What is the type of connection that exists between the interferrence of plate and members?

Question

What is the type of connection that exists between the interferrence of plate and members?

(OP)

6 Jan 14 15:59

I created a model using plates and members. I need to know what the type of connection (fixed or pinned exists where the plate nodes interfere with the a member. I want it to be fixed. But it seems like it is acting like a pinned joint. I double clicked on the plates to see the type of joints. It shows me all four corners are fixed. I do not know why it is acting as pinned joints though. Please help.

JoshPlumSE (Structural) · Answer 1 · 2014-01-06 18:36:04

The default is for FIXED and it is only pinned if you specifically pin the ends of the member or the corners of the plate.

The only exception to this is the "drilling degree of freedom" for the plate. Since plate elements do not consider drilling degree of freedom you cannot expect members to have rotational connectivity to plates in this direction. If this is what you're dealing with, then you will want to review the "Modeling Tips" section of the help file. I believe the first two sub-topics deal with the issue and how to address it for a couple of common scenarios. My guess is that this is what is happening in your model.

kabindrabhattarai (Mechanical) · Answer 2 · 2014-01-07 09:56:13

Ok Thanks Josh. I have attached a picture to make it clear (please click on the link). The member I'm dealing with is one continuous beam with two nodes N1 and N2. There actually are no intermediate nodes on the member where it connects to the plates (plates form the three pipes). So the only joint I could control is the plate nodes that connect to the member. I know they are fixed but during calculation, they act as if they are pinned to the member.

http://files.engineering.com/getfile.aspx?folder=5...

-Kabindra

http://files.engineering.com/getfile.aspx?folder=5e5d06e1-35f1-48f7-a104-e6

JoshPlumSE (Structural) · Answer 3 · 2014-01-07 11:43:48

The image looks okay to me... provided that those beams are defined as Physical members.

You might take a look a the member color coding option for "phys segments". That will show you a color change everywhere a member picks up an internal joint. It is possible that the joints for your pipes only appear to be at the centerline of the member. Maybe they're really offset from the physical member which would cause it to not pick up those joints.

You might also try running a model merge to merge out any duplicate joints or such.

kabindrabhattarai (Mechanical) · Answer 4 · 2014-01-07 12:12:10

I just checked. The beam is a physical member. So it should be picking up the internal joint. I have tried running a model merge. It shows that the number of nodes merged is always zero.

If the joints were really not on the centerline of the member, it would not even act as a pinned joint; am I correct? I know the forces are being transferred but for some reason the moment is not being transferred.

JoshPlumSE (Structural) · Answer 5 · 2014-01-07 13:39:14

Moment should be transferring then. Perhaps its small enough that you don't see much of a spike in the member moment diagram?

If its a simple or relatively small model, then you might post it here. Otherwise, this might be something that you want to contact RISA tech support about directly.

kabindrabhattarai (Mechanical) · Answer 6 · 2014-01-07 16:25:23

You may be right that the moment is not very big enough. Thanks you for your help Josh.

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What is the type of connection that exists between the interferrence of plate and members?