an extruded shape (the web) locked on the Reference Lines an Planes . Test again - flexing the parameters. Load into a project. Test again ...The Sweeps would be the last touch.

Constantin Stroescu
BIM Manager AGD
Message 5 of 10

My biggest problem with Revit right now is building parametric families and trying to figure out what action drives what change in the movements of the model.  It's simply not clear the way they set this program up and they dropped the ball on what would have been some useful features.  When working in projects you can select items in an error report and they hilight orange in the model.  They chose not to do the same in the family editor.  It would also have been nice if there was some way to select a parameter or dimension and see all the entities affected by them highlight, including other dimensions and parameters, because right now I keep getting lost.

 

The second biggest problem is dealing with angles.  Look at the Family2.rfa that I've attached to this reply.  There are two extrusions labelled Box 1 with a flat top and Box 2 with a slanted top.  There are three parameters.

1. box 1 height

2. box 2 left height

3. box 2 right height

The "box 1 height" parameter moves the top of box 1 up and down with no problems.  But try controlling the height of box 2.  The "box 2 left height" parameter moves the left side of Box 2 up and down without any problems but the "box 2 right height parameter" only moves the reference plane.  Now as far as I can tell I connected the the corners of the extrusion sketch to the planes the same way.

  1. I'm editing the sketch of the extrusions (pink lines); working plane is Center Front/Back
  2. I hover over an edge of the extrusion and cycle with Tab till I see the whole outline shaded in blue.
  3. I click once and the extrusion turns darker blue and there are empty circles around the endpoints.
  4. I drag the upper left endpoint up till it snaps to the left height reference plane.
  5. I do the exact same thing with the upper right endpoint.
  6. At no point does Revit offer a padlock to lock the endpoint to the plane (apparently you can only constrain planes to planes).
  7. I click the green check and open Family Types and change the parameters.

Only the left corner moves up and down with its reference plane.  I just don't get it.

 

I tried other methods too by the way.  See the attached Family3.rfa  

 

I tried dimensioning point to point and labelling the dimension.  I also went into the left hand elevation and dimensioned to the lines of the extrusion corners I wanted to control.  When I tried to change the parameters in Family Types I get a error telling me a Constraint is not satisfied.  Of course it doesn't tell me what constraint, except by an ID number I have no way of knowing how to track back to its source.

 

So tell me, what is the proper way to control a pitched surface?   It seems to be explained nowhere and I understand now why all the student models in revit look like buildings by Neutra.

 


AutoCAD 2010


AutoCAD 2015


Revit 2015

Message 6 of 10
loboarch
in reply to: kwg06516

When workign with angles in a family you need to use reference lines rather than reference planes.  In your simple example you are trying to set an angle for a section of an extrusion by setting the heights at either end.  You actually need a reference line with an endpoint on one side of the box.  Then a angle parameter which is used to rotate the reference line.  Then the angled edge of the extrusion sketch is aligned and locked to the reference line.  Now by changing the angle parameter the top of the box will change with the angle.  I also provided an additional reference plane on the right side to hold that edge in place as the angle increased.

 

If you want to be able to set both heights explicitly then the angle would need to become a formula which uses some trigonometry to get the angle and set the parameter correctly.

 

Revised file is attached so you can see what I did.



Jeff Hanson
Principal Content Experience Designer
Revit Help |
Message 7 of 10

Image 197.png

Constantin Stroescu
BIM Manager AGD
Message 8 of 10

Locking both ends of a reference line will work too.  Smiley Happy  For some reason I just started by setting an angle parameter instead.



Jeff Hanson
Principal Content Experience Designer
Revit Help |
Message 9 of 10
kwg06516
in reply to: kwg06516

I'm still on 2013 and I need to get upgraded but there've been too many 12 hour days.  I've got some time to do it today so don't resubmit your models.  Thanks to all of you for your suggestions.

 

I know about reference lines.  I used them in the PEMB frame model afterall.  What has bothered me about them is ensuring that the endpoints remain locked to the refrence planes.  Revit seems to only offer one padlock even though the endpoint was snapped to an intersection.  Maybe that padlock serves the intersection but it's drawn with a line pointing to one of the planes and there's only one so it's ambiguous.  They also haven't functioned properly all of the time.  When I first started putting the reference lines together for the PEMB frame I closed all the padlocks but after a few adjustments with the family types editor one end of the reference line would come undone from the intersection and move along just one of the two reference planes.  Also offset reference lines would grow in length or move about along their parallel constraint with each adjustment.  I solved that issue by locking the endpoints to two vertical reference planes.

 

I also want to know what family type template I should have used for the frame.  The beam template doesn't seem to work right if the length is anything other than the intitial 50 feet, otherwise some constraint errors regarding the bracing elements keep popping up.

 


AutoCAD 2010


AutoCAD 2015


Revit 2015

Message 10 of 10

when I said lock to intersection that means lock to both planes one by one...see the Capture Recording I "ve post in Project Chronicle a few minutes ago..

 

https://chronicle.autodesk.com/Main/Details/bf3fe38c-557b-4d83-817b-20114f4bfa46

Constantin Stroescu
BIM Manager AGD

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