RISA locked joint problem

Question

RISA locked joint problem

AuEng99 (Civil/Environmental)

(OP)

26 Sep 12 22:09

I have a model that I am working on for a flat roof building. I know it may not sound good, but I used the flat roof to ease my calculation checks. I have added the sub mesh on the metal plate as recommended in an earlier post. However, now I am getting a lot of locked joints. Can anyone explain to me how to unlock these? Also, in the Load Combinations, is the Dead load the only Y value that receives a -1? The model is attached.

www.gulfcoastinfrastructure.com

AuEng99 (Civil/Environmental) · Answer 1 · 2012-09-26 22:41:38

I am not sure the attachment went through correctly, so here it is again. Also, I need to mention that the problem with locked joints began when I click all the roof truss members and specified that they should allow rotation transfer.

JoshPlumSE (Structural) · Answer 2 · 2012-09-27 12:08:12

You attached a results file, not the input file. The files have the same name, but the input file will be listed with a *.r3d extension (i.e. file type = RIS-3D File). The *.__s, and *.__r files are binary results files which cannot be opened without the input file.

AuEng99 (Civil/Environmental) · Answer 3 · 2012-09-27 13:06:21

RE: RISA locked joint problem

AuEng99 (Civil/Environmental)

(OP)

27 Sep 12 13:06

Here is the .r3d file.

JoshPlumSE (Structural) · Answer 4 · 2012-09-27 18:40:15

Model wasn't attached to your last post. Have you considered just sending it into the RISA tech support group? If you're current (or close to current) then you should be able to expect a much quicker turn around.

AuEng99 (Civil/Environmental) · Answer 5 · 2012-09-27 21:32:36

Sorry Josh, I thought that I reattached it in a post after lunch.

http://files.engineering.com/getfile.aspx?folder=adf3c719-cf0d-4b56-b8d0-a3

JoshPlumSE (Structural) · Answer 6 · 2012-09-28 11:48:42

The bottom chord of your truss is pinned-pinned at each panel point. This is fine for a 2D model, but it becomes unstable uin the transverse direction for a 3D truss.

Personally, I would change the member end relases for the internal truss members to fixed-fixed. After all, it really is one piece of wood, isn't it? If not, then it needs to be braced in the Z direction in some way or it will be unstable.

On another note, the bases of your columns are set using the "Fixed" boundary condition code. You may want to change this to the "reaction" boundary condition code. The effect on the model is essentially the same. But, the "fixed" boundary condition code asks the program to suppress the calculation of joint reactions. So, you will not be able to see how much force goes into your base plates.

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RISA locked joint problem